JPH03101395A - Variable data decoder - Google Patents

Abstract

PURPOSE:To respond to a fast transmission line after reducing the scale of H/W by monitoring the data accumulation quantity of a post-reception buffer (rear RBF), and stopping the readout of data from a pre-resin buffer (front RBF) when the accumulation quantity exceeds a prescribed threshold value. CONSTITUTION:An accumulation quantity monitor 87 always monitors the data accumulation quantities of the rear RBFs 831-83n, and outputs overflow information 88 to a front RBF control part 84 when the accumulation quantities of the rear RBFs 831-83n exceed a threshold value set in advance. The front RBF control part 84 receiving the information stops the readout of the data from the front RBF 81. Therefore, no more data is accumulated in the rear RBFs 831-83n. And serial data 71 corresponding to the data accumulated in the rear RBFs 831-83n originally are accumulated in the front RBF 81. In such a way, the scale of the H/W can be reduced and correspondence to the fast transmission line can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a variable length data decoder that decodes entropy encoded image data.

[Conventional technology]

Figure 2 is from the Television Journal Society vol. 1.43 No. 6.
This is a block diagram of the video codec described in pp. 603 to 612, including transmission paths.

In the figure, 1 is a conversion unit for digitizing the input video signal, and 2 is an input unit for inputting the output signal of the N-conversion unit 1.
3 is a high-efficiency encoding unit; 4 is an entropy encoding unit that further converts the high-efficiency code into an entropy code; 5 is an entropy code; T is the transmission control unit (transmission side) that sends the code to the transmission path 6, and T is the transmission control unit (reception side) that receives the entropy code from the transmission path 6.
I), 8a is an entropy decoding unit (variable length data decoder) that decodes the received entropy code into video data that is a high efficiency code, 9 is a high efficiency decoder that decodes the high efficiency code into a video signal sequence, and 10 is a 7 Omatsu inverse conversion part, 11
is a D/A converter that reproduces a video signal.

In addition, FIG. 3 shows the entropy decoding unit 8a shown in FIG.
FIG. 2 is a block diagram showing a conventional configuration.

In the figure, T1 is serial data that is encoded video data output from the transmission control unit 7, 81 is a pre-receive buffer (hereinafter referred to as pre-RBF) that temporarily stores this serial data T1, and 821 is ~82n is a variable length decoding unit (decoding means) that decodes the entropy code;
31 to 83m are post-receive buffers (hereinafter referred to as "back RBF") that temporarily store data output by the variable length decoders 821-82n, and 84a is a pre-receive buffer that controls reading and writing of the front RBF 81. control unit, 8
5 is a rear receiving buffer control unit that controls reading and writing of rear RBFs 831 to 83n; 861 to 86n;
is decoded video data output to the high-efficiency decoding section 9.

Next, the operation of the video codec will be explained with reference to FIG. The video signal output from the TV right camera is
After being digitized by a converter 1, the format converter 2 converts it into a video signal sequence in a format suitable for high-efficiency codes. Here, the video signal sequence is often made into a block made up of a plurality of adjacent pixels. In this case, the high-efficiency encoding unit 3 compresses the amount of information by applying an encoding algorithm on a block-by-block basis and converting the video signal into a plurality of video data such as average values and quantized values. Further, the entropy encoding unit 4 performs variable length encoding and multiplexing on this video data by entropy encoding such as Huffman encoding. Then, the transmission control unit (transmission JrlA>5) sends the encoded video data to the transmission path 6.The amount of information (total number of bits) of the data for each 17 frames sent to the transmission path 6 is ,
Due to the nature of entropy encoding, it varies greatly depending on the characteristics of the input video signal.

On the other hand, the transmission control unit (reception 111) 7 receives encoded video data from the transmission path 6, and entropy decoding unit 8a
Output to. The entropy decoding unit 8a decodes and separates encoded video data. At the same time, transmission line 6
The increase or decrease in data on the time axis is buffered in units of blocks used for encoding. The high-efficiency decoding unit S, which receives the decoded video data, decodes the video signal sequence.

This video signal series is inversely converted by a format inverse converter 10 to become the same signal as the output signal of the Φ converter 1, and further outputted as a video signal by a D/A converter 11.

Next, the operation of the entropy decoding section 8a will be explained with reference to FIG. The serial data outputted by the transmission control unit (reception@) T is encoded video data with low redundancy, and is written to the front RBF 81 in synchronization with a clock corresponding to the transmission speed of the transmission line 6. The front RBF control unit 84 & includes variable length decoding units 821 to 82 provided corresponding to individual encoded video data (for example, average value, quantization value, etc.) according to the variable length decoding algorithm.
The video data is separated by reading data from the previous RBF 81 and allocating it to the RBF 81. Here, reading data from the previous RBF 81 is generally performed as follows.
This is performed at a frequency that is a multiple of the video sampling clock cycle. The variable length decoding units 821 to 82n decode the entropy codes constituting the respective encoded video data to generate decoded video data 861 to 861 to be generated in bursts.
86n, RBF831 after each video data dedicated
~Write to 83n. Then, the rear RBF control section 85
By reading the decoded video data 861 to 86n stored in the rear RBFs 831 to 83n in parallel in block units in synchronization with the video sampling clock, fluctuations in the video data on the time axis are buffered. Here, the former RB
Comparing the effects of F 81 and post-RBF 831-g3n, the effects of both are completely independent. Tsut 夛, former RB
The main function of F81 is speed conversion to synchronize the serial data 71 synchronized with the transmission path clock to the clock for variable length decoding, and when the transmission time per block is smaller than the variable length decoding time, RBF8
The accumulation amount of 1 shows an increasing trend. Note that the hardware (H/W) scale of the previous RBF 81 can be reduced by rounding, which is applicable to multiplexed data with low redundancy.

On the other hand, the rear RBF831 to $3n buffer the variable-length decoding time and the video data readout time on a block-by-block basis, so that the video data readout time per block is longer than the variable-length decoding time per block. When the amount of water is also large, the amount of accumulation tends to increase. Furthermore, since the target is parallel data that has inherent redundancy, the H/W scale becomes large.

[Problem to be solved by the invention]

The conventional variable length data decoder is configured as described above.
Therefore, when setting the capacities of the front RBF 81 and the rear RBFs 831 to Hn, both are optimized and set independently, so there is a problem that the overall scale increases.

This invention was made to solve the above-mentioned problems, and it reduced the scale of trade compared to the conventional one.
It is an object of the present invention to provide a variable length data decoder that can cope with high-speed transmission paths and operates without problems even when variable length data with short code words is continuously input.

[Means to solve the problem]

The variable length data decoder according to the present invention includes a pre-RBF for inputting entropy-encoded data and temporarily storing this data, and a decoding means for reading data from the pre-RBF and outputting a plurality of video data. and a rear RBF for temporarily accumulating the video data output by the decoding means, the amount of data accumulated in the rear RBF is monitored, and if the amount of data exceeds a predetermined threshold; To,
A storage amount monitoring means for stopping reading of data from the previous RBF is provided.

[Effect]

The storage amount monitoring means in this invention limits the increase in the storage amount of the rear RBF by stopping the reading of data from the front RBF when the storage amount of the rear RBF exceeds a threshold value. , reduce the capacity of the rear RBF, and reduce the capacity of the front RBF.
This contributes to reducing the total capacity, including the capacity of

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, reference numeral 84 denotes a previous RBF control unit that suspends reading of the previous RBF 81 upon receiving the overflow notification 88;
Reference numeral 7 denotes a storage amount monitor (storage amount monitoring means) for monitoring the data storage amount of the rear RBFs 831 to 83n, and the other components are denoted by the same reference numerals and are the same as those shown in FIG.

Next, the operation will be explained. The entropy decoding section (variable length data decoder) 8 shown in FIG. 1 is used, for example, in the video codec shown in FIG. 2. The basic operation of the entropy decoding section 80 is the same as that shown in FIG. 3, so the explanation thereof will be omitted here.

Here, the operation when the entropy decoding section 8 is connected to the high-speed transmission line 6 will be explained. In this case, the previous RBF
The amount of data stored in 81 tends to increase in proportion to the transmission speed. This is because as the transmission speed increases, the time for transmitting data from block to block decreases, and the variable length decoding time from block to block also becomes relatively smaller.

This tendency shows that when the data length per block becomes shorter,
This problem becomes even more noticeable when the codewords of the entropy codes that make up the block become shorter.

On the other hand, if the data length of the block is short, the rear R
The decoding time for each block of the variable length decoding units 821 to 82n is relatively small compared to the reading time for each block of the BFs 831 to 83n. This is because the bit length of the decoded video data is relatively long compared to the code length of the entropy code.

Therefore, in this case, the amount of data stored in the rear RBFs 831 to 83n also increases. From the above, the transfer speed of the serial data 11 is high in the front RBF 81 and the rear RBF 831''83n, which originally operate independently.

Moreover, when the data length of each block is short, both data storage amounts increase.

Further, the capacities of the rear RBFs 831 to 83n shown in FIG. 1 are also reduced (optimal values determined from transmission speed, entropy coding efficiency, etc.). The storage amount monitor 8T is the rear RB
Constantly monitor the amount of data accumulated on F831-83n, and
When the accumulated amount of the BFs 831 to 83n exceeds a preset threshold value, an over 70-notification 88 is output to the previous RBF control unit 84. The previous RBF control unit 84 that received this overflow notification 88 controls the previous RBF 8
Since reading data from 1 is stopped, the rear RBF8
No more data is stored in 31-83m. Then, serial data T1 corresponding to data that should originally be stored in the rear RBFs 831 to 83n is stored in the front RBF 81.

Therefore, more serial data T1 will be stored in the previous RBF 81 than when reading is not stopped, but since the entropy code for each block at this point is short, the amount of increase is relatively small. The target is small.

In this way, the rear RBF831 with a large H/W scale
It is possible to reduce the capacity of ~83n, increase the capacity of the front RBF 81 which can be achieved with a small-scale narrowing, and organically combine the front RBF 81 and the rear RBF 831-83n using the storage amount monitor 81. In addition, the total buffer capacity can be made smaller than that of the conventional method while maintaining normal buffering operation.

〔Effect of the invention〕

As described above, according to the present invention, the variable length data decoder monitors the data storage amount of the rear RBF by the storage amount monitoring means, and when the storage amount exceeds a predetermined threshold, the data from the previous RBF is Since the structure is configured so that reading is stopped, the data buffering operation can be performed normally even when the transmission speed becomes high, and the overall size of the file W can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a variable length data decoder according to an embodiment of the present invention, Fig. 2 is a block diagram showing a video codec and transmission path, and Fig. 3 shows a conventional variable length data decoder. It is a block diagram. 6 is a transmission path, γ is a transmission control unit (receiving side), 8 is an entropy decoding unit (variable length data decoder), 9 is a high efficiency decoding unit, 81 is a pre-reception buffer, 821 to 82n are variable length decoding units (decoding means), 831 to 83n are rear reception buffers, 84 is a front reception buffer control section, 85 is a rear reception buffer control section, and 87 is a storage amount monitor (storage amount monitoring means). In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A pre-receive buffer that inputs entropy-encoded data and temporarily stores this data; reads the data from the pre-receive buffer; decodes the read data; and outputs multiple pieces of video data. In a variable length data decoder, the variable length data decoder includes a decoding means for decoding, and a post-reception buffer for temporarily accumulating the video data outputted by the decoding means, the amount of data accumulated in the post-reception buffer is monitored, and A variable length data decoder comprising: storage amount monitoring means for stopping reading of the data from the pre-reception buffer when the data storage amount exceeds a predetermined threshold value.