JPH10191342A - Device and method for compressing video data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently use the recording capacity of a recording medium and also to compress and encode video data so that the quality of video may be highly maintained. SOLUTION: An encoder 20 performs odd number compression and encoding by using a fixed quantization value Q that is set by a controlling computer 14, and outputs data quantity of compressed video data. The computer 14 calculates target data quantity TB that is used for the next compression and encoding based on the data quantity. The encoder 20 undergoes even number compression and encoding by using the quantity TB that is calculated by the computer 14, and calculates the value Q that is used for the next compression and encoding. The quantity TB is optimized by repeating the odd number and even number compression and encoding, and final compression and encoding is performed by using the optimized quantity TB.

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 and method for compressing and encoding video data according to the MPEG system or the like and generating compressed video data suitable for a transmission rate of a transmission path.

[0002]

2. Description of the Related Art Recently, video data is subjected to motion compensation processing (MC), discrete cosine transform (DCT) processing, quantization processing, variable-length coding processing, and the like. MPEG to compress and encode data
An MC-DCT method such as a method is used.

In such a compression encoding process, if the compression rate is reduced and the data amount of the compressed video data is increased, the quality of the video is generally improved, the compression rate is increased, and the data amount of the compressed video data is reduced. In general, the quality of an image is reduced. Therefore, in order to keep the image quality high, it is desirable to lower the compression ratio. On the other hand, when the compressed video data is recorded on a recording medium such as an MO disk or transmitted via a communication line, the data amount (data rate) of the compressed video data needs to be suppressed to a certain value or less.

Therefore, in order to generate compressed video data suitable for a recording medium or a communication line while maintaining high video quality, a quantization value (quantization index) used for a quantization process is appropriately adjusted. It is important that the data amount (data rate) of the compressed video data be equal to or less than the recording capacity of the recording medium or the transmission rate of the communication line.

SUMMARY OF THE INVENTION The present invention has been made from the above-mentioned viewpoints, and compresses and encodes video data, effectively uses the recording capacity of a recording medium or the transmission capacity of a communication line, and maintains video quality at a high level. It is an object of the present invention to provide a video data compression device and a video data compression method capable of generating compressed video data of a possible data amount (data amount). Also, the present invention, by appropriately controlling the quantization value,
It is an object of the present invention to provide a video data compression apparatus and a video data compression method capable of effectively utilizing the recording capacity of a recording medium or the transmission capacity of a communication line and maintaining high video quality.

[0006]

In order to achieve the above object, a video data compression apparatus according to the present invention comprises at least:
A quantizing means for quantizing the video data subjected to the predetermined processing by a quantization value set from the outside, a data quantity counting means for counting a data quantity of the compressed video data, and a k-th compression In the processing, the quantization value is generated so that the data amount of the compressed video data becomes the same as the value indicated by the target data amount set from the outside, and the first quantization is set to the quantization means. A video data compression means for compressing the input video data, the video data compression means comprising a value generation means; Generating the target data amount in the compression processing of the target data amount generation means to be set in the quantization value generation means, based on the quantization value generated in the k-th compression processing,
A second quantization value generation unit configured to generate a fixed quantization value in the (k + 1) -th compression process and to set the fixed quantization value in the quantization unit.

Preferably, the video data compression means compresses the input video data into a plurality of types of pictures, and the quantization means converts each of the video data pictures into a compressed picture type. The data amount counting unit counts the data amount of each of the plurality of types of pictures, and the first quantization value generation unit determines that the data amount of each of the plurality of types of pictures is A quantized value corresponding to each type of the compressed picture is generated so that the value of the target data amount of each type of the compressed picture becomes the same as the value indicated by the target data amount. Based on the data amount of each of the plurality of types of pictures, the k-th picture
A target data amount of each of the plurality of types of pictures in the first compression process is generated, and the second quantization value generation unit generates a plurality of types of pictures based on the generated quantization values of the plurality of types of pictures. A fixed quantization value is generated for each type of picture.

The video data compression apparatus according to the present invention performs, for example, motion compensation processing, DCT processing, quantization processing, and variable-length coding processing on input video data, and performs recording capacity of a recording medium or communication. Compressed video data having a data amount (data rate) equal to or less than the transmission capacity of the line and substantially equal to the data amount (data rate) is generated.

In the video data compression apparatus according to the present invention, the video data compression means generates compressed video data by compressing and encoding input video data according to, for example, the MPEG system. In the video data compression means, the quantization means uses, for example, a quantization value set for each type (picture type) of a picture (I picture, P picture and B picture) after compression from the outside, and , And quantizes the DCT coefficients generated by the motion compensation processing and the DCT processing to generate quantized data. That is, the quantization means quantizes the DCT coefficient which becomes an I-picture after compression with the quantization value for the I-picture, quantizes the DCT coefficient which becomes a P-picture after compression with the quantization value for the P-picture, and B2 after the compression. A DCT coefficient to be a picture is quantized by a quantization value for a B picture.

The data amount coefficient means counts the data amount of each picture type of the compressed video data obtained by further performing variable length coding processing on the generated quantized data for each predetermined unit period. The data amounts of the I picture, B picture, and P picture generated for each unit period are obtained.

In a certain (k-th) compression process, the first quantization value generating means calculates the data amount of the compressed video data in each unit period based on the data amount of each picture type in the previous compression process. The target data amount generation unit generates a quantization value for each picture type that is equal to or less than the target data amount of each unit period generated for each picture type and is substantially equal to the target data amount, and sequentially to the quantization unit, Set.

[0012] The target data amount generating means is provided in the previous (k-1)
In the (second) compression process, the data amount counting means counts and calculates a target data amount for each unit period of each picture type in a certain (k-th) compression process based on the data amount of each picture type. , In the quantization value generation means. The second quantization value generation means includes, for example,
By also calculating the average value of the quantization values of each picture type used in a certain (k-th) compression encoding, the fixed-value quantization value used in the next (k + 1) -th compression encoding is calculated. Calculate and set to quantization means.

That is, the video data generating means includes, for example,
In the odd (k-1) th compression encoding, compression encoding is performed using the fixed quantization value set by the second quantization value generation means, and the data amount of each picture type is reduced for each unit period. In the next (k-th, even-numbered) compression encoding, the target data amount generation means performs the following for each unit period of the data amount of each picture type based on the counted value of the data amount of each picture type. Is calculated (target data amount).

[0014] For example, the second quantized value generating means, for example, in each of the even (k) -th compression encodings, generates a quantized value of each picture type generated by the first quantized value generating means of the video data generating means. Calculate the average value of the
In the first (odd number) compression encoding, the quantization value is set as a quantization value of each picture type used in the video data generation means. Thus, the quantization value and the target data amount are optimized for each compression encoding,
Video data compressed and encoded by the final compression encoding using the target data amount predicted by the sufficiently optimized fixed value quantization value is finally output.

[0015] In the video data compression method according to the present invention, the video data which has been subjected to the predetermined processing is converted into at least
The data is quantized and compressed by an externally set quantization value, the data amount of the compressed video data is counted, and in the k-th compression process, the data amount of the compressed video data is set from the outside. The quantization value is generated so as to be the same as the value indicated by the target data amount, and based on the data amount of the compressed video data counted in the (k-1) th compression processing, the k-th quantization process is performed. The target data amount in the compression processing is generated, and a fixed quantization value in the (k + 1) th compression processing is generated based on the quantization value generated in the kth compression processing.

Preferably, the input video data is compressed into a plurality of types of pictures, each picture of the video data is quantized by a quantization value of each type of the compressed picture, and the plurality of types of pictures are compressed. The data amount of each picture is counted, and each of the plurality of types of pictures is compressed so that the data amount of each of the plurality of types of pictures becomes the same as the value indicated by the target data amount of each of the types of compressed pictures. And generating a target data amount of each of the plurality of types of pictures in the k-th compression process based on the counted data amounts of the plurality of types of pictures. Based on the quantization value of each of the plurality of types of pictures, a fixed quantum To generate a value.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, a first embodiment of the present invention will be described.

The video data compression apparatus 1 Figure 1 is a diagram showing the configuration of a video data compression apparatus 1 according to the present invention. As shown in FIG. 1, a video data compression device 1 according to the present invention includes a digital video tape recorder (V
TR) or the like, a recording device 12, a control computer 14, and an encoder 20.

The video data compression apparatus 1 performs so-called two-pass encoding using these components. That is,
In the first compression encoding process (first pass), the video data compression device 1 compresses and encodes non-compressed video data using a fixed quantization value Q, and performs a predetermined unit period (for example, GOP) Of the compressed video data (generated code amount GB; GB).

Further, the video data compression device 1 includes:
In the second compression encoding process (second pass), a target data amount TB for each unit period is calculated based on the generated code amount GB for each unit period obtained in the first pass, and the generated code amount for each unit period is calculated. The non-compressed video data is compression-encoded again so that the amount GB becomes substantially equal to the target data amount TB, thereby generating final compressed video data.

Control Computer 14 The control computer 14 controls the operation of each component of the video data compression device 1. Further, the control computer 14 calculates the total sum of the generated code amounts GB during the second pass compression encoding based on the generated code amount GB of the compressed video data for each unit period during the first pass compression encoding. For example, a target data amount that is less than or equal to the recording capacity of a recording medium (VTR tape) used in the recording device 12 and is substantially the same as this recording capacity, and that can maintain the quality of the compressed video data VOUT as a whole high. TB is calculated for each unit period and set in the encoder 20.

The reproducing apparatus 10 reproduces the non-compressed video data VIN at the time of compression encoding in the first pass and the second pass, and outputs it for the compression encoding by the encoder 20. Recording device 12 The recording device 12 records the compressed video data VOUT obtained by the second pass compression encoding.

Encoder 20 FIG. 2 is a diagram showing the configuration and processing contents of the encoder 20 (FIG. 1) in the first embodiment. FIG. 2A shows the first time of the encoder 20 in the first embodiment (FIG. 1). 1
(B) shows the processing contents of the second pass (second pass) of the encoder 20 in the first embodiment.

As shown in FIGS. 2A and 2B, the encoder 20 shown in FIG.
0, a scan conversion blocker 202, a motion detector 204,
Subtraction circuit 206, DCT section 208, quantization section 210, variable length coding section (VLC) 212, inverse quantization section 214, inverse DCT (IDCT) section 216, addition circuit 218, motion compensation section 222, buffer (buffer) 224 and a code amount control unit 24.

The encoder 20 operates in accordance with the control of the control computer 14 by these components in the same manner as a general MPEG encoder.
By performing a CT process and a variable-length encoding process, a picture of input video data is converted into a GOP (group) composed of a combination of an I picture, a P picture, and a B picture.
of picture).

As shown in FIGS. 2A and 2B,
The operation in the first pass and the operation in the second pass of the encoder 20 are different, and in the first compression encoding, the operation shown in FIG.
As shown in FIG. 1A, the control computer 1 applies uncompressed video data VIN input from the playback device 10.
The compression encoding is performed using the fixed quantization value Q set from step No. 4, the generated code amount GB per unit period of the compressed video data obtained as a result of the compression encoding processing is counted, and the control computer 14 The operation to output to is performed.

Further, in the second compression encoding, as shown in FIG. 2B, the encoder 20 sets the generated code amount GB per unit period from the control computer 14 for each unit period. The video data is compression-encoded to be substantially the same as the target data amount TB,
2 is output.

The picture rearranging section 200 is a component of the encoder 20.
Is the uncompressed video data VI input from the playback device 10 according to the picture type after the compression and encoding under the control of the picture type control unit 250.
The N pictures are rearranged in an order suitable for compression encoding and output to the scan conversion blocking unit 202.

The scan conversion blocking unit 202 performs field / frame conversion on the video data input from the picture rearranging unit 200, further converts the video data into macroblocks, and outputs the macroblocks to the motion detection unit 204 and the subtraction circuit 206. The motion detection unit 204 includes a scan conversion blocking unit 202.
Then, the video data input from is processed in units of macroblocks to detect the motion, a motion vector indicating the motion of the video is generated, and output to the motion detection unit 204.

The subtraction circuit 206 outputs, to the DCT unit 208, the video data of a picture that becomes an I-picture after compression encoding among the pictures included in the video data input from the scan conversion blocking unit 202. Further, the subtraction circuit 206 includes the scan conversion blocking unit 2.
02, the output video data of the motion compensator 222 is subtracted from the video data of a picture that becomes a P picture or a B picture after compression encoding among the pictures included in the video data input from
Output to T section 208.

The DCT unit 208 performs DCT processing on video data that becomes an I-picture after compression encoding and prediction error data of a P-picture or a B-picture after compression encoding that are input from the subtraction circuit 206. The DCT coefficient obtained as a result of the DCT processing is output to quantization section 210.

The quantizing section 210 uses a fixed quantization value Q set by the control computer 14 at the time of compression encoding in the first pass, and the code amount control section 24 at the time of compression encoding in the second pass. The DCT coefficient input from the DCT unit 208 is quantized by the quantization value Q set for each period, and the variable length encoding unit 212 is quantized as quantized data.
And output to the inverse quantization unit 214.

The variable length coding unit 212 includes a quantization unit 210
The variable-length encoding is performed on the quantized data input from for example by a run-length encoding method to generate compressed video data, and the compressed video data is output to the buffer 224. Inverse quantization unit 21
4 is a quantization unit 21 for the input quantized data.
The DCT coefficient is reproduced by performing processing opposite to 0, and is output to the inverse DCT section 216.

The inverse DCT section 216 performs the reverse process of the DCT section 208 on the input DCT coefficients to reproduce video data, and outputs the video data to the addition circuit 218. The addition circuit 218 adds up the video data input from the inverse DCT unit 216 and the video data input from the motion compensation unit 222 to reproduce the video data, and outputs the video data to the motion compensation unit 222.

The buffer 224 counts the generated code amount GB of the compressed video data input from the variable length coding unit 212 for each unit period and outputs it to the control computer 14 during the first pass compression coding. During the second pass compression encoding, the compressed video data VOUT input from the variable length encoding unit 212 is buffered and stored in the recording device 12.
And the generated code amount GB is sequentially counted for each unit period and output to the code amount control unit 24.

The motion compensating unit 222 performs a motion compensating process on the video data input from the adding circuit 218 using the motion vector input from the motion detecting unit 204.
Output to subtraction circuit 206 and DCT section 208.

Code amount control unit 24 The code amount control unit 24 sequentially receives the target data amount TB set for each unit period from the control computer 14 and the buffer 224 at the time of compression encoding in the second pass. Based on the generated code amount GB, the quantization value Q is adjusted so that the generated code amount GB of the compressed video data for each unit period becomes equal to the target data amount TB.
Set to 0.

The operation of the video data compression device 1 according to the first embodiment will be described below.

According to the control of the computer 14 for the first pass , the reproducing apparatus 10
Reproduces the uncompressed video data VIN from a VTR tape or the like, and outputs it to the encoder 20. Encoder 20
2 performs the first-pass compression encoding process shown in FIG. 2A under the control of the control computer 14.

That is, the quantization unit 210 of the encoder 20
, The fixed quantization value Q
Is set, and the quantization unit 210 includes the picture rearrangement unit 200 to the DCT unit 208 and the inverse quantization unit 214 to
The DCT coefficient generated by the motion compensation unit 222 is quantized by a fixed quantization value Q, and the quantized data is output to the variable length coding unit 212.

The variable length coding unit 212 includes a quantization unit 210
, Performs variable-length encoding on the quantized data input from, and outputs the compressed video data to the buffer 224. The buffer 224 counts the generated code amount GB of the compressed video data input from the variable length coding unit 212, and outputs it to the control computer 14 for each unit period.

The control computer 14 includes the encoder 2
0 based on the generated code amount GB per unit period inputted from the buffer 224 of 0.
Calculate B.

According to the control of the second-pass compression / coding control computer 14, the playback device 10
Reproduces the same uncompressed video data VIN from the VTR tape or the like as in the first pass compression encoding, and outputs the same to the encoder 20. Each component of the encoder 20 performs the second-pass compression encoding process shown in FIG. 2B under the control of the control computer 14.

That is, the code amount control unit 2 of the encoder 20
In 4, the target data TB calculated as described above is set for each unit period by the control computer 14,
The code amount control unit 24 sequentially generates, based on the set target data amount TB, a quantization value Q that makes the generated code amount GB of the compressed video data for each unit period substantially equal to the target data amount TB, This is set in the quantization unit 210.

The quantization section 210 includes a picture rearrangement section 200 to a DCT section 208 and an inverse quantization section 214 to
The DCT coefficients generated by the motion compensation unit 222 are sequentially converted from the code amount control unit 24 for each unit period by the quantized value Q
, And the quantized data is encoded by the variable-length encoding unit 212.
Output to

The variable length coding unit 212 includes a quantization unit 210
The variable-length coding is performed on the quantized data input from, and compressed video data VOUT is generated and output to the recording device 12 via the buffer 224. The recording device 12 converts the compressed video data input via the buffer 224 into a VTR
Record on a recording medium such as a tape.

FIG. 3 is a table exemplifying the generated code amount GB of the compressed video data obtained by the first pass compression encoding by the video data compression apparatus 1 shown in FIG.
FIG. 4 is a chart illustrating the generated code amount GB of the compressed video data obtained by the second pass compression encoding by the video data compression device 1 shown in FIG. Note that FIGS. 3 and 4 illustrate a case where the unit period is a time required for compression-coding 15 pictures.

When the unit period is the time for compressing and encoding 15 pictures, and the data rate of the compressed video data VOUT is 6 Mbps, the data amount allocated per unit period is 3 Mbits. Here, FIG.
By the first pass compression encoding shown in (A), the total sum of the generated code amounts GB of the compressed video data in a certain unit period becomes as shown in FIG.
In the case of 1744380 bits, the control computer 14 sets the generated code amount GB of the compressed video data VOUT in the corresponding unit period in the second-pass compression encoding shown in FIG. 3,000 for the first pass
Target data amount T so as to be 000/1744380 times
B may be calculated and set in the code amount control unit 24. In this way, the generated code amount GB of the compressed video data VOUT obtained by the second pass compression encoding is, for example, as shown in FIG.
It is as shown in.

As described above, according to the two-pass encoding by the video data compression device 1, it is possible to effectively use the recording capacity of the recording medium and to compress and encode the video data while keeping the video quality high. it can. In particular, since the two-pass encoding process requires at least two times for reproducing the non-compressed video data, real-time performance (real-time performance) is required when transmitting the compressed video data via a communication line. Although it is not necessarily suitable for applications that require it, it is suitable for applications that do not require real-time properties (real-time properties), such as when generating compressed video data to be recorded on a recording medium.

Second Embodiment Hereinafter, a second embodiment of the present invention will be described.

Background of the Second Embodiment First, the background of the second embodiment will be described. FIG. 2 (A),
According to the two-pass encoding shown in (B), as illustrated in FIGS. 3 and 4, in the second-pass compression encoding, the recording capacity of the recording medium is more increased in the first-pass compression encoding. Can also be used effectively.

However, the quantization value Q used in the first-pass compression encoding is determined by the complexity of the picture data VIN,
Alternatively, the difference between the fixed quantized value Q and the quantized value Q used in the second pass compression encoding is large regardless of the speed (difficulty) of the motion, and the first pass compression is large. In some cases, the target data amount TB can be calculated only approximately from the generated code amount GB obtained by encoding. Therefore, the target data amount TB used in the second pass is not always an optimum value, and depending on the contents of the picture data VIN, the recording capacity of the recording medium and the actual compressed video data V
The error between OUT and the generated code amount GB becomes very large.

The second embodiment of the present invention has been made from such a viewpoint, and changes the operation of the encoder 20 (FIGS. 1 and 2) of the video data compression device 1 (FIG. 1).
The target data amount TB used in the even-numbered compression encoding is calculated by performing the odd-numbered compression-encoding using the fixed quantized value Q by performing the compression-encoding more times, and calculating the calculated target data. The optimum value of the target data amount TB is calculated by repeating the process of performing the even-numbered compression encoding using the amount TB and calculating the fixed quantization value Q used in the odd-numbered compression encoding. By performing final compression encoding using the optimized target data amount TB, the recording capacity of the recording medium is more effectively used, and the quality of the video is further improved.

Components of the Video Data Compressor 1 The video data compressor 1 will be described with reference to FIGS.
Among the constituent parts of the first embodiment, those that perform operations different from those in the first embodiment will be described.

FIG. 5 is a diagram showing the operation of the encoder 20 (FIG. 1) in the second embodiment. FIG. 5 (A) shows an odd number of times of the encoder 20 [2i-1 passes (1 ≦ i ≦ m; 2 ≤
m)] shows the operation in the compression encoding of the first time, and FIG. 8B shows the operation of the encoder 20 in the compression encoding of the even number of times (2i pass). FIG. 6 shows that the control computer 14
It is a flowchart figure which shows the process which calculates the average value of the quantization value Q calculated | required in the even-numbered compression encoding.

Unless otherwise specified, the operation of the components of the video data compression device 1 (FIG. 1) is the same as in the first embodiment, and is shown in FIGS. 5 (A) and 5 (B). The functions and operations of the components of the encoder 20 are shown in FIG.
Are the same as the components of the encoder 20 indicated by the same reference numerals.

In the first compression encoding, the control computer 14 controls the initial value of the fixed quantization value Q in the quantization unit 210 of the encoder 20 in the same manner as in the first embodiment. In the subsequent odd-numbered (3, 5,...) Compression encoding, for example, as shown in FIG. The fixed quantization value Q is optimized by obtaining the average value of the used quantization values Q and set to the encoder 20.

The control computer 14 calculates the code amount GB of the compressed video data for each unit period generated in the immediately preceding odd (1, 3, 5,...) Compression encoding, as shown in FIG. ), The target code amount TB for each unit period used for the even-numbered compression encoding is optimized by calculation, and the code amount control unit 24 of the encoder 20 is optimized.
Set to.

Referring to FIG. 6, control computer 14
Will further describe the process of calculating the quantization value Q. As shown in FIG. 6, in step 100 (S100), the control computer 14 initializes the variables i and sum used for calculating the average value of the quantization values Q (values are set to 0). In step 102 (S102), the control computer 14 determines whether or not the variable i is equal to a numerical value m (the number of even-numbered compression encoding processes in the second embodiment).
If they are equal, the process proceeds to S108, where the variable i is a numerical value m
If it is less than the value, the process proceeds to S104.

In step 104 (S104), the control computer 14 accumulates the quantized value Q input from the code amount control unit 24 (sum ← sum + Q).
In step 106 (S106), the control computer 14 increments the variable i (i ← i + 1). In step 108 (S108), the control computer 14 calculates the average value Qave of the quantized values Q by dividing the cumulative sum of the quantized values Q by the numerical value m (Qave).
← sum / m).

[0061] Encoder 20 The encoder 20, as described above, even more times,
The video data VIN is compression-encoded. That is, as shown in FIG. 5A, the encoder 20 performs odd-numbered compression encoding using the fixed quantization value Q set from the control computer 14, and obtains the result of the compression encoding. The generated code amount GB of the compressed video data is output to the control computer 14.

As shown in FIG. 5B, the encoder 20 performs even-numbered compression encoding using the target data amount TB set for each unit period by the control computer 14, and performs even-numbered compression encoding. The value of the quantization value Q used in the compression encoding is output to the control computer 14. In addition, the encoder 20 transmits the compressed video data VOUT generated using the target data amount TB optimized by the control computer 14 to the recording device 12 via the buffer 224 in the final even-numbered compression encoding. Output.

[0063] component code amount control unit 24, the code amount control unit 24 of the encoder 20, as shown in FIG. 5 (B), as well as in the first embodiment, the even-numbered compression coding, control A quantization value Q is generated based on a target data amount TB set from the computer 14,
By setting to 0, the generated code amount GB of the compressed video data is controlled. In addition, the code amount control unit 24 is configured as shown in FIG.
As shown in (B), the quantization value Q generated in the even-numbered compression encoding is output to the control computer 14.

As shown in FIG. 5A, the buffer 224 outputs the generated code amount GB per unit period of the compressed video data generated in the odd-numbered compression encoding to the control computer 14. I do. Further, the buffer 224 is provided as shown in FIG.
As shown in the figure, the compressed video data VO generated using the target data amount TB optimized by the control computer 14 in the final even (2m) -th compression encoding.
The UT is output to the recording device 12.

Operation of Video Data Compression Device 1 The operation of the video data compression device 1 according to the second embodiment will be described below with further reference to FIG. FIG.
It is a flowchart figure which shows operation | movement of the video data compression apparatus 1 in embodiment.

As shown in FIG. 7, step 200 (S2
In (00), the control computer 14 initializes a variable i (i ← 1). In step 201 (S201), the control computer 14 sets the initial value of the fixed quantization value Q in the quantization unit 210 of the encoder 20, and controls the playback device 10 to play back the uncompressed video data VIN. .

In step 202 (S202), the encoder 20 converts the video data VIN input from the playback device 10 into the code amount control unit 2 by the control computer 14.
Compression encoding is performed using the fixed quantization value Q set to 4 [(2i-1) pass encoding]. Control computer 14
Captures the generated code amount GB per unit period of the compressed video data output from the buffer 224 of the encoder 20.

In step 204 (S204), the control computer 14 sets the target data amount T per unit period based on the generated code amount GB fetched in the process of S202, for example, as in the first embodiment.
B is calculated and set in the code amount control unit 24 of the encoder 20.

In step 206 (S206), the control computer 14 controls the reproducing apparatus 10 to reproduce the same video data VIN. The encoder 20 compression-encodes the video data VIN so that the generated code amount GB after the compression encoding becomes equal to the value indicated by the target data amount TB set in the code amount control unit 24 [2i-pass code] ). In the last compression encoding, the control computer 14 controls the recording device 12 to record the compressed video data VOUT generated by the encoder 20.

In step 208 (S208), the control computer 14 sets a value obtained by doubling the variable i and a numerical value m
And if i × 2 = m, the processing is terminated and i × 2 = m
If <m, the process proceeds to S210. Step 210
In (S210), the control computer 14 increments the variable i (i ← i + 1).

In step 212 (S212), the control computer 14 takes in the quantized value Q generated by the code amount control unit 24 at the time of compression encoding in S206. In step 214 (S214), the control computer 14 performs, for example, the processing shown in FIG.
The fixed quantization value Q in the next compression encoding is calculated by calculating the average of the quantization values Q generated by the code amount control unit 24 at the time of the compression encoding in 206, and is set in the code amount control unit 24. .

Modification 1 Hereinafter, a first modification of the second embodiment will be described with reference to FIG. FIG. 8 is a flowchart illustrating a process according to a first modification of the second embodiment of the present invention.

The MPEG system compresses and encodes video data into a combination of an I picture, a P picture, and a B picture. If quantization is performed using different quantization values Q according to the properties of these pictures, the quality of the compressed video data can be further improved and the recording capacity of the recording medium can be more effectively used. . From the above viewpoint, the first modification example calculates the quantization value Q shown in S214 of FIGS. 6 and 7 so as to calculate the quantization value Q of each of the I picture, the P picture, and the B picture. The processing is improved.

As shown in FIG. 8, step 300 (S3
00), the control computer 14 sets each of the variables (i, N _i , N _p , N _b , sum _i , sum _p , sum
_b ) is cleared to zero. In step 302 (S302), the control computer 14 compares the variable i with the numerical value m, and if i = m, proceeds to the process of S320, where i <
In the case of m, the process proceeds to S304.

In step 304 (S 304), the control computer 14 sets the quantized value Q fetched from the code amount control unit 24 of the encoder 20 to the I picture, P
Which of the picture type and the B picture is used to generate the picture type is detected.
If it is used for generating a picture, S3
Proceeding to step 06, if the quantized value Q is used for generating a P picture, proceed to step S310, and if the quantized value Q is used for generating an I picture , The process proceeds to S314.

In step 306 (S306), the control computer 14 cumulatively adds the quantization value Q used for the B picture among the quantization values Q fetched from the code amount control unit 24 (sum _b ← sum _b + Q).
In step 308 (S308), the control computer 14 increments the variable N _b.

In step 310 (S310), the control computer 14 cumulatively adds the quantized value Q used for the P picture among the quantized values Q fetched from the code amount control unit 24 (sum _p ← sum _p + Q).
In step 312 (S308), the control computer 14 increments the variable N _p.

In step 314 (S310), the control computer 14 cumulatively adds the quantized value Q used for the I picture among the quantized values Q fetched from the code amount control unit 24 (sum _i ← sum _i + Q).
In step 316 (S308), the control computer 14 increments the variable N _i. In step 318 (S318), the control computer 14
Increments the variable i.

[0079] In Step 320 (S320) odor control computer 14 divides the accumulated sum of the quantization value Q which is used for B-picture calculated in the processing in S306 the variable N _b, the processing of S310 Is divided by the variable N _p , and the cumulative addition value of the quantization value Q used for the I picture calculated in the process of S314 is calculated by dividing the cumulative addition value of the quantization value Q used for the P picture calculated in divided by the variable N _i, calculated B-picture, the average value Qave _b quantized value Q used to generate the respective P picture and I picture, Qave _p, the Qave _i.

The average value Q of the quantized values Q used for generating each picture type calculated in the process of S320
ave _b , Qave _p , Qave _i are the encoder 20
Is set in the code amount control unit 24, and the code amount control unit 24
DCT coefficients of pictures that become B pictures, P pictures, and I pictures after compression encoding are respectively quantized by average values Qave _b , Qave _p , and Qave _i to generate quantized data. Output to long encoding section 212.

Modification 2 Hereinafter, a second modification of the second embodiment will be described with reference to FIG. FIG. 9 shows a second modification of the second embodiment,
FIG. 2 is a diagram illustrating a configuration of a video data compression device 2. Note that among the components of the video data compression device 2 shown in FIG. 9, the same components as those of the video data compression device 1 shown in FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 9, the video data compression device 2
The playback device 10, recording device 12 is constituted by a control computer 14 and the 2m encoder 20 ₁ to 20 _2m, the encoder 20 _2i-1 of the odd-numbered is compression-encoded in S202 shown in FIG. 7 The process [(2i-1) pass encoding] is performed, and the even-numbered encoder _202i performs the compression encoding process [2i pass encoding] in S202 shown in FIG.

The control computer 14 generates a target data amount TB to be set in the odd-numbered encoder _202i based on the generated code amount GB of the compressed video data generated by the odd-numbered encoder _202i-1. Become The encoder _202m uses the optimized target data amount TB,
Finally, the video data VIN is compression-encoded to generate compressed video data VOUT and output it to the recording device 12.

Each component of the video data compression apparatus 1 and the encoder 20 is configured by software as long as equivalent functions and performance can be realized.
Regardless of whether it is constituted by hardware, it can be replaced with another means having the same function and performance. Also, the compression encoding methods shown as the second embodiment and the two modifications thereof can be used in combination as long as they do not conflict with each other.

As described above, according to the second embodiment of the present invention, the odd-numbered compression encoding is performed using the fixed quantization value Q, and the target data used in the even-numbered compression encoding is used. The amount TB is calculated, the even-numbered compression encoding is performed using the calculated target data amount TB, and the process of calculating the fixed quantization value Q used in the odd-numbered compression encoding is repeated. Data amount T
B can be optimized. Therefore, by performing the final compression encoding using the optimized target data amount TB, the recording capacity of the recording medium can be more effectively used, and the quality of the video can be further improved.

[0086]

As described above, according to the video data compression apparatus and method according to the present invention, video data is compression-encoded, and the recording capacity of a recording medium or the transmission capacity of a communication line is effectively used. Thus, it is possible to generate compressed video data of a data amount (data amount) capable of maintaining high video quality. Further, according to the video data compression apparatus and method according to the present invention, by appropriately controlling the quantization value, the recording capacity of the recording medium or the transmission capacity of the communication line can be effectively used, and the quality of the video can be reduced. Can be kept high.

[Brief description of the drawings]

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

FIGS. 2A and 2B are diagrams showing a configuration and processing contents of an encoder (FIG. 1) in the first embodiment, wherein FIG. 2A shows processing contents of a first (first pass) processing of the encoder in the first embodiment; (B) shows the processing content of the second (second pass) of the encoder in the first embodiment.

3 is a table illustrating a generated code amount GB of compressed video data obtained by a first-pass compression encoding performed by the video data compression device illustrated in FIG. 2A.

FIG. 4 is a table illustrating an example of a generated code amount GB of compressed video data obtained by a second-pass compression encoding performed by the video data compression device illustrated in FIG.

FIG. 5 is a diagram showing the operation of the encoder (FIG. 1) in the second embodiment, where (A) is an odd number of [2i−1 passes (1 ≦ i ≦ m; 2 ≦ m)] shows the operation in the compression encoding, and (B) shows the operation in the even-number (2i pass) compression encoding of the encoder.

FIG. 6 is a flowchart illustrating a process in which the control computer calculates an average value of the quantized values Q obtained in the even-numbered compression encoding.

FIG. 7 is a flowchart illustrating an operation of the video data compression device according to the second embodiment.

FIG. 8 is a flowchart illustrating a process according to a first modification of the second embodiment of the present invention.

FIG. 9 is a diagram illustrating a second modification of the second embodiment.

[Explanation of symbols]

1, 2, ... video data compression device, 10 ... reproduction device, 12 ...
Recording device, 14 ... control computer, 20, 20 ₁ ~
20 _2m ... Encoder, 200 ... Picture rearranging part,
202: scan conversion blocker, 204: motion detector,
206: subtraction circuit, 208: DCT unit, 210: quantization unit, 212: variable length coding unit, 214: inverse quantization unit, 2
16 ... Inverse DCT sections 216, 218 ... Adder, 222 ... Motion compensation section, 224 ... Buffer, 24 ... Code amount control section.

Claims (5)

[Claims] At least a quantizing means for quantizing video data which has been subjected to predetermined processing by a quantization value set from the outside, a data amount counting means for counting a data amount of compressed video data, And in the k-th compression processing, the quantization unit generates the quantization value so that the data amount of the compressed video data is equal to a value indicated by a target data amount set from the outside. A video data compression means for compressing input video data, comprising: first quantization value generation means for setting; and a data amount of compressed video data counted in the (k-1) th compression processing The target data amount in the k-th compression processing is generated based on the target data amount generation means to be set in the quantization value generation means, and the quantization value generated in the k-th compression processing is Zui, the first (k + 1) -th fixed generates quantized values in the compression process, the image data compression device having a second quantization value generating means for setting the quantization means. 2. The video data compression means compresses input video data into a plurality of types of pictures, and the quantization means converts each of the pictures of the video data into a quantized picture of each of the compressed picture types. The data amount counting means counts the data amount of each of the plurality of types of pictures, and the first quantization value generation means calculates the data amount of each of the plurality of types of pictures after compression. Generating a quantized value corresponding to each of the compressed picture types so that the target data amount of each of the picture types is the same as the value indicated by the target data amount. Generating a target data amount for each of the plurality of types of pictures in the k-th compression process based on a data amount of each of the types of pictures 2. The method according to claim 1, wherein the second quantization value generation unit generates fixed quantization values for each of the plurality of types of pictures based on the generated quantization values for each of the plurality of types of pictures. Video data compression device. 3. The video data that has been subjected to a predetermined process is quantized by at least a quantization value set from the outside and subjected to compression processing, and the data amount of the video data after compression is counted. In the compression processing, the quantization value is generated so that the data amount of the compressed video data becomes the same as the value indicated by the target data amount set from the outside. In the (k-1) th compression processing, The target data amount in the k-th compression processing is generated based on the counted data amount of the compressed video data, and the (k + 1) -th (k + 1) -th data is generated based on the quantization value generated in the k-th compression processing. A video data compression method for generating a fixed quantization value in the second compression process. 4. Compressing input video data into a plurality of types of pictures, quantizing each of the pictures of the video data by a quantization value of each of the types of compressed pictures, Corresponding to each of the types of compressed pictures so that the data amount of each of the plurality of types of pictures is the same as the value indicated by the target data amount of each of the types of compressed pictures. And generating a target data amount of each of the plurality of types of pictures in the k-th compression process based on the counted data amount of each of the plurality of types of pictures. The fixed quantization value for each of multiple types of pictures is calculated based on the quantization value for each of the Video data compression method of claim 3 formed. 5. The video data that has been subjected to a predetermined process is quantized by at least a quantization value set from the outside and subjected to a compression process, and the data amount of the video data after compression is counted. In the compression processing, the quantization value is generated so that the data amount of the compressed video data becomes the same as the value indicated by the target data amount set from the outside. In the (k-1) th compression processing, The target data amount in the k-th compression processing is generated based on the counted data amount of the compressed video data, and the (k + 1) -th (k + 1) -th data is generated based on the quantization value generated in the k-th compression processing. A recording medium on which a program for generating a fixed quantization value in the second compression processing is recorded.