JPH1075443A - Video data compressor and compressing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of a video image after compression as a while by adjusting a generated bit amount in response to complicatedness of a pattern for each part of video data. SOLUTION: A real difficulty data calculation circuit 282 calculates real difficulty data D1 corresponding to a data amount after compression based on index data denoting complicatedness of a pattern of a video image (ME residue, flatness and intra AC and activity). A parameter calculation circuit 286 adjusts a parameter Rj ' in response to the occupant amount of a VBV(video buffering verifier) buffer. An object data amount calculation circuit 284 multiplies a multiple based on the real difficulty data Dj with the parameter Rj ' adjusted by the parameter calculation circuit 286 to calculate the object data amount Tj denoting the object value of the data amount of the video image after compression. A quantization index QIND is calculated from the object data amount Tj and used for the compression coding to realize rate control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video data compression apparatus for compressing and encoding non-compressed video data and a method thereof.

[0002]

2. Description of the Related Art Uncompressed digital video data is stored in a moving picture (MPEG) format.
I-picture (intra c
oded picture), B picture (bi-directionaly predi
ctive coded picture) and P-picture (predictive coded picture)
GOP (group of pictur) composed of coded pictures
es) When recording on a recording medium such as a magneto-optical disk (MO disk) by compression-encoding in units, the data amount (bit amount) of the compressed video data after compression-encoding is expanded and decoded. It is necessary to keep the quality of the subsequent video high or less while keeping the recording capacity of the recording medium or less or the transmission capacity of the communication line or less.

For this purpose, first, non-compressed video data is preliminarily compression-encoded and the data amount after compression-encoding is estimated (first pass). Next, the compression rate is adjusted based on the estimated data amount. Then, compression encoding is performed so that the data amount after the compression encoding becomes equal to or less than the recording capacity of the recording medium (second pass).
(Hereinafter, such a compression encoding method is also referred to as “two-pass encoding”).

However, if compression encoding is performed by two-pass encoding, it is necessary to perform the same compression encoding process twice on the same non-compressed video data, which takes time. Further, since the final compressed video data cannot be calculated by one compression coding process, the captured video data cannot be directly compression-coded and recorded in real time (real time).

[0005] The present invention has been made in view of the above-mentioned problems of the prior art.
It is an object of the present invention to provide a video data compression device and a video data compression device capable of compressing and encoding audio / video data to a predetermined data amount or less. Further, the present invention can compress and encode video data almost in real time.
It is an object of the present invention to provide a video data compression device and a method thereof capable of obtaining a high quality video after decompression decoding. Further, the present invention provides a video data compression device and a video data compression method capable of performing a compression encoding process by estimating a data amount after compression encoding and adjusting a compression ratio without using two-pass encoding. With the goal.

[0006]

In order to achieve the above object, a video data compression apparatus according to the present invention converts uncompressed video data of a moving image into compressed video data (compressed video data).
A video data compression device for compressing the video data to a data rate that satisfies a condition determined based on a VBV buffer that buffers the video data, wherein difficulty data calculation means for calculating difficulty data indicating the complexity of the video of the uncompressed video data; V
On the basis of the data amount (occupied data amount) of the compressed video data buffered in the BV buffer and the calculated difficulty data, the data amount after compression into a predetermined number of uncompressed video data pictures (assigned data Data amount allocating means for allocating the amount of data, and target value calculating means for calculating a target value of the data amount of the uncompressed video data after compression based on the calculated difficulty data and the allocated data amount, for each picture; Compression means for compressing the uncompressed video data by a predetermined compression method so that the data amount after compression becomes the calculated target value.

Preferably, the difficulty data calculation means calculates a data amount of the uncompressed video data after compression as the difficulty data.

Preferably, when the occupied data amount of the VBV buffer is equal to or more than a predetermined threshold, the data amount allocating means complicates the video of the uncompressed video data based on the calculated difficulty data. The target value calculating means increases the value of the target value as the image of the uncompressed video data becomes more complicated, and increases the value of the target value. The simpler the image, the smaller the target value.

Preferably, the data amount allocating means calculates a reference value obtained by equally distributing all data amounts given to the compressed video data to all pictures, from a data amount of the generated picture of the compressed video data. A difference value is calculated by subtraction, and when the compression of the uncompressed video data is completed, the allocated data amount is calculated so that the sum of the calculated difference values becomes a value close to a negative value of zero.

Preferably, the target amount calculating means multiplies a value obtained by dividing the total of the difficulty data of a predetermined number of pictures by the difficulty data of the latest picture by the calculated allocation data amount to calculate the target value. calculate.

Preferably, the compression means converts the uncompressed video data into a plurality of types of pictures (I picture,
(P picture and B picture or a combination thereof) in a predetermined order.

Preferably, the difficulty data calculating means includes, as the difficulty data, a ME residual of a picture compressed to a P picture or a B picture, a flatness of a picture compressed to an I picture, and intra AC data. And activity or a combination thereof.

Preferably, the data amount allocating means adds, as the predetermined threshold value of the occupied data amount of the VBV buffer, to the latest I-picture data amount according to the data rate of the generated compressed video data. Value, or
A numerical value obtained by adding a fixed addition value is used.

Preferably, the data amount allocating means determines whether or not the occupied data amount of the VBV buffer is equal to or greater than a predetermined threshold, and the compression means compresses the uncompressed video data into a P picture. Immediately after doing.

A video data compression apparatus according to the present invention is a video data compression apparatus which stores uncompressed video data of a moving picture in a predetermined combination and order of a plurality of types of pictures (I picture, P picture and B picture) by, for example, the MPEG system. It compresses and encodes into a type sequence, suppresses the data amount of the video data (compressed video data) after the compression and encoding to less than the recording capacity of a recording medium or the like, and complies with MPEG VBV (vi).
deo buffering verifier) Generates compressed video data that satisfies the constraint condition on the occupancy of the buffer and has high quality of the video after decompression decoding.

In the video data compression device according to the present invention, the difficulty data calculation means generates difficulty data indicating the complexity (simplicity) of the video of the uncompressed video data. As the difficulty data generated by the difficulty data calculation means, for example,
The ME residual, actual difficulty data D _j corresponding to the data amount of the compressed video data obtained by pre-compression-coding the uncompressed video data, or a flatness (flatness) newly defined to indicate the flatness of the video. ), Intra AC (intra
-AC), the quantization value (MQUAN
Activity used to calculate (T)
y) and global complexity (global comp
lexity) is used.

The data amount allocating means estimates a predetermined margin or more in the VBV buffer, for example, a data amount of the latest I picture, in the VBV buffer so that underflow does not occur in the VBV buffer for buffering the compressed video data. Only when the compressed video data larger than the data amount is buffered, the allocated data amount indicating the data amount that can be allocated to the compressed picture of the non-compressed video data is adjusted. Note that the determination of the data amount of the compressed video data buffered in the VBV buffer does not need to be performed each time the compression unit generates a picture of the compressed video data, and the data amount in the VBV buffer depends on the determination. It is preferable that the compression be performed immediately after the compression unit that has the optimum value generates the P picture.

The adjustment of the allocated data amount by the data amount allocating means is performed, for example, by equally allocating the maximum data amount (maximum data amount; for example, the recording capacity of a recording medium) allowed as a whole to the compressed video data. When the occupation amount of the VBV buffer is equal to or more than a predetermined value (when underflow will not occur)
In addition, a predetermined number (L) of pictures having complex images are assigned more data than the reference value, and pictures having simple pictures are assigned less data than the reference value. The data amount of the data does not exceed the maximum data amount, and the data amount of the compressed video data is substantially equal to the maximum data amount.

When adjusting the amount of data allocated by the data amount allocating means, not only the condition for the underflow of the VBV buffer is set, but the data rate of the compressed video data naturally exceeds the VBV buffer. It is necessary to satisfy the condition that it does not occur.

The target amount calculating means multiplies, for example, a value obtained by dividing the difficulty data of the latest picture by the total value of the difficulty data of the L pictures by the allocation data calculated by the data amount allocating means. A target value of the data amount after compression for each picture of the compressed video data is calculated. As described above, the maximum data amount can be effectively used by the data amount allocating unit and the target amount calculating unit, and a large amount of compressed video data is generated from a complex video picture requiring a large amount of data, The compressed video data of a small data amount is generated from a picture of a simple video requiring a small data amount, and the quality of the video of the compressed video data is improved as a whole.

The compression means compresses the non-compressed video data according to, for example, the MPEG method in a predetermined picture type sequence so that the data amount after compression encoding becomes substantially the target value calculated by the target amount calculation means. Encode.

The video data compression method according to the present invention compresses uncompressed video data of a moving image to a data rate that satisfies a condition determined based on a VBV buffer that buffers video data after compression (compressed video data). A video data compression method based on the amount of data until the VBV buffer underflows and the complexity of the video of the picture of the uncompressed video data. And the compressed data amount of the uncompressed video data based on the complexity of the picture of the picture of the uncompressed video data and the calculated allocated data amount. Is calculated for each picture, and the data amount of the uncompressed video data after compression is calculated by a predetermined compression method. It was compressed to be the target value.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a first embodiment of the present invention will be described. By compression encoding video data such as the MPEG method, when compression encoding video data with a high degree of difficulty, such as a pattern with many high frequency components or a pattern with a lot of motion, distortion due to compression is likely to occur. Become. For this reason, it is necessary to compress and encode video data having a high degree of difficulty at a low compression ratio. For compressed video data obtained by compressing and encoding data having a high degree of difficulty, a compressed image of video data having a pattern having a low level of difficulty is obtained. It is necessary to allocate a larger amount of target data than data.

As described above, in order to adaptively allocate the target data amount to the degree of difficulty of the video data, the two-pass encoding method shown as the prior art is effective. However, the two-pass encoding method is not suitable for real-time compression encoding. The simplified two-pass encoding method shown as the first embodiment has been made to solve the problem of the two-pass encoding method, and the compressed video data obtained by preliminary compression-encoding the non-compressed video data The difficulty level of the uncompressed video data is calculated from the difficulty level data, and the FI level is calculated based on the difficulty level calculated by the preliminary compression encoding.
The compression rate of the uncompressed video data delayed by a predetermined time by the FO memory or the like can be adaptively controlled.

FIG. 1 is a diagram showing the configuration of a video data compression device 1 according to the present invention. As shown in FIG. 1, the video data compression apparatus 1 includes a compression encoding unit 10 and a host computer 20. The compression encoding unit 10 includes an encoder control unit 12, a motion estimator 14,
Simple 2-pass processing unit 16, second encoder (encoder) 1
8, and the simple two-pass processing unit 16 includes a FIFO memory 160 and a first encoder 162. The video data compression device 1 uses these components to generate uncompressed video data VI input from external devices (not shown) such as an editing device and a video tape recorder device.
For N, the above-described simple two-pass encoding is realized.

In the video data compression device 1, the host computer 20 controls the operation of each component of the video data compression device 1. Also, the host computer 20
The data amount of the compressed video data generated by the encoder 162 of the simple two-pass processing unit 16 preliminarily compression-encoding the non-compressed video data VIN, the value of the DC component (DC component) of the DCT-processed video data, and the DC component The power value of the (AC component) is received via the control signal C16, and the difficulty of the picture of the compressed video data is calculated based on the received values. Further, the host computer 20 based on the calculated difficulty, assigned to each picture of the target amount of data T _j of the compressed video data encoder 18 is generated via a control signal C18, the quantization circuit 166 of the encoder 18 (FIG. 3 ), And the compression rate of the encoder 18 is adaptively controlled on a picture basis.

The encoder controller 12 determines whether or not there is a picture of the uncompressed video data VIN by the host computer 20.
And performs a pre-process for compression encoding for each picture of the uncompressed video data VIN. That is, the encoder control unit 12 rearranges the input non-compressed video data in the order of encoding, performs picture / field conversion, and performs 3: 2 pull-down processing (movie processing) when the non-compressed video data VIN is video data of a movie. Of the 24 frames / sec video data into 30 frames / sec video data, and removes the redundancy before the compression encoding.
The FIF of the simple 2-pass processing unit 16 is used as the video data S12.
Output to the O memory 160 and the encoder 162. The motion detector 14 detects a motion vector of the uncompressed video data, and outputs the motion vector to the encoder control unit 12 and the encoders 162 and 18.

In the simple 2-pass processing unit 16, the FIFO
The memory 160 converts the video data S12 input from the encoder control unit 12 into, for example, uncompressed video data VIN
Is delayed by the time of L (L is an integer) picture input, and is output to the encoder 18 as delayed video data S16.

FIG. 2 is a simplified two-pass processing unit 1 shown in FIG.
6 is a diagram illustrating a configuration of a sixth encoder 162. FIG. The encoder 162 includes, for example, as shown in FIG.
4. DCT circuit 166, quantization circuit (Q) 168, variable length coding circuit (VLC) 170, inverse quantization circuit (IQ)
172, inverse DCT (IDCT) circuit 174, addition circuit 1
Is a general video data compression encoder composed of the video data S12 and the motion compensation circuit 178. The input video data S12 is compression-coded by the MPEG method or the like, and the amount of compressed video data for each picture is determined. Output to the host computer 20.

The addition circuit 164 subtracts the output data of the addition circuit 176 from the video data S12,
6 is output. The DCT circuit 166 includes the addition circuit 1
For example, the video data input from 64 is converted to 16 pixels ×
Discrete cosine transform (D
CT), converts the data in the time domain into the data in the frequency domain, and outputs the data to the quantization circuit 168. Further, the DCT circuit 166 controls the DCT of the video data after the DCT.
The value of the component and the power value of the AC component are output to the host computer 20.

The quantization circuit 168 converts the frequency domain data input from the DCT circuit 166 into a fixed quantization value Q
And the variable length coding circuit 17 as quantized data.
0 and output to the inverse quantization circuit 172. The variable-length coding circuit 170 performs variable-length coding on the quantized data input from the quantization circuit 168, and converts the amount of compressed video data obtained as a result of the variable-length coding into a control signal C
16 to the host computer 20. The inverse quantization circuit 172 inversely quantizes the quantized data input from the variable length encoding circuit 168, and outputs the inversely quantized data to the inverse DCT circuit 174.

The inverse DCT circuit 174 includes the inverse quantization circuit 17
Inverse DCT processing is performed on the inversely quantized data input from 2 and output to the adding circuit 176. Addition circuit 1
76 is the output data of the motion compensation circuit 178 and the inverse DC
The output data of the T circuit 174 is added and output to the addition circuit 164 and the motion compensation circuit 178. The motion compensation circuit 178 performs a motion compensation process on the output data of the addition circuit 176 based on the motion vector input from the motion detector 14, and outputs the result to the addition circuit 176.

FIG. 3 is a diagram showing a configuration of the encoder 18 shown in FIG. As shown in FIG.
Has a configuration in which a quantization control circuit 180 is added to the encoder 162 shown in FIG. The encoder 18
With these components, based on the target amount of data T _j set from the host computer 20, the motion compensation process to the L picture delayed by the delayed video data S16 by the FIFO memory 160, DCT processing, quantization processing and The variable-length encoding processing is performed to generate compressed video data VOUT in the MPEG format or the like, and output the same to an external device (not shown).

In the encoder 18, the quantization control circuit 180 sequentially monitors the data amount of the compressed video data VOUT output from the variable length quantization circuit 170, and finally starts from the j-th picture of the delayed video data S16. data amount of the compressed video data generated is, so as to approach the target amount of data T _j set from the host computer 20,
The quantization value Q _j to be set in the quantization circuit 168 is sequentially adjusted. The variable-length quantization circuit 170 outputs the compressed video data VOUT to the outside, and also outputs the delayed video data S1
6 is output to the host computer 20 via the control signal C18, the actual data amount _Sj of the compressed video data VOUT obtained by compression-encoding 6.

Hereinafter, a simplified two-pass encoding operation of the video data compression device 1 according to the first embodiment will be described. FIGS. 4A to 4C are diagrams illustrating the operation of the simple two-pass encoding of the video data compression device 1 according to the first embodiment. The encoder control unit 12 controls the video data compression device 1
4A, the encoder control unit 12 performs preprocessing such as rearranging the pictures in the encoding order, and as shown in FIG. 4A, the FIFO memory 160 and the encoder 162. Note that the encoder control unit 12
, The order of picture encoding shown in FIG. 4 and the like differs from the order of display after decompression decoding.

The FIFO memory 160 delays each picture of the input video data S12 by L pictures and outputs the delayed picture to the encoder 18. Encoder 16
Reference numeral 2 denotes a data amount of compression-encoded data obtained by compression-encoding a picture of the input video data S12 in a preliminary and sequential manner, and compression-encoding a j-th (j is an integer) picture; And outputs the DC component value and AC component power value of the video data to the host computer 20.

For example, the delay input to the encoder 18
The video data S16 is stored in the L memory by the FIFO memory 160.
As shown in FIG. 4 (B),
As described above, the encoder 18 determines the j-th
(J is an integer) picture (picture of FIG. 4B)
-A), the encoder 162
Are L-pins from the j-th picture of the video data S12.
The (j + L) -th picture ahead of the kuture (FIG. 4
This means that picture b) of (B) is compression-encoded.
You. Therefore, the encoder 18 transmits the delayed video data S16.
When starting the compression encoding of the j-th picture,
The encoder 162 is configured to j-th to
(J + L-1) -th picture (range of FIG. 4B)
c) the compression encoding has been completed and these pictures
Difficulty data D after compression encoding_j, D _{j + 1}, D_{j + 2},
…, D_{j + L-1}Is already calculated by the host computer 20.
Has been issued.

The host computer 20 calculates the following equation (1).
As a result, the encoder 18 sets the j-th
A target data amount T _j to be allocated to the compressed video data obtained by compression-coding the third picture is calculated, and the calculated target data amount T _j is set in the quantization control circuit 180.

[0039]

(Equation 1)

Where D _j is the video data S
12 is the actual difficulty data of the 12 th picture,
R ′ _j is the average of the target data amount that can be allocated to the j-th to (j + L−1) -th pictures of the video data S12 and S16, and the initial value of R ′ _j (R ′
₁ ) is a target data amount that can be allocated to each picture of the compressed video data on average, and is expressed by the following equation (2). Each time the encoder 18 generates one picture of the compressed video data, Updated as shown.

[0041]

(Equation 2)

[0042]

(Equation 3)

Note that the numerical bit rate (Bit rat
e) is based on the transmission capacity of the communication line and the recording capacity of the recording medium.
Data amount per second (bit amount)
The picture rate (Picture rate) is
Number of pictures per second (30 pictures / sec.
(NTSC), 25 sheets / second (PAL))
_{j + L}Is a picture determined according to the picture type
Shows the average amount of data per group. DC of encoder 18
The T circuit 166 is configured to output the delayed video data S16
DCT processing is performed on the j-th picture, and a quantization circuit 168
Output to The quantization circuit 168 is a DCT circuit 1
Frequency domain of the j-th picture input from
Of the target data amount T by the quantization control circuit 180._j
Quantized value Q adjusted based on_jQuantized by
Output to the variable length coding circuit 170 as encoded data.
You. The variable length coding circuit 170
Variable quantized data of the input j-th picture
After long encoding, the target data amount T_jData volume close to
And outputs the compressed video data VOUT.

Similarly, as shown in FIG. 4B, when the encoder 18 compresses and encodes the (j + 1) -th picture (the picture a 'in FIG. 4C) of the delayed video data S16. , The encoder 162 completes the compression encoding of the (j + 1) -th to (j + L) -th pictures (range c ′ in FIG. 4C) of the video data S12,
The actual difficulty data D _{j + 1} , D _{j + 2} , D of these pictures
_{j + 3} ,..., D _{j + L} have already been calculated by the host computer 20.

The host computer 20 uses the following equation (1).
The encoder 18 determines the (j + 1) th of the delayed video data S16.
A target data amount T _{j + 1} to be allocated to compressed video data obtained by compression-encoding the third picture is calculated and set in the quantization control circuit 180 of the encoder 18.

The encoder 18 is connected to the host computer 2
From 0, the (j + 1) -th picture is compression-encoded based on the _scale data amount _Tj set in the quantization control circuit 180, and compressed video data VOUT having a data size close to the target data size _{Tj + 1} is generated. And output. In the same manner, the video data compression device 1 similarly converts the k-th picture of the delayed video data S16 into a quantized value Q _k (k = j + 2,
j + 3,...) are changed for each picture, and are sequentially compression-encoded and output as compressed video data VOUT.

As described above, according to the video data compression apparatus 1 shown in the first embodiment, the degree of difficulty of the pattern of the non-compressed video data VIN is calculated in a short time, and the compression ratio according to the calculated degree of difficulty is calculated. Thus, the non-compressed video data VIN can be adaptively compression-encoded. That is, according to the video data compression apparatus 1 shown in the first embodiment, unlike the two-pass encoding method, the non-compressed video data VI
N based on the degree of difficulty of the picture
IN can be compression-encoded, and can be applied to applications requiring real-time performance such as live broadcasting. In addition to the data multiplexing apparatus 1 according to the present invention, the data multiplexing apparatus 1 according to the present invention uses the data amount of the compressed video data compressed and encoded by the encoder 162 as difficulty data as it is, Various configurations can be adopted, such as simplification.

Second Embodiment Hereinafter, a second embodiment of the present invention will be described. In the simple two-pass encoding method shown in the first embodiment, the input non-compressed video data contains almost one GOP (for example, 0.5 GOP).
This is an excellent method that can compress and encode only by giving a delay of about (second) to generate compressed video data of an appropriate data amount.

However, these systems require two encoders. In general, an encoder that compresses and encodes video data requires large-scale hardware, is very expensive even if integrated, and is large in size. Therefore, these methods require two encoders.
This necessitates a reduction in cost, size, and power saving of a device that realizes these methods. The shorter the time delay required for the compression encoding is, the better. However, the processing for calculating the actual difficulty data D _j and the prediction difficulty data D _j ′ and the preliminary compression encoding itself require processing time for several pictures. Since it is necessary, these processes themselves cause a hindrance to shortening of the time delay.

The second embodiment has been made in order to solve such a problem, and uses only one encoder, and is equivalent to the simple two-pass encoding system and the prediction simple two-pass encoding system. It is an object of the present invention to provide a video data compression method that can generate compressed video data of a data amount and has a shorter time delay required for processing.

FIG. 5 is a diagram showing an outline of the configuration of the video data compression apparatus 2 according to the present invention in the second embodiment. FIG. 6 is a diagram showing a detailed configuration of the compression encoding unit 24 of the video data compression device 2 shown in FIG. FIG.
In FIG. 6 and FIG. 6, the same components as those of the video data compression device 1 (FIGS. 1 to 3) described in the first embodiment among the components of the video data compression device 2 are denoted by the same reference numerals. Is shown.

As shown in FIG. 5, the video data compression device 2
Replaces the compression encoding unit 10 of the video data compression device 1 (FIGS. 1 to 3) with a compression encoding unit 24 that is obtained by removing the encoder 162 from the compression encoding unit 10;
Is replaced by the encoder control unit 22, and the buffer memory (buf
fer) 182 is adopted. As shown in FIG.
The compression encoding unit 24 includes a video rearrangement circuit 220, a scan conversion / macroblock conversion circuit 222, and a statistic calculation circuit 224. Other components of the compression encoding unit 24 are the same as those of the compression encoding unit 10. Is adopted.

Similarly to the encoder control unit 12, the encoder control unit 22 notifies the host computer 20 of the presence / absence of a picture of the non-compressed video data VIN. Is performed. In the encoder control unit 22,
The video rearrangement circuit 220 rearranges the input uncompressed video data in the order of encoding.

Scan conversion / macroblock circuit 222
Performs picture / field conversion, and performs 3: 2 pull-down processing or the like when the uncompressed video data VIN is movie video data. The statistic calculation circuit 224 processes statistics such as flatness and intra AC from a picture which is processed by the video rearrangement circuit 220 and the scan conversion / macroblock conversion circuit 222 and is compression-coded into an I picture. Calculate the amount.

The video data compression apparatus 2 uses these components to calculate the statistics (flatness, flatness, etc.) of the uncompressed video data.
Intra-AC) and the prediction error amount of motion prediction (ME residual) are used instead of the difficulty of the picture of the uncompressed video data VIN, and adaptively set the target similarly to the video data compression device 1 (FIGS. 1 and 2). By calculating the data amount _Tj and performing high-precision feedforward control, the non-compressed video data VIN is compression-encoded into compressed video data having an appropriate data amount. In the video data compression device 2, the target data amount _Tj is determined by the motion detector 14 and the statistic calculation circuit 224 of the encoder control unit 22 based on the index data detected in advance. The compression coding method in the data compression device 2 is
Forward rate control (FFRC; feed f
oward rate control).

The ME residual is defined as the sum of absolute values or the sum of squares of the difference between the picture to be compressed and the video data of the reference picture. It is calculated from the following picture, and expresses the speed of movement of the video and the complexity of the picture, and has a correlation with the degree of difficulty and the data amount after compression, like the flatness.

Since the I picture is compression-coded without referring to other pictures, the ME residual cannot be obtained, and flatness and intra AC are used as parameters replacing the ME residual. The flatness is a parameter newly defined as an index indicating the spatial flatness of an image to realize the image data compression device 2, and indicates the complexity of the image. It has a correlation with the difficulty (degree of difficulty) and the amount of data after compression. Intra AC is a video data compression device 2
Is a parameter newly defined as the sum of variances with video data for each DCT block in the DCT processing unit in the MPEG system, and indicates the complexity of the video as well as the flatness. Has a correlation with the difficulty of the picture and the amount of data after compression.

Hereinafter, the ME residual, flatness, and intra AC will be described. In the simple two-pass encoding method and the predictive simple two-pass encoding method described in the first embodiment, the actual difficulty data D _j indicates the difficulty of the picture pattern, and the target data amount T _j is the actual difficulty data D _j.
It is calculated based on _j .

[0059] In addition, the data quantity of the compressed video data encoder 18 generates, in order to approach the value indicated by the target amount of data T _j, control of the quantization value Q _j in the quantization circuit 168 (FIG. 2, FIG. 6) Is performed. Thus, obtained without compression encoding video data, the real difficulty data D _j similarly to the picture of the video data complexity parameters appropriate indicating the (difficulty), quantization in the quantization circuit 168 of the encoder 18 If it can be obtained before the processing, the encoder 162
(FIGS. 1 and 2) can be omitted, and the object of shortening the processing delay time can be achieved. ME residual, flatness and intra AC is because it has a strong correlation with the real difficulty data D _j, it is suitable to achieve this purpose.

[0060] treated compression coding with reference to the relationship between another picture of the ME residual and the real difficulty data D _j, when generating a P picture and B-picture, the motion detector 14 becomes compressed Picture (input picture)
Is searched for a macroblock in which the sum of absolute values or the sum of squares of the difference value between the macroblock of interest and the referenced picture (reference picture) is minimized, and a motion vector is obtained. As described above, the ME residual is defined as a value obtained by summing the absolute sum or the square sum of the minimum difference value of each macroblock when calculating a motion vector for the entire picture.

[0061] Figure 7, the video data compression apparatus 1 is a diagram showing the correlation between the ME residual and the real difficulty data D _j when generating a P picture. 8, the video data compression apparatus 1 is a diagram showing the correlation between the ME residual and the real difficulty data D _j when generating a B picture. 7 and 8, actual difficulty data D
_{As j} , the data amount of the compressed video data obtained by the encoder 18 performing the compression encoding using the fixed quantization value (hereinafter, the same in FIGS. 10 and 11) is used. Standard image standardized by CCIR [che
er (cheer leaders), mobile (mobile and calender),
tennis (table tennis), diva in (diva with noise)] and other images graph showing the relationship between the ME residual and the real difficulty data D _j obtained when compressed and encoded by actually MPEG2 scheme (resort) There, 7 and 8, the vertical axis of the graph (dIFFICULTY) indicates the real difficulty data D _j, the horizontal axis (me resid) indicates the ME residual. As can be seen with reference to FIGS. 7 and 8, the ME residual is the actual difficulty data D
_{Has a} very strong correlation with _j . Therefore, after compression P
Instead of the actual difficulty data D _j of a picture or a B picture, the ME residual is represented by a target data amount T
can be used to generate _j .

[0062] Flatness and relations 9 between the real difficulty data D _j is a diagram showing a calculation method of flatness. As shown in FIG. 9, the flatness first divides each DCT block, which is a unit of DCT processing in the MPEG system, into small blocks of 2 pixels × 2 pixels, and then diagonally separates these small blocks. The difference value of the pixel data (pixel value) is calculated, and the difference value is compared with a predetermined threshold value.
It is calculated by obtaining the total number of small blocks in which the difference value is smaller than the threshold value for each picture. Note that the value of the flatness becomes smaller as the picture pattern of the video is more spatially complicated, and becomes larger when the picture is flat.

[0063] Figure 10 is a video data compression apparatus 1 is a diagram showing the correlation between the flatness and the real difficulty data D _j when generating an I picture. Note that FIG.
, Like FIG. 7 and FIG. 8 shows the relationship between the normalized standard image and actually compressed by the MPEG2 system and other image coding and flatness and the real difficulty data D _j obtained when by the CCIR FIG. 10 is a graph.
, The vertical axis (difficulty) of the graph is the actual difficulty data D
_j , and the horizontal axis (flatness) indicates flatness. FIG.
As shown in FIG. 0, there is a strong negative correlation between the flatness and the actual difficulty data D _j , and the actual difficulty data D _j can be approximated by a method such as substituting the flatness into a linear function. Recognize.

[0064] Relationship intra AC between intra AC and the real difficulty data D _j, for each DCT block, and each pixel value pixels in a DCT block, the absolute value of the difference between the average value of pixel values in the DCT block It is calculated as a sum. That is, the intra AC can be obtained by the following Expression 4.

[0065]

(Equation 4)

[0066] Figure 11 is a video data compression apparatus 1 is a diagram showing the correlation between the intra AC and the real difficulty data D _j when generating an I picture. Note that FIG.
, Like FIG. 7 and FIG. 8 shows the relationship between the normalized standard image and actually compressed by the MPEG2 system and other image coding and intra AC and the real difficulty data D _j obtained when by the CCIR FIG. 11 is a graph.
, The vertical axis (difficulty) of the graph is the actual difficulty data D
_j , and the horizontal axis (intra AC) indicates intra AC. FIG.
As shown in FIG. 1, there is a strong positive correlation between the intra AC and the actual difficulty data D _j , and the actual difficulty data D _j can be approximated by a method such as substituting the intra AC into a linear function. Recognize.

[0067] As described so far, it can be seen the real difficulty data D _j can be approximated by a linear function or the like by the indicator data (statistical amount). Therefore, the actual difficulty data D _{j for} each picture type can be calculated as shown below.

The actual difficulty data D _j is approximated by the ME residual according to the following equation 5 for the P picture and the following equation 6 for the B picture. As for the I-picture, the real difficulty data D _j by the same approximate expression to Equation 5 and 6 can be approximated by determining flatness and intra AC or Izu thereof.

[0069]

(Equation 5)

[0070]

(Equation 6)

Further, in the simple two-pass encoding method shown in the first embodiment, the target data amount T _j is calculated by substituting the actual difficulty data D _j obtained by these approximations into the equation 1. You.

Hereinafter, the actual difficulty data D _j is approximated by the ME residual, flatness and intra AC, and the non-compressed video data is compressed and encoded by the simple two-pass encoding method. The operation will be described. In the encoder control unit 22, the video rearranging circuit 220
Rearranges the pictures in the encoding order of the uncompressed video data VIN, and the scan conversion / macroblocking circuit 222
The statistic calculation circuit 224 performs picture-field conversion and the like, and performs the arithmetic processing shown in FIG. 9 and Expression 4 on the picture compressed and coded into the I-picture to obtain the statistic such as flatness and intra AC. Is calculated.

The motion detector 14 calculates the P picture and the B picture
A motion vector is generated for a picture to be compression-encoded into a picture, and an ME residual is calculated. FI
The FO memory 160 delays the input video data by L pictures.

The host computer 20 includes the motion detector 1
4 is applied to the ME residual generated to generate the approximation of the actual difficulty data D _j , and the same arithmetic processing as Expressions 5 and 6 is performed to obtain the flatness and intra to approximate the real difficulty data D _j by the AC. Further, the host computer 20, the real difficulty data D _j approximated into equation 1 to calculate the target amount of data T _j, set the target amount of data T _j calculated for the quantization control circuit 180 of the encoder 18.

The DCT circuit 166 of the encoder 18 performs DCT processing on the j-th picture of the delayed video data. The quantization circuit 168 converts the frequency domain data of the j-th picture input from the DCT circuit 166 into
Quantized by the quantization value Q _j of the quantization control circuit 180 is adjusted based on the target amount of data T _j. Variable-length coding circuit 170, and variable length coding the j-th picture of the quantized data inputted from the quantization circuit 168, substantially, it generates the compressed video data VOUT of the data amount close to the target amount of data T _j Then, the data is output to the outside via the buffer memory 182.

In the TM5 system or the like, the following equation (7) is used to calculate the quantization value (MQUANT) of a macroblock.
The statistic called activity shown in FIG. Activity, as well as the flatness and intra AC, because it has a strong correlation with the real difficulty data D _j, using the activity instead of these parameters, approximating the real difficulty data D _j, to perform compression coding The video data compression device 2 may be configured as follows.

[0077]

(Equation 7)

The operation of the video data compression apparatus 2 has been described above by taking the simple two-pass encoding shown in the first embodiment as an example. It goes without saying that it can be performed. Further, the same modification as the video data compression device 1 shown in the first embodiment can be made to the video data compression device 2 shown in the second embodiment.

Third Embodiment Prior to the description of the third embodiment of the present invention, the background and purpose of the video data compression apparatus according to the present invention in the third embodiment will be described with reference to FIG. FIG.
Video data compression apparatuses 1 and 2 (FIG. 1) using the compression algorithm shown in TM5 according to the MP @ ML method of PEG.
FIGS. 3, 5, and 6) show the temporal change of the occupation amount _Bn of the VBV buffer when the fixed-length encoding is performed while the data amount (the amount of generated bits) of the GOP of the compressed video data is kept substantially constant. It is a figure showing an evaluation result of a change. In FIG. 12, the vertical axis indicates the amount of compressed video data buffered in the VBV buffer, and the horizontal axis indicates the passage of time.

The compression algorithm shown in TM5 is excellent in that the amount of compressed video data per GOP can be made substantially constant. However, in the MPEG fixed-rate encoding method in which the data rate of the compressed video data is a fixed value, it is not always necessary to make the data amount constant in GOP units.

This fixed-rate encoding system satisfies the constraints required by a virtual VBV buffer (video buffering verifier buffer) for buffering the video data after compression encoding, that is, the buffering in the VBV buffer. The compressed video data is only used when the data amount (occupation amount B _n ) of the compressed video data does not exceed a specified value (overflow occurs) or, on the contrary, does not fall below a specified value (underflow occurs). Request to.

According to the MP @ ML scheme, the
When compression encoding is performed using a compression algorithm,
In a 1.8Mbit VBV buffer
Occupancy B of compressed video data_nWhen you evaluate
As shown in FIG. _nChanges at a high value and VB
Do you know that the V buffer cannot always be used effectively?
You.

The reason that the VBV buffer cannot be used effectively is
The occupation amount _Bn of the VBV buffer changes at a high value because the buffering capacity of the VBV buffer is about 1.8.
This is because the data amount of the picture of the compressed video data, which is a unit of input / output of the VBV buffer, is small despite the large Mbit. As described above, when generating compressed video data of a low data rate, regardless of the complexity of the video of the uncompressed video data, if the data amount of a predetermined number of pictures (GOPs) is made substantially constant, The quality of the video obtained by decompressing the compressed video data obtained by compressing and encoding the non-compressed video data of the non-compressed video part is extremely deteriorated. The quality is relatively better. Accordingly, when viewed as a whole, a large amount of unevenness occurs in the compressed video data, and the picture becomes unstable and the quality deteriorates.

The feedback rate control method shown in the third embodiment has been made in view of such a problem, and the VBV is controlled within the range of the constraints required by the VBV buffer.
An object of the present invention is to improve the quality of compressed video data as a whole by effectively using the buffering capacity of a V-buffer and allocating a data amount according to a picture to each part of non-compressed video data.

FIG. 13 is a diagram showing the configuration of the encoder 26 according to the present invention in the third embodiment. In FIG. 13, among the components of the encoder 26, FIG.
3 and FIGS. 5 and 6, the same components as those of the encoder 18 are denoted by the same reference numerals.

The encoder 26 is a video data compression device 2
This device is used in place of the encoder 18 shown in FIGS. 5 and 6, and as shown in FIG.
Has a quantization control unit 260 including a global complexity calculation circuit (GC calculation circuit) 262, a target data amount calculation (T _j calculation) circuit 264, and a quantization index generation circuit 266 in place of the quantization control circuit 180. Then, irrespective of the host computer 20, the occupation amount B _n of the compressed video data in the VBV buffer and the actual difficulty data D _j or the global complexity X _I ,
X _p, is calculated configured to be able to target amount of data T _j and the quantization value Q _j (quantization index QIND) based on X _B.

The encoder 26 performs feedback control on the quantization process of the quantization circuit 168 based on the data amount of the compressed video data by only one encoder using these constituent parts, and responds to the picture for each non-compressed video data portion. Compressed video data is generated by allocating the compressed data amount to improve the quality of the compressed video data.

Operation of each component of encoder 26 Hereinafter, of each component of encoder 26, a portion (quantum) different from encoder 18 of video data compression devices 1 and 2 (FIGS. 1, 3, 5, and 6) will be described. The operation of the activation control unit 260) will be described. Operation of the GC Calculation Circuit 262 The GC calculation circuit 262 determines the data amounts S _I , S _p , and S of the compressed video data output from the variable length coding circuit 170.
_B and the average value Q _I of quantized values the quantization circuit 168 is used for quantization, Q _p, based on the Q _B, the global complexity X _I of each picture type, X _p, calculates X _B , The target data amount calculation circuit 264, the quantization index generation circuit 266, and the host computer 20 as required.

The global complexity X _I ,
X _p and X _B are calculated for each picture type in the first step (step 1) of the MPEG TM5 method,
[X (I, P, B) ; X I = S I Q I, X p = S
_p Q _p, is defined as X _B = S _B Q _B, the global complexity X _I, X _p, X _B is, I-picture, respectively, the real difficulty data D P picture and B-picture
_I , D _p , D _B, and approximately the same value (X _I , X _p , X _B ≒ D _I ,
D _p , D _B ).

[0090] SUMMARY target data amount calculation circuit 264 of the operation the operation of the target data amount calculation circuit 264 (treatment), GC calculation circuit 262 global complexity X _I input from, X _p,
Approximates the X _B real difficulty data D _j of each picture type,
Further, the target data amount T _{j of} each picture of each picture type is determined based on the occupation amount B _n of the VBV buffer.
Is calculated to perform rate control. Note that the target data amount T _j calculated by the target data amount calculation circuit 264 is output to the quantization index generation circuit 266.

[0091] The method of calculating the target amount of data T _j First, a basic method for calculating the target amount of data T _j in the target data amount calculation circuit 264. As mentioned above,
The actual difficulty data D _j of each picture type is substantially the same as the global complexity X _I , X _p , and X _B , respectively. Accordingly, the target data amount calculation circuit 264 can calculate the global complexity X _I, X _p, from X _B of each picture type target amount of data T _j. In each of the above relational expressions, the weighting coefficients K _p ,
K _B are coefficients introduced in order to perform weighted differently for each picture type in the target amount of data T _j, the weighting coefficient K _p, larger the value of K _B, respectively, the target data of the I picture Compared to the quantity T _j
Target amount of data T _j of the picture and B-picture is reduced. For example, in TM5 of MPEG system, the weighting coefficients K _p, K _B is a fixed value, respectively _{1.0,1.4 (K p = 1.0, K} B = 1.4, default value) is there.

As described above, the MPEG5 TM5 system
In the P picture, the global of the I picture
Le Complex City X_IP-picture glow against
Balcomplex City X_pTarget data amount according to the ratio of
T_jIs given, and the B picture is
Global Complexity X_IB picture for
Global Complexity X_BIntentionally than the ratio of
Small target data amount T _jIs given.

Next, a rate control method in the target data amount calculation circuit 264 will be described. A parameter R plays an important role in the rate control of the TM5 system of MPEG. This parameter R indicates the amount of data that can be assigned to the remaining pictures of the rate control unit (eg, GOP) in the MPEG system.

Here, the video data compression devices 1 and 2 (FIG. 1)
In FIGS. 3, 5 and 6, for example, the picture of the first half of the GOP is complicated (actual difficulty data D _j).
And the global complexity X _I , X _p , X _B, etc. are large), and if a large amount of data is assigned to the first half of the GOP, the parameter R for the second half of the GOP becomes extremely small. Or a negative number, and the amount of data to be allocated to the second half of the GOP may be insufficient.

As described above, in the video data compression apparatuses 1 and 2, the value of the parameter R may be extremely small or may be a negative value.
0 (FIGS. 1 and 5) is GO, which is a control unit of rate control.
In order to keep the data amount of each P constant, the data amount that is excessively allocated to the first half of the GOP is compensated by allocating a small amount of data to the second half of the GOP. Because it is assigned. In the host computer 20,
The parameter R is thus used for the process of compensating the data amount in a relatively short period such as a GOP.

On the other hand, in the target data amount calculation circuit 264 of the encoder 26, the rate control is not performed only with the parameter R for making the data amount constant in such a short control unit. The parameter R _j ′ that evenly allocates the remaining data amount is controlled so that the data amount over a long period is constant within the range.

That is, the target data amount calculation circuit 264 controls the parameter R _j ′ to allocate an excessive amount of data to a picture included in a certain period of the uncompressed video data, The target data amount _Tj is adjusted so as not to compensate during the period in which the quality of the compressed video data is likely to be deteriorated, to compensate in a period during which the quality of the compressed video data is small even if a small amount of data is allocated even if a small amount of data is allocated. Further, the target data amount calculation circuit 264 updates the value of the parameter R _j ′ by performing the same processing as in Expression 3 every time the encoder 26 compression-encodes one picture.

[0098] Considering for VBV buffer, however, when adjusting so many data quantity of the compressed video data parameter R _j '(high data rate), it is difficult to predict the increase in the data amount of the compressed video data , VBV buffer may underflow. Therefore, when rate control is performed to increase the amount of compressed video data, future VB
In consideration of the V buffer occupancy B _n , the target data amount calculation circuit 264 adjusts the parameter R _j ′ only when the VBV buffer occupancy B _n (the remaining data amount of the compressed video data) is large. .

In order to realize the rate control in consideration of the occupation amount _Bn of the VBV buffer described above, the target data amount calculation circuit 264 further performs the processing described below. That is, the target data amount calculation circuit 264 calculates the amount of data to be allocated to a portion where the video of video data is complicated.
It is determined not based on the data rate of the compressed video data output from the encoder 26 but on the data amount until the VBV buffer underflows.

The target data amount calculation circuit 264 calculates the total value (debt) of the data amount to be allocated to a portion where the video of the video data is complicated at a rate higher than a predetermined data rate as a parameter sum-supplement (initial value 0). stored as performs rate control as reducing the value of the parameter sum-supplement in total is smaller values of the real difficulty data D _j of a predetermined number of picture compression encoding uncompressed video data is completed The rate control is performed so that the value of the parameter sum-supplement at the time point becomes a negative value very close to 0. However,
The target data amount calculation circuit 264, when the fullness B _n of the VBV buffer is small, the real difficulty regardless of the value of the data D _j, of each picture of the video data target amount of data T _j
Is controlled so as to reduce the value of, and the occurrence of underflow is prevented.

The processing contents of the target data amount calculation circuit 264
Summary The following, further with reference to FIGS. 14 and Equation, describing the target amount of data T _j by the target data amount calculation circuit 264 in detail. FIG. 14 is a flowchart showing the processing of the target data amount calculation circuit 264 shown in FIG. FIG.
As shown in (5), in step 500 (S500),
The target data amount calculation circuit 264 checks the occupation amount _Bn of the VBV buffer, and determines whether a sufficient amount of compressed video data is buffered in the VBV buffer and there is room to prevent underflow. If there is room, the process proceeds to S502, and if there is no room, S5
Proceed to step 12.

The threshold VBV- _R'j- Margin shown in the following equation 8 is used for determining the occupancy _Bn of the VBV buffer.

[0103]

(Equation 8)

Note that in equation 8, last-I-genbit is
VBV-Margin is the latest I-picture data volume.
It is a constant for the underflow measures when calculating the target amount of data T _j, frame-bit is the data amount per picture. As shown in Expression 8, the threshold value VBV-R ' _j- Marg
Last calculation of in-picture data amount of last-I-genbi
By using t, the occurrence of underflow can be almost completely prevented even when the encoder 26 next generates compressed video data of an I-picture having a large data amount. The target data amount calculation circuit 264 calculates the VBV
By comparing the buffer occupancy _Bn with the threshold value VBV- _R'j- Margin, it is determined whether or not the VBV buffer has room in the process of S500.

Further, the target data amount calculation circuit 264
The determination of the VBV buffer occupancy _Bn in the process 500 need not necessarily be performed each time the encoder 26 compresses and encodes a picture, and may be performed, for example, only immediately after the encoder 26 generates a P picture.

This is for the following reason. That is, the occupancy of the VBV buffer is reduced immediately after the encoder 26 generates the I picture, but the occupancy is usually recovered before the next I picture is generated.
6, the target data amount calculation circuit 264 does not need to make a determination in the process of S500. Conversely, immediately after the encoder 26 generates a B picture with a small data amount, the target data amount Calculation circuit 26
This is because if the S. 4 makes the determination in the processing of S500, it may erroneously determine that the VBV buffer has sufficient margin before the underflow occurs, and may cause the VBV buffer to underflow.

In step 502 (S502), the eye
The target data amount calculation circuit 264 calculates the N data shown in Expression 9-1 below.
Global Complexity of Picture X_I,
X_p, X _BIs greater than or equal to a threshold Th1
to decide. Sum-difficulty value is greater than threshold Th1
If the threshold is greater than the threshold Th1, the process proceeds to S504.
If there is, the process proceeds to S508. Note that the threshold Th1
Is the parameter R_j’To increase the compressed video data
Increase the amount of data in the
R_j’Value to reduce the amount of compressed video data
It is important to decide what to do.

In step 504 (S504), the target data amount calculation circuit 264 determines whether or not the parameter R _j ′ is larger than the threshold value (G + Th2) as shown in the following equation 9-2. When the value of the parameter R _j ′ is equal to the threshold (G +
If it is larger than Th2), the process proceeds to S506,
If it is smaller than the threshold value (G + Th2), the process proceeds to S516 (G = Nx bit-rate / picture-rate).

[0109]

(Equation 9)

In step 506 (S 506), the target data amount calculation circuit 264 calculates, for example, the following equation 10-1
Thus, the data amount (supply data amount) supplement to be added (supplied) to the parameter R _j ′ is calculated. Equation 10
The parameter β (0 <β <1) in -1 is defined as shown in Expression 10-2, and is a parameter for determining the amount of data until the VBV buffer underflows. The value of the parameter β And the greater the margin of the VBV buffer against underflow, the greater the value of the supplementary data amount supplement.

[0111]

(Equation 10)

The threshold value Th3 in the expression 10-1 is a constant for determining the value of the supplementary data amount supplement.
MAX-supplement is a limit value for limiting the supply data amount supplement.

The sum-difficulty value is (Th1 + Th
If the value is larger than 3), the value of the fractional term on the right side of Expression 10-1 becomes larger than 1. Therefore, the value of the supply data amount supplement is corrected as shown in Expression 11 below.

[0114]

[Equation 11]

In step 508 (S508), the target data amount calculation circuit 264 sets the parameter sum-suppleme
It is determined whether or not nt is a positive value, and whether or not the supplementary data amount supplement that has been supplied to the portion where the picture of the video data is complicated is not completely compensated (debt is present). If there is a debt, the process proceeds to S510, and if there is no debt, the process proceeds to S512.

In step 510 (S510), the target data amount calculation circuit 264 sets the value of the parameter β in the expression 10-1 to 1 in order to compensate for the supply data amount supplement supplied to a portion having a complicated picture of the video data. Then, a negative supply data amount supplement shown in the following Expression 12 is calculated.
By adding the negative supply data amount supplement to the parameter R _j ′ (S514), the data amount of the compressed video data is reduced, and the parameter sum-supplement can be made closer to 0 (repayment of debt).

[0117]

(Equation 12)

In step 512 (S512), the target data amount calculation circuit 264 determines that there is a possibility that an underflow may occur in the VBV buffer, and calculates a negative supply data amount supplement by Expression 13 below. By adding the negative supply data amount supplement to the parameter R _j ′ (S514), the data amount of the compressed video data is reduced, and the underflow of the VBV buffer is prevented.

[0119]

(Equation 13)

In step 514 (S514), the target data amount calculation circuit 264 updates the parameter R _j ′ and the sum-supplement by the following equations (14) and (15).

[0121]

[Equation 14]

[0122]

(Equation 15)

[0123] In step 516 (S516), the target data amount calculation circuit 264 calculates the target amount of data T _j as shown in the following equation 16, and outputs the same to the quantization index generation circuit 266.

[0124]

(Equation 16)

However, in equation 16, N _I , N _p , N
_B indicates the number of I pictures, P pictures, and B pictures appearing in one GOP, and when the structure of one GOP is N = 1 and M = 3, N _I = 1 and N _p =
4, a N _B = 10.

[0126] In step 518 (S518), the quantization index generation circuit 266 generates the quantization index QIND based on the target amount of data T _j to the target data amount calculation circuit 264 has generated, with respect to the quantization circuit 168 Output.

In step 520 (S520), the components of the encoder 26 other than the quantization control unit 260
The non-compressed video data is compression-coded based on the quantization index QIND generated by the quantization index generation circuit 266. In step 522 (S522), the target data amount calculation circuit 264 increments the variable j.

Operation of Quantization Index Generation Circuit 266 Hereinafter, the operation (processing) of the quantization index generation circuit 266 will be described with reference to FIG. The quantization index generation circuit 266 is, for example, a MPEG5 TM5
2nd and 3rd stages (Step 2 and Step 3)
Similarly to the above, the target data amount T _j inputted from the target data amount calculation circuit 264 and the global complexity X _I , X _p , X _B inputted from the GC calculation circuit 262.
, And outputs the quantization index QIND to the quantization circuit 168.

[0129] Incidentally, the quantization index in the quantization circuit 168, a data to be used as an index indicating the combination of quantization values Q _j that changes for each macro block as a unit of quantization, the quantized value Q
_It is equivalent to _j . That is, the quantization circuit 16 receiving the quantization index from the quantization index generation circuit 266
Numeral 8 converts the data into a combination of quantization values Q _j indicated by the received quantization index, and quantizes the video data input from the DCT circuit 166.

The operation of encoder 26 (FIG. 13) will be described below. The motion detector 14 performs processing such as generation of a motion vector as in the first embodiment. The encoder control unit 22 performs a picture rearrangement process and the like as in the first embodiment.

When the encoder 26 (FIG. 13)
Every time the compression encoding for the
0 GC calculation circuit 262
From the quantization index of the path 266, the quantization value Q_jThe average of
Calculate the value and quantize Q_jAverage and compressed video data
Data amount S_jFrom Global Complexity
X _I, X_p, X_BIs calculated. Target data amount calculation circuit 2
Reference numeral 64 denotes a target data amount calculation circuit 264 for the compressed video data.
Is the most recently generated as described with reference to FIG.
Target data amount T of each picture type_jCalculate
You.

The quantization index generation circuit 266 calculates a quantization index based on the calculated target data amount T _j and the global complexity X _I , X _p , X _B , and sends it to the quantization circuit 168 of the encoder 26. Set. The DCT circuit 166 includes the first embodiment and the second embodiment.
As in the embodiment, the DCT process is performed on the next picture.

The quantization circuit 168 converts the DCT-processed video data into a set quantization index into a quantization value Q _j and performs a quantization process using the obtained quantization value Q _j . Variable-length coding circuit 170, as well as in the first embodiment and the second embodiment performs-length coding, substantially, to generate compressed video data of the data amount close to the target amount of data T _j, The data is output via the buffer memory 182.

The contents of the processing of the encoder 26 shown as the third embodiment are the same as those of the video data compression devices 1 and 2 (FIGS. 1 to 3 and FIG. 3) shown in the first and second embodiments. 5, FIG. 6). The target data amount calculation circuit 264 of the encoder 26, be configured to calculate the target amount of data T _j by using the real difficulty data D _j, using the global complexity X _I, X _p, X _B The target data amount _Tj may be calculated.

The processing performed by the quantization control unit 260 in the encoder 26 is performed by the video data compression devices 1 and 2.
In FIGS. 1 to 3, 5, and 6, the processing can be performed by the host computer 20. Further, the expressions defining each parameter shown in the third embodiment are examples, and each expression can be changed according to the configuration and use of the encoder 26. Further, the encoder 26 shown in the third embodiment can be modified as shown in the first embodiment and the second embodiment.

FIG. 15 shows that the encoder 26 (FIG. 13) uses the MP @ ML system of MPEG to compress the G of compressed video data.
FIG. 13 is a diagram illustrating an evaluation result of a change over time of the occupancy _Bn of the VBV buffer when the fixed-length encoding is performed while keeping the data amount of the OP substantially constant. In FIG. 15, the vertical axis indicates the amount of compressed video data buffered in the VBV buffer, and the horizontal axis indicates time.

When the fixed length encoding is performed while the GOP data amount of the compressed video data is kept substantially constant by the encoder 26 described above, the occupation amount _Bn of the VBV buffer occupancy _Bn becomes as shown in FIG. Fig. 1
2 compared to the case where the video data compression devices 1 and 2 (FIGS. 1 to 3, FIG. 5, and FIG. 6) shown in FIG.
It can be seen that the VBV buffer is effectively used within the range of the constraints required by the VBV buffer. Further, according to the encoder 26, for each part of the uncompressed video data,
By allocating the data amount according to the picture, the quality of the compressed video data can be improved as a whole.

Fourth Embodiment Hereinafter, a feedforward rate control method will be described as a fourth embodiment of the present invention. The feed-forward rate control method effectively utilizes the buffering capacity of the VBV buffer within the range of the constraints required by the VBV buffer, and allocates a data amount corresponding to a picture to each uncompressed video data portion. An object is to improve the quality of compressed video data as a whole.

FIG. 16 is a diagram showing the configuration of the video data compression device 4 according to the fourth embodiment of the present invention. FIG. 17 is a diagram showing a configuration of the encoder 28 shown in FIG. FIG. 18 illustrates the quantization control unit 280 illustrated in FIG.
FIG. 3 is a diagram showing the configuration of FIG. In FIGS. 16 to 18, the video data compression device 1 shown in FIGS. 1 to 3, 5, 6, and 13 among the components of the video data compression device 4 is shown.
2 and the same components as those of the encoder 26 are denoted by the same reference numerals.

As shown in FIG. 16, the video data compression device 4 includes video data compression devices 2 and 3 (FIGS. 5, 6, and 1).
A configuration in which the encoder 18 of 3) is replaced with an encoder 28 is adopted. Also, as shown in FIG.
Adopts a configuration in which the quantization control circuit 180 is replaced by a quantization control unit 280, and as shown in FIG.
Reference numeral 80 denotes an actual difficulty data (D _j ) calculation circuit 282, a target data amount (T _j ) calculation circuit 284, and a parameter (R _j ′).
Calculation circuit 286 and quantization index generation circuit 28
8.

The quantization control unit 280 controls the encoder 26
As in FIG. 13, the host computer 20
Independent of the index data [statistics; flatness (FIGS. 9 and 10), intra AC (FIG. 11), activity (Equation 7) and ME residual (FIGS. 7 and 10 described in the second embodiment) 8)] and a target data amount T based on the occupation amount B _n of the compressed video data in the VBV buffer.
_j and quantization value Q _j (quantization index QIND)
Can be calculated.

The video data compression device 4 performs feedforward control on the quantization processing of the quantization circuit 168 by using only one encoder based on the data amount of the compressed video data by using these constituent parts. Compressed video data is generated by allocating a data amount corresponding to the picture to improve the quality of the compressed video data.

Operation of Each Component of Video Data Compressor 4 Hereinafter, video data compressors 1, 2, and 3 (FIGS. 1 to 3, FIG. 5, FIG. 6, The operation of the part (quantization control unit 280) different from that of FIG. 13) will be described. Actual Difficulty Data Calculation Circuit 282 Calculation Circuit The actual difficulty data calculation circuit 282 calculates the index data (P picture and B picture as shown in Expressions 5 and 6 by approximation using the ME residual) input from the motion detector 14. The actual difficulty data D _j of the encoder control unit 22 is calculated, and the approximation by the index data (flatness, intra AC and activity) input from the statistic calculation circuit 224 of the encoder control unit 22 is performed. The actual difficulty data D _j of the picture is calculated, and the parameter calculation circuit 2
86 and the parameter calculation circuit 286.

Operation of Target Data Amount Calculation Circuit 284 The target data amount calculation circuit 284
Similarly to the target data amount calculation circuit 264 of 3), the processing shown in Expression 1 is performed in the first embodiment, the actual difficulty data D _j input from the actual difficulty data calculation circuit 282, and the parameter calculation circuit 286. , The target data amount T _j of each picture of each picture type is calculated based on the parameter R _j ′, and rate control is performed.

[0145]Operation of the parameter calculation circuit 286 The parameter calculation circuit 286 calculates the target data of the encoder 26.
Similarly to the data amount calculation circuit 264 (FIG. 13), Equations 8 to 1 are used.
5 and the processing shown in FIG._j’
Adjust and update. However, the parameter calculation circuit 28
6 is the expression 16 in the processing of S516 shown in FIG.
, The target data amount T _jCalculate the amount
Output to the child index generation circuit 288.

Operation of Quantization Index Generation Circuit 288
Similarly to the quantization index generation circuit 266 (FIG. 13), generates a quantization index QIND based on the target amount of data T _j input from the target data amount calculation circuit 284, and outputs the same to the quantization circuit 168 .

Hereinafter, the operation of the video data compression device 4 will be described. Actual difficulty data calculation circuit 28 of quantization control section 280
2, from the index data (ME residual, flatness, intra AC and activity) input from the motion detector 14 and the encoder control unit 22, the actual difficulty data D _j is calculated as shown in Expressions 5 and 6. calculate.

The parameter calculation circuit 286 is obtained by the following equations (8) to (1).
As shown in FIG. 5, the rate control is performed by adjusting the parameter R _j ′ according to the occupancy of the VBV buffer and the complexity of the picture of the video data. Target data amount calculation circuit 284
Is the parameter R adjusted by the parameter calculation circuit 286.
_j ′ is substituted into Equation 1 to calculate a target data amount T _j .

[0149] quantization index generation circuit 288, quantization index QI from the calculated target amount of data T _j
ND is calculated. Quantization control unit 280 of encoder 28
The other parts compress and encode the non-compressed video data using the quantization index QIND calculated by the parameter calculation circuit 286.

The processing contents of the video data compression device 4 shown as the fourth embodiment are the same as those of the first to third embodiments.
Video data compression devices 1 and 2 (FIGS.
3, 5 and 6). In addition, the processing performed by the quantization control unit 280 in the video data compression device 4 is compared with the video data compression devices 1 and 2 (FIGS.
In FIG. 6), the processing can be performed by the host computer 20. In addition, the modifications shown in the first to third embodiments can be applied to the video data compression device 4 shown in the fourth embodiment.

Fifth Embodiment Hereinafter, as a fifth embodiment of the present invention, a modified example of the operation of the encoder 26 shown in the third embodiment will be described. Up to here, the simple two-pass encoding method has been described in the first embodiment, and the FFRC method has been described in the second embodiment.
Further, in the third and fourth embodiments, the feedback rate control method and the feedforward rate control method for adjusting the amount of compressed video data according to the occupancy of the VBV buffer have been described.

In the TM5 of the MPEG system, the parameter R is
In each method shown in the first to fourth embodiments, the target data amount _Tj is calculated using the parameter _Rj '(Equation 1 and the like). By each of these methods, the part of the uncompressed video data where the picture is very difficult (encoding difficulty is high)
When compression encoding is to be performed on compressed video data having a low data rate, no matter how large the quantization value Q _j (quantization index QIND) is increased to increase the compression ratio and reduce the data amount, the data is actually generated. The data amount of the compressed video data exceeds the target data amount T _j , the values of the parameters R, R _j ′ decrease rapidly, and the parameters R, R _{j in} the last picture of the rate control unit (for example, GOP) The value of _j 'may become 0 or less.

For example, in the case of TM5 of MPEG, when the value of the parameter R becomes 0 or less, each picture has the minimum data amount (frame-bit / 8; where frame-bit is a desired picture of the compressed video data). Per data rate). As described above, when a picture to which the minimum amount of data is allocated is compression-encoded into compressed video data having a data rate as low as 1/8 of the desired data rate, the quality of the compressed video data obtained from such a portion becomes remarkable. Will drop.

Further, for example, if the compression encoding process of the non-compressed video data for which the picture of the video is difficult is continued for a long time, the values of the parameters R and R _j 'become very small, and the picture of the video of the non-compressed video data becomes very small. even after becomes easy, for a while, the parameter R, 'did not recover the value of a certain amount to the large positive value, the parameter R, R _j' R _j all the way until the value of is restored, the minimum amount of data Allocated to each GOP, the distortion of the compressed video data increases. On the other hand, the parameter R _j ′ is originally
Is the average value of the amount of data allocated to the L pictures corresponding to the delay time of
L) does not deviate significantly.

[0155] The fifth embodiment of the present invention has been made in view of the problems described above, a complicated pattern of the image of the non-compressed video data (the value of the real difficulty data D _j is large),
Even when the value of the data amount _Sj of the compressed video data actually generated is larger than the target data amount _Tj , the quality of the compressed video data can be kept high and the video is complicated. The object of the present invention is to recover the value of the parameter R _j ′ when the picture is changed from a simple picture to a simple picture, and to calculate the target data amount calculation circuit of the quantization control unit 260 of the encoder 26 shown in the third embodiment. 264 (FIG. 13).

In the fifth embodiment, the encoder 26
Are the VBV buffer occupancy B _n and the global complexity X _I , as in the third embodiment.
X _p, and feedback control of the target amount of data T _j based on the X _B, further, by limiting that the parameter R _j 'is equal to or less than a predetermined lower limit value, similar to the rate control in the third embodiment The effect is obtained, and a remarkable decrease in the quality of the compressed video data is prevented.

[0157]Operation of target data amount calculation circuit 264 Hereinafter, the video data pressure among the components of the encoder 26 will be described.
Compression devices 1 and 2 and an encoder 26 (FIGS.
5, Fig. 6, Fig. 13) Target data amount calculation with different processing contents
The operation (processing content) of the output circuit 264 will be described. Goal Day
The data amount calculation circuit 264 is the same as in the third embodiment.
Is the global controller input from the GC calculation circuit 262.
Plexity X_I, X_p, X_BFruit of each picture type
Difficulty data D_jAnd further occupy the VBV buffer.
Weight B _nOf the picture type based on the
Each target data amount T_jIs calculated and rate control is performed.
U.

[0158] Rate control method target data amount calculation circuit 264, as well as in the third embodiment, 'to adjust the parameter R _j' parameter R _j in consideration of the occupancy of the VBV buffer, the global complexity X _I, X _p, by multiplying the multiplier calculated from X _B or the like to adjust the target amount of data T _j. However, the third
Unlike the fifth embodiment, in the fifth embodiment, the target data amount calculation circuit 264 uses the parameter R _j ′
To set the lower limit R _min respect, the parameter R _j 'calculated in the same way as in the third embodiment, the lower limit value R _min
When [R _j ′ <R _min ], [R _j ′ = R
_min ] so that the parameter R _j ′ is limited so as not to be lower than the lower limit value R _min . As the lower limit value R _min , for example, [R _min = frame-bit × L × 3/4] or [R
_min = frame-bit × L × １ ／].

As shown in equation 3 in the first embodiment,
And the data amount of the j-th picture is S_jAnd the
The data amount of the (j + L) th picture is S_{j + L}And
Parameter R according to the culture type_j’
Data amount is F_{j + L}Then the next parameter R
_{j + 1}’Is (R_j'-S_j+ F_{j + L}) [R_{j + 1}’=
R_j'-S_j+ F_{j + L}]. However, the next
Parameter R_{j + 1}’(= R _j'-S_j+ F_{j + L}) Is also below
Limit value R_minThe following [R_{j + 1}’<R_min]
You. In this case, the next parameter R_{j + 1}’Is given by
As shown in FIG._minRestrict to

[0160]

[Equation 17]

As in the third embodiment, the target data amount calculation circuit 264 calculates the total value (debt amount) of the data amount to be allocated to a complicated portion of the video data.
Is stored as a parameter sum-supplement. Therefore,
If the value of the parameter R _j ′ is not limited to the lower limit value R _min as described above, the parameter su
When the m-supplement is updated and the value of the parameter R _j ′ is limited to the lower limit value R _min , the supplementary data amount supplement is cumulatively added and the parameter sum-su
Update pplement.

[0162]

(Equation 18)

The processing contents of the target data amount calculation circuit 264
Conclusion Hereinafter, the rate control processing by the target data amount calculation circuit 264 in the fifth embodiment will be described in detail with reference to FIG. FIG. 19 is a flowchart illustrating the processing of the target data amount calculation circuit 264 according to the fifth embodiment. As shown in FIG. 19, the target data amount calculation circuit 264 performs the same processing as the processing shown in FIG. 14 in the third embodiment.

In step 600 (S600), the target data amount calculation circuit 264 proceeds to S602 or S612 according to the occupation amount _Bn of the VBV buffer. Note that the target data amount calculation circuit 264 may determine the occupancy _Bn of the VBV buffer in the process of S600 only immediately after the encoder 26 generates a P picture.

[0165] In step 602 (S602), the target data amount calculation circuit 264 determines whether N pieces of the real difficulty data D _j sum value of the sum-DIFFICULTY Do larger than the threshold Th1 whether the picture by Formula 9-1 Then, the process proceeds to S604 or S608 according to the determination result. Step 6
04 (S604), the target data amount calculation circuit 26
4 is that the parameter R _j ′ is equal to the threshold (G + T
h2) to determine whether the number is larger than
It proceeds to the processing of 606 or S616.

In step 606 (S606), the target data amount calculation circuit 264 calculates, for example, the formulas 10-1 and 1
The supplementary data amount supplement is calculated from 0-2 and Expression 11. In step 608 (S608), the target data amount calculation circuit 264 determines whether or not the supply data amount supplement has been compensated, and according to the determination result, S61.
0 or the process proceeds to S612. Step 610 (S6
In 10), the target data amount calculation circuit 264 calculates a negative value of the supplementary data amount supplement by Expression 12 in order to compensate the supplementary data amount supplementation.

In step 612 (S612), the target data amount calculation circuit 264 calculates the negative value of the supplementary data amount supplement by the equation (13) to prevent the VBV buffer from underflowing. In step 614 (S614), the target data amount calculation circuit 264 calculates
Parameter R _j by ', calculates the sum-supplement, the parameter R _j' if falls below the lower limit value R _min limits the parameter R _j 'to the lower limit value R _min.

[0168] In step 616 (S616), the target data amount calculation circuit 264 calculates the target amount of data T _j as shown in Equation 16. Step 618 (S61
In 8), the encoder 26 performs a compression encoding process using the quantization index QIND. Step 62
0 (S620), the target data amount calculation circuit 264
Calculates and updates the next parameter R _{j + 1} ′ according to Equation 3.

In step 622 (S622), the target data amount calculation circuit 264 calculates the next parameter R _{j + 1} '.
Is larger than the lower limit value _Rmin . If the next parameter R _{j + 1} ′ is larger than the lower limit value R _min , S6
The process proceeds to the process of S28, and if not large, proceeds to the process of S624. In step 624 (S624), the target data amount calculation circuit 264 limits the next parameter R _{j + 1} ′ to the lower limit value R _min .

In step 626 (S626), the target data amount calculation circuit 264 calculates the parameter
Update sum-supplement. Step 628 (S62
In 8), the target data amount calculation circuit 264 calculates the variable j
Is incremented.

Hereinafter, the operation of the encoder 26 (FIG. 13) in the fifth embodiment will be described. The motion detector 14
Processing such as generation of a motion vector is performed in the same manner as in the first embodiment and the third embodiment. The encoder control unit 22 performs a picture rearrangement process and the like as in the first embodiment and the like. FIFO memory 160
Delays the input video data by L pictures, as in the first embodiment.

The encoder 26 (FIG. 13) has one picture
Every time the compression encoding for the
0 GC calculation circuit 262
From the quantization index of the path 266, the quantization value Q_jThe average of
Calculate the value and quantize Q_jAverage and compressed video data
Data amount S_jFrom Global Complexity
X _I, X_p, X_BIs calculated. Target data amount calculation circuit 2
Reference numeral 64 denotes a target data amount calculation circuit 264 for the compressed video data.
Is the glow for each of the most recently generated picture types.
Balcomplex City X_I, X_p, X_BBased on the figure
As explained with reference to 19, the target of the next picture
Data amount T_jIs calculated.

The quantization index generation circuit 266 calculates a quantization index based on the calculated target data amount T _j and the global complexity X _I , X _p , X _B , and sends it to the quantization circuit 168 of the encoder 26. Set. The DCT circuit 166 performs DCT processing on the next picture, as in the first embodiment.

The quantization circuit 168 converts the DCT-processed video data into a set quantization index into a quantization value Q _j , and performs a quantization process using the obtained quantization value Q _j . Variable-length coding circuit 170, as well as in such the first embodiment, performs-length coding, substantially, to generate compressed video data of the data amount close to the target amount of data T _j, via the buffer memory 182 Output.

Modification Example A modification example of the fifth embodiment will be described below. The improved feedback rate control method shown in the fifth embodiment is different from the video data compression devices 1, 2, 4 (FIGS. 1 to 3) shown in the first, second, and fourth embodiments. , FIG. 5, FIG. 6, FIG. 16 to FIG. 18). In the fifth embodiment, the target data amount calculation circuit 264, has been described for calculating the target amount of data T _j in view of the VBV buffer, the target data amount T _j without considering the VBV buffer The operation of the target data amount calculation circuit 264 may be changed so as to generate

Referring to FIG. 20, a modified example in which the operation of video data compression apparatus 1 (FIGS. 1 to 3) is changed and the improved feedback rate control shown in the fifth embodiment is applied will be described. . FIG. 20 shows a video data compression device 1 (FIG. 1).
FIG. 11 is a flowchart illustrating processing when the operations of FIGS. 3 to 3 are changed and the improved feedback rate control shown in the fifth embodiment is performed. As shown in FIG. 20, the host computer 20 of the video data compression apparatus 1 does not perform the rate control in consideration of the VBV buffer, and therefore does not perform the processing corresponding to S600 to S614 shown in FIG.
Only processes corresponding to 6 to 628 are performed.

In step 700 (S700), the host computer 20 of the video data compression device 1
To calculate the target data amount _Tj . Step 702
In (S702), the encoder 18 performs a compression encoding process using the quantization index QIND. In step 704 (S704), the host computer 20 calculates and updates the next parameter R _{j + 1} ′ according to Expression 3.

In step 706 (S706), the host computer 20 determines whether or not the next parameter R _{j + 1} ′ is larger than the lower limit R _min, and proceeds to the processing of S712 or S608 according to the determination result. Step 70
8 (S708), the host computer 20
The next parameter R _{j + 1} ′ is limited to a lower limit R _min .

In step 710 (S710), the host computer 20 calculates the parameter sum-
Update supplement. In step 712 (S712), the host computer 20 increments the variable j. Note that in the video data compression device 4 (FIGS. 16 to 18), the feedforward rate control shown in the fourth embodiment is improved, and is equivalent to the improved feedforward rate control shown in the fifth embodiment. In order to obtain the effect, the operation of the parameter calculation circuit 286 of the video data compression device 4 may be changed and each processing shown in FIG. 14 may be executed. However, in this case, in the process of S616, it is necessary to calculate the target data amount _Tj by Expression 1 instead of Expression 16.

Also, in the processing shown in FIG. 20, by replacing the parameter R _j ′ with the parameter R in the MPEG TM5, the improved feedback rate control method can be applied to the MPEG TM5 itself. . However, the parameter R in the TM5 of the MPEG takes a large value for the picture at the beginning of the GOP, but is almost zero for the end of the GOP. As a parameter R having such a property, a fixed lower limit R _min [eg, R _min
= −2 × frame-bit] can be set,
The effect is thin.

Therefore, when the improved feedback rate control method is applied to the MPEG TM5 itself, FIG.
As shown in FIG. 1, by introducing a function that determines the lower limit value _Rmin , the same effect as in the fifth embodiment can be obtained.

That is, in TM5 of MPEG, G
The parameter R for the picture of the first part of the OP is
So that it is bigger for the last picture
Since the value of the parameter R approaches 0, the point in FIG.
As illustrated by the line, the lower limit R at the beginning of the GOP_minThe value of the
Becomes (N / 2 × frame-bit), and the lower limit R
_minDraw a straight line such that the value of (-N / 2 × frame-bit)
When the parameter R falls below this straight line, the fifth actual
Same as the improved feedback rate control method shown in the embodiment.
Thus, the parameter R is set to the lower limit R on the straight line._minLimited to
The difference value may be stored as another parameter.

The processing performed by the quantization control unit 260 of the encoder 26 in the fifth embodiment can be performed by the host computer 20. Further, the expressions defining each parameter shown in the fifth embodiment are examples, and each expression can be changed according to the configuration and use of the encoder 26.

As described above, according to the improved feedback rate control method shown in the fifth embodiment, the picture pattern of the input video data is difficult with respect to the data rate after compression, and the data amount becomes large. Even in the case where it is too long, the rate control can be performed while maintaining the distribution of the data amount according to the picture type, and the quality of the compressed video data can be improved. Also, because the lower limit is set, even if the picture of the video of difficult input video data becomes simple,
The parameters R and R _j ′ can be recovered so that a large amount of data is allocated to the compressed video data within a short time, and the occurrence of unevenness in the quality of the compressed video data can be prevented.

Sixth Embodiment Hereinafter, as a sixth embodiment of the present invention, a modified example (improved feedforward rate control method) of the operation of the video data compression device 4 (FIG. 16) shown in the fourth embodiment will be described. explain. The improved feedforward rate control method is different from the feedforward rate control method shown in the fourth embodiment in that the value of the data amount _Sj of the compressed video data actually generated is larger than the target data amount _Tj . Even if there is, the quality of the compressed video data can be kept high, and the value of the parameter R _j ′ when the video changes from a complicated picture to a simple picture is improved so as to be quickly recovered. .

[0186] In the sixth embodiment, the video data compression apparatus 4, fullness B _n and the index data of the VBV buffer feeds the target data amount T _j based on the (ME residual, flatness, intra AC and activity) By performing forward control and further restricting the parameter R _j ′ from being equal to or less than a predetermined lower limit, the same effect as the rate control in the fourth embodiment can be obtained.
Prevents a significant decrease in the quality of compressed video data.

Operation of Each Component The following describes the target data amount calculation circuit 284 of the quantization control unit 280 (FIG. 17), which is different from the video data compression device 4 in processing among the components of the video data compression device 4. The operation (processing content) of the parameter calculation circuit 286 (FIG. 18) will be described. Operation of the Target Data Amount Calculation Circuit 284 The target data amount calculation circuit 284 uses the actual difficulty data D _j (D
_I , D _p , D _B ) and the parameter calculation circuit 286
The target data amount T _j of each picture type is calculated based on the occupation amount B _n of the V buffer and the parameter R _j ′ calculated from the actual difficulty data D _j .

Operation Rate Control Method of Parameter Calculation Circuit 286 As in the fourth embodiment, the parameter calculation circuit 286 controls the rate control by adjusting the value of the parameter R _j ′ in consideration of the occupancy of the VBV buffer. I do.
However, the parameter calculation circuit 286 calculates the parameter R _j ′
Is set to the lower limit _Rmin , and when the parameter R _j ′ becomes equal to or less than the lower limit R _min [R _j ′ <R _min ], [R _j
j ′ = R _min ], and the parameter R _j ′ is the lower limit value R _min
Restrict the following. As the lower limit value R _min , for example, a value such as [R _min = frame-bit × L × 3/4] or [R _min = frame-bit × L × 1/4] is used.

As shown in Equation 3, the j-th picture
Data volume is S_jAnd the j + L-th picture
Is S_{j + L}And depending on the picture type
Parameter R_j’Is F_{j + L}Is
In the case, the next parameter R _{j + 1}’Is [R_{j + 1}’
= R_j'-S_j+ F_{j + L}]. However, the following
Parameter R_{j + 1}’(= R_j'-S_j+ F_{j + L}) Also
Lower limit R_minThe following [R _{j + 1}’<R_min]
is there. In this case, the next parameter R_{j + 1}’In equation 1
As shown in FIG._minRestrict to

Further, the parameter calculation circuit 286 stores the debt amount as a parameter sum-supplement. Therefore, the value of the parameter R _j ′ is changed to the lower limit value R _min as described above.
If not limited to, the updates the parameter sum-supplement as shown in Equation 15, the parameters in the case where the value of R _j 'is limited to the lower limit value R _min is replenished data as shown in Equation 18 Add the quantity supplementment and add the parameter su
Update m-supplement.

[0191]The processing contents of the parameter calculation circuit 286 remain unchanged.
Stop Hereinafter, referring to FIG. 19 again, the sixth embodiment will be described.
Rate control processing by the parameter calculation circuit 286 and
The details of the processing of the related part will be described in detail. Step 60
0 (S600), the parameter calculation circuit 286
Is the occupancy B of the VBV buffer._nAccording to S602 or
Proceeds to the process of S612. Note that the parameter calculation circuit 2
Reference numeral 86 denotes the occupation of the VBV buffer in the processing of S600.
Quantity B _nEncoder 28 generates a P-picture
It may be performed only immediately after doing.

[0192] In step 602 (S602), the parameter calculation circuit 286, the value of the sum sum-DIFFICULTY the real difficulty data D _j of the N pieces of picture is determined whether the threshold is greater than Th1 by Equation 9-1, The process proceeds to S604 or S608 according to the determination result. Step 60
4 (S604), the parameter calculation circuit 286
Is that the parameter R _j ′ is equal to the threshold (G + Th
It is determined whether there is more than 2), and S6 is performed according to the determination result.
It proceeds to the processing of 06 or S616.

In step 606 (S606), the parameter calculation circuit 286 calculates, for example,
−2 and Expression 11 are used to calculate the supplementary data amount supplement. In step 608 (S608), the parameter calculation circuit 286 determines whether or not the supplementary data amount supplement has been compensated, and proceeds to S610 or S612 according to the determination result. Step 610 (S61
In 0), the parameter calculation circuit 286 calculates a negative value of the supplementary data amount supplement by Expression 12 in order to compensate the supplementary data amount supplementation.

At step 612 (S612), the parameter calculation circuit 286 calculates the negative value of the supplementary data amount supplement according to the equation (13) to prevent the VBV buffer from underflowing. In step 614 (S614), the parameter calculation circuit 286 calculates the parameters R _j ′ and the sum-supplement according to Expressions 14 and 15, and if the parameter R _j ′ is equal to or less than the lower limit R _min , the parameter R _j 'To the lower limit R _min .

In step 616 (S616), the target data amount calculation circuit 284 is different from the target data amount calculation circuit 264 of the encoder 26 shown in the fifth embodiment in that the target data amount calculation circuit The data amount _Tj is calculated. In step 618 (S618), the encoder 28 performs a compression encoding process using the quantization index QIND. In step 620 (S620), the parameter calculation circuit 286 calculates the next parameter R _{j + 1} ′ according to Equation 3 and updates it.

In step 622 (S622), the parameter calculation circuit 286 determines whether or not the next parameter R _{j + 1} ′ is larger than the lower limit R _min . If the next parameter R _{j + 1} ′ is larger than the lower limit value R _min , S62
The process proceeds to the process of S8, and if not large, proceeds to the process of S624. In step 624 (S624), the parameter calculation circuit 286 limits the next parameter R _{j + 1} ′ to the lower limit R _min .

In step 626 (S626), the parameter calculation circuit 286 calculates the parameter su
Update m-supplement. Step 628 (S628)
In, the parameter calculation circuit 286 increments the variable j.

The operation of the video data compression device 4 (FIG. 16) in the sixth embodiment will be described below. Motion detector 1
4 performs processing such as generation of a motion vector and an ME residual. The encoder control unit 22 performs processing such as picture rearrangement processing and generation of index data (flatness, intra AC and activity). The FIFO memory 160 delays the input video data by L pictures.

Each time the encoder 28 (FIG. 16) completes the compression encoding of one picture, the quantization controller 28
The actual difficulty data calculation circuit 282 of the actual difficulty data D _j
Is calculated. The parameter calculation circuit 286 calculates the parameter R _j ′ as shown in FIG. 19, and the target data amount calculation circuit 284 calculates the actual difficulty data D _j (D _I ,
D _p , D _B ) and the target data amount T _j by equation (1).
Is calculated.

[0200] quantization index generation circuit 288, based on the calculated target amount of data T _j, and calculates the quantization index, set to the quantization circuit 168 of the encoder 28. The DCT circuit 166 performs DCT processing on the next picture, as in the first embodiment.

The quantization circuit 168 converts the DCT-processed video data into a set quantization index into a quantization value Q _j and performs a quantization process using the obtained quantization value Q _j . Variable-length coding circuit 170, as well as in such the first embodiment, performs-length coding, substantially, to generate compressed video data of the data amount close to the target amount of data T _j, via the buffer memory 182 Output.

Modification Referring to FIG. 20 again, video data compression apparatus 1
A modified example in which the operation of FIGS. 1 to 3 is changed and the improved feedforward rate control shown in the sixth embodiment is applied will be described. Since the host computer 20 of the video data compression apparatus 1 does not perform the rate control in consideration of the VBV buffer, it does not perform the processing corresponding to S600 to S614 shown in FIG. 19, but performs only the processing corresponding to S616 to 628.

In step 700 (S700), the host computer 20 of the video data compression device 1
To calculate the target data amount _Tj . Step 702
In (S702), the encoder 18 performs a compression encoding process using the quantization index QIND. In step 704 (S704), the host computer 20 calculates and updates the next parameter R _{j + 1} ′ according to Expression 3.

At step 706 (S706), the host computer 20 determines whether or not the next parameter R _{j + 1} ′ is larger than the lower limit R _min, and proceeds to the processing of S712 or S608 according to the determination result. Step 70
8 (S708), the host computer 20
The next parameter R _{j + 1} ′ is limited to a lower limit R _min .

In step 710 (S710), the host computer 20 calculates the parameter sum-
Update supplement. In step 712 (S712), the host computer 20 increments the variable j.

In the processing shown in FIG. 20, by replacing the parameter R _j ′ with the parameter R in the MPEG TM5, the improved feedforward rate control method can be applied to the MPEG TM5 itself. is there. However, the parameter R in the TM5 of the MPEG takes a large value for the picture at the beginning of the GOP, but is almost zero for the end of the GOP. As a parameter R having such a property, a fixed lower limit value R _min [eg, R
_min = −2 × frame-bit] can be set, but the effect is small.

Therefore, when applying the improved feedforward rate control method to the TM5 of MPEG,
As shown in FIG. 21, the same effect as that of the sixth embodiment can be obtained by introducing a function that determines the lower limit value _Rmin .

That is, in TM5 of MPEG, G
Since the value of the parameter R approaches 0 for the picture at the end so that the parameter R becomes large for the picture at the beginning of the OP, as shown in FIG. If the value of R _min is (N / 2 × fram
e-bit), and the value of the lower limit R _min at the end of the GOP is (-N /
2 x frame-bit) and draw a straight line
Is smaller than this straight line, the parameter R is limited to the lower limit value R _min on the straight line, and the difference value is stored as another parameter, similarly to the improved feedforward rate control method shown in the sixth embodiment. I just need. Also, the expressions defining each parameter shown in the sixth embodiment are examples,
Each equation can be changed according to the configuration and use of the video data compression device 4.

As described above, according to the improved feedforward rate control system shown in the sixth embodiment,
Even when the picture pattern of the input video data is difficult with respect to the data rate after compression and the data volume is too large, it is possible to control the rate while maintaining the distribution of the data volume according to the picture type. Data quality can be improved. In addition, since the lower limit is set, even when the picture of the video of the difficult input video data is simplified, the parameters R and R _j ′ are set so that a large amount of data is allocated to the compressed video data in a short time. Thus, the quality of the compressed video data can be prevented from being uneven.

[0210]

As described above, according to the video data compression apparatus and method according to the present invention, audio / video data is compression-coded to a predetermined data amount or less without using two-pass encoding. Can be. Further, according to the video data compression apparatus and method thereof according to the present invention, video data can be compression-encoded substantially in real time, and high-quality video can be obtained after decompression decoding. Further, according to the video data compression apparatus and the method thereof according to the present invention, the compression rate can be adjusted by estimating the data amount after compression and encoding, and the compression and encoding processing can be performed without using two-pass encoding. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a video data compression device according to the present invention.

FIG. 2 is a diagram illustrating a configuration of an encoder of a simple two-pass processing unit illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a configuration of an encoder illustrated in FIG. 1;

FIGS. 4A to 4C are diagrams illustrating an operation of a simple two-pass encoding of the video data compression device according to the first embodiment.

FIG. 5 is a diagram showing an outline of a configuration of a video data compression device according to the present invention in a second embodiment.

6 is a diagram showing a detailed configuration of a compression encoding unit of the video data compression device 2 shown in FIG.

[7] The video data compression apparatus (Fig. 1-3, 5, 6) is a diagram showing the correlation between the ME residual and the real difficulty data D _j when generating a P picture.

[8] video data compression apparatus (Fig. 1-3, 5, 6) is a diagram showing the correlation between the ME residual and the real difficulty data D _j when generating a B picture.

FIG. 9 is a diagram illustrating a method of calculating flatness.

[10] The video data compression apparatus (FIGS. 1 to 3, 5, 6) by a diagram showing the correlation between the flatness and the real difficulty data D _j when generating an I picture.

FIG. 11 is a diagram illustrating an intra AC used when an I picture is generated by a video data compression apparatus (FIGS. 1, 3, 5, and 6).
And is a graph showing the correlation between the real difficulty data D _j.

FIG. 12 shows a video data compression apparatus (FIG. 1, FIG. 3, FIG. 5, and FIG. 6) that performs fixed length encoding while maintaining the GOP generation bit amount of compressed video data almost constant by MPEG MP @ ML system. FIG. 10 is a diagram showing an evaluation result of a change over time in the occupancy amount _Bn of the VBV buffer when the above operation is performed.

FIG. 13 is a diagram showing a configuration of the encoder shown in FIG.

FIG. 14 is a flowchart illustrating a process of a target data amount calculation circuit illustrated in FIG. 13;

FIG. 15 shows the occupancy _Bn of the VBV buffer when the encoder (FIG. 13) performs fixed-length encoding while maintaining the GOP data amount of the compressed video data substantially constant by the MPEG @ ML method of MPEG. It is a figure showing the evaluation result of a change with time.

FIG. 16 is a diagram showing a configuration of a video data compression device according to the present invention in a fourth embodiment.

FIG. 17 is a diagram illustrating a configuration of the encoder illustrated in FIG. 16;

FIG. 18 is a diagram illustrating a configuration of a quantization control unit illustrated in FIG. 17;

FIG. 19 is a flowchart illustrating a process of a target data amount calculation circuit according to the fifth embodiment.

FIG. 20 is a flowchart showing a process when the operation of the video data compression device (FIGS. 1 to 3) is changed and the improved feedback rate control shown in the fifth embodiment is performed.

FIG. 21 is a diagram illustrating a function that determines a lower limit value R _min used when the improved feedback rate control method described in the fifth embodiment is applied to the TM5 of MPEG.

[Explanation of symbols]

1, 2, 4 video data compression device, 10, 24 compression encoding unit, 12, 22 encoder control unit, 14 motion detector, 16 simple 2-pass processing unit, 160 FIFO memory, 162, 18 , 26, 28 ... encoder, 260,
280: quantization control unit, 262: GC calculation circuit, 282
… Actual difficulty data calculation circuit, 284, 264… target data amount calculation circuit, 286… parameter calculation circuit, 266, 2
88 quantization index generation circuit, 164 addition circuit, 166 DCT circuit, 168 quantization circuit, 170
... Variable length coding circuit, 172 ... Inverse quantization circuit, 174 ...
Inverse DCT circuit, 176 addition circuit, 178 motion compensation circuit, 180 quantization control circuit, 182 buffer memory, 20 host computer.

Claims (18)

[Claims] 1. A VBV for buffering uncompressed video data of a moving image and compressed video data (compressed video data)
What is claimed is: 1. A video data compression device for compressing data to a data rate that satisfies a condition determined based on a buffer, a difficulty data calculation unit that calculates difficulty data indicating complexity of video of the uncompressed video data, and buffering in the VBV buffer. Data for allocating a compressed data amount (allocated data amount) to a predetermined number of uncompressed video data pictures based on the data amount (occupied data amount) of the compressed video data and the calculated difficulty data Amount allocation means; target value calculation means for calculating a target value of the data amount of the uncompressed video data after compression based on the calculated difficulty data and the allocated data amount; and the non-compressed video data. Compression means for compressing the data by a predetermined compression method so that the data amount after compression becomes the calculated target value. Video data compression device. 2. The video data compression device according to claim 1, wherein said difficulty data calculation means calculates a data amount of said uncompressed video data after compression as said difficulty data. 3. The data amount allocating means, when the occupied data amount of the VBV buffer is equal to or more than a predetermined threshold, if the video of the uncompressed video data is complex based on the calculated difficulty data. The target value calculating means increases the value of the target value as the video of the uncompressed video data becomes more complex, and the video of the uncompressed video data becomes larger. 2. The video data compression apparatus according to claim 1, wherein the simpler the value, the smaller the target value. 4. The data amount allocating means subtracts a reference value obtained by equally allocating all data amounts given to the compressed video data to all pictures from a data amount of a picture of the generated compressed video data. To calculate the difference value,
4. The video data compression device according to claim 3, wherein when the compression of the uncompressed video data is completed, the allocated data amount is calculated such that the total sum of the calculated difference values is close to a negative value of 0. 5. 5. The target amount calculating means calculates the target value by multiplying a value obtained by dividing a total of difficulty data of a predetermined number of pictures by difficulty data of the latest picture by the calculated allocation data amount. The video data compression device according to claim 3. 6. The compression means for compressing the uncompressed video data into a picture type sequence including a plurality of types of pictures (I picture, P picture, B picture or a combination thereof) in a predetermined order. 4. The video data compression device according to 3. 7. The difficulty data calculating means includes: as the difficulty data, an ME residual of a picture compressed into a P picture or a B picture, a flatness of a picture compressed into an I picture, intra AC data, and an activity. The video data compression apparatus according to claim 6, wherein the video data compression apparatus calculates the global complexity or a combination thereof. 8. The data amount allocating means according to claim 1, wherein said predetermined threshold value of the occupied data amount of said VBV buffer is a latest I-value.
7. The video data compression device according to claim 6, wherein a numerical value obtained by adding an added value according to a data rate of the generated compressed video data or a fixed added value to a picture data amount is used. 9. The data amount allocating means determines whether or not the occupied data amount of the VBV buffer is equal to or greater than a predetermined threshold value, immediately after the compression means compresses the uncompressed video data into a P picture. The video data compression device according to claim 8, wherein 10. VB for buffering uncompressed video data of a moving image, and compressed video data (compressed video data)
A video data compression method for compressing to a data rate that satisfies a condition determined based on a V-buffer, wherein the amount of data until the VBV buffer underflows and the complexity of a picture of a picture of the uncompressed video data are reduced. And assigning a data amount after compression (allocated data amount) to a predetermined number of the pictures of the uncompressed video data based on the complexity of the video of the picture of the uncompressed video data and the calculated allocated data amount. Calculating, for each picture, a target value of the data amount of the uncompressed video data after compression so that the data amount after compression of the non-compressed video data becomes the calculated target value by a predetermined compression method. Video data compression method to compress. 11. The video data compression method according to claim 10, wherein a data amount after compression of said non-compressed video data is used as data indicating a video complexity of a picture of said non-compressed video data. 12. When the occupied data amount of the VBV buffer is equal to or larger than a predetermined threshold, based on the calculated difficulty data, the more complicated the image of the uncompressed image data, the more the allocated data amount becomes. The value is increased, and the more complex the image of the uncompressed video data, the greater the value of the target value, and the simpler the image of the uncompressed video data, the smaller the value of the target value. The video data compression method according to claim 10. 13. A difference value is calculated by subtracting a reference value obtained by equally distributing all data amounts given to the compressed video data to all pictures from the data amount of the generated compressed video data pictures, 13. The video data compression method according to claim 12, wherein when the compression of the non-compressed video data is completed, the allocated data amount is calculated such that the total sum of the calculated difference values is close to a negative value of zero. 14. The video according to claim 12, wherein said uncompressed video data is compressed into a picture type sequence including a plurality of types of pictures (I picture, P picture, B picture or a combination thereof) in a predetermined order. Data compression method. 15. The video according to claim 13, wherein the target value is calculated by multiplying a value obtained by dividing the sum of difficulty data of a predetermined number of pictures by the difficulty data of the latest picture and the calculated allocated data amount. Data compression method. 16. The ME residual of a picture compressed into a P picture or a B picture as the difficulty data,
14. The video data compression method according to claim 13, wherein flatness, intra AC data, activity, global complexity, or a combination thereof, of a picture compressed into an I picture is calculated. 17. An addition value or a fixed addition value according to the data rate of the generated compressed video data, as the predetermined threshold value of the occupied data amount of the VBV buffer, as the predetermined threshold value. 14. The video data compression method according to claim 13, wherein the added numerical value is used. 18. The video data compression method according to claim 17, wherein the determination as to whether or not the occupied data amount of the VBV buffer is equal to or larger than a predetermined threshold is made immediately after the uncompressed video data is compressed into a P picture. .