VIDEO DATA COMPRESSION WITH INTEGRATED LOSSY AND LOSSLESS COMPRESSION

• US 20090257485A1
• Filed: 04/15/2008
• Published: 10/15/2009
• Est. Priority Date: 04/15/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Youn, Jeongnam
• Granted Patent: US 8,194,736 B2
• Time in Patent Office: Days
• US Class Current: 375/240.10
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/428 Recompression, e.g. by spatial or temporal decimation
• CPC Class Codes: H04N 19/433 characterised by techniques for memory access
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression

Abstract

A method and apparatus to compress video data to smaller size and embed extra information into the compressed data using the integrated lossy and lossless compressions is described. The method can be used to compress reference frames of a video codec (coder/decoder) combines codec where the small noise is critical and to reduce bus bandwidth. Data transfer between an encoder and an external frame memory connected via an external bus in a video codec is reduced by compressing data from the encoder prior to inputting into the frame memory over the external bus, and decompressing the compressed data from the frame memory after retrieving over the external bus. Reference frames are compressed to variable size without causing any considerable artifact to reduce bus bandwidth between the encoder core and external memory. In the method, lossy and lossless compression is integrated to maximize the compression efficiency.

Claims

1. A method for reducing data transfer between an encoder and an external frame memory connected via an external bus in a video codec, comprising:

compressing data from the encoder prior to inputting into the frame memory over the external bus; and

decompressing the compressed data from the frame memory after retrieving over the external bus.

2. The method of claim 1, wherein the data is compressed by lossless compression.

3. The method of claim 1, wherein the data is compressed by lossy compression.

4. The method of claim 1, wherein the data is compressed by combination of lossless compression and lossy compression.

5. The method of claim 1, further comprising segmenting each frame into smaller blocks prior to compressing.

6. The method of claim 5, wherein the frames are luminance frames and chrominance frames.

7. The method of claim 5, wherein each block is compressed by first predicting and compressing each original block, and then determining if the number of bits used during compression is within an allowed range.

8. The method of claim 5, further comprising segmenting the segmented blocks into subblocks having a different level of compression;

wherein inside one compression block, lossy and lossless subblocks can be integrated together.

9. The method of claim 7, further comprising packing the compressed data into a packet and storing the packet in the frame memory if the number of bits used during compression is within an allowed range.

10. The method of claim 7, further comprising trying to compress the data by lossy compression if the number of bits used during compression is not within an allowed range.

11. The method of claim 10, wherein lossy compression is performed by reducing the precision of the original data.

12. The method of claim 10, further comprising generating a noise compensation bit to indicate the amount of noise introduced during compression

13. The method of claim 10, wherein the data is processed by an uncompression process if lossy compression is not allowed.

14. The method of claim 4, further comprising embedding extra information in each compressed block without losing original information in the block, at least one said extra information comprising a compressed/uncompressed block indication, and at least one said extra information comprising a lossy/lossless indication.

15. The method of claim 4, further comprising determining a maximum precision that is needed to represent the residual data in each block, and applying this for the compression of the block.

16. The method of claim 4, further comprising:

segmenting each block into subblocks;

determining a maximum precision for each subblock; and

compressing each subblock using the maximum precision for that subblock.

17. The method of claim 9, wherein the compressed data from frame memory is decompressed by first determining if each block is compressed, and if compressed, decoding each block using the same precision used in compressing the block.

18. The method of claim 17, wherein determining if each block is compressed is performed by reading an embedded compressed/uncompressed bit.

19. The method of claim 17, further comprising determining if the block is compressed by lossy compression, and if so, compensating the decompressed block to reduce noise.

20. The method of claim 19, wherein determining if the block is compressed by lossy compression is performed by reading an embedded lossy/lossless bit.

21. The method of claim 19, wherein compensating the decompressed block comprises reading a noise compensation bit.

22. The method of claim 17, further comprising, if a block is not compressed, determining if the data was compressed by lossy compression, and if so decoding the data and if not reading all the data.

23. The method of claim 13, wherein the uncompression process is performed by first processing the first pixel by reading the first pixel, taking some bits out of the first pixel and sending the removed bits to FIFO, reading additional bits of header and attaching the header bits to the remaining bits of the first pixel, storing the result in a compression buffer, decompressing the processed first pixel, and storing the decompressed first pixel in a decompression buffer.

24. The method of claim 23, wherein the uncompression process is further performed starting with the second pixel by predicting the current pixel value from the previous decompressed pixel, computing the residual between the current and predicted values, determining the number of bits required for the residual, and embedding a stop flag bit and a contained previous bit and any FIFO data in available bits.

25. The method of claim 3:

wherein in said lossy compression, compression noise is compensated by estimating noise in compression and embedding noise information in a compressed block; and

wherein noise is compensated during decompression.

26. The method of claim 3, wherein during compression the least significant bit is truncated and the majority truncated bit is set as a noise compensation bit, and during decompression the least significant bits are set to the majority truncated bit.

27. In a video codec having an encoder core and an external frame memory connected to the encoder core via an external bus, the improvement comprising:

a compression unit at the output of the encoder for compressing data from the encoder prior to inputting into the frame memory via the external bus; and

a decompression unit at the input of the encoder for decompressing the compressed data from the frame memory after retrieving over the external bus.