FR2652214A1 - Device for coding information intended to be transmitted and/or stored after data rate reduction - Google Patents

Abstract

Device for coding information of the image type, represented, on the one hand, by input signals intended to be transmitted and/or stored after data rate reduction and, on the other hand, by first information relating to the movement between these signals, the said coding device comprising a coding stage (20). This device also comprises, for processing the said input signals of defined rank: (a) a stage (50) called stage for estimating movement by identical blocks, bounded by or within information batches, on the basis, on the one hand, of the current input signals to be processed and, on the other hand, of the signals processed during the preceding processing cycle, and also of the said first movement information, the said stage being intended to deliver second movement information; (b) a stage (40) called stage for prediction on the basis, on the one hand, of the said previously processed signals and, on the other hand, of the said second movement information, the said stage being intended, for the purposes of the coding, to deliver signals corrected by the said second movement information; (c) a stage called stage for selection of the signal to be coded. Application: system for storage of data on compact discs.

Description

 The present invention relates to a device for encoding information, and in particular two-dimensional information, arranged in batches of periodic information of the image type1 of successively odd and even ranks, represented on the one hand by signals of a determined rank intended for be transmitted and / or stored after reduction of flow, and secondly by first information relating to the movement between these signals and intended after their estimation, to be substituted, in said representation, for complementary signals of opposite rank while being related to the determined rank signals which surround them, said coding device comprising a coding stage.

 This invention finds a particularly interesting application in the case where the information to be encoded is representative of animated images and where a compact disc is used to support information transmitted and / or stored.

 The transmission and / or storage of a very large amount of information, associated for example with images, generally involve the compression of the signals to be transmitted and / or stored, that is to say a reduction in a report to be determined, of their number. The reduction ratio is determined inter alia by the fact that a sufficient quantity of signals must be kept so as not to degrade the overall information they carry, for example, in the context of the application cited, by the fact that that we must maintain an acceptable image quality.

 Most of the coding methods currently known to achieve this rate reduction are based on orthogonal transformations, of the discrete cosine transformation type, which allow a reduction of flow in a ratio of the order of 10 to 1. An example of such transformations is described in U.S. Patent No. 4,339,474. However, for a good number of applications, and for example in the application to the storage and processing of images on compact disc, this report is not sufficient.

A previous French patent application No. 8908186, filed June 20, 1989 by the applicant company, describes a signal processing device that allows for a complementary reduction treatment in a ratio of 2 to 1. I. device, intended to be d in a general manner included in a transmission and / or signal storage system which comprises on the one hand a transmission stage and, on the other hand, after transmission and / or storage of the signals transmitted on a limited bandwidth medium necessitating said rate reduction processing, a receiving and / or reading stage of the transmitted and / or stored signals, itself essentially comprises the following subsets
a motion estimation circuit between batches of signals of the same size (between successive images in the case where the signals to be transmitted and / or stored are representative of animated images)
- a temporal subsampling circuit
- a filter and spatial subsampling circuit in a 1/2 report
and a decision-making circuit for controlling, according to the output of the motion estimation circuit, the selection of one or the other of the outputs of the temporal subsampling circuit and the filtering circuit and spatial subsampling in a 1/2 report.

 In one of the embodiments described in said application, the temporal subsampling circuit (in a ratio 1/2) is a switch controlled at a frequency equal to half the repetition frequency of the input signals of the processing device. signals, and it thus eliminates one image out of two in the sequence of the image signals, for example the even images. The motion estimation circuit then acts on the non-eliminated images, the odd images in the example given, in order to find the direction of movement from one to the other of them and to allow the reconstruction of the non-image images later. As the signals are generally processed in blocks, the motion estimation circuit, more precisely, seeks for each of these blocks the direction of the movement, in order to deduce later (on reception and / or reading of the transmitted and / or stored signals) an approximation of the different blocks composing the non-transmitted images, on the one hand from the motion information thus obtained, and on the other hand from the contents of two successive images adjacent to an eliminated image.

The motion estimation circuit used comprises for example two image memories and a block correlator. Such correlators are already known, for example from the article by JR Jain and AK Jain, "Displacement measurement and its application in interframe image coding", IEEE Transactions on Communications, vol.COM-29, n012, dec.1981, pages The correlation motion estimation thus proposed has the effect of determining, for each block, eliminated images (I21, for example, in a series of images).
I1, 12, 13, 14, 15, etc ...) a displacement vector D such that one can deduce from this knowledge of D an approximation 12, 14, etc. of the image eliminated from the half-sum of the non-eliminated images which surround it, according to a relation of the following type, in the case of 12 to reconstitute between II and 13
β (X) = (1/2) (I1 (XD) + I3 (X + D)) where X is the spatial index of the current image point, I1, 12, 13 the original images, D the displacement (in image points), and Î2 the desired approximation of the intensity of the point X of the current block of the eliminated image.

Expressed in other words, this motion estimation amounts to searching for each block, represented by a current point of spatial index X, a vector D such that the expression
2
E (DFD (X, D)) for all blocks is minimal.

In said expression, DFD, which comes from the corresponding English terms, UDisplaced Frame Difference ", is the approximation error attached to the current block and equivalent, for that block, to the sum of the squares of the approximation errors on all the points of the block, so this approximation error has the expression
E (I2 (X) - (1/2) (I3 (X + D) + Ii (xD))) 2,
(blocks) and it is this expression whose minimal value is sought. The displacement vector selected is the one that is associated with this minimum value, after a comprehensive test of all possible motion vectors in a search range delimited by horizontal and vertical values
Dx and Dy respectively.

 In the processing device described, the normal mode of operation is that of the block motion estimation, which allows a subsequent motion compensation and is therefore called compensated mode (English, Scompensated mode *). However, the motion estimation circuit may be faulty (noise too large, movement too fast causing this circuit to come out of its operating range, objects with contradictory movements, etc.) and, in such situations, the circuit spatial filtering and subsampling replaces it. The normal operating mode is thus replaced, in this case, by an uncompensated mode called fallback mode (in English, "fall-back mode *).

 This spatial filtering and subsampling circuit, which replaces the motion estimation circuit when the compensated mode switches to a fallback mode, comprises, in the example described, a spatial filtering circuit limiting the bandwidth of the circuits. signals, then two parallel channels, the first of which comprises a first spatial subsampling circuit in a ratio 1/2 (line sub-sampling, orthogonal subsampling, etc.) and the second circuit comprises a circuit delay (equal to the period of the input signals) and a second spatial subsampling circuit in a ratio 1/2, similar to or complementary to that made by the first. A signalman finally selects one of the outputs of these first and second spatial subsampling circuits, so as to deliver, from the samples of two successive images, a complete image, at the frequency half of that of the signals input, obtained by mixing two previously filtered images.

 The criterion of failure of the motion estimation circuit is controlled by a decision circuit which determines, in parallel channels, what would be on the one hand the motion-compensated interpolation error, in the case, in the case of a compensated mode operation, and secondly, similarly, the error in fallback mode. Following these calculations in parallel, a comparison of the two results leads to selecting the lowest result and to deliver for each image block corresponding mode information, indicating that this block will be transmitted and / or stored in mode compensated, or on the contrary in fallback mode, without eliminating one image out of two in the latter case.

 The signal processing method described in the cited application, and whose essential characteristics have just been recalled with the aid of a description of its implementation, thus makes it possible to remedy the shortcomings noted in terms of reduction of flow, with most current signal coding methods.

 However, by associating with these now traditional methods the method thus described, it appears that simplifications of the signal processing, associated with new possibilities for reducing the flow rate, can be implemented.

 The object of the invention is to provide a signal coding device that allows a simple and economical way of reducing the amount of information to be transmitted more than in the case of previous embodiments.

For this purpose, the invention relates to a coding device characterized in that it also comprises, for the processing of said signals of determined rank
(a) a so-called motion estimation stage with identical blocks delimited by or within said information batches of said determined rank, starting on the one hand from the current signals to be processed and on the other hand from previously processed signals; , and also said first motion information located between these current signals and these previously processed signals, said circuit being intended to deliver second motion information
(b) a so-called prediction stage starting from a part of said previously processed signals and secondly from said second movement information, said circuit being intended to deliver, for encoding purposes, signals corrected by said second movement information
(c) a so-called selection stage of the signal to be coded.

 Classical motion estimators have a fairly long computation time. Thanks to the structure proposed here, a simplification of the signal processing is obtained by taking advantage of the fact that a motion estimation concerning the input signals of the present coding device has already been carried out, and that of this motion estimate can be deduced, according to the invention, new motion information to change the conditions of the coding process in the desired direction of a reduction in the calculation time and also the flow.

 In an embodiment that is both simple and advantageous, the motion estimation stage comprises a first subassembly for determining an intermediate vector from said first motion information and a second correction sub-set of the motion estimation stage. value of this intermediate vector, delivering said second motion information. These first and second subassemblies may for example each comprise an addressing circuit, a subtractor, a squared elevator, an adder and a comparator.

 Preferably, the so-called previously processed signals are supplied to the prediction stage by a so-called reconstruction stage connected in parallel in the coding stage and executing the inverse operations of those already executed, on the input signals of said phase stage. encoding, at the point of connection to this coding stage. The reconstruction stage thus provided may for example comprise, at the output of an orthogonal transformation circuit and quantization itself provided in the coding stage, an inverse orthogonal transformation and quantization circuit followed, in series, by a circuit for reconstituting the signal present before selection of the signal to be encoded and of a memory. The size of this memory is, in general, intended to contain one of the batches of periodic information of successively even and odd ranks, an image in the case of the particular application cited.

 In the simplest embodiment of the coding device according to the invention, the selection stage is a subtracter. In an alternative embodiment providing an energy test on the input signals, this selection stage is an inter / intra decision circuit.

 In another important variant embodiment, in which said signals of determined rank are intended to be transmitted in two distinct modes and are accompanied by corresponding additional information indicating this mode, the signal reconstitution circuit comprises a switch controlled by said additional information. , a switchman and, in parallel between this switch and this switch, two separate processing channels according to said corresponding additional information. In the case of this variant, the selection stage is preferably an inter / intra decision circuit, and one of the processing channels is split into two distinct parallel processing channels according to said decision.

The features and advantages of the invention will now appear more precisely in the description which follows and in the accompanying drawings, given as non-limiting examples and in which:
FIG. 1 shows a first exemplary embodiment of the coding device according to the invention
FIG. 2a illustrates for an image block the principle of interpolation with motion compensation
FIG. 2b shows an example of associating a neighborhood of blocks, in an untransmitted image, with a block of the following image transmitted
FIG. 2c illustrates the principle of approximate determination of new motion information
FIG. 3 shows an exemplary embodiment of the motion estimation stage delivering these new motion information.
FIG. 4 illustrates the principle of correction of the movement information obtained as a result of said approximate determination
FIGS. 5 and 6 show two other embodiments of the coding device according to the invention
FIG. 7 shows another exemplary embodiment of a coding device
FIG. 8 illustrates, in the case of signals U, the spatial subsampling processing performed on the color difference U and V signals constituting the chrominance component; ;
FIG. 9 shows an exemplary embodiment of the motion estimation stage of the coding device of FIG. 7.
FIGS. 10 and 11 show two exemplary embodiments of a decoding device corresponding respectively to the coding device of FIG. 6 and that of FIG. 7.

 The following description is made first with reference to FIG. 1. It will first be assumed that, in the case of the application described here by way of nonlimiting example, it is desired to transmit and / or record sequences of images. animated non-interlaced luminance format (consisting of 288 lines of 352 pixels per line per image), and including both the U and V chrominance components (also 352 x 288 pixels), at the original frequency of 25 hertz, with a desired bit rate of 1.2 Mbit / second. It is also assumed that these original images were, as regards their luminance component, processed according to the principle of subsampling described in the aforementioned French patent application No. 8908186, and recalled above.

 The preliminary realization of this treatment therefore leads to having now, for the luminance, on the one hand image blocks classified into so-called compensated blocks or so-called folding blocks according to whether they will be transmitted and / or stored in compensated mode or in fallback mode, and on the other hand displacement vectors associated with these blocks. The displacement vectors are associated with each block, of size pxq for example, even rank images then eliminated (this choice is given only as an example, and one could also choose to transmit the even images and eliminate odd pictures). The classification into compensated blocks or fallback blocks can be performed on blocks of different size from the previous ones, which will be noted p 'x q' for example.

 In the case of the particularly interesting application where the signals to be encoded include information representative of animated images with one or more compact disks as support for transmitted and / or stored signals, the best results have been obtained for p = q = 16 and p '= q' = 8. But this assumption is by no means restrictive and the processing described below is applicable to other block sizes as well as other image formats.

 It will also be assumed, in the example described with reference to FIG. 1, that the information available at the input of the coding device is only moving compensation blocks, and it will be generalized later in the case where this information includes blocks. fallback. These input signals, in the case of a luminance component of image signals, correspond here to successive images at a frequency of 12.5 Hz, divided into blocks of 8 × 8 image points, and respectively accompanied by displacement vectors D constituting first motion information.

 The coding device of FIG. 1 comprises a so-called selection stage, in this case a subtracter 10, the output of which is connected to a stage constituting the coding string proper. This coding chain itself comprises, here, an orthogonal and quantization transformation circuit 21 (delivering a block classification information C according to their activity generally defined using thresholds, as a function of subjective tests related to the contrasts, to the greater or lesser uniformity, etc ...), a variable length coding circuit 22, a buffer memory 23 delivering with a constant bit rate the coded signals Sc, and a flow control circuit 24 (delivering information N of nor -malization). The auxiliary information C and N are transmitted, because they will be used on reception, during inverse orthogonal transformation and quantization operations. An example of such a coding chain is described, for example, in the aforementioned US-A-4394774 patent or, in an even more advantageous embodiment, in the French patent application filed on September 29, 1987 under the name of Registration 8713429.

 The subtractor 10 receives on the one hand the input signals of the device, constituted here by image blocks B compensated in motion, and on the other hand the output B 'of a stage 40 called prediction, and sends to the input of the circuit 21 of the coding chain the difference between this motion-compensated block B received as an input signal and the signal B 'which is a predicted block as indicated below. Thus, the encoding chain, instead of successively coding all the blocks of an image li, then all the blocks of an image I3, only encodes the difference between these images. More precisely, this inter-coding process -image is equivalent to coding, for each block of the images, the difference between a block B of the current image 13 and a block B 'of the image I1 previously processed and reconstructed, taking into account a displacement vector D' between B and B '. This new displacement vector D 'constitutes a second motion information.

 The predicted block B 'is provided by the prediction stage 40 which samples in the reconstructed previous image (11, when the current image is I3) the samples of the block corresponding to B but spatially shifted from the vector D' and called BR . These reconstructed blocks BR are in this case provided by a reconstruction stage 30, here comprising, in series and at the output of the orthogonal transformation and quantization circuit 21, a circuit 31 for inverse orthogonal transformation and quantization, a circuit 32 for reconstituting the signal present before the selection of the signal to be effectively encoded (also receiving the input D 'and the output B' of the prediction stage 40 and performing the operation opposite to that performed by the selection stage 10), and a image memory 33.It is the output of this image memory 33 which is connected to the prediction stage 40 to provide it with the blocks BR. The vectors D 'constituting the second motion information are provided by a so-called motion estimation stage 50 operating as indicated now.

 The prediction stage 40 is here, in fact, an addressing circuit of the memory 33 as a function of the displacement vectors D 'supplied by the motion estimation stage 50. This prediction stage may include, at the Following the addressing circuit, a so-called prediction filter, intended in particular to improve the prediction and coding. The circuit 32 of the reconstruction stage 30 is, in the example described, an adder followed by an addressing circuit for writing in the memory 33.

It has previously been considered that at each block B2 (of size pxq for example) even images 12, I4, etc., eliminated (and then interpolated), were associated with a displacement vector D, represented in the diagram of FIG. (which, to illustrate this principle in general, shows three successive images 12n-1 'I2nr 12n + 1> as well as, in images I1 and I3 (then coded) surrounding 12, the corresponding blocks B1 and B3 taking into account this D. If we consider (see FIG. 2b representing a sequence of images I2n-I1 I2n1 I2n + 1
I2n + 2) in the transmitted image to be encoded, for example, a block B2n + 1r B3 for example, of size p 'x q', it is possible to associate with this block B3 any neighborhood composed of nii blocks B2n (B2 for example, with i varying from 1 to n) in the division of the image 12n into blocks of size px q. It is then probable that the displacement vector, denoted D ', which represents the movement of the block B3 between the image I1 and the image
I3 is close to twice one of the vectors Di associated with blocks B2 (see Figure 2c).

The motion estimation stage 50 therefore has the function of testing each of these vectors Di and of determining the best of them, then of making a correction on this selected vector. The stage 50, represented in FIG. 3, comprises on the one hand a first subset 51 of vector determination. This subset 51, which performs the test function, must determine that of the vectors Di which minimizes the expression E (I3 (x) - I1 (x-2Di)) Z for each block of size p 'x q', I3 (x) being the current image and I1 (x-2Di) the reconstructed and shifted image of -2Di, and includes successively for this purpose
an addressing circuit 510, which takes from the image memory 33 the samples of the reconstructed image ji corresponding to those of the block B3 and shifted by (-2Di), for the vector Di considered
a subtractor 511, which makes the difference between I3 (x), current image, and I1 (x-2Di), reconstructed and offset image
a square elevator 512 of the difference thus obtained
an adder 513, over the entire block B3, squared differences thus obtained
a comparator 514, which determines that of the vectors Di thus leading to the weakest result, this selected vector being noted D'int.

The stage 50 further comprises a second subset 52 of vector correction. This subassembly 52, intended to perform a correction of + 1 pixel (see FIG. 4) on each component of the vector D'int selected by the subset 51, successively comprises elements 520 to 524 similar to the elements of subassembly 51, except that the addressing circuit 520, instead of receiving the different vectors Di to be tested, receives
From int and apply to it the eight different correction possibilities of + 1 picture element (as shown in the neighborhood example of Figure 2c). This time, at the output of the comparator 524, and hence of the motion estimation stage 50, the vector D 'is obtained which is used to make the prediction on the block B3.In general, each comparator, 514 or 524, compares results in pairs and selects the lowest, but it could also ensure the interim storage of all results before selecting one of them. It will also be specified that instead of providing two subsets 51 and 52 in series, only a single subset could be provided that first performs the vector determination function and then the vector correction function thus determined. Such a solution saves some circuits but leads in return to a slightly slower operation.

 In a second embodiment, represented in FIG. 5, of the coding device according to the invention, the selection stage is no longer a simple subtractor 10, but a circuit 100 called inter / intra decision, which is specified here. below the structure and function.

This variant embodiment is of interest when it is desired to refine the coding of the blocks by carrying out a treatment that is different according to the energy contained in the different frequency components of the current signals to be processed. The inter / intra decision circuit 100 comprises on the one hand a first circuit 101 for calculating the energy contained, by block B of the signals to be processed, in the components other than the DC component. The inter-intra decision circuit 100 also comprises a subtracter 102, receiving on the one hand the samples corresponding to a current block B on the other hand the samples corresponding to the block
B 'predicts corresponding, and followed by a second energy calculation circuit 103. This circuit 103 likewise calculates the energy contained in this sample block constituted at the output of the subtractor 102 of B and B' (still out of component keep on going). A comparator 104 then receives the output of the energy calculation circuits 101 and 103 and selects, according to the result of this comparison, one or the other of two modes of coding known as inter-image coding and intra-image coding ( inter and intra coding in the general case). In either case, an additional information Ml specifying said coding mode is transmitted, because it will be necessary, on reception, for the reconstruction of the images. This information M1 is also supplied to the signal reconstitution circuit 32 of the reconstruction stage 30.

 In a third embodiment, represented in FIG. 6, the coding device according to the invention must adapt to the fact that the motion estimation circuit which made it possible to obtain the vectors D associated with the input signals. B can, as reported, be failing.

In this case, the input information of the encoding device is no longer only moving compensation blocks, but can also be fallback blocks. An additional information M2 then accompanies, of course, this input information to indicate the nature of the blocks and the mode of operation, compensated or fallback, which made it possible to obtain them. This additional information M2 is transmitted on the one hand, since it will be necessary, on reception for the reconstruction of the images, and on the other hand supplied to the inter / intra decision circuit 100 as well as to the signal reconstitution circuit 32. of the reconstruction stage 30.

In this third embodiment, the inter / intra decision circuit 100 receives the additional information
M2, so that the coding mode is forced intra when presented at the input B of the coding device of the fallback blocks, and the reconstruction stage 30 is modified, as follows. at the output of the circuit 31, unchanged, of orthogonal transformation and inverse quantization, the circuit 32 is now replaced by a circuit 320 for reconstituting the signal present before selecting the signal to be coded, the output of this reconstitution circuit 320 being supplied to the memory 33.

 The reconstitution circuit 320 firstly comprises a switch 321, controlled by the information M2 to make the selection between a compensated mode processing and a fallback mode processing. In the case (denoted CP) of the compensated mode processing, each block, as we have seen, may be coded inter or intra, depending on the position of a switch 322 receiving the output C of the switch 321 and controlled by the information M1, and the output of this switch is then sent to a switch 323, either directly in the case of intra coding, or, in the case of inter coding, via an adder 324 which receives on a second input the output of the prediction stage 40 to add it to the output of the switch 322 present on its first input.

In the case (denoted R) of the processing in repolished mode, a spatial subsampling circuit 325 receives the output R of the switch 321 in order to keep in each folding block only the samples belonging to the current image to be reconstructed. The compensated mode blocks are similarly sampled, the intra output of the switch 322 and the output of the adder 324 being supplied to the circuit 325 for this purpose. A circuit 326 then receives the samples present on the output of this circuit 325 to interpolate the missing samples of the fallback blocks. After this interpolation, the output of the circuit 326 is sent to the switcher 323 to reinsert the blocks in fallback mode in the reconstructed image. The output of the switcher 323, on which this reconstructed image is present, is sent to the memory 33.

 In the case where the input signals of the coding device correspond to the color difference signals U and V - that is to say to the chrominance component - of the moving picture sequence, said input signals have not been subjected, like the luminance, to the preliminary carrying out of a treatment leading to a classification of the blocks of image in compensated blocks or blocks of fold. however, it is possible, as with luminance, to take into account that motion information D is available at the same time as said input signals to provide an improved coding device.

 Such a coding device is represented, in a particular embodiment, in FIG. 7. The device represented firstly comprises a spatial filtering stage 205 of the chrominance signals, comprising successively a space pre-filtering circuit 206 operating separately on the signals U and on the signals V and a spatial subsampling circuit 207. In fact, since the content of chrominance components is poorer at high frequencies than that of luminance components, a first reduction in flow is obtained by a spatial subsampling of each of the U and V signals.

 This spatial subsampling, here by a factor of 4, is represented in FIG. 8 for the U signals for example, but is similar for the V signals. In this FIG. 8, the image points of the component are represented. chrominance by the corresponding U or V symbol, and surrounded by a circle those which the subsampling retains. It can thus be seen that at a block of 4 x 4 image points of the signals U (or V, in a similar way) corresponds a block 16 × 8 in luminance (or eight 4 × 4 blocks), that is to say say that a block of 8 x 8 samples U (or V) covers the same spatial extent as a 32 x 16 block of luminance.

 More generally, the spatial subsampling of the chrominance component causes a chrominance Bchr block of p x q U (or V) samples to be coded to correspond to n luminance B blocks whose set covers the same spatial extent. The coding device therefore, in the case of chrominance, provides a motion estimator for determining, for the image block to be reconstructed, which displacement vector can be used for this reconstruction among the set of displacement vectors. Di (i varying from 1 to n) attached to said luminance blocks Bi.Furthermore, here we will reconstruct, on the one hand, a chrominance image of even rank, denoted by ÎChr2, IChr4, etc., with respect to in the image of opposite rank Ichor1, 1cher3 'etc ... which precedes it, and on the other hand an image of chrominance of odd rank, denoted Îchr3 1chr5' etc ..., compared to the image of the same rank Ichor1 Ichr3r etc ...

which precedes it.

The coding device of FIG. 7 thus comprises, following the spatial filtering stage 205, the selection stage, then a stage 220 constituting the coding string and identical to stage 20. The stage of selection here is an inter / intra decision circuit 210 of the same structure as the circuit 100 of FIGS. 5 and 6. This stage 210 receives, on the one hand, the output blocks B of the spatial filtering stage and, on the other hand, the output blocks B 'of a prediction stage 240, identical to the stage 40 of FIGS. 1, 5 and 6 and therefore constituted, like itself, an addressing circuit of the output memory of a stage of reconstruction 230 similar to the stage 30. The stage 210 delivers as previously additional information M1, relating to the mode of coding inter or intra and which is also transmitted, since necessary to the reception. The address of the memory is carried out in displacement vector function D 'provided by an estimation stage 250 and c here, again, the second motion information. In the reconstruction stage 230, the reconstruction circuit, referenced 232 and situated between an inverse orthogonal transformation and quantization circuit 31 and an image memory 33, is similar to that of FIG. 6, with the following exceptions:
the absence of classification into compensated blocks and fallback blocks makes the channel including the circuits 321, 325, 326 unnecessary, and these elements are therefore eliminated, the output of the circuit 31 then being directly connected to the input of the circuit 322
- The switch 323 is no longer useful and is replaced by a switch operating here at the rate of 12.5 hertz to send to the memory 33 that the only images needed, here the odd pictures.

The motion estimation stage 250, shown in FIG. 9, here comprises a single subset of vector determination. Indeed, due to the lower definition and the poorer content of the chrominance at high frequencies, the correction on the selected vector, made in the case of the luminance by the subset 52, is no longer necessary here. The vector determination is carried out on the one hand from the input signals B to be processed, on the other hand signals already processed during the previous processing cycle and therefore available at the output of the reconstruction stage 230, and also said first motion information. This subset is quite similar to the subset 51 described above, and the motion estimator realizes the choice of vector which minimizes the same criterion as in the case of luminance. These first motion informations are here the n Di vectors attached to the n blocks
Bi luminance that correspond to the chrominance block considered. The vector determination subassembly which here constitutes the motion estimation stage 250 firstly comprises an addressing circuit 251, receiving on a first input said previously processed signals, that is to say the BR blocks. output of the reconstruction stage 230, and on a second input the n vectors Di constituting the first motion information. The addressing circuit 251 is followed by a subtractor 252, a square elevator 253, an adder 254, and a comparator 255.

 we must here distinguish two situations. In the first situation, for the determination of second movement information D 'relating to the movement between an image of odd rank and the even rank image which succeeds it, for example between 11 and 12, between I3 and I4, etc. the addressing circuit 251 directly receives the vectors Di, and the subtracter 252 receives on its second input, not connected to the addressing circuit, the current signals, which at this instant correspond to I2, I4, etc. On the other hand, in the second situation, when the stage 250 makes the determination of second movement information D 'relating to the movement between successive odd-rank images, for example between 11 and 13 between 13 and Is, etc., the addressing circuit 251 receives the vectors Di this time through a multiplier by two, the current signals present on the second input of the subtractor 252 now corresponding to I3r 15, etc .... Indeed, in the first case, the second The motion information is approximated by the order of magnitude of the first motion information, while in the second case it is approximately twice as large as the first motion information.

 Conversely, when signals have been coded in coding devices such as those just described, prior to their transmission and / or storage, their decoding must be provided to allow reconstruction of the original signals.

 In the case where these original signals (on transmission, before coding) correspond to the luminance signals of a television image sequence, an example embodiment of suitable decoding device is shown in FIG. 10 In this decoding device, the transmitted and / or stored signals are first sent to a buffer memory 310, at the output of which is provided a variable-length decoding circuit 320. This circuit 320 provides, for the different successive blocks, quantized coefficients, which are then sent to a circuit 330 for inverse orthogonal quantization and transformation, the inverse quantization being carried out using a standard signal delivered on transmission by the flow control circuit 24 and then transmitted and / or stored, in view precisely of the reverse operation on reception during decoding.

 The decoding device of FIG. 10 also comprises a circuit 340 for reconstructing information batches from, on the one hand, the output signals of the inverse orthogonal inverse quantization and transformation circuit 330, on the other hand prediction information previously determined (during a previous reconstruction cycle), and also information M1 (inter or intra coding) and M2 (compensated or fallback blocks). The output of this circuit 340 is sent to a storage circuit 360, via a signal processing circuit 350 such as that described in the French patent application No. 8908187, that is to say a downsampling and interpolation stage with or without motion compensation.

 The signals thus transmitted to the subsampling and interpolation stage generally comprise, for each batch of information such as an image in the application more particularly described, partly of the reconstructed blocks corresponding to the compensated mode and encoded either inter or intra, and partly blocks in fallback mode. Storage in the storage circuit 360 completes the reconstruction cycle and provides signals useful for determining said prediction information and the next reconstruction cycle. This prediction information is determined in a prediction circuit 370 receiving a part of the output of the storage circuit 360 and secondly the second movement information D ', and here is, in fact, an addressing circuit of the circuit 360 taking into account the movements indicated by this information D'.

 In the case where the original signals (at the transmission before coding) correspond to the chrominance signals of a sequence of television images, another embodiment of the decoding device is shown in FIG. 310r circuits 320, 330, 360, 370 are, in this device, identical to the circuits with the same references in Figure 10. The reconstruction circuit 340 is very similar to the previous, the only difference being that in the case of Figure 11 , it does not receive M2 information since there is no distinction for chrominance between compensated or fallback blocks. The output of this reconstruction circuit 340 is sent on the one hand to a circuit 450 for reinterpolation of the coupler difference signals, whose output is intended to be supplied to a display device, and on the other hand to a switch 480 , operating here at a rate of 12.5 hertz and inserted between the circuit 340 and the storage circuit 360 to eliminate a batch of information reconstructed out of two and select only that which is useful for the prediction, according to the same principle of the odd-image selection switch in the reconstruction circuit 232 of FIG. 7.

Of course, from the embodiments described, variants may be proposed. It has been seen in particular that the processing operations concerning the U and V color difference signals are carried out separately, for example the spatial pre-filtering performed by the circuit 206, the decisions taken by the circuit 210. On the contrary, it is possible to choose to perform these in this case, the test function performed by the vector determination subset of the motion estimation stage is also common and is then concretized by a determination of that of the vectors Di which also minimizes, for U or for V the expression given above, but now the following expression
E (I2 (x) - ji (x-Di)) 2+ E (12 (x) - r1tx-Di)) 2
UV or the following expression
E (I3 (x) - ji (x-2Di)) 2 + E (I3 (x) - I1 (x-2Di) 2
UV according to whether one is in one or the other of the two situations defined above (movement between images of odd and even ranks, or between odd-rank images), the vectors thus selected being transmitted and / or stored in such a way common for U and V.

Claims (11)

claims 1. Device for encoding information, and in particular two-dimensional information, arranged in batches of periodic information of the image type <of successively odd and even ranks, represented on the one hand by so-called input signals of determined rank , intended to be transmitted and / or stored after rate reduction, and secondly by first information relating to the movement between these signals and intended, after their estimation, to be substituted, in said representation, for complementary signals of opposite rank while being related to the signals of determined rank which surround them, said coding device comprising a coding stage, characterized in that it also comprises, for the processing of said input signals of determined rank  (a) a so-called motion estimation stage with identical blocks, these blocks being delimited by or within said information batches of said determined rank, starting from the current input signals to be processed, d on the other hand signals processed during the previous processing cycle, and also said first motion information, said stage being intended to deliver second motion information  (b) a so-called prediction stage starting on the one hand from said previously processed signals and secondly on said second movement information, said stage being intended to deliver, for coding purposes, signals corrected by said second movement information;  (c) a so-called selection stage of the signal to be coded. Coding device according to claim 1, characterized in that the motion estimation stage comprises a first subassembly for determining an intermediate vector from said first motion information and a second correction sub-set. the value of this intermediate vector, delivering said second motion information. 3. coding device according to claim 2, characterized in that said subassemblies for intermediate vector determination and correction of this vector each comprise in series an addressing circuit, a subtractor, a squared elevator, a summator and a comparator. 4. Encoding device according to one of claims 1 to 3, characterized in that the previously processed signals are supplied to the prediction stage by a so-called reconstruction stage connected in parallel in the coding stage and executing the operations. inverse of those already executed, on the input signals of said coding stage, at the point of connection to this coding stage. 5. Coding device according to claim 4, characterized in that the reconstruction stage comprises, at the output of an orthogonal transformation circuit and quantization provided in the coding stage, an orthogonal transformation circuit and inverse quantization followed, in series, a circuit for reconstituting the signal present before selecting the signal to be encoded and a memory. 6. coding device according to claim 5, characterized in that the size of the memory is that of one of said batches of periodic information rows successively odd and even. 7. Encoding device according to one of claims 1 to 6 characterized in that the selection stage is a subtracter. 8. Encoding device according to one of claims i to 6r characterized in that the selection stage is an inter / intra decision said circuit. 9. Encoding device according to one of claims 7 and 8, characterized in that the signal reconstitution circuit comprises an adder followed by an addressing circuit for writing in the memory. Coding device according to one of Claims 5 and 6 in which said signals of determined rank are accompanied by corresponding additional information indicating this mode, characterized in that the signal reconstitution circuit comprises a switch controlled by said additional information. , a switcher, andr in parallel between this switch and this switch, two separate processing channels according to said corresponding additional information. 11. Encoding device according to claim 10, characterized in that the selection stage is an inter / intra decision circuit and in that one of the channels is split into two separate parallel processing channels according to said decision.