Patent Grant
10805623
This Application is a Section 371 National Stage Application of International Application No. PCT/FR2017/050094, filed Jan. 17, 2017, which is incorporated by reference in its entirety and published as WO 2017/129880 A1 on Aug. 3, 2017, not in English.
The present invention pertains generally to the field of the coding and decoding of data.
The invention may thus in particular apply to the coding of digital images and of sequences of digital images, such as implemented in current AVC (the abbreviation standing for “Advanced Video Coding”) and HEVC (the abbreviation standing for “High Efficiency Video Coding”) video coders and their extensions (MVC, 3D-AVC, MV-HEVC, 3D-HEVC, etc. . . . ), and to the corresponding decoding.
Current video coders (MPEG, H.264, HEVC, . . . ) use a block-wise representation of the video sequence. The images are split up into blocks, which may be split up again in a recursive manner. Next, each block is coded by intra-image or inter-image prediction. Thus, certain images are coded by spatial prediction (Intra prediction), other images are also coded by temporal prediction (Inter prediction) with respect to one or more coded-decoded reference images, with the aid of a motion compensation known by the person skilled in the art.
A residual block, also called a prediction residual, corresponding to the original block decreased by a prediction, is coded for each block. The residual blocks are transformed with the aid of a mathematical transform operation, and then quantized with the aid of a mathematical quantization operation for example of scalar type. A one-dimensional list of coefficients is obtained on completion of the quantization.
The coefficients of this list are then coded in the form of bits by an entropy coding whose aim is to code the coefficients without loss.
The bits obtained after entropy coding are written into a data signal or stream which is intended to be transmitted to the decoder.
In a manner known per se, such a signal comprises:
Once the stream has been received by the decoder, the decoding is done image by image, and for each image, block by block. For each block, the corresponding elements of the stream are read. The inverse quantization, the inverse scan operation, and the inverse transform of the coefficients of the blocks are performed so as to produce the decoded prediction residual. Next, the prediction of the block is calculated and the block is reconstructed by adding the prediction to the decoded prediction residual.
More particularly during data coding of HEVC type, the aforementioned entropy coding, which may be for example of arithmetical or Huffman type, is performed in the following manner:
A drawback of such a coding is that the coded data signal to be transmitted to a decoder contains a non-negligible number of data, thus not making it possible to optimize the reduction in the compression gain of the coded data. This results in unsatisfactory compression performance.
One of the aims of the invention is to remedy the drawbacks of the aforementioned prior art.
For this purpose, a subject of the present invention relates to a method for coding data in the form of a data signal, which is noteworthy in that, for a current data set, it implements the following:
Such a provision advantageously makes it possible to apply on coding a technique for omitting data to a large number of data contained in a data set to be coded, as a function of the value of an information item representative of a characteristic of the coded data of this set, which information item will allow the decoder to retrieve all the data which were omitted during coding. It is thus possible, by hiding these numerous data, to substantially reduce the signaling cost.
Such an information item representative of a characteristic of the coded data of said data set consists for example in the number of coded data, in the parity of the sum of coded data, in the size of the set of coded data, in the number of non-zero data of this set.
In a particular embodiment, the coding method according to the invention comprises, subsequent to the coding of the data of the data set, with the exception of the at least one data item of the set, the following:
Such a provision allows the coder to resolve the conflict which may appear on completion of the comparison, in the case where the first and second characteristics of the decoded data are both equally compatible with the information item representative of a characteristic of the coded data.
For this purpose, the coder simulates a first type and a second type of decoding of the coded data contained in the signal part, so as to select, from among the first and the second type of decoding, the one which is compatible with the information item representative of a characteristic of the coded data.
In an advantageous manner, an information item representative of this selection is inserted into the data signal to be transmitted to the decoder.
Correlatively, the invention further relates to a device for coding data in the form of a data signal, which is noteworthy in that it comprises a processing circuit which, for a current data set, is designed to:
In a corresponding manner, the invention relates to a method for decoding a coded data signal, which is noteworthy in that, for at least one part of the signal, it implements the following:
Such a provision advantageously allows the decoder to reconstruct in an autonomous manner all the data associated with the at least one signal part which have not been coded and which have been omitted by the coder, by virtue:
The information item representative of a characteristic of the coded data which are contained in the at least one signal part can according to the coding/decoding context:
In a particular embodiment, the selection of the first or of the second value of the at least one data item which is necessary for the decoding of the data of the at least one signal part is implemented:
The decoder thus implements a comparison of the information item representative of a characteristic of the coded data which are contained in the at least one signal part with the results of at least two possible combinations of decoding of the data of the at least one signal part, so as to select the correct combination, that is to say the one which is the most compatible with this information item.
In a particular embodiment, in the case where each of the first and second characteristics of the decoded data is equal to the information item representative of a characteristic of the coded data which are contained in the at least one signal part, the selection of the first or of the second value of the at least one data item which is necessary for the decoding of the data of the at least one signal part is implemented by determining, in the at least one signal part, an information item representative of the selection to be applied between the first or the second value.
Such a provision advantageously allows the decoder to identify directly in the at least one signal part received, the correct decoding combination to be applied.
Correlatively, the invention further relates to a device for decoding a coded data signal, which is noteworthy in that it comprises a processing circuit which, for at least one part of the signal, is designed to:
The various aforementioned modes or characteristics of embodiment can be added independently or in combination with one another, to the operations implemented in the course of the decoding method such as is defined hereinabove.
The invention also envisages a computer program comprising instructions for the execution of the steps of the coding or decoding method hereinabove, when the program is executed by a computer.
Such a program can use any programming language, and be in the form of source code, object code, or of code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.
Yet another subject of the invention also envisages a recording medium readable by a computer, and comprising instructions of computer programs such as mentioned hereinabove.
The invention also envisages a recording medium readable by a computer on which is recorded a computer program, this program comprising instructions suitable for the implementation of the coding or decoding method according to the invention, such as are described hereinabove.
The recording medium can be any entity or device capable of storing the program. For example, the medium can comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, a USB key, or a magnetic recording means, for example a hard disk.
Moreover, the recording medium can be a transmissible medium such as an electrical or optical signal, which can be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network of Internet type.
Alternatively, the recording medium can be an integrated circuit into which the program is incorporated, the circuit being suitable for executing or for being used in the execution of the aforementioned coding or decoding method.
Other characteristics and advantages will become apparent on reading a preferred embodiment described with reference to the figures in which:
Generally, the present invention applies to the coding of various types of digital data, such as for example audio data, image data or else video data.
According to one embodiment of the invention, the method for coding data which will now be described is used to code an image according to a binary data signal close to that obtained by a coding compliant with any one of the current or forthcoming video coding standards.
In this embodiment, the coding method according to the invention is for example implemented in a software or hardware manner by modifications of a coder initially compliant with the HEVC standard. The coding method according to the invention is represented in the form of an algorithm comprising steps C1 to C6 such as represented in
According to the embodiment of the invention, the coding method according to the invention is implemented in a coding device CO represented in
As illustrated in
On initialization, the code instructions of the computer program PG_C are for example loaded into a RAM memory, MR_C, before being executed by the processing circuit CT_C.
The coding method represented in
In the course of a step C1 represented in
It should be noted that in the sense of the embodiment described here, the term “block” signifies coding unit. The latter terminology is in particular used in the HEVC standard “ISO/IEC/23008-2 Recommendation ITU-T H.265 High Efficiency Video Coding (HEVC)”.
In particular, such a coding unit groups together sets of pixels of rectangular or square shape, also called blocks or macroblocks.
Such a coding unit could, in a future standard, also group together sets of pixels exhibiting other geometric shapes.
Said blocks B1, B2, . . . , Bi, . . . , BR are intended to be coded according to a predetermined order of scan, which is for example of the lexicographic type. This signifies that the blocks are coded one after another, from left to right, and then from top to bottom.
Other types of scan are of course possible. Thus, it is possible to split the image ICj into several sub-images called slices and to apply a splitting of this type to each sub-image independently. It is also possible to code not a succession of lines, as explained hereinabove, but a succession of columns. It is also possible to scan the lines or columns in either direction.
Moreover, each block can itself be divided into sub-blocks which are themselves subdivisible.
In the course of a step C2 represented in
In the course of a step C3 of
In the example described here, data is intended to mean the pixels of the current block Bi.
It should however be noted that data is also intended to mean the pixels of a predicted block obtained with the aid of a prediction of the current block Bi with respect to a predictor block which is selected subsequent to setting various inter, intra or other predetermined modes of prediction into competition, for example by minimizing a distortion bitrate criterion well known to the person skilled in the art.
In a manner known per se, as a function of the context or of the coding standard used, such a transform is for example a transform of DCT (the abbreviation standing for “Discrete Cosine Transform”), DST (the abbreviation standing for “Discrete Sine Transform”) type, of DWT (the abbreviation standing for “Discrete Wavelet Transform”) type or else of LT (the abbreviation standing for “Lapped Transform”) type. These transforms are stored previously in a list LTS, in the buffer memory MT_C of the coder CO of
On completion of step C3, a transformed data block Bti is obtained.
Such an operation is performed by a transform calculation device MTR_C, such as represented in
In the course of a step C4 represented in
Step C4 is implemented by a quantization device MQ_C such as represented in
In the course of a step C5 represented in
More particularly during data coding of HEVC type, which may be for example of arithmetical or Huffman type, the data of the quantized block Bqi that are able to be coded are determined in the following manner:
In the course of a sub-step C51 of
According to the invention, the choice of said at least one data item of the quantized block Bqi not to be coded is predetermined at the coder.
For example, in the case of an HEVC coding, said at least one data item which is not coded is for example the first syntax element “greater_than_one”. According to the coding context, a predetermined choice such as this may pertain to the second syntax element “greater_than_one”, the first two syntax elements “greater_than_one”, etc. . . .
In the example represented, it is considered that the first syntax element “greater_than_one” has a value V1.
Alternatively, it may be the syntax element “greater_than_two”, the syntax element “significant_coeff”, the syntax element “remaining_level” or else the syntax element “sign”. In an alternative embodiment, it may be another syntax element, such as an intra prediction mode, an intra or inter prediction mode indicator, or else a motion vector.
According to the invention, in the course of a sub-step C52 of
According to an example, the syntax elements determined during the coding of the quantized block Bqi are counted and their number constitutes the “reference_trace” information item.
By way of variant, the “reference_trace” information item can indicate:
Subsequent to sub-step C52, in the course of step C6 of
Step C6 is implemented by a data signal construction device MCF, such as represented in
The data signal part Fi is thereafter delivered via the output SOR_C of the coder CO of
In a manner known per se, the data signal part Fi furthermore comprises certain information encoded by the coder CO, such as the type of prediction (Inter or Intra) which has been optionally applied, and if relevant, the prediction mode selected, the index of the predictor block selected, the reference image index and the motion vector that are used in the mode of Inter prediction, an index IT associated with the transform applied in the course of the aforementioned step C3.
Furthermore, in step C6, according to a possible embodiment, the “reference_trace” information item is inserted, in compressed form or not, into the signal part According to an alternative embodiment, the “reference_trace” information item is not inserted into the signal part Fi.
The coding steps C1 to C6 of
According to an optional embodiment represented in
Such a step is implemented by a decoding device MD_C represented in
In the course of a step C502 of
Steps C5021 and C5022 can be implemented in any order.
In the course of a step C503 of
In the case where the quantity of syntax elements Q1 is different from the quantity Q2 of syntax elements, in the course of a step C504a) of
In the case where the quantities Q1 and Q2 of syntax elements are both equal to the “reference_trace” information item, in the course of a step C504b) of
In the example represented, it is the first value V1 of the syntax element “greater_than_one”.
Steps C503 and C504a)/b) are implemented by a calculation device CAL_C represented in
In the course of a step C505 of
We shall now describe an illustration of the optional embodiment described in
For example, on the basis of the “reference_trace” information item, the decoding device MD_C of
In the course of step C501, are then generated 24 possible combinations of decoding values of the data of the block Bqi, i.e. sixteen values V1, V2, . . . , V16, such as for example:
For example, it is assumed that among these sixteen possible decoding values, it is the value V7, such as for example V7={0,1,1,0}, which allows error-free reconstruction of the data of the quantized block Bqi.
In the course of step C502 of
In the course of step C503 of
If the sixteen quantities of syntax elements are all different, in the course of step C504a) of
If at least two quantities of syntax elements are equal, for example Q2 and Q7, in the course of step C504b) of
In this case, in the course of step C505 of
Detailed Description of the Decoding Part
Generally, the present invention applies to the decoding of a signal of various type of coded digital data, such as for example audio data, image data or else video data.
According to one embodiment of the invention, the decoding method which will now be described is used to decode a data signal representative of an image or of a sequence of images, said signal being able to be decoded by a decoder compliant with any one of the current or forthcoming video decoding standards.
In this embodiment, the decoding method according to the invention is for example implemented in a software or hardware manner by modifications of such a decoder, complying for example with the HEVC standard.
The decoding method according to the invention is represented in the form of an algorithm comprising steps D1 to D10 such as represented in
According to this embodiment, the decoding method according to the invention is implemented in a decoding device or decoder DO represented in
As illustrated in
On initialization, the code instructions of the computer program PG_D are for example loaded into a RAM memory, MR_D, before being executed by the processing circuit CT_D.
The decoding method represented in
For this purpose, information items representative of the current image ICj to be decoded are identified in the data signal ϕ received at the input ENT_D of the decoder DO and such as is delivered on completion of the coding method of
With reference to
Such a determination step D1 is implemented by a stream analysis identification device MI_D, such as represented in
In the example represented, the blocks B1, B2, . . . , Bi, . . . , BR to be decoded are for example of size 4×4 pixels.
In the course of a step D2 represented in
In the course of a step D3 represented in
Step D3 is implemented by a decoding device MD_D represented in
More particularly during data decoding of HEVC type, which may be for example of arithmetical or Huffman type, the “reference_trace” information item indicates for example the number of syntax elements which have been determined in the coding sub-step C51 of
By way of variant, the “reference_trace” information item can indicate:
According to a possible embodiment, the “reference_trace” information item is read directly in the signal part Fi, and then optionally decompressed if this information item was compressed on coding.
According to an alternative embodiment, the “reference_trace” information item is deduced in an autonomous manner by the decoding device MD_D. Such a deduction is for example implemented in the case where the decoder DO decodes the last block BR of the current image ICj. Indeed, in this specific case, and if the “reference_trace” information item indicates the number of syntax elements determined on coding for the block BR, the number of syntax elements to be decoded contained in the corresponding signal part F1R of the coded data signal ϕ corresponds to the number of syntax elements that remain to be decoded in the signal ϕ.
In the course of a step D4 represented in
Such a data item necessary for the decoding of the data contained in the set Ei is, in the example represented of an HEVC decoding, the first syntax element “greater_than_one” which has the value V1.
In a manner corresponding to the coder, the choice of such an at least one syntax element is predetermined at the decoder. According to the coding context, a predetermined choice such as this may pertain to the second syntax element “greater_than_one”, the first two syntax elements “greater_than_one”, etc. . . .
Alternatively, it may be the syntax element “greater_than_two”, or else the syntax element “significant_coeff”. In an alternative embodiment, it may be another syntax element, such as an intra prediction mode, an intra or inter prediction mode indicator, or else a motion vector.
In the course of a step D5 of
Steps D51 and D52 can be implemented in any order.
In the course of a step D6 of
Step D6 is implemented by a calculation device CAL_D represented in
With reference to
At D61, the calculation device CAL_D compares the quantity of syntax elements Q1 and the quantity of syntax elements Q2 with the “reference_trace” information item.
In the case where the quantities of syntax elements Q1 and Q2 are different:
In the example represented, the value selected is the value V1 of the syntax element “greater_than_one”.
In the case where the quantity of syntax elements Q1 and the quantity of syntax elements Q2 are both equal to the “reference_trace” information item, at D62b), the decoding device MD_D of
The decoding device MD_D then transmits the information item “combination_id” to the calculation device CAL_D or else the calculation device CAL_D requests this information item from the decoding device MD_D, when the quantity of syntax elements Q1 and the quantity of syntax elements Q2 are both equal to the “reference_trace” information item.
In the course of a step D7 of
On completion of step D7, there is then reconstructed the block of quantized coefficients Bqi which was obtained on completion of the quantization step C4 of
We shall now describe an illustration of the decoding method which has just been described hereinabove.
In step D3, the information item representative of a characteristic of the data set Ei which is determined is for example the “reference_trace” information item.
In the course of step D4 of
In the course of step D4, are then generated 24 possible combinations of decoding values of the data of the block Bqi, i.e. sixteen values V1, V2, . . . , V16, such as for example:
In the course of step D5 of
In the course of step D61 of
In the case where the sixteen quantities of syntax elements are all different from one another, in the course of step D62a) of
In the course of step D63a) of
In the case where at least two quantities of syntax elements are both equal to the “reference_trace” information item, for example Q2 and Q7, in the course of step D62b), the decoding device MD_D of
In the course of step D7 of
In the course of a step D8 of
Step D8 is implemented by means of an inverse quantization device MQ−1_D, such as represented in
In the course of a step D9 represented in
On completion of step D9 there is obtained a block BDi of decoded data. In the example described here, data is intended to mean the pixels of the decoded block BDi.
It should however be noted that data is also intended to mean the pixels of a decoded residual block in the case where a prediction of the current block Bi was implemented on coding. In this case, a block BDi of decoded data is obtained after having implemented a prediction inverse to that implemented on coding.
Step D9 is implemented by a transform calculation device MTR−1_D, such as represented in
In the course of a step D10 represented in
Such a step is implemented by an image reconstruction device URI such as represented in
The decoded image IDj is then delivered via the output SOR_D of the decoder DO of
The decoding steps D1 to D10 which have just been described hereinabove are implemented for all the blocks B1, B2, . . . , Bi, . . . , BR to be decoded of the current image ICj considered, in a predetermined order which is for example lexicographic order.
It goes without saying that the embodiment which has been described hereinabove has been given purely by way of wholly nonlimiting indication, and that numerous modifications may easily be made by the person skilled in the art without however departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16 50758 | Jan 2016 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2017/050094 | 1/17/2017 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2017/129880 | 8/3/2017 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20190045205 A1 | Feb 2019 | US |
