JPH08149413A - Variable bit rate encoder, recorder and recording medium - Google Patents

Abstract

PURPOSE: To reproduce an images of high quality by controlling a quantization parameter so as to reduce the difference between the code quantity of the data acquired by quantizing and encoding the video signals of a prescribed period and the allocated code quantity that is calculated based on the encoding hardness. CONSTITUTION: A detector 101 detects the encoding difficulty of video signals for a prescribed period, and a code quantity allocator 102 outputs the allocated code quantity X based on the encoding difficulty detected by the detector 101. Then a code quantity controller 103 decides a quantization parameter DP based on the code quantity X. A delay unit 105 delays the video signals by a degree equal to the calculation processing time of both detector 101 and allocator 102. These delayed signals are quantized by a secondary quantizer 106 based on the parameter DP and then encoded by a secondary encoder 107. The controller 103 controls the DP for a prescribed period of the relevant data so that the difference is reduced between the code quantity Y measured by a code quantity measuring instrument 104 and the code quantity X. Then a recorded signal processor 110 processes the signals and these signals are recorded on an optical disk 112 by a recording head 111. Thus the images of high quality can be reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable bit used when a video signal is compression-encoded and recorded on a recording medium such as an optical disk or a magnetic disk, or when it is transmitted using a variable bit rate transmission system. The present invention relates to a rate video encoding device, a video recording device that records encoded data in a recording medium, or a recording medium that records a video signal.

[0002]

2. Description of the Related Art Generally, as a video signal coding method, a transform coding method in which an image is divided into blocks composed of a plurality of adjacent pixels and orthogonal transform such as discrete cosine transform is performed for each block is generally used. Has become. In this method, the transform coefficient is quantized with a predetermined quantization width, and compression coding is performed using variable length coding such as Huffman coding.

Further, in the coding of a moving image such as a television signal, interframe coding is performed by utilizing the spectacular sense between each frame. In the inter-frame coding, the target frame is predicted by using a frame positioned before or after the frame to be coded temporally as a reference frame, and the prediction error signal is coded and transmitted or recorded. Inter-frame prediction is performed for each block including a plurality of pixels, and the motion amount of each block is transmitted or recorded together with a prediction error signal.

Since these use a variable length code, the amount of generated bits cannot be recognized until after the encoding process. Therefore, in order to keep the generated bit amount within the predetermined allocated bit amount, the generated bit amount is compared with the allocated bit amount, and feedforward control is performed to update the allocated bit amount of the next video signal according to the comparison result. How to do it is generally known.

Further, the generated code amount of variable-length coded data, such as a method of controlling the generated code amount by estimating the quantization width closest to the target target code amount by performing encoding processing with a plurality of quantization widths. Has been proposed for various code amount control methods for efficiently approaching the target code amount (Japanese Patent Laid-Open No. 4-91).
587, JP-A-5-227520, and JP-A-6-1973.
29).

[0006] These control the code amount on the encoding device side so that the data occupying amount of the input buffer memory on the reproducing device side does not break down when the transmission rate of the encoding for communication, broadcasting, etc. is constant. There was a need.

On the other hand, since the difficulty of compression coding differs depending on the temporal information amount and spatial information amount of the video signal, if the video signal is encoded with a predetermined fixed bit amount, the image quality cannot be kept constant. Variable bit rate coding has been proposed to solve the problem that the image quality deteriorates remarkably in difficult images. This is a method used when transmitting using a variable-rate bit-rate transmission system, or for optical discs, magnetic discs, and other devices that support encoding at a variable bit rate. As this variable bit rate coding method, a method of fixing the quantization width in the quantization processing and maintaining the image quality is generally used. Also, a variable bit rate coding method has been proposed in which the quantization width is adaptively changed according to the moving speed of the image (Japanese Patent Laid-Open No. 6-86264).

Further, in the case of recording a video signal on a recording medium, there is a method of assigning a code amount according to an image scene in accordance with the entire recording capacity and performing encoding (Japanese Patent Publication No. 6-55536). In this method, the image signal is encoded by the primary encoding means, the code amount is assigned according to the generated code amount at that time, and the image signal is encoded again. Therefore, two-pass encoding is performed.

[0009]

However, if the purpose is to record on a medium such as a read-only optical disc, real-time encoding processing is not necessary, but in the case of a rewritable recording medium, real-time encoding processing is not required. There was a problem that it was necessary to realize the encoding process. Also, the encoding process must be performed at a bit rate that does not exceed the maximum data transfer rate at the time of recording or reproducing. Further, in variable bit rate coding, an image with a low coding difficulty may have a too low bit rate depending on the balance of the coding difficulty of the image, and the image quality may be deteriorated in the image with a low difficulty. Further, when recording on a recording medium while performing variable bit rate encoding in real time, efficient encoding processing can be performed if code amount allocation that makes full use of the recording capacity of the medium is realized.

In view of the above points, the present invention is directed to recording a video signal on a recording medium such as an optical disk or a magnetic disk.
Alternatively, when transmitting using a transmission system compatible with a variable bit rate, code amount allocation that is adapted to a video signal and defines the maximum bit rate and the minimum bit rate is performed with a small delay time, enabling real-time processing. A variable bit rate video encoding device is provided, and further, a video recording device that allocates a code amount based on the recording capacity of a recording medium to efficiently record the recording medium, and a recording medium recorded by the previous period video recording device. The purpose is to provide.

[0011]

[Means for Solving the Problems] To achieve the above object,
A variable bit rate video encoding device of the present invention is an encoding difficulty detecting means for detecting a difficulty in encoding a video signal in a predetermined period, and a code amount for converting the difficulty according to a predetermined conversion characteristic to generate an assigned code amount. Allocating means, secondary quantizing means for quantizing the video signal, secondary coding means for variable length coding the output of the secondary quantizing means to generate secondary coded data, and It is configured by a code amount control unit that determines a quantization parameter in the secondary quantization unit so that the difference between the code length of the predetermined period of the next encoded data and the assigned code amount becomes small,
The video recording apparatus of the present invention further comprises means for recording on a recording medium in the variable bit rate video encoding apparatus.

Further, the variable bit rate coding device of the present invention is a variable bit rate coding device which performs coding processing so that the coding amount in a predetermined period becomes a coding amount corresponding to a video signal and generates secondary coded data. Means, a fixed bit rate encoding means for performing encoding processing by performing code amount control so that the code amount in the second predetermined period becomes a predetermined code amount Bmax, and generating third-order encoded data; and the secondary encoding. Means for measuring the code amount Bv of data generated in the second predetermined period; comparing means for comparing the measured code amount Bv with the predetermined code amount Bmax; One of the secondary coded data and the tertiary coded data is selected and output, and the code amount Bv is the predetermined code amount B.
When the value is larger than max, the switching means is configured to select and output the tertiary encoded data in the second predetermined period, and output the secondary encoded data otherwise. The video recording apparatus of (1) further comprises means for recording on a recording medium in the variable bit rate video encoding apparatus.

The video recording apparatus of the present invention records a code string obtained by compressing and coding a video signal on a recording medium, and a recording for outputting the recordable capacity of the recording medium. A capacity detecting unit, a code amount allocating unit that defines a code amount to be allocated to a predetermined period by the recordable capacity and a time when the video signal is not yet recorded, and a video signal of the predetermined period with the allocated code amount. And means for performing compression encoding processing.

Further, the recording medium of the present invention, the encoding difficulty detecting means for detecting the difficulty of encoding the video signal in the first predetermined period, and the difficulty is converted according to a predetermined conversion characteristic to generate an assigned code amount. Code amount allocating means, a secondary quantizing means for quantizing a video signal, and a secondary coding means for variable length coding the output of the secondary quantizing means to generate secondary coded data. A code amount control unit that determines a quantization parameter in the secondary quantization unit so that a difference between a code length of the first predetermined period of the secondary coded data and the assigned code amount becomes small, It is recorded by a video recording device configured by means for recording the secondary encoded data on the recording medium.

[0015]

As a result, the assigned code amount is obtained according to the difficulty of encoding the video signal, and the encoding process is performed at a compression rate according to each scene with a small encoding delay. Moreover, although the encoding process is performed at a variable bit rate, the encoded data that is output is encoded without exceeding a predetermined maximum encoding rate. Further, the encoding process is performed at the encoding rate according to the recordable capacity of the recording medium.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the video recording apparatus of the present invention will be described below with reference to the drawings. Since the video recording device is a device for recording the encoded data obtained by performing the encoding processing using the variable bit rate video encoding device of the present invention on the recording medium, the implementation of the variable bit rate video encoding device. The same applies to the example.

FIG. 1 shows a block diagram of a video recording apparatus according to a first embodiment of the present invention. The input video signal is input to the encoding difficulty detector 101. The coding difficulty detector 101 detects the difficulty of coding a video signal in a predetermined period, and outputs a higher coding difficulty as the coding distortion increases at the same coding rate.
The code amount assigner 102 outputs the assigned code amount according to the detected coding difficulty. It is sufficient to output a large allocated code amount as the encoding difficulty increases. On the other hand, the input video signal is input to the delay device 105, and the delay device 105 delays the video signal by the calculation processing time of the coding difficulty detector 101 and the code amount allocation device 102. The delayed video signal is input to the secondary quantizer 106 and is quantized with a quantization width proportional to the quantization parameter determined by the code amount controller 103. The quantized signal is subjected to variable length coding processing by the secondary encoder 107 to generate secondary encoded data.
The code amount measuring device 104 measures the generated code amount of the generated secondary encoded data for a predetermined period. Code amount controller 103
Determines and outputs the quantization parameter in the secondary quantizer 106 so that the difference between the assigned code amount determined by the code amount allocator 102 and the code amount measured by the code amount measuring device 104 becomes small. . The secondary encoded data generated by the secondary encoder 107 is the recording signal processor 1
An error correction process, a recording signal modulation process, and the like are performed by 10, and recording is performed on the optical disc 112 by the recording head 111.

With this configuration, the encoding process is performed with a code amount according to the degree of difficulty in encoding each scene of the video signal, and the image quality can be made uniform in the entire video. Further, the delay amount in encoding is defined by the delay device 105, but it is possible to process within the real time range by deciding the assigned code amount as needed.

FIG. 2 is a block diagram showing an example of the encoding difficulty detector 101 described in the first embodiment. The input video signal is input to the primary quantizer 201 and quantized by a predetermined provisional quantifier parameter. The quantized data is subjected to variable length coding processing by the primary encoder 202. The code amount measuring unit 203 measures the generated code amount of the primary encoded data generated by the primary encoder 202 for a predetermined period, and outputs the generated code amount as the encoding difficulty level. When quantization is performed with a fixed quantization parameter, the resolution of the quantization process is relatively increased for an image signal with a high degree of coding difficulty in which the signal amplitude changes in a complicated manner, and the generated code amount increases, but the signal amplitude changes. In the case of an image signal having a small coding difficulty and a low coding difficulty, the resolution of the quantization processing is relatively low, and thus the generated code amount is reduced. Therefore, the code amount generated when the quantization process is performed with the fixed quantization parameter can be regarded as the encoding difficulty level.

In FIG. 14, the encoding difficulty detector 101
3 shows a block diagram of an example of FIG. FIG. 14 shows the encoding difficulty detector of FIG. 2 further provided with a multiplier 1401. The multiplier 1401 obtains the product of the quantization parameter used in the primary quantizer 201 and the output of the code amount measuring device 203, and outputs the result of this product as the encoding difficulty. It is generally known that the quantization parameter and the generated code amount are almost inversely proportional to each other. Therefore, the product of the quantization parameter and the generated code amount is almost constant. Therefore, with this configuration, it is not necessary to fix the quantization parameter in the primary quantizer 201, and the coding difficulty can be detected.

In the coding process, between frames,
Alternatively, predictive coding between fields may be performed. In this case, the generated code amount indicates the spatial encoding difficulty within the screen, and at the same time indicates the temporal encoding difficulty between the screens.

Further, the encoding process in the encoding difficulty detection is performed by the same encoding method as the encoding process for obtaining the output encoded data, whereby the more accurate encoding difficulty can be detected. . This is because when performing coding processing by a hybrid coding method that uses both the intra-frame coding method and the inter-frame predictive coding method, the coding method in the coding difficulty detection is matched frame by frame. It is possible to detect the degree of difficulty.

FIG. 3 is a block diagram showing an embodiment of the code amount assigner 102 described in the first embodiment. FIG.
In the code amount allocator, the coding difficulty is multiplied by the predetermined amount a by the multiplier 301, and the adder 302 adds the predetermined amount b to obtain the allocated code amount. With this configuration, the coding difficulty can be linearly converted to obtain the assigned code amount.

The linear conversion characteristic may be determined by a plurality of modes as shown in the block diagram of FIG. The parameter determiner 401 determines the coefficients a and b according to a plurality of modes such as a standard mode, a high image quality mode, and a long-time recording mode. The determined coefficients a and b are the multiplier 4
02, is input to the adder 403, and the coding difficulty is linearly converted in the same manner as the code amount allocation shown in FIG. With such a configuration, the assigned code amount can be defined with the optimum conversion characteristic for each mode.
For example, if the coefficient a in the long-time recording mode is set smaller than the coefficient a in the high image quality mode, the total code amount of the entire image can be suppressed in the long-time recording mode, and the recording can be performed on the recording medium for a long time. Therefore, in the high image quality mode, a sufficient allocated code amount can be given and high image quality can be maintained.

The code amount assigner 102 may assign the code amount so that the assigned code amount falls within a predetermined range. Thereby, the maximum coding rate or the minimum coding rate can be defined.

The method of detecting the coding difficulty may be the method described with reference to FIG. 2 or FIG. 14, but is not limited to this, and any method may be used as long as it shows the difficulty of coding.

FIG. 5 is a block diagram of a video recording apparatus according to the second embodiment of the present invention. The input video signal is input to the encoding difficulty detector 101, and the encoding difficulty of a predetermined period is detected. Further, the activity detector 501 detects the activity of the input video signal for a predetermined period. The parameter determiner 502 outputs the coefficient a in the multiplier 301 and the coefficient b in the adder 302 according to the detected activity. Multiplier 301 and adder 30
2 outputs the assigned code amount from the encoding difficulty detected using the obtained coefficient. Thereafter, similarly to the first embodiment, the secondary quantizer 106 and the secondary encoder 107 perform the encoding process with the assigned code amount for the video signal to generate the secondary encoded data. The generated secondary encoded data is recorded signal processor 1
10. Recording is performed on the optical disk 112 by the recording head 111.

Since the degree of coding difficulty is generally low for a video with small activity, it is not necessary to increase the allocation code amount, but if the allocation code amount is too small, the image quality deteriorates due to coding distortion. In particular, in an image with low activity, coding distortion is likely to be conspicuous, which may cause a large deterioration in image quality. Therefore, by configuring as described above, the linear conversion characteristic is changed depending on the activity, and as a result, the non-linear conversion is performed on the coding difficulty to obtain the allocated code amount, which further corresponds to the characteristic of the image signal. The encoding process can be realized, and a high-quality reproduced image can be obtained.

The activity may be detected by the correlation amount of the image signal level within the screen, the correlation amount of the image signal level between the screens, or both of them. Further, as the correlation amount of the image signal level, the variance value of the image signal level, the average of absolute value errors from the average value of the signal levels in the screen, or the like may be used.

FIG. 6 is a block diagram of a video recording apparatus according to the third embodiment of the present invention. The input video signal is input to the encoding difficulty detector 101, and the encoding difficulty of a predetermined period is detected. The average value detector 601 detects the average value of the image signal level of the input video signal for a predetermined period. The parameter determiner 602 calculates the multiplier 3 according to the detected average value.
The coefficient a of 01 and the coefficient b of the adder 302 are output. Hereinafter, as in the second embodiment, the multiplier 301 and the adder 302 determine the assigned code amount from the coding difficulty.
The secondary encoded data generated by encoding the video signal with the obtained allocation code amount is recorded on the optical disc 112.

Since an image having a low signal level generally has a low coding difficulty, it is not necessary to increase the allocation code amount, but if the allocation code amount becomes too small, image quality deterioration due to coding distortion occurs. In particular, in a dark image with a low signal level, when the image brightness is increased, coding distortion is likely to be conspicuous, which may cause a large deterioration in image quality. Therefore, by configuring as described above, the linear conversion characteristic is changed according to the average value of the signal level, and as a result, the allocation code amount is obtained by performing the non-linear conversion with respect to the coding difficulty, thereby further reducing the image signal Encoding processing according to the characteristics can be realized, and a high-quality reproduced image can be obtained.

FIG. 7 is a block diagram of a fourth video recording apparatus of the present invention. The input video signal is input to the encoding difficulty detector 101, and the encoding difficulty of a predetermined period is detected.

The recording capacity detector 702 detects the recordable capacity of the recording medium for recording. The parameter determiner 701 outputs the coefficient a in the multiplier 301 and the coefficient b in the adder 302 according to the detected recording capacity. Hereinafter, as in the second embodiment, the multiplier 301 and the adder 302 determine the assigned code amount from the coding difficulty. The secondary encoded data generated by encoding the video signal with the obtained allocation code amount is the recording / reproducing head 70.
3 is recorded on the optical disk 112.

The parameter determiner 701 reduces the coefficients a and b as the recording capacity of the recording medium decreases.
As a result, the allocated code amount is reduced and the recording time of the video signal can be extended. Also, when the recording capacity is sufficient, a reproduced image with high image quality can be obtained by selecting appropriate coefficients a and b. In this way, it is possible to define the characteristic of obtaining the allocated code amount according to the recording capacity of the recording medium,
It is possible to efficiently record on the recording medium.

In the above-described embodiment, the coding difficulty is linearly converted to obtain the assigned code amount, but the present invention is not limited to this. For example, a correspondence table that associates the encoding difficulty level with the allocation code amount may be provided, and the allocation code amount may be obtained from this correspondence table.

Further, a plurality of correspondence tables may be provided, and the correspondence table may be selected according to a plurality of coding modes for code amount allocation. Further, the correspondence table may be determined based on the image signal activity or the average value of the image signal levels.

FIG. 8 shows a block diagram of a video recording apparatus according to the fifth embodiment of the present invention. Similarly to the fourth embodiment of FIG. 7, the input video signal is quantized by the secondary quantizer 106 and subjected to variable length coding processing by the secondary encoder 107 to obtain secondary coded data. To be The secondary encoded data is subjected to error correction processing and modulation processing by the recording signal processor 110 and recorded on the optical disk 112 by the recording / reproducing head 703. The recording capacity detector 703 detects the recordable capacity of the optical disk 112. The code amount assigner 801 defines the assigned code amount based on the recording capacity detected by the recording capacity detector 702 and the unrecorded time of the video signal to be recorded. The code amount measuring device 104 measures the code amount of the secondary encoded data in a predetermined period. The code amount controller 103 is a code amount assigner 801.
The quantization parameter in the secondary quantizer 106 is defined so that the difference between the assigned code amount obtained by the above method and the code amount of the secondary encoded data obtained by the code amount measuring device 104 becomes small. .

When the unrecorded time of the video signal to be recorded is large and the recording capacity of the optical disk 112 is small, the code amount allocator 801 reduces the allocated code amount, the unrecorded time is short, and the recording capacity is sufficient. In some cases, by giving a sufficient allocation code amount, it is possible to record all the video signals to be recorded on the recording medium, and it is possible to perform efficient encoding processing according to the recording capacity.

FIG. 9 shows a video recording apparatus according to the sixth embodiment of the present invention. In FIG. 9, the input video signal is input to the variable bit rate encoder 901. The variable bit rate encoder 901 performs a coding process with a code amount according to an image to generate secondary coded data. here,
Any method may be used to generate the secondary encoded data having a variable bit rate. On the other hand, the video signal is the third-order quantizer 904.
Is quantized by the quantization parameter defined by the code amount controller 902, and variable length coding processing is performed by the tertiary encoder 905 to generate tertiary encoded data. The second code amount measuring device 903 measures the code amount of the third-order encoded data in a predetermined period, and the measured code amount is input to the code amount controller 902. The code amount controller 902 defines the quantization parameter used by the third-order quantizer 904 so that the coding rate of the third-order coded data becomes Bmax. Therefore, the third-order coded data is data with a fixed coding rate of a predetermined coding rate Bmax.

The comparator 906 outputs the output of the first code amount measuring device 104, which is the code amount of the secondary encoded data, and the output of the second code amount measuring device 903, which is the code amount of the tertiary encoded data. Compare. The switching unit 907 outputs the second-order coded data or the third-order coded data according to the output of the comparator 906.
The coded data having a small code amount is selected and output.

With this configuration, the maximum coding rate of the coded data output as the coding apparatus is limited to the predetermined maximum coding rate Bmax. The maximum data transfer rate is determined by each system, whether it is recorded on or reproduced from a recording medium on an optical disk or magnetic disk, or when data is transferred using a variable transfer rate compatible transmission system. , If the data transfer exceeds the maximum transfer rate, the buffer in the data input section will underflow, and proper data transfer cannot be performed. Therefore, it is necessary to specify the maximum bit rate even in variable bit rate coding. Therefore, the maximum bit rate can be defined by the configuration described in the present embodiment, and the coding bit rate coding process according to the image can be performed.

Although the output of the second code amount measuring device 903, which is the code amount of the third-order encoded data, is used as the input of the comparator 906, the present invention is not limited to this, and the predetermined value defined by the predetermined amount Bmax is a third-order value. The code amount of the encoded data may be used.

Further, in FIG. 9, a means for performing fixed bit rate coding with a predetermined amount Bmax is provided so as to define the maximum bit rate of the output coded data, but with the same configuration, the minimum bit rate of the output coded data is provided. Can also be defined. In this case, the code amount controller 902 controls the code amount by a predetermined amount Bmin, and the comparator 906 generates the code amount of the secondary encoded data output from the variable bit rate encoder 901 by the tertiary encoder 905. When it is detected that the code amount is smaller than the code amount of the third-order encoded data, the switching device 907 selects the third-order encoded data as the output encoded data, and in other cases, the second-order encoded data is selected and output. Thus, the minimum bit rate can be specified.

FIG. 10 is a block diagram of a video recording apparatus according to the seventh embodiment of the present invention. The video recording apparatus in FIG. 10 is configured by configuring the variable bit rate encoder 901 in the video recording apparatus in FIG. 9 with the video encoding processing section described in FIG.

The coding difficulty detector 101 detects the difficulty of coding the input video signal for a predetermined period, and the code amount assigner 102 outputs the assigned code amount according to the detected difficulty.
The delay device 105 delays the input video signal by the processing time for obtaining the allocated code amount. The delayed video signal is quantized by the secondary quantizer 106. At this time, quantization is performed with a quantization width proportional to the quantization parameter output by the first code amount controller 103. The quantized data is subjected to variable length coding processing by the secondary encoder 107 to generate secondary encoded data. First code amount measuring device 104
Measures the amount of generated code of the secondary encoded data in a predetermined period. The first code amount controller 103 outputs a quantization parameter that reduces the difference between the assigned code amount and the generated code amount for a predetermined period.

The video signal delayed by the delay unit 105 is further input to the third-order quantizer 904 and quantized by the quantization parameter generated by the second code amount controller 902. The output of the third-order quantizer 904 is subjected to variable length coding processing by the third-order encoder 905 to generate third-order coded data. The second code amount measuring device 903 measures the generated code amount of the third-order encoded data in a predetermined period. The generated code amount of the third-order encoded data is input to the second code amount controller 902. The second code amount controller 902 determines the quantization parameter in the third-order quantizer 904 so that the coding bit rate of the third-order coded data becomes a predetermined maximum coding bit rate Bmax. Therefore, the third-order encoded data is fixed bit rate data having a predetermined encoding bit rate Bmax. The comparator 905 compares the code amount of the secondary encoded data measured by the first code amount measuring device 104 with the code amount of the tertiary encoded data measured by the second code amount measuring device 903. The comparison result of the comparator 906 is input to the switch 907. The switch 907 selects and outputs either one of the secondary encoded data and the tertiary encoded data according to the comparison result of the comparator 906,
Of the secondary coded data and the tertiary coded data, the coded data with the smaller code amount is selected and output.

With this configuration, the maximum coding rate of the coded data output as the coding apparatus can be limited to the predetermined maximum coding rate Bmax.

FIG. 11 shows a block diagram of a video recording apparatus according to the eighth embodiment of the present invention. The video recording apparatus of FIG. 11 is for obtaining the encoding difficulty level in the encoding processing unit at the fixed encoding rate in the video recording apparatus of FIG. The principle of obtaining the coding difficulty is the same as that of the coding difficulty detector described in FIG. Similar to the video recording device of FIG. 10, a cubic quantizer 904 and a cubic encoder 905.
The video signal is subjected to fixed coding rate coding processing at the coding rate Bmax to generate tertiary coded data. On the other hand, the secondary quantizer 106 and the secondary encoder 107 perform variable coding rate coding processing to generate secondary coded data. The secondary coded data and the tertiary coded data are selected by the switch 907 and recorded on the optical disk 112 according to the code amount in a predetermined period. The assigned code amount of the secondary encoded data is determined by the code amount assigner 102 according to the degree of encoding difficulty. Here, the output of the second code amount measuring device 903, which is the code amount of the third-order encoded data in a predetermined period, and the output of the second code amount controller 902, which is the quantization parameter in the third-order quantizer 904, are Multiplier 11
The result of multiplication by 01 is input to the code amount assigner 102 as the encoding difficulty.

It is known that the generated code amount and the quantization parameter at the time of quantization and encoding are almost in inverse proportion to each other, and the product of the issuer code amount and the quantization parameter is almost constant. Therefore, the product of the code length of the third-order encoded data obtained by the fixed encoding rate control and the quantization parameter at that time can be treated as the encoding difficulty, and the encoding difficulty detector and the maximum encoding rate Bmax can be used. It can also be used as the fixed coding rate coding processing unit.

FIG. 12 shows a block diagram of a video recording apparatus according to the ninth embodiment of the present invention. Similarly to the seventh embodiment, the input video signal is output by the third-order quantizer 904, third-order encoder 905, code amount controller 902 and second code amount measuring device 903 at a predetermined maximum coding rate Bmax. Fixed bit rate encoding processing is performed to generate tertiary encoded data. On the other hand, the input video signal is the secondary quantizer 1
Quantization is performed with a predetermined fixed quantization parameter in 06, and variable length coding processing is performed in the secondary encoder 107 to generate secondary encoded data. Here, since the quantization parameter is fixed, the generated secondary coded data is variable bit rate data. The first code amount measuring device 104 measures the code amount of the secondary encoded data for a predetermined period. The comparator 906 compares the output of the first code amount measuring device 104, which is the code amount of the secondary encoded data, with the output of the second code amount measuring device 903, which is the code amount of the tertiary encoded data. The switching unit 907 selects and outputs the coded data having the smaller code amount from the secondary coded data and the tertiary coded data according to the comparison result in the comparator 906.

With this configuration, the variable bit rate coded data obtained by quantization with the fixed quantization parameter and the fixed bit rate coded data having the maximum coding rate Bmax are codes having a low coding rate. The encoded data is output, and as a result, the maximum encoding rate of the output encoded data of the encoding device is the predetermined encoding rate Bmax.
Can be restricted with.

FIG. 13 shows a block diagram of a variable bit rate video encoding apparatus according to the tenth embodiment of the present invention.
Similarly to the seventh embodiment, the input video signal is processed by a third-order quantizer 904, a third-order encoder 905, and a code amount controller 90.
2. The second code amount measuring device 903 generates the third-order coded data with a fixed bit rate at a predetermined maximum coding rate Bmax. On the other hand, the input video signal is quantized by the secondary quantizer 106, and then the secondary encoder 107 performs variable length coding processing to generate secondary coded data. The activity detector 1301 detects the activity of the input video signal. Quantization parameter determiner 13
02 specifies the quantization parameter used in the secondary quantizer 106 according to the detected activity. The quantization parameter determiner 13025 may output a large quantization parameter as the activity increases. By doing so, it is possible to reduce coding distortion by performing quantization processing with a fine quantization parameter in a flat image with small activity. Further, in an image with low activity, even if the quantization parameter is reduced, the amount of increase in the generated code amount is not large, and efficient encoding is possible. On the other hand, in an image with a large activity, the coding distortion is not noticeable even if the quantization parameter is increased, and the generated code amount can be suppressed from becoming too large.

The first code amount measuring device 104 measures the code amount of the secondary encoded data in a predetermined period, and the second code amount measuring device 903 measures the code amount of the tertiary encoded data in a predetermined period. The comparator 906 compares the output of the first code amount measuring device 104 and the output of the second code amount measuring device 903. The switching unit 907 selects and outputs the coded data having the smaller code amount from the secondary coded data and the tertiary coded data according to the comparison result of the comparator 906. The selected encoded data is recorded on the optical disc 112.

With this configuration, of the variable bit rate coded data obtained by quantizing with the quantization parameter defined by the image activity and the fixed bit rate coded data of the maximum coding rate Bmax, Coded data having a low coding rate is output, and as a result, the maximum coding rate of the output coded data of the coding device can be limited to a predetermined coding rate Bmax.

The activity may be detected by the correlation amount of the image signal level in the screen, the correlation amount of the image signal level between the screens, or both of them. Further, as the correlation amount of the image signal level, the variance value of the image signal level, the average of absolute value errors from the average value of the signal levels in the screen, or the like may be used.

Although the video signal is recorded on the optical disk in the above-described embodiment of the video recording apparatus, the present invention is not limited to this, and any recording medium such as a magnetic disk may be used.

The coding method may be a transform coding method such as a DCT coding method, a frequency division coding method such as a subband coding method, or a vector quantization coding. It doesn't matter what the method is.

Further, it may be an intra-frame or intra-field coding method, an inter-frame or inter-field coding method, or a hybrid coding method combining these.

When recording on a recording medium, other data signals such as audio signals may be recorded on the recording medium.

[0060]

As described above, according to the present invention, the coding process is performed with the code amount according to the difficulty of coding each scene of the video signal, and the image quality can be made uniform in the entire video, and the code to be assigned is assigned. It is also possible to process within the real-time range by determining the amount at any time.

Furthermore, the average value of the pixel level of the image signal,
Alternatively, by defining the assigned code amount according to the activity, the encoding process according to the characteristics of the image signal is performed, and a reproduced image with high image quality can be obtained.

Further, when recording on a recording medium, by defining the characteristic of obtaining the allocated code amount according to the recordable capacity of the recording medium and the unrecorded time of the video signal,
The video signal can be efficiently recorded on the recording medium.

Further, in performing variable bit rate encoding, a predetermined maximum encoding bit rate can be defined, so that the encoding process can be performed without exceeding the maximum transfer rate in data transfer at the variable transfer rate. You can

[Brief description of drawings]

FIG. 1 is a block diagram of a video recording device according to a first embodiment of the invention.

FIG. 2 is a block diagram of an example of a coding difficulty detector 101.

FIG. 3 is a block diagram of an example of a code amount assigner 102.

FIG. 4 is a block diagram of an example of a code amount assigner 102.

FIG. 5 is a block diagram of a video recording device according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a video recording apparatus according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a video recording apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram of a video recording apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram of a video recording apparatus according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram of a video recording apparatus according to a seventh embodiment of the present invention.

FIG. 11 is a block diagram of a video recording apparatus according to an eighth embodiment of the present invention.

FIG. 12 is a block diagram of a video recording apparatus according to a ninth embodiment of the present invention.

FIG. 13 is a block diagram of a video recording apparatus according to a tenth embodiment of the present invention.

FIG. 14 is a block diagram of an example of a coding difficulty detector 101.

[Explanation of symbols]

 101 coding difficulty detector 102 code amount allocation arrival 103 code amount controller 104 code amount measuring device 105 delay device 106 secondary quantizer 107 secondary encoder 110 recording signal processor 111 recording head 112 optical disc 201 primary quantization Unit 202 Primary encoder 203 Code amount measurer 301 Multiplier 302 Adder 401 Parameter determiner 402 Multiplier 403 Adder 501 Activity detector 502 Parameter determiner 601 Average value detector 602 Parameter determiner 701 Parameter determiner 702 Record Capacity detector 703 Recording / reproducing head 801 Code amount allocator 901 Variable bit rate encoder 902 Code amount controller 903 Code amount measuring device 904 Third-order quantizer 905 Third-order encoder 906 Comparator 907 Switcher 1101 Multiplier 13 1 activity detector 1302 quantization parameter determiner 1401 multiplier

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G06F 15/66 330 A

Claims (38)

[Claims] 1. A coding difficulty detecting means for detecting a difficulty in coding a video signal in a first predetermined period, and a code amount allocating means for converting the difficulty according to a predetermined conversion characteristic to generate an allocated code amount. Secondary quantizing means for quantizing a video signal; secondary coding means for variable length coding the output of the secondary quantizing means to generate secondary coded data; and the secondary coded data And a code amount control unit that determines a quantization parameter in the secondary quantization unit so that the difference between the code length in the first predetermined period and the assigned code amount becomes small. Variable bit rate encoder. 2. A primary quantizing means for quantizing the video signal with a quantizing width proportional to a predetermined provisional quantifier parameter, and a variable-length code for the output of the primary quantizing means. And a primary encoding means for generating primary encoded data, and a means for measuring the code length of the primary encoded data in a first predetermined period and outputting the code length as a difficulty level. The variable bit rate encoding device according to claim 1. 3. A primary quantizing means for quantizing the video signal with a quantizing width proportional to a predetermined primary quantizing parameter, and a variable length code for the output of the primary quantizing means. Primary encoding means for performing the encoding process to generate the primary encoded data, means for measuring the code length of the primary encoded data in the first predetermined period, and calculating the product of the primary quantization parameter and the code length. 2. The variable bit rate encoding device according to claim 1, further comprising means for outputting the result of the product as a difficulty level. 4. The variable bit rate coding apparatus according to claim 1, wherein the conversion characteristic in the code amount allocating means is defined according to a plurality of modes. 5. The variable bit rate coding apparatus according to claim 1, further comprising means for measuring the activity of the image signal, wherein the conversion characteristic in said code amount allocating means is defined according to said activity. 6. The means for measuring the activity comprises:
6. The variable bit rate coding device according to claim 5, wherein a correlation amount at a pixel level within a screen, between screens, or both is measured. 7. The variable according to claim 1, further comprising means for measuring an average value of the image signal level for a predetermined period, wherein the conversion characteristic in the code amount allocating means is defined according to the average value. Bit rate encoder. 8. When the secondary encoded data is recorded on a recording medium, the conversion characteristic in the code amount allocating means is defined according to the recordable capacity of the recording medium or the time for recording the video signal. The variable bit rate encoding device according to claim 1, characterized in that. 9. The code amount assigning means obtains an assigned code amount by linearly converting the degree of difficulty.
A variable bit rate encoding device as described. 10. The code amount assigning means comprises a predetermined correspondence table for associating the difficulty level with the assigned code amount, and the assigned code amount is defined by the correspondence table. Variable bit rate encoder. 11. The variable bit rate coding apparatus according to claim 1, wherein the code amount allocating means limits each allocated code amount in the predetermined period to fall within a predetermined range. 12. A fixed bit rate encoding means for performing encoding processing by performing code amount control so that the code amount of a second predetermined period becomes a predetermined code amount Bmax, and third-order encoded data, and the secondary. Means for measuring the code amount Bv in which the encoded data is generated in the second predetermined period, comparing means for comparing the measured code amount Bv with the predetermined code amount Bmax, and depending on the output of the comparing means. , One of the secondary coded data and the tertiary coded data is selected and output, and when the code amount Bv is larger than the predetermined code amount Bmax, the tertiary code in the second predetermined period. 2. The variable bit rate coding device according to claim 1, further comprising a switching unit that selects and outputs the coded data and outputs the secondary coded data when it is not. 13. A means for defining the primary quantization parameter by controlling the code amount so that the code length of the primary encoded data in a second predetermined period becomes a predetermined code length Bmax, and the secondary encoded data. Of the code length Bv of the second predetermined period
Of the primary coded data and the secondary coded data depending on the output of the comparing means, the comparing means for comparing the measured code length Bv with the predetermined code length Bmax. One of them is selected and output, and when the code length Bv is larger than the predetermined code length Bmax, the primary coded data is selected and output in the second predetermined period, and when not, the secondary coded data is output. 4. The variable bit rate encoding device according to claim 3, further comprising a switching unit that outputs encoded data. 14. A variable bit rate coding means for performing coding processing so as to generate secondary coded data so that the code amount for a predetermined period becomes a code amount according to a video signal, and a code amount for a second predetermined period. To a predetermined code amount Bmax, the bit rate is controlled so as to perform a coding process to generate tertiary coded data, and the secondary coded data is generated in the second predetermined period. Means for measuring the code amount Bv, the measured code amount Bv and the predetermined code amount Bmax
According to the output of the comparing means for comparing and the comparing means, one of the secondary coded data and the tertiary coded data is selected and output, and the code amount Bv is the predetermined code amount. When it is larger than Bmax, the third-order encoded data is selected and output in the second predetermined period,
Otherwise, the variable bit rate coding device is configured with a switching unit that outputs the secondary coded data. 15. The variable bit rate encoding means comprises:
15. The secondary coded data is generated by quantizing a video signal with a quantizing width proportional to a predetermined fixed quantizing parameter and then performing a variable length coding process.
A variable bit rate encoding device as described. 16. The variable bit rate encoding means comprises:
Means for detecting the activity of the video signal, means for determining the quantization parameter according to the activity, means for quantizing the video signal with a quantization width proportional to the quantization parameter, and quantized data 15. A variable length coding means is provided.
A variable bit rate encoding device as described. 17. The variable bit rate coding apparatus according to claim 16, wherein the means for detecting the activity measures a pixel level correlation amount within a screen, between screens, or both. 18. A variable bit rate coding means for coding and generating secondary coded data so that the code amount for a predetermined period becomes a code amount according to a video signal, and a code amount for a second predetermined period. To a predetermined code amount Bmin, the bit rate is controlled so as to perform a coding process to generate tertiary coded data, and the secondary coded data is generated in the second predetermined period. Means for measuring the code amount Bv, the measured code amount Bv and the predetermined code amount Bmin
According to the output of the comparing means for comparing and the comparing means, one of the secondary coded data and the tertiary coded data is selected and output, and the code amount Bv is the predetermined code amount. When it is smaller than Bmin, the third-order encoded data is selected and output in the second predetermined period,
Otherwise, the variable bit rate coding device is configured with a switching unit that outputs the secondary coded data. 19. An encoding difficulty detecting means for detecting a difficulty in encoding a video signal in a first predetermined period, and a code amount allocating means for converting the difficulty with a predetermined conversion characteristic to generate an allocated code amount. Secondary quantizing means for quantizing a video signal; secondary coding means for variable length coding the output of the secondary quantizing means to generate secondary coded data; and the secondary coded data Of code amount control means for determining the quantization parameter in the secondary quantization means so that the difference between the code length in the first predetermined period and the assigned code amount becomes small, and the secondary coded data is recorded. A recording apparatus comprising: a recording means on a medium. 20. A primary quantizing means for quantizing the video signal with a quantizing width proportional to a predetermined provisional quantifier parameter, and a variable length code for an output of the primary quantizing means. And a primary encoding means for generating primary encoded data, and a means for measuring the code length of the primary encoded data in a first predetermined period and outputting the code length as a difficulty level. 20. The recording device according to claim 19. 21. A primary quantization means for quantizing a video signal with a quantization width proportional to a predetermined primary quantization parameter by the encoding difficulty detecting means, and a variable length code for an output of the primary quantization means. Primary encoding means for performing the encoding process to generate the primary encoded data, means for measuring the code length of the primary encoded data in the first predetermined period, and calculating the product of the primary quantization parameter and the code length. 20. The recording apparatus according to claim 19, further comprising means for outputting the result of the product as a difficulty level. 22. The recording apparatus according to claim 19, wherein the conversion characteristic in the code amount allocation means is defined according to a plurality of modes. 23. The recording apparatus according to claim 19, further comprising means for measuring the activity of the image signal, wherein the conversion characteristic in the code amount allocating means is defined according to the activity. 24. The recording apparatus according to claim 23, wherein the activity measuring means measures a pixel level correlation amount within a screen, between screens, or both. 25. A recording apparatus according to claim 19, further comprising means for measuring an average value of the image signal level for a predetermined period, wherein the conversion characteristic in the code amount allocation means is defined according to the average value. apparatus. 26. The conversion characteristic in the code amount allocating means is defined according to the recordable capacity of the recording medium or the time for recording the video signal.
9. The recording device according to item 9. 27. The recording apparatus according to claim 19, wherein the code amount assigning unit obtains an assigned code amount by linearly converting the difficulty level. 28. The code amount allocating means comprises a predetermined correspondence table for associating the difficulty level with the allocation code amount, and the allocation code amount is defined by the correspondence table. Recording device. 29. The recording apparatus according to claim 19, wherein the code amount assigning unit limits each assigned code amount within the predetermined period to fall within a predetermined range. 30. Fixed bit rate coding means for performing coding processing by performing code amount control so that the code amount in the second predetermined period becomes a predetermined code amount Bmax, and third-order coded data; and the secondary. Means for measuring the code amount Bv in which the encoded data is generated in the second predetermined period, comparing means for comparing the measured code amount Bv with the predetermined code amount Bmax, and depending on the output of the comparing means. , One of the secondary coded data and the tertiary coded data is selected and output, and when the code amount Bv is larger than the predetermined code amount Bmax, the tertiary code in the second predetermined period. 2. The apparatus further comprises switching means for selecting and outputting the encoded data and outputting the secondary encoded data otherwise, and means for recording the output of the switching means on a recording medium. 9. The recording device according to item 9. 31. A means for determining the primary quantization parameter by controlling the code amount so that the code length of the primary encoded data in a second predetermined period becomes a predetermined code length Bmax, and the secondary encoded data. Of the code length Bv of the second predetermined period
Of the primary coded data and the secondary coded data depending on the output of the comparing means, the comparing means for comparing the measured code length Bv with the predetermined code length Bmax. One of them is selected and output, and when the code length Bv is larger than the predetermined code length Bmax, the primary coded data is selected and output in the second predetermined period, and when not, the secondary coded data is output. 22. The recording apparatus according to claim 21, comprising a switching unit for outputting encoded data and a unit for recording the output of the switching unit on a recording medium. 32. Variable bit rate coding means for performing coding processing to generate secondary coded data so that the code amount for a predetermined period becomes a code amount according to a video signal, and a code amount for a second predetermined period. To a predetermined code amount Bmax, the bit rate is controlled so as to perform a coding process to generate tertiary coded data, and the secondary coded data is generated in the second predetermined period. Means for measuring the code amount Bv, the measured code amount Bv and the predetermined code amount Bmax
According to the output of the comparing means for comparing and the comparing means, one of the secondary coded data and the tertiary coded data is selected and output, and the code amount Bv is the predetermined code amount. When it is larger than Bmax, the third-order encoded data is selected and output in the second predetermined period,
If not, the recording device comprises a switching unit that outputs the secondary encoded data and a unit that records the output of the switching unit on a recording medium. 33. The variable bit rate encoding means,
33. The secondary coded data is generated by performing a variable length coding process after quantizing a video signal with a quantization width proportional to a predetermined fixed quantization parameter.
The recording device described. 34. The variable bit rate encoding means,
Means for detecting the activity of the video signal, means for determining the quantization parameter according to the activity, means for quantizing the video signal with a quantization width proportional to the quantization parameter, and quantized data 33. Means for performing variable length coding.
The recording device described. 35. The recording apparatus according to claim 34, wherein the means for detecting the activity measures a correlation amount at a pixel level within the screen, between screens, or both. 36. Variable bit rate coding means for coding and generating secondary coded data so that the code amount for a predetermined period becomes a code amount according to a video signal, and a code amount for a second predetermined period. To a predetermined code amount Bmin, the bit rate is controlled so as to perform a coding process to generate tertiary coded data, and the secondary coded data is generated in the second predetermined period. Means for measuring the code amount Bv, the measured code amount Bv and the predetermined code amount Bmin
According to the output of the comparing means for comparing and the comparing means, one of the secondary coded data and the tertiary coded data is selected and output, and the code amount Bv is the predetermined code amount. When it is smaller than Bmin, the third-order encoded data is selected and output in the second predetermined period,
If not, the recording device comprises a switching unit that outputs the secondary encoded data and a unit that records the output of the switching unit on a recording medium. 37. A video recording device for recording a code string obtained by compressing and encoding a video signal on a recording medium, the recording capacity detecting means outputting a recordable capacity of the recording medium, and the recording. Code amount allocating means for defining a code amount to be allocated in a predetermined period with a possible capacity and a time in which the video signal is not yet recorded, and a video signal in the predetermined period is compression-encoded and encoded with the allocated code amount. A recording apparatus comprising: a unit for outputting data; and a unit for recording the encoded data on the recording medium. 38. Encoding difficulty detecting means for detecting a difficulty in encoding a video signal in a first predetermined period, and code amount allocating means for converting the difficulty with a predetermined conversion characteristic to generate an allocated code amount. Secondary quantizing means for quantizing a video signal; secondary coding means for variable length coding the output of the secondary quantizing means to generate secondary coded data; and the secondary coded data The code amount control means for determining the quantization parameter in the secondary quantization means so that the difference between the code length of the first predetermined period and the assigned code amount becomes small; A recording medium recorded by a video recording device configured by recording means on the recording medium.