JPH04122174A - Encoding device - Google Patents

Abstract

PURPOSE:To decide a succeeding state transition suitable for the tendency in the increase/decrease in a code degree order by providing the history of the tendency in the increase/decrease in a probability with another state by the history of the past transition so as to separate the route of the state transition. CONSTITUTION:A history management table 57 stores a state number to be transited next based on a coding symbol for each state and a context resident state generated by a context reference table 13 is revised to a succeeding state and when prediction value conversion is commanded, a prediction value with respect to a context is revised simultaneously and the history of the state transition is managed. A coder 18 receives A coding symbol outputted from a symbol converter 14 and a code degree number outputted from a probability estimate table 15 to implement coding outputs a code. Thus, a succeeding state transition destination suitable for the state is decided.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention sets encoding parameters and decoding parameters according to the generation status of encoded symbols or decoded symbols whose pixels are converted in encoding one image. The present invention relates to an encoding device that improves encoding efficiency by dynamically switching.

[Prior Art] FIG. 4 is a block diagram showing an encoding section in a conventional encoding device. In FIG. 4, 11 is an image input section that inputs an image pixel by pixel; 12 is a memory control section that controls a memory that stores pixel data input from the image input section 11; A context for the encoded pixel is generated from the pixel data, a predicted value and a stay state number that are updated during the encoding process are stored in the context, and the corresponding predicted value and stay state number are generated by inputting the context. 14 is a symbol converter that compares the predicted value shown in the context reference table 13 with the actual coded pixel and converts it into a coded symbol; 15 corresponds to the state of the staying state number shown in the context reference table 13; The code order, which is the index of the probability estimation, is memorized,
A probability estimation table 16 indicating the code order counts the number of occurrences of dominant symbols of the encoded symbols output from the symbol converter with respect to the code order indicated by the probability estimation table 15, and calculates the number of occurrences of dominant symbols set in the state. 18 is a symbol converter 14 that controls the count value depending on whether the symbol has been reached or not and whether an inferior symbol has occurred.
19 is a transmission line that transmits the code output from the encoder 18 to the decoding unit It is.

Furthermore, FIG. 5 is a block diagram showing a decoding section in a conventional encoding device. In FIG.

31 is a transmission path for transmitting codes from the encoding unit; 32 is a memory control unit that controls a memory that stores decoded pixel data; and 33 is a memory control unit that generates a context for decoded pixels from the pixel data stored in the memory control unit 32. A context reference table 34 stores predicted values and stay state numbers that are updated during the decoding process for that context, and indicates the corresponding predicted values and stay state numbers based on context input; 34 is a context guest reference table 33;
A probability estimation table 35 stores the index of the probability estimate value corresponding to the state of the stay state number indicated by and indicates the code order, and 35 stores the code received from the transmission path 31 and the code order indicated by the probability estimation table 34. A decoder 36 that performs decoding as an input and outputs decoded symbols counts the number of occurrences of dominant symbols of the decoded symbols output from the decoder 35 with respect to the code order indicated by the probability estimation table 34, and changes the number of dominant symbols to that state. A counter 38 controls the count value depending on whether a set count number has been reached and whether an inferior symbol has occurred. Pixel converter for comparing and converting into pixels, 39
is an image output unit that receives pixels converted by the pixel converter and outputs them as an image.

Next, the operation will be explained.

First, the operation of the encoding section in a conventional encoding device will be explained. The image input section 11 inputs nine images pixel by pixel and sequentially sends them to the memory control section 12 and symbol converter 14. The memory control unit 12 stores the processed pixels in the memory and outputs the pixels requested by the context reference table 13. The context reference table 13 generates a context for a coded pixel from the pixel data stored in the memory control unit 12, and indicates a stay state number and predicted value for the context.

The symbol converter 14 converts the pixel input from the one-image input unit 11 and the predicted value shown in the context reference table 13 into encoded symbols represented by their match/mismatch (hereinafter, the encoded symbols in the case of a match are referred to as dominant symbols). Convert to a dominant symbol, and in the case of a mismatch, a recessive symbol). The probability estimation table 15 stores the code order, which is the index of the probability estimate value corresponding to the state of the stay state number indicated by the context reference table 13, and indicates the code order. The counter 16 is prepared for each code degree indicated by the probability estimation table 15, and calculates the number of dominant symbols converted by the symbol converter 14, and when a count value set for the code degree is reached or an inferior symbol occurs. In this case, reinitialize the context reference table 13.
If the encoded symbol is a dominant symbol, the code order corresponding to the context within is updated by a predetermined step up, and if the coded symbol is a recessive symbol, it is updated by a predetermined step down. However, if the code degree is the maximum, the code degree is left as is, and if it is the minimum, the code degree is left as is and the predicted value is updated.

The encoder 18 receives the encoded symbols output from the symbol converter 14 and the code order output from the context reference table 13, performs encoding, and outputs a code. The output code is transmitted to the decoding section through the transmission path 19.

Next, the operation of the decoding section in the conventional encoding device will be explained. The code output from the encoder is transmitted through transmission path 3.
Received from 1. The memory control unit 32 stores the decoded pixels in the memory and outputs the pixels requested by the context reference table 33. Context reference table 3
3 generates a context for a decoded pixel from the pixel data stored in the memory control unit 32, and indicates a staying state number and predicted value for the context.

The probability estimation table 34 is the context reference table 3
The code order, which is the index of the estimated probability value corresponding to the state of the stay state number indicated by 3, is stored.

Indicates its code order. The decoder 35 receives the code received from the transmission path 31 and the code order outputted from the probability estimation table 34 and performs decoding.

Output the decoded symbols. The counter 36 is prepared for each code degree indicated by the context reference table 33,
When the dominant symbol decoded by the decoder 35 is decoded, the code degree corresponding to the context in the context reference table 33 is increased by a predetermined step if the encoded symbol is a dominant symbol, and the code degree corresponding to the context in the context reference table 33 is increased by a predetermined step, and the code order is increased by a predetermined level for the inferior symbol. If so, update it by lowering it by a predetermined level. However, if the code degree is the maximum, the code degree is left as is, and if it is the minimum, the code degree is left as is and the predicted value is updated. Pixel converter 38
converts the decoded symbol decoded by the decoder 35 into a pixel, and if the decoded symbol is a dominant symbol, the predicted value indicated by the context reference table 33 is used as the pixel value, and if the decoded symbol is an inferior symbol, the value other than the predicted value is used as the pixel value. value. The image output unit 39 outputs the pixels converted by the 9-pixel converter 38 as an image.

FIG. 6 is an explanatory diagram of the state transition of a conventional encoding device, for example, IBM J, RES, DEVELOP, VOL.
32 No.

6 NOVEMBER 1988, page 756. FIG. 6 shows an example of a logarithm of 6, where the circles in FIG. 1 indicate the states and the numbers within the 2 circles indicate the code order of the states. The code order is a number for identifying groups in which coded symbols and decoded symbols are divided by their probability of occurrence, and the smaller the code order, the smaller the probability of occurrence. In FIG. 6, one state corresponds to one code order. When the counter count value of the dominant symbol that has occurred in the state is reached, the state transitions according to the arrow M in the figure, and when an inferior symbol occurs, the state transitions along the arrow in the diagram, and in Figure 6, the code order changes by one step. are doing. When changing the state, if the code degree is the maximum, the code degree is left unchanged, and if the code degree is the minimum, the code degree is left unchanged and the predicted value is updated.

[Problem to be solved by the invention] Since the conventional encoding device is configured as described above,
The next code order is determined depending on the current code order and whether the symbol that has appeared is a dominant symbol or a recessive symbol. In addition, when multiple contexts share the same counter, even if contexts with the same code degree have different trends in increasing or decreasing the code degree, the transition paths overlap, canceling out the trends and causing the state to change. There was a problem that the transition became inappropriate.

This invention was made in order to solve the above-mentioned problems.Even if the code degree is the same, by assigning different states in consideration of the history of past transitions, it is possible to solve the problem in contexts where the tendency of increase/decrease in the code degree is different. The object of the present invention is to obtain an encoding device that performs state transitions suitable for past trends in increase/decrease in code order by varying the transition paths.

[Means for Solving the Problem] The encoding device according to the claimed invention is such that the code orders of contexts corresponding to encoded symbols during encoding or decoded symbols during decoding are the same. In addition, the increase/decrease tendency of the probability is set as a separate state depending on the past transition history, so that the state transition path is independent, and a more suitable state transition destination can be determined based on the past transition.
When multiple contexts share the same counter, the next state transition destination suitable for that state can be determined by transitioning the contexts with the same state transition history along the same route. 6 [Operation] Even if the code order of the context corresponding to the encoded symbol during encoding or the decoded symbol during decoding is the same, the encoding device in the claimed invention increases or decreases the probability thereof. The trend is set as a separate state depending on the past transition history, the state transition path is made independent, and a more suitable state M destination is determined based on the past transition.
When multiple contexts share the same counter, by transitioning the contexts with the same state transition history along the same route, it is possible to determine the next state transition destination suitable for that state.

"Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an encoding section in an encoding device. In FIG. 1, numeral 57 is determined from the coded symbol and the stay state number indicated by the context reference table 13 when the counter is reinitialized. History management that updates the staying state number for the context generated in the context reference table 13 in the next state of that state, updates the predicted value for the context at the same time when predicted value conversion is instructed, and manages the history of the state transition. It's a table. Other parts are the same as those shown in FIG. 4 with the same reference numerals.

Further, FIG. 2 is a block diagram showing a decoding section in the encoding device. In FIG. 2, 77 is determined from the decoded symbol and the staying state number indicated by the context reference table 33 when the counter 36 is reinitialized. A history that manages the state transition history by updating the staying state number for the context generated by the context reference table 33 in the next state of that state, and simultaneously updating the predicted value for the context when the predicted value conversion is instructed. This is a management table. Other parts are the same as those shown in FIG. 5 with the same reference numerals.

Next, the operation will be explained.

First, the operation of the decoding section in the encoding device will be explained. The image input section 11 inputs one image pixel by pixel and sequentially sends it to the memory control section 12 and symbol converter 14. The memory control unit 12 is.

Processed pixels are stored in memory and necessary pixel data is indicated in a context reference table 13. The context reference table 13 generates a context for a coded pixel from the pixel data stored in the memory control unit 12, and indicates a stay state number and predicted value for the context. The symbol converter 14 converts the pixels input from the one-image input unit 11 and the predicted values indicated by the context reference table 13 into coded symbols. Probability estimation table 15
indicates the code order corresponding to the stay state number indicated by the context reference table 13. The counter 16 is prepared for each state corresponding to the stay state number indicated by the context reference table 13, and counts the number of dominant symbols converted by the symbol converter 14, and counts the number of dominant symbols converted by the symbol converter 14 when the count number set for that state is reached and the counter 16 counters the inferior symbol. Reinitializes the count value when this occurs. The history management table 57 contains encoded symbols (dominant symbols, inferior symbols) for each state.
It stores the state number to which the next transition should be made, updates the staying state of the context generated in the context reference table 13 to the next state, and updates the predicted value for the context at the same time when predicted value conversion is instructed. ,
Manage the history of state transitions. The encoder 18 receives the encoded symbols output from the symbol converter 14 and the code order output from the probability estimation table 15, performs encoding, and outputs a code. The output code is transmitted from the transmission line 19 to the decoding section.

Next, the operation of the decoding section in the encoding device will be explained. The code output from the encoding section is.

It is received from the transmission path 31. The memory control unit 32 stores decoded pixels in the memory and indicates necessary pixel data in a context reference table 33.

The context reference table 33 generates a context for a coded pixel from the pixel data stored in the memory control unit 32, and indicates a traffic congestion number and a predicted value for the context. The probability estimation table 34 shows the code order corresponding to the stay state number shown in the context reference table 33.

The decoder 35 inputs the code received from the transmission path 31 and the code order indicated by the probability estimation table 34, performs decoding, and outputs decoded symbols. The counter 36 is prepared for each state corresponding to the stay state number indicated by the guest reference table 33.

The number of superior symbols decoded by the decoder 35 is counted, and the count value is reinitialized when the count number set for that state is reached or when an inferior symbol occurs.

The history management table 77 stores decrypted symbols (
The state number to which the next transition should be made is stored in the context reference table 33.
The staying state of the context generated in is updated to the next state, and when predicted value conversion is instructed, the predicted value for the context is updated at the same time, and the history of state transitions is managed. The pixel converter 38 converts the decoded symbol output from the decoder 35 into a pixel, and if the decoded symbol is a dominant symbol, the pixel value is the predicted value indicated by the context reference table 33, and if the decoded symbol is an inferior symbol, it is a value other than the predicted value. Let be the pixel value.

The image output unit 39 outputs the pixels converted by the 7-pixel converter 38 as an image.

Moreover, FIG. 3 is an explanatory diagram of state transition of the encoding device of the present invention. FIG. 3 shows an example in which the number of code degrees is six, as in FIG. It is the same as Figure 6. In FIG. 3, the history of past transitions is divided into three stages, with the lower row representing the state transition, LM for interruption, and the upper stage representing the state transition through MM. When an inferior symbol occurs, the state always transitions to the lower stage. In the figure, the code degree is transitioned from the upper MM to the lower transition state, which is two steps lower.1 For example, the number of steps to lower the code degree may be determined for each transition state, as in state 15.36. can.

[Effects of the Invention] As described above, according to the present invention, even if the code orders of the contexts corresponding to the coded symbols at the time of encoding or the decoded symbols at the time of decoding are the same, Since we created separate states and made state transition paths independent based on the history of past transitions, the trend of increase or decrease in probability can be determined by changing the code degree by transitioning contexts with the same history of past transitions along the same path. This has the effect of making it possible to determine the next state transition suitable for the tendency of .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an encoding section of an encoding device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a decoding section of an encoding device according to an embodiment of the present invention. FIG. 3 is an explanatory diagram of the state transition of the encoding device according to an embodiment of the present invention, FIG. 4 is a block diagram showing the configuration of the encoding section of the conventional encoding device, and FIG. 5 is the conventional encoding device. FIG. 6 is a block diagram showing the configuration of the decoding section of the device, and is an explanatory diagram of state transition of the conventional encoding device. 11 is an image input section, 12.32 is a memory control section 13.3
3 is a context reference table, 14 is a symbol converter, 16.36 is a counter, 18 is an encoder, 19.31 is a transmission path, 35 is a decoder, 38 is a pixel converter, 39 is an image output unit, 15.34 is a probability estimation table, and 57.77 is a history management table. In addition. In the figure. Same symbols are the same. or a significant portion.

Claims (2)

[Claims] (1) Convert the pixels of the input image into encoded symbols, and create a pattern (
Hereafter referred to as context. ) In the encoding unit of the encoding device that encodes pixels by dynamically switching encoding parameters according to the occurrence situation of the value taken by the encoded pixel,
An image input section that inputs images pixel by pixel, a memory control section that controls a memory that stores pixel data input from the image input section, and encoded pixels from the pixel data stored in the memory control section. A context reference table showing the predicted value and stay state number that is updated during the encoding process for that context, and the predicted value shown on the context reference tape and the actual encoded pixel are compared. A symbol converter that converts into a coded symbol, a probability estimation table that stores a code order which is an index of a probability estimate value corresponding to a stay state number indicated by the context reference table, and indicates the code order, a stay state indicated by the context reference table. Counts the number of occurrences of dominant symbols of the encoded symbols output from the symbol converter for the state of the state number, and counts based on whether the count number set for that state has been reached and whether an inferior symbol has occurred. Based on the counter that controls the value, information on whether it is a dominant symbol or a subordinate symbol, and the content of the value of the counter, the staying state number indicated in the context reference table is updated to the state number of the next state set in advance, and predicted value conversion is performed. When instructed, the history management table simultaneously updates the predicted value for the context and manages the history of its state transition, and encodes the encoded symbol output from the symbol converter and the code order indicated by the probability estimation table as input. 1. An encoding device comprising: an encoder that performs encoding and outputs a code; and a transmission path that transmits the code output from the encoder to a decoder. (2) By decoding the received code as a decoded symbol, the decoding parameters are changed according to the occurrence status of the value taken by the decoded pixel for each context, which is the pattern taken by the reference pixel from the decoded pixel. In a decoding unit of an encoding device that decodes pixels by switching between pixels, there is a transmission path for transmitting codes from the encoding unit, a memory control unit that controls a memory that stores decoded pixel data, and a memory control unit that controls a memory that stores decoded pixel data. A context for the decoded pixel is generated from the pixel data that has been generated, and the predicted value and stay state number that are updated during the decoding process are stored in that context, and the corresponding predicted value and stay state number are generated by inputting the context. a probability estimation table that stores the code order, which is an index of the probability estimate value corresponding to the state of the stay state number indicated by the context reference table, and indicates the code order; a code received from the transmission path and the above code order; A decoder that performs decoding using the code order indicated by the probability estimation table as input and outputs a decoded symbol, and the number of occurrences of dominant symbols of the decoded symbols output from the decoder for the staying state indicated by the context reference table. A counter that controls the count value depending on whether the count value set in the state has been reached and whether an inferior symbol has occurred, information on whether the symbol is a superior symbol or an inferior symbol, and the contents of the value of the above counter. Based on this, the stay state number indicated in the context reference table is updated to the state number of the next state set in advance, and when predicted value conversion is instructed, the predicted value for the context is simultaneously updated and the history of the state transition is managed. a pixel converter that converts the predicted value generated from the context reference table into pixels according to the decoded symbol output from the decoder;
An encoding device comprising: a decoding section including an image output section that receives pixels converted by the pixel converter and outputs them as pixels.