Video coding with optimized low complexity variable length codes

• US 5,563,593 A
• Filed: 03/18/1994
• Issued: 10/08/1996
• Est. Priority Date: 03/18/1994
• Status: Expired due to Term

• Current Assignee: Multimedia Patent Trust
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Puri, Atul
• Primary Examiner(s): Young, Brian K.
• Application Number:
  US08/215,341
• Time in Patent Office: 935 Days
• Field of Search: 341/67, 341/50, 341/63, 341/106
• US Class Current: 341/67
• CPC Class Codes: H03M 7/42 using table look-up for the coding or decoding process, e.g. using read-only memory H03M7/4006 takes precedence
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/169 characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/91 Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Abstract

A novel group of optimized variable word-length codes for intra coded pictures is disclosed. Hardware complexity and implementation cost is minimized by only optimizing the variable word-length codes for intra coded pictures for a small, but frequently occurring number of discrete cosine transform events. A table of variable word-length codes conforming to the Motion Pictures Expert Group Phase 1 ("MPEG-1") standard may be used for the remaining number of less frequently occurring events. In an illustrative example of the invention, the MPEG-1 variable word-length code table is also used to code non-intra pictures which advantageously allows for totally compatible operation with the MPEG-1 standard.

Claims

1. An apparatus for performing variable word-length coding comprising:

a means for receiving video signals each having a run-length and a level, the video signals representing at least a portion of an intra-coded picture;

a means for performing variable word-length coding of the video signals in accordance with the following table;

space="preserve" listing-type="tabular">______________________________________ RUN LEVEL LENGTH 1 2 3 4 5 6 7 8 ______________________________________ 0 3 4 5 6 7 7 8 9 1 4 6 8 9 9 2 6 8 9 11 3 6 9 4 7 9 5 7 10 6 8 7 8 8 8 9 8 10 8 11 9 12 9 13 9 14 10 15 10 16 11 ______________________________________ RUN LEVEL LENGTH 9 10 11 12 13 14 15 ______________________________________ 0 9 9 9 9 9 9 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ______________________________________

in which the values on the abscissa each represent the level of a video signal, the values on the ordinate each represent the run-length of a video signal, and the entries in the table each represent a number of bits in codes to be assigned to a video signal.

2. The apparatus of claim 1 wherein said table includes a plurality of additional entries which are compatible with the Motion Pictures Expert Group Phase 1 standard.

3. The apparatus of claim 1 wherein a Motion Pictures Expert Group Phase 1 compatible variable word-length code is utilized to encode non-intra coded video signals.

4. The apparatus of claim 3 further including a means for adaptively selecting a first or a second coding mode.

5. The apparatus of claim 4 wherein said first coding mode utilizes variable word-length coding entries in said table.

6. The apparatus of claim 5 wherein said second coding mode utilizes Motion Pictures Expert Group Phase 1 compatible variable word-length coding.

7. The apparatus of claim 4 wherein said means for adaptively selecting are responsive to a picture type received by said means for receiving.

8. The apparatus of claim 1 wherein said variable word-length coding is performed on a segment of the received video signal wherein said segment is selected from the group consisting of blocks, macroblocks, and pictures.

9. The apparatus of claim 3 wherein said non-intra coded video signals includes inter-coded video signals.

10. The apparatus of claim 1 wherein said non-intra coded video signal includes predicted-coded video signals.

11. The apparatus of claim 1 wherein one or more MPEG-1 variable word-length codes are utilized when a received video signal has a combination of run-length and level for which there is no entry in said table.

12. A method for performing variable word-length coding comprising:

receiving video signals each having a run-length and a level, the video signals representing at least a portion of an intra-coded picture;

performing variable word-length coding of the video signals in accordance with the following table;

space="preserve" listing-type="tabular">______________________________________ RUN LEVEL LENGTH 1 2 3 4 5 6 7 8 ______________________________________ 0 3 4 5 6 7 7 8 9 1 4 6 8 9 9 2 6 8 9 11 3 6 9 4 7 9 5 7 10 6 8 7 8 8 8 9 8 10 8 11 9 12 9 13 9 14 10 15 10 16 11 ______________________________________ RUN LEVEL LENGTH 9 10 11 12 13 14 15 ______________________________________ 0 9 9 9 9 9 9 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ______________________________________

in which the values on the abscissa each represent the level of a video signal, the values on the ordinate each represent the run-length of a video signal, and the entries in the table each represent a number of bits in codes to be assigned to a video signal.

13. The method of claim 12 wherein one or more MPEG-1 variable word-length codes are utilized when a received video signal has a combination of run-length and level for which there is no entry in said table.

14. The method of claim 12 further including a step of adaptively selecting a first or a second coding mode.

15. The method of claim 12 wherein said first coding mode utilizes variable word length coding entries in said table.

16. The method of claim 15 wherein said second coding mode utilizes Motion Pictures Expert Group Phase 1 compatible variable word-length coding.

17. The method of claim 16 wherein said step of adaptively selecting is responsive to a picture type received during said step of receiving video signals.

18. The method of claim 12 wherein said variable word-length coding is performed on a segment of the received video signal wherein said segment is selected from the group consisting of blocks, macroblocks, and pictures.