Region-based refresh strategy for video compression

• US 6,304,295 B1
• Filed: 01/08/1999
• Issued: 10/16/2001
• Est. Priority Date: 09/18/1998
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation), Sarnoff Corporation (SRI International, Inc.)
• Original Assignee: LG Electronics, Inc. (LG Corporation), Sarnoff Corporation (SRI International, Inc.)
• Inventors: Krishnamurthy, Ravi, Sethuraman, Sriram
• Primary Examiner(s): Kelley, Chris
• Assistant Examiner(s): PHILIPPE, GIMS S
• Application Number:
  US09/227,520
• Time in Patent Office: 1,012 Days
• Field of Search: 375/240, 348/699, 348/407.1, 348/413.1, 348/416.1, 348/845.1, 348/845.2, 348/466, 348/419.1, 348/409.1, 348/384, 348/402.1, 348/423.1, 348/415.1, 348/420.1, 395/200.77
• US Class Current: 348/420.1
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• 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 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/162 User input
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/192 the adaptation method, adaptation tool or adaptation type being iterative or recursive
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/198 including smoothing of a sequence of encoding parameters, e.g. by averaging, by choice of the maximum, minimum or median value
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 19/523 with sub-pixel accuracy
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/65 using error resilience
• CPC Class Codes: H04N 19/66 : involving data partitioning, i.e. separation of data into packets or partitions according to importance
• CPC Class Codes: H04N 19/68 : involving the insertion of resynchronisation markers into the bitstream
• CPC Class Codes: H04N 19/69 : involving reversible variable length codes [RVLC]
• CPC Class Codes: H04N 19/895 : in combination with error concealment

Abstract

Frames in a video sequence are divided into two or more regions and a specified number of macroblocks are selected in each region for intra-coding. Depending on the particular implementation, for one or more of the regions, the intra-macroblocks are selected randomly, while at least one other region is dividing into a specified number of slices with the least-recently intra-coded macroblock in each slice selected for intra-coding. When an error is detected at the decoder, the decoder discards data in the corresponding packet and applies a concealment strategy that involves using motion-compensated data if the motion vectors were accurately decoded; otherwise, using non-motion-compensated reference data for the macroblocks affected by the discarding of data. The refresh strategy of the present invention can be used to provide the resulting encoded bitstream with resilience to transmission errors, while maintaining an acceptable degree of video compression.

Claims

1. A method for compressing frames of a video sequence, comprising the steps of:

(a) dividing each frame into two or more regions, each region comprising a plurality of macroblocks;

(b) selecting one or more macroblocks in each region to be intra-coded, wherein, for each frame, selection of the one or more macroblocks in each region is independent of selection of the one or more macroblocks in every other region of the frame; and

(c) encoding each frame, wherein the selected macroblocks are intra-coded.

2. The invention of claim 1, wherein, for at least one of the regions, the one or more macroblocks to be intra-coded are selected randomly in the region.

3. The invention of claim 1, wherein, for at least one other of the regions, the region is divided into two or more slices, and a least-recently intra-coded macroblock in each slice is selected for intra-coding for each frame.

4. The invention of claim 3, wherein a specified selection rule is applied if there are two or more least-recently intra-coded macroblocks in a slice.

5. The invention of claim 1, wherein:

step (a) comprises the step of dividing each frame into a most-important region, a less-important region, and a least-important region; and

step (b) comprises the steps of;

(1) randomly selecting a first specified number of macroblocks in the least-important region to be intra-coded;

(2) randomly selecting a second specified number of macroblocks in the less-important region to be intra-coded; and

(3) dividing the most-important region into a third specified number of slices and selecting a least-recently intra-coded macroblock in each slice for intra-coding.

7. The invention of claim 1, wherein, for at least one of the regions, the one or more macroblocks to be intra-coded are selected randomly in the region.

8. The invention of claim 1, wherein, for at least one other of the regions, the region is divided into two or more slices, and a least-recently intra-coded macroblock in each slice is selected for intra-coding for each frame.

9. The invention of claim 8, wherein a specified selection rule is applied if there are two or more least-recently intra-coded macroblocks in a slice.

10. The invention of claim 1, wherein:

step (a) comprises the step of dividing each frame into a most-important region, a less-important region, and a least-important region; and

step (b) comprises the steps of;

(1) randomly selecting a first specified number of macroblocks in the least-important region to be intra-coded;

(2) randomly selecting a second specified number of macroblocks in the less-important region to be intra-coded; and

(3) dividing the most-important region into a third specified number of slices and selecting a least-recently intra-coded macroblock in each slice for intra-coding.

15. The invention of claim 1, wherein each frame is divided into two or more regions based on content of the frame.

6. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for compressing frames of a video sequence, the method comprising the steps of:

(a) dividing each frame into two or more regions, each region comprising a plurality of macroblocks;

(b) selecting one or more macroblocks in each region to be intra-coded, wherein, for each frame, selection of the one or more macroblocks in each region is independent of selection of the one or more macroblocks in every other region of the frame; and

(c) encoding each frame, wherein the selected macroblocks are intra-coded.

16. The invention of claim 6, wherein each frame is divided into two or more regions based on content of the frame.

11. A method for decoding a compressed video bitstream, comprising the steps of:

(a) receiving the compressed video bitstream, wherein the compressed video bitstream was encoded by;

(1) dividing each frame into two or more regions, each region comprising a plurality of macroblocks;

(2) selecting one or more macroblocks in each region to be intra-coded, wherein, for each frame, selection of the one or more macroblocks in each region is independent of selection of the one or more macroblocks in every other region of the frame; and

(3) encoding each frame, wherein the selected macroblocks are intra-coded; and

(b) decoding the compressed video bitstream, wherein, if an error is detected in a data packet of the compressed video bitstream, then data in the packet are discarded and a concealment strategy is implemented for macroblocks corresponding to the discarded data.

12. The invention of claim 11, wherein the concealment strategy comprises:

(1) using motion-compensated data for the corresponding macroblocks, if motion vectors are accurately decoded; and

(2) using non-motion-compensated reference data for the corresponding macroblocks, if the motion vectors are not accurately decoded.

13. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for decoding a compressed video bitstream, the method comprising the steps of:

(a) receiving the compressed video bitstream, wherein the compressed video bitstream was encoded by;

(1) dividing each frame into two or more regions, each region comprising a plurality of macroblocks;

(2) selecting one or more macroblocks in each region to be intra-coded, wherein, for each frame, selection of the one or more macroblocks in each region is independent of selection of the one or more macroblocks in every other region of the frame; and

(3) encoding each frame, wherein the selected macroblocks are intra-coded; and

(b) decoding the compressed video bitstream, wherein, if an error is detected in a data packet of the compressed video bitstream, then data in the packet are discarded and a concealment strategy is implemented for macroblocks corresponding to the discarded data.

14. The invention of claim 13, wherein the concealment strategy comprises:

(1) using motion-compensated data for the corresponding macroblocks, if motion vectors are accurately decoded; and

(2) using non-motion-compensated reference data for the corresponding macroblocks, if the motion vectors are not accurately decoded.