Patent Application
20130170746
The present principles relate generally to video encoding and decoding and, more particularly, to methods and apparatus for example-based data pruning using intra-frame patch similarity.
Data pruning is a video preprocessing technology that achieves better video coding efficiency by removing part of the input video data before the input video data is encoded. The removed video data is recovered at the decoder side by inferring the removed video data from the decoded data. One example of data pruning is image line removal, which removes some of the horizontal and vertical scan lines in the input video.
In a first approach, a new data pruning method called example-based data pruning is employed, in which external videos or video frames that have been previously transmitted to the decoder side are used to train an example patch library. The patch library is then used to prune and recover the video data.
There have been several efforts to explore using data pruning to increase compression efficiency. For example, in a second approach and a third approach, a texture replacement based method is used to remove texture regions at the encoder side, and re-synthesize the texture regions at the decoder side. Compression efficiency is gained because only synthesis parameters are sent to the decoder, which are smaller than the regular transformation coefficients. In a fourth approach and a fifth approach, spatio-temporal texture synthesis and edge-based inpainting are used to remove some of the regions at the encoder side, and the removed content is recovered at the decoder side, with the help of metadata such as region masks. However, the fourth and fifth approaches need to modify the encoder and decoder so that the encoder/decoder can selectively perform encoding/decoding for some of the regions using the region masks. Therefore, it is not exactly an out-of-loop approach (i.e., the encoder and decoder need to be modified). In a sixth approach, a line removal based method is proposed to rescale a video to a smaller size by selectively removing some of the horizontal or vertical lines in the video with a least-square minimization framework. The sixth approach is an out-of-loop approach, and does not require modification of the encoder/decoder. However, completely removing certain horizontal and vertical lines may result in loss of information or details for some videos.
Some preliminary research on data pruning for video compression has been conducted. For example, in a seventh approach, a data pruning scheme using sampling-based super-resolution is presented. The full resolution frame is sampled into several smaller-sized frames, therefore reducing the spatial size of the original video. At the decoder side, the high-resolution frame is re-synthesized from the downsampled frames with the help of metadata received from the encoder side. In an eighth approach, an example-based super-resolution based method for data pruning is presented. A representative patch library is trained from the original video. Afterwards, the video is downsized to a smaller size. The downsized video and the patch library are sent to the decoder side. The recovery process at the decoder side super-resolves the downsized video by example-based super-resolution using the patch library. However because there is substantial redundancy between the patch library and downsized frames, it has been discovered that it may be difficult to achieve compression gain using the eighth approach.
In the aforementioned first approach, an example-based data pruning method creates a patch library using the video frames that have been sent to the decoder side and uses the patch library to prune and recover video frames. However, this method does not consider the intra-frame patch dependency, which may happen if there are repetitive textures or patterns in a video frame.
In the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC) Moving Picture Experts Group-4 (MPEG-4) Part 10 Advanced Video Coding (AVC) Standard/International Telecommunication Union, Telecommunication Sector (ITU-T) H.264 Recommendation (hereinafter the “MPEG-4 AVC Standard”), intra-frame block prediction is realized by block prediction from the neighboring blocks. However, long-range similarity of non-neighboring blocks is not exploited to increase compression efficiency.
These and other drawbacks and disadvantages of these approaches are addressed by the present principles, which are directed to methods and apparatus for example-based data pruning using intra-frame patch similarity.
According to an aspect of the present principles, there is provided an apparatus for encoding a picture in a video sequence. The apparatus includes a patch library creator for creating a first patch library from an original version of the picture and a second patch library from a reconstructed version of the picture. Each of the first patch library and the second patch library includes a plurality of high resolution replacement patches for replacing one or more pruned blocks during a recovery of a pruned version of the picture. The apparatus also includes a pruner for generating the pruned version of the picture from the first patch library. The apparatus further includes a metadata generator for generating metadata from the second patch library. The metadata is for recovering the pruned version of the picture. The apparatus additionally includes an encoder for encoding the pruned version of the picture and the metadata. The first patch library includes a plurality of patch clusters, and the pruned version of the picture is generated by dividing the original version of the picture into a plurality of overlapping blocks, searching for candidate patch clusters from among the plurality of patch clusters for each of the plurality of overlapping blocks based on respective distance metrics from each of the plurality of overlapping blocks to respective centers of each of the plurality of patch clusters, identifying a best matching patch from the candidate patch clusters based on one or more criterion, and pruning a corresponding one of the plurality of overlapping blocks to obtain a pruned block there for when a difference between the corresponding one of the plurality of overlapping blocks and the best matching patch is less than a threshold difference. A patch dependency graph having a plurality of nodes and a plurality of edges is used for the searching. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
According to another aspect of the present principles, there is provided a method for encoding a picture in a video sequence. The method includes creating a first patch library from an original version of the picture and a second patch library from a reconstructed version of the picture. Each of the first patch library and the second patch library includes a plurality of high resolution replacement patches for replacing one or more pruned blocks during a recovery of a pruned version of the picture. The method also includes generating the pruned version of the picture from the first patch library. The method further includes generating metadata from the second patch library. The metadata is for recovering the pruned version of the picture. The method additionally includes encoding the pruned version of the picture and the metadata. The first patch library includes a plurality of patch clusters, and the pruned version of the picture is generated by dividing the original version of the picture into a plurality of overlapping blocks, searching for candidate patch clusters from among the plurality of patch clusters for each of the plurality of overlapping blocks based on respective distance metrics from each of the plurality of overlapping blocks to respective centers of each of the plurality of patch clusters, identifying a best matching patch from the candidate patch clusters based on one or more criterion, and pruning a corresponding one of the plurality of overlapping blocks to obtain a pruned block there for when a difference between the corresponding one of the plurality of overlapping blocks and the best matching patch is less than a threshold difference. A patch dependency graph having a plurality of nodes and a plurality of edges is used for the searching. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
According to still another aspect of the present principles, there is provided an apparatus for recovering a pruned version of a picture in a video sequence. The apparatus includes a divider for dividing the pruned version of the picture into a plurality of non-overlapping blocks. The apparatus also includes a metadata decoder for decoding metadata for use in recovering the pruned version of the picture. The apparatus further includes a patch library creator for creating a patch library from a reconstructed version of the picture. The patch library includes a plurality of high resolution replacement patches for replacing the one or more pruned blocks during a recovery of the pruned version of the picture. The apparatus additionally includes a search and replacement device for performing a searching process using the metadata to find a corresponding patch for a respective one of the one or more pruned blocks from among the plurality of non-overlapping blocks and replace the respective one of the one or more pruned blocks with the corresponding patch. The signature is respectively created for each of the one or more pruned blocks, and the pruned version of the picture is recovered by comparing respective distance metrics from signatures for each of the plurality of high resolution patches to signatures for each of the one or more pruned blocks, sorting the respective distance metrics to obtain a rank list for each of the one or more pruned blocks, wherein a rank number in the rank list for a particular one of the one or more pruned blocks is used to retrieve a corresponding one of the plurality of high resolution patches in the patch library to be used to replace the particular one of the one or more pruned blocks. A patch dependency graph having a plurality of nodes and a plurality of edges is used to recover the pruned version of the picture. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
According to a further aspect of the present principles, there is provided a method for recovering a pruned version of a picture in a video sequence. The method includes dividing the pruned version of the picture into a plurality of non-overlapping blocks. The method also includes decoding metadata for use in recovering the pruned version of the picture. The method further includes creating a patch library from a reconstructed version of the picture. The patch library includes a plurality of high resolution replacement patches for replacing the one or more pruned blocks during a recovery of the pruned version of the picture. The method additionally includes performing a searching process using the metadata to find a corresponding patch for a respective one of the one or more pruned blocks from among the plurality of non-overlapping blocks and replace the respective one of the one or more pruned blocks with the corresponding patch. The signature is respectively created for each of the one or more pruned blocks, and the pruned version of the picture is recovered by comparing respective distance metrics from signatures for each of the plurality of high resolution patches to signatures for each of the one or more pruned blocks, sorting the respective distance metrics to obtain a rank list for each of the one or more pruned blocks, wherein a rank number in the rank list for a particular one of the one or more pruned blocks is used to retrieve a corresponding one of the plurality of high resolution patches in the patch library to be used to replace the particular one of the one or more pruned blocks. A patch dependency graph having a plurality of nodes and a plurality of edges is used to recover the pruned version of the picture. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
According to a still further aspect of the present principles, there is provided an apparatus for encoding a picture in a video sequence. The apparatus includes means for creating a first patch library from an original version of the picture and a second patch library from a reconstructed version of the picture. Each of the first patch library and the second patch library includes a plurality of high resolution replacement patches for replacing one or more pruned blocks during a recovery of a pruned version of the picture. The apparatus also includes means for generating the pruned version of the picture from the first patch library. The apparatus further includes means for generating metadata from the second patch library, the metadata for recovering the pruned version of the picture. The apparatus additionally includes means for encoding the pruned version of the picture and the metadata. The first patch library includes a plurality of patch clusters, and the pruned version of the picture is generated by dividing the original version of the picture into a plurality of overlapping blocks, searching for candidate patch clusters from among the plurality of patch clusters for each of the plurality of overlapping blocks based on respective distance metrics from each of the plurality of overlapping blocks to respective centers of each of the plurality of patch clusters, identifying a best matching patch from the candidate patch clusters based on one or more criterion, and pruning a corresponding one of the plurality of overlapping blocks to obtain a pruned block there for when a difference between the corresponding one of the plurality of overlapping blocks and the best matching patch is less than a threshold difference. A patch dependency graph having a plurality of nodes and a plurality of edges is used for the searching. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
According to an additional aspect of the present principles, there is provided an apparatus for recovering a pruned version of a picture in a video sequence. The apparatus includes means for dividing the pruned version of the picture into a plurality of non-overlapping blocks. The apparatus also includes means for decoding metadata for use in recovering the pruned version of the picture. The apparatus further includes means for creating a patch library from a reconstructed version of the picture. The patch library includes a plurality of high resolution replacement patches for replacing the one or more pruned blocks during a recovery of the pruned version of the picture. The apparatus additionally includes means for performing a searching process using the metadata to find a corresponding patch for a respective one of the one or more pruned blocks from among the plurality of non-overlapping blocks and replace the respective one of the one or more pruned blocks with the corresponding patch. The signature is respectively created for each of the one or more pruned blocks, and the pruned version of the picture is recovered by comparing respective distance metrics from signatures for each of the plurality of high resolution patches to signatures for each of the one or more pruned blocks, sorting the respective distance metrics to obtain a rank list for each of the one or more pruned blocks, wherein a rank number in the rank list for a particular one of the one or more pruned blocks is used to retrieve a corresponding one of the plurality of high resolution patches in the patch library to be used to replace the particular one of the one or more pruned blocks. A patch dependency graph having a plurality of nodes and a plurality of edges is used to recover the pruned version of the picture. Each of the plurality of nodes represents a respective one of the plurality of overlapping blocks, and each of the plurality of edges represents a respective dependency of at least the respective one of the plurality of overlapping blocks.
These and other aspects, features and advantages of the present principles will become apparent from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings.
The present principles may be better understood in accordance with the following exemplary figures, in which:
The present principles are directed to methods and apparatus for example-based data pruning using intra-frame patch similarity.
The present description illustrates the present principles. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the present principles and are included within its spirit and scope.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the present principles and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.
Moreover, all statements herein reciting principles, aspects, and embodiments of the present principles, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.
Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative circuitry embodying the present principles. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (“DSP”) hardware, read-only memory (“ROM”) for storing software, random access memory (“RAM”), and non-volatile storage.
Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.
In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements that performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The present principles as defined by such claims reside in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein.
Reference in the specification to “one embodiment” or “an embodiment” of the present principles, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present principles. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment”, as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment.
It is to be appreciated that the use of any of the following “/”, “and/or”, and “at least one of”, for example, in the cases of “A/B”, “A and/or B” and “at least one of A and B”, is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and/or C” and “at least one of A, B, and C”, such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as readily apparent by one of ordinary skill in this and related arts, for as many items listed.
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A first output of an encoder controller 205 is connected in signal communication with a second input of the frame ordering buffer 210, a second input of the inverse transformer and inverse quantizer 250, an input of a picture-type decision module 215, a first input of a macroblock-type (MB-type) decision module 220, a second input of an intra prediction module 260, a second input of a deblocking filter 265, a first input of a motion compensator 270, a first input of a motion estimator 275, and a second input of a reference picture buffer 280.
A second output of the encoder controller 205 is connected in signal communication with a first input of a Supplemental Enhancement Information (SEI) inserter 230, a second input of the transformer and quantizer 225, a second input of the entropy coder 245, a second input of the output buffer 235, and an input of the Sequence Parameter Set (SPS) and Picture Parameter Set (PPS) inserter 240.
An output of the SEI inserter 230 is connected in signal communication with a second non-inverting input of the combiner 290.
A first output of the picture-type decision module 215 is connected in signal communication with a third input of the frame ordering buffer 210. A second output of the picture-type decision module 215 is connected in signal communication with a second input of a macroblock-type decision module 220.
An output of the Sequence Parameter Set (SPS) and Picture Parameter Set (PPS) inserter 240 is connected in signal communication with a third non-inverting input of the combiner 290.
An output of the inverse quantizer and inverse transformer 250 is connected in signal communication with a first non-inverting input of a combiner 219. An output of the combiner 219 is connected in signal communication with a first input of the intra prediction module 260 and a first input of the deblocking filter 265. An output of the deblocking filter 265 is connected in signal communication with a first input of a reference picture buffer 280. An output of the reference picture buffer 280 is connected in signal communication with a second input of the motion estimator 275 and a third input of the motion compensator 270. A first output of the motion estimator 275 is connected in signal communication with a second input of the motion compensator 270. A second output of the motion estimator 275 is connected in signal communication with a third input of the entropy coder 245.
An output of the motion compensator 270 is connected in signal communication with a first input of a switch 297. An output of the intra prediction module 260 is connected in signal communication with a second input of the switch 297. An output of the macroblock-type decision module 220 is connected in signal communication with a third input of the switch 297. The third input of the switch 297 determines whether or not the “data” input of the switch (as compared to the control input, i.e., the third input) is to be provided by the motion compensator 270 or the intra prediction module 260. The output of the switch 297 is connected in signal communication with a second non-inverting input of the combiner 219 and an inverting input of the combiner 285.
A first input of the frame ordering buffer 210 and an input of the encoder controller 205 are available as inputs of the encoder 200, for receiving an input picture. Moreover, a second input of the Supplemental Enhancement Information (SEI) inserter 230 is available as an input of the encoder 200, for receiving metadata. An output of the output buffer 235 is available as an output of the encoder 200, for outputting a bitstream.
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A second output of the entropy decoder 345 is connected in signal communication with a third input of the motion compensator 370, a first input of the deblocking filter 365, and a third input of the intra predictor 360. A third output of the entropy decoder 345 is connected in signal communication with an input of a decoder controller 305. A first output of the decoder controller 305 is connected in signal communication with a second input of the entropy decoder 345. A second output of the decoder controller 305 is connected in signal communication with a second input of the inverse transformer and inverse quantizer 350. A third output of the decoder controller 305 is connected in signal communication with a third input of the deblocking filter 365. A fourth output of the decoder controller 305 is connected in signal communication with a second input of the intra prediction module 360, a first input of the motion compensator 370, and a second input of the reference picture buffer 380.
An output of the motion compensator 370 is connected in signal communication with a first input of a switch 397. An output of the intra prediction module 360 is connected in signal communication with a second input of the switch 397. An output of the switch 397 is connected in signal communication with a first non-inverting input of the combiner 325.
An input of the input buffer 310 is available as an input of the decoder 300, for receiving an input bitstream. A first output of the deblocking filter 365 is available as an output of the decoder 300, for outputting an output picture.
As noted above, the present principles are directed to methods and apparatus for example-based data pruning using intra-frame patch similarity.
In accordance with the present principles, this application discloses a new approach that takes advantage of patch similarity within a video frame. The patch similarity within an image happens in many real-world pictures where there are repetitive textures or patterns in the pictures such as, for example, a picture with wall papers as the background. The within-picture patch similarity is discovered by a clustering algorithm, and a patch library is created for pruning and recovery. However, since the same frame is used for both creating patch library and for pruning/recovery, the patch dependency problems have to be resolved in order to ensure artifact-free recovery.
The present principles provide an improvement of our previous approach by training the patch library at the decoder side using previously sent frames or existing frames, rather than sending the patch library through one or more communication channels. Moreover, the data pruning is realized by replacing some blocks in the input frames with flat regions to create “mixed-resolution” frames.
As noted above, in the MPEG-4 AVC Standard, intra-frame block prediction is realized by block prediction from the neighboring blocks. However, long-range similarity of non-neighboring blocks is not exploited to increase compression efficiency. Advantageously, the present principles provide a method for pruning an input video so that the input video can be more efficiently encoded by a video encoder. The present principles take advantage of the similarity of image patches within a video frame to further increase the compression efficiency.
In accordance with the present principles, intra-frame patch similarity is used to train an example patch library and prune a video and recover the pruned video. Error-bounded clustering (the modified K-means clustering) is used for efficient patch searching in the library. To improve compression efficiency, a mixed-resolution data pruning scheme is used, where blocks are replaced by flat blocks to reduce the high-frequency signal.
The present principles may involve the use of patch signature matching, a matching rank list, and rank number encoding to increase the efficiency of metadata (best-match patch position in library) encoding. Moreover, a method is disclosed for encoding the block coordinates using the flat block identification based on color variation.
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The patch library is a pool of high resolution patches that can be used to recover pruned image blocks. Turning to
To speed up computation, the horizontal and vertical dimensions of the training frames are reduced to one quarter of the original size. Also, the clustering process is performed on the patches in the downsized frames. In one exemplary embodiment, the size of the high-resolution patches is 16×16 pixels, and the size of the downsized patches is 4×4 pixels. Therefore, the downsize factor is 4. Of course, other sizes can e used, while maintaining the spirit of the present principles.
For the patch library for metadata encoding, the clustering process and clean-up process are not performed, therefore it includes all possible patches from the reconstructed frame. However, for every patch in the patch library created from the original frames, its corresponding patch can be found in the patch library created from the reconstructed frame using the coordinates of the patches. This would make sure that metadata encoding can be correctly performed. For the decoder side, the same patch library without clustering is created using the same decoded video frames for metadata decoding and pruned block recovery.
For the patch libraries created using decoded frames at both the encoder and decoder side, another process is conducted to create the signatures of the patches. The signature of a patch is a feature vector that includes the average color of the patch and the surrounding pixels of the patch. The patch signatures are used for the metadata encoding process to more efficiently encode the metadata, and used in the recovery process at the decoder side to find the best-match patch and more reliably recover the pruned content. Turning to
The metadata encoding process is described herein below. In the pruned frame, sometimes the neighboring blocks of a pruned block for recovery or metadata encoding are also pruned. Then the set of surrounding pixels used as the signature for search in the patch library only includes the pixels from the non-pruned blocks. If all the neighboring blocks are pruned, then only the average color 701 is used as the signature. This may end up with bad patch matches since too little information is used for patch matching, that is why neighboring non-pruned pixels 702 are important.
Similar to standard video encoding algorithms, the input video frames are divided into Group of Pictures (GOP). The pruning process is conducted on the first frame of a GOP. The pruning result is propagated to the rest of the frames in the GOP afterwards.
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Thus, the input frame is first divided into non-overlapping blocks per step 910. The size of the block is the same as the size of the macroblock used in the standard compression algorithms, in our current implementation, 16×16 pixels. A search process then is followed to find the best-match patch in the patch library per step 920. This search process is illustrated in
The preceding approach is different from the aforementioned first approach, since in the first approach the patches in the input frames are used to create patch library and recover the pruned blocks, thus resulting in block dependency problem, meaning that the needed patches for recovery may not be available when a block is being recovered. This problem is solved by following two solutions provided by the present principles: pruning with causal recovery; and pruning using a dependency graph.
In the case of pruning with causal recovery, for a pruned block, the search process (also the recovery process at the decoder side) will only look at the patches preceding the pruned block in the coordinates in the patch library. Turning to
b) Pruning with Dependency Graph
The limitation of the above approach is that there may be no example patches available for the blocks at the top of a frame. This problem may be solved by a full-frame patch search with the help of a patch dependency graph. The patch dependency graph is a directed acyclic graph (DAG), where each node of the graph represents a candidate block for pruning, and each edge represents the dependency of the blocks. Turning to
The method for obtaining a recovery sequence is further described as follows:
1. Find all end nodes (i.e., the nodes that do not depend on other nodes) in the graph and save the corresponding block coordinates (here the block coordinates are represented as the block IDs as shown in
2. Find a node in the graph with maximum indegree, i.e., a node corresponding to the block upon which depends a maximum number of other blocks. Remove the node in the graph, do not save the IDs of the block (i.e., the block will not be pruned). Repeat this procedure until there are new end nodes emerging in the graph. Then the algorithm goes back to step (1). The block is not pruned because the block cannot be recovered using the available pixels (decoded pixels and recovered pixels) in the frame. On the other hand, other blocks may depend on this block to recover. Therefore, in order to prune maximum number of blocks, the block upon which depends the maximum number of other blocks is found. After the block is kept unpruned (i.e., removed from the graph), there may be new end nodes emerging, and then step (1) can be used to prune the block again.
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By using the above algorithm, a block recovery sequence which ensures that the best-matching patch is available will be obtained when a corresponding block is being recovered during the recovery process.
After the blocks are identified for pruning, a process is conducted to prune the block. There could be different pruning strategies. For example, replacing the high-resolution blocks with low-resolution blocks may be one strategy that is used. However, it is discovered that it is difficult for this approach to achieve significant compression efficiency gain. Therefore, in the current system, a high-resolution block is simply replaced with a flat block, in which all pixels have the same color value, which is the average of the color values of the pixels within the original block. The block replacement process creates a video frame where some parts of the frame have high-resolution and some parts have low-resolution; therefore, such a frame is called as mixed-resolution frame. Turning to
Metadata encoding includes two components (see
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During the pruning process, for each block, the system would search the best match patch in the patch library and output a patch index in the patch library for a found patch if the distortion is less than a threshold. Each patch is associated with its signature (i.e., its color plus surrounding pixels in the decoded frames). During the recovery process in the decoder side processing, the color of the pruned block and its surrounding pixels are used as a signature to find the correct high-resolution patch in the library.
However, due to noise, the search process using the signature is not reliable, and metadata is needed to assist the recovery process to ensure reliability. Therefore, after the pruning process, the system will proceed to generate metadata for assisting recovery. For each pruned block, the search process described above already identifies the corresponding patches in the library. The metadata encoding component will simulate the recovery process to encode the metadata. A new patch library will be created using the decoded pruned frame to ensure the patch library is exactly the same as that in the decoder side. The frame is divided into overlapping patches and signatures are created for the patches. During the recovery simulation process, the patch library has to be dynamically updated because some pruned blocks will be recovered during the process. The process is illustrated in
For decoding (see
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Besides the rank number metadata, it is necessary to send the locations of the pruned blocks to the decoder side. This is done by block ID encoding (see
To further reduce redundancy, it is possible to have a differential coding scheme to compute the difference between an ID number to its previous ID number, and encode the difference sequence. For example, assuming the ID sequence is 3,4,5,8,13,14, the differentiated sequence becomes 3,1,1,3,5,1. The differentiation process makes the numbers closer to 1, therefore resulting in a number distribution with smaller entropy. The differentiated sequence then can be further encoded with entropy coding (e.g., Golomb code in our current implementation). Thus, the format of the final metadata is shown as follows:
where flag is a signaling flag to indicate whether or not the block ID sequence is a false positive ID sequence, the threshold is the variance threshold for flat block identification, the encoded block ID sequence is the encoded bit stream of the pruned block IDs or the false positive block IDs, and the encoded rank number sequence is the encoded bit stream of the rank numbers used for block recovery.
For the rest of the frames in a GOP, some of the blocks in the frames will be also replaced by flat blocks. The positions of the pruned blocks in the first frame can be propagated to the rest of the frames by motion tracking. Different strategies are tried to propagate the positions of the pruned blocks. One approach is to track the pruned blocks across frames by block matching, and prune the corresponding blocks in the subsequent frames (i.e., replace the tracked blocks with flat blocks). However, this approach does not result in good compression efficiency gain because, in general, the boundaries of the tracked blocks do not align with the coding macro blocks. As a result, the boundaries of the tracked blocks create a high frequency signal in the macro blocks. Therefore, a simpler alternative approach is currently used to set all the block positions for the subsequent frames to the same positions as the first frame. Namely, all the pruned blocks in the subsequent frames are collocated with the pruned blocks in the first frame. As a result, all of the pruned blocks for the subsequent frames are aligned with macro block positions.
However, this approach would not work well if there is motion in the pruned blocks. Therefore, one solution to solve the problem is to detect calculate the motion intensity of the block (see
If the motion intensity is larger than a threshold, the block would not be pruned. Another more sophisticated solution, which is our current implementation, is to calculate the motion vectors of the pruned blocks in the original video by finding the corresponding block in the previous frame (see
The recovery process takes place at the decoder side. The patch library is created before the recovery process by obtaining all the overlapping patches and creating the signatures using the first decoded frame in the GOP. However, different from the aforementioned first approach, the patch library has to be dynamically updated during the recovery process, because the pruned blocks in the frame will be replaced with the recovered blocks during the recovery process.
For the first frame in a GOP, the recovery process starts with decoding the metadata (see
Turning to
After the block ID sequence is available, for each pruned block, the average color and surrounding pixels of this block will be taken as the signature to match with the signatures in the patch library. However, if the neighboring blocks of the block for recovery are also pruned, then the set of surrounding pixels used as the signature for search only includes the pixels from the non-pruned blocks. If all the neighboring blocks are pruned, then only the average color is used as the signature. The matching process is realized by calculating the Euclidean distances between the signature of the query block and those of the patches in the library. After all the distances are calculated, the list is sorted according to the distances, resulting in a rank list. The rank number corresponding to the pruned block then is used to retrieve the correct high-resolution block from the rank list.
Turning to
Turning to
It is to be appreciated that the block recovery using example patches can be replaced by traditional inpainting and texture synthesis based methods.
Note that for the pruning scheme with dependency graph as described above, the recovery process has to follow the order of the block IDs in the ID sequence so that whenever a block is being recovered, its corresponding patch is available in the patch library. Furthermore, after each block is recovered, the patch library has to be updated, i.e., the patches overlapping with the block have to be replaced with new patches and the signatures for those patches and their neighbors have to be recalculated.
For the rest of the frames in a GOP, for each pruned block, if the motion vector is not available, the content of the block can be copied from the co-located block in the previous frame. If the motion vector is available, then it is possible to use the motion vector to find the corresponding block in the previous frame, and copy the corresponding block to fill the pruned block. Turning to
Block artifacts may be visible since the recovery process is block-based. A deblocking filter, such as the in-loop deblocking filter used in the MPEG-4 AVC Standard encoder, can be applied to reduce the block artifacts.
These and other features and advantages of the present principles may be readily ascertained by one of ordinary skill in the pertinent art based on the teachings herein. It is to be understood that the teachings of the present principles may be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof.
Most preferably, the teachings of the present principles are implemented as a combination of hardware and software. Moreover, the software may be implemented as an application program tangibly embodied on a program storage unit. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit.
It is to be further understood that, because some of the constituent system components and methods depicted in the accompanying drawings are preferably implemented in software, the actual connections between the system components or the process function blocks may differ depending upon the manner in which the present principles are programmed. Given the teachings herein, one of ordinary skill in the pertinent art will be able to contemplate these and similar implementations or configurations of the present principles.
Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present principles is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present principles. All such changes and modifications are intended to be included within the scope of the present principles as set forth in the appended claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/403,107 entitled EXAMPLE-BASED DATA PRUNING USING INTRA-FRAME PATCH SIMILARITY filed on Sep. 10, 2010 (Technicolor Docket No. PU100196). This application is related to the following co-pending, commonly-owned, patent applications: (1) International (PCT) Patent Application Serial No. PCT/US11/000107 entitled A SAMPLING-BASED SUPER-RESOLUTION APPROACH FOR EFFICENT VIDEO COMPRESSION filed on Jan. 20, 2011 (Technicolor Docket No. PU100004);(2) International (PCT) Patent Application Serial No. PCT/US11/000117 entitled DATA PRUNING FOR VIDEO COMPRESSION USING EXAMPLE-BASED SUPER-RESOLUTION filed on Jan. 21, 2011 (Technicolor Docket No. PU100014);(3) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR ENCODING VIDEO SIGNALS USING MOTION COMPENSATED EXAMPLE-BASED SUPER-RESOLUTION FOR VIDEO COMPRESSION filed on Sep. XX, 2011 (Technicolor Docket No. PU100190);(4) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR DECODING VIDEO SIGNALS USING MOTION COMPENSATED EXAMPLE-BASED SUPER-RESOLUTION FOR VIDEO COMPRESSION filed on Sep. XX, 2011 (Technicolor Docket No. PU100266);(5) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR ENCODING VIDEO SIGNALS USING EXAMPLE-BASED DATA PRUNING FOR IMPROVED VIDEO COMPRESSION EFFICIENCY filed on Sep. XX, 2011 (Technicolor Docket No. PU100193);(6) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR DECODING VIDEO SIGNALS USING EXAMPLE-BASED DATA PRUNING FOR IMPROVED VIDEO COMPRESSION EFFICIENCY filed on Sep. XX, 2011 (Technicolor Docket No. PU100267);(7) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR ENCODING VIDEO SIGNALS FOR BLOCK-BASED MIXED-RESOLUTION DATA PRUNING filed on Sep. XX, 2011 (Technicolor Docket No. PU100194);(8) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR DECODING VIDEO SIGNALS FOR BLOCK-BASED MIXED-RESOLUTION DATA PRUNING filed on Sep. XX, 2011 (Technicolor Docket No. PU100268);(9) International (PCT) Patent Application Serial No. XXXX entitled METHODS AND APPARATUS FOR EFFICIENT REFERENCE DATA ENCODING FOR VIDEO COMPRESSION BY IMAGE CONTENT BASED SEARCH AND RANKING filed on Sep. XX, 2011 (Technicolor Docket No. PU100195);(10) International (PCT) Patent Application Serial No. XXXX entitled METHOD AND APPARATUS FOR EFFICIENT REFERENCE DATA DECODING FOR VIDEO COMPRESSION BY IMAGE CONTENT BASED SEARCH AND RANKING filed on Sep. XX, 2011 (Technicolor Docket No. PU110106);(11) International (PCT) Patent Application Serial No. XXXX entitled METHOD AND APPARATUS FOR ENCODING VIDEO SIGNALS FOR EXAMPLE-BASED DATA PRUNING USING INTRA-FRAME PATCH SIMILARITY filed on Sep. XX, 2011 (Technicolor Docket No. PU100196);(12) International (PCT) Patent Application Serial No. XXXX entitled PRUNING DECISION OPTIMIZATION IN EXAMPLE-BASED DATA PRUNING COMPRESSION filed on Sep. XX, 2011 (Technicolor Docket No. PU10197).
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/50924 | 9/9/2011 | WO | 00 | 3/7/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61403107 | Sep 2010 | US |
