Method and apparatus for VC-1 to MPEG-2 video transcoding

• US 20070030902A1
• Filed: 08/05/2005
• Published: 02/08/2007
• Est. Priority Date: 08/05/2005
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Cote, Guy, Joch, Anthony, Winger, Lowell
• Granted Patent: US 7,903,739 B2
• Time in Patent Office: Days
• US Class Current: 375/240.160
• CPC Class Codes: H04N 19/112 according to a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/16 for a given display mode, e.g. for interlaced or progressive display mode
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 19/42 characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A method for transcoding from a VC-1 format to an MPEG-2 format is disclosed. The method generally comprises the steps of (A) decoding an input video stream in the VC-1 format to generate a picture; (B) determining a first mode indicator for the picture; and (C) coding the picture into an output video stream in the MPEG-2 format using one of (i) an MPEG-2 field mode coding and (ii) an MPEG-2 frame mode coding as determined from the first mode indicator.

Claims

1. A method for transcoding from a VC-1 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said VC-1 format to generate a picture;

(B) determining a first mode indicator for said picture; and

(C) coding said picture into an output video stream in said MPEG-2 format using one of (i) an MPEG-2 field mode coding and (ii) an MPEG-2 frame mode coding as determined from said first mode indicator.

2. The method according to claim 1, wherein said output video stream uses an MPEG-2 field macroblock mode while both (i) said picture in said input video stream has a VC-1 field coding and (ii) said output video stream uses an MPEG-2 interlaced frame coding.

3. The method according to claim 1, further comprising the step of:

determining a discrete cosine transform mode indicator for each of a plurality of macroblocks of said picture in said input video stream.

4. The method according to claim 3, wherein said coding of said picture into an output video stream is based on a respective one of said discrete cosine transform mode indicators for each of said macroblocks in said output video stream.

5. The method according to claim 1, wherein said input video stream uses a motion vector switch, further comprising the step of:

reversing a direction of a second motion vector relative to a first motion vector into a first reference frame.

6. The method according to claim 5, further comprising the step of:

scaling said second motion vector into a second reference frame temporarily opposite said first reference frame.

7. The method according to claim 6, wherein said scaling in based on a first temporal distance to said first reference frame relative to a second temporal distance to said second reference frame.

8. A method for transcoding from a VC-1 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said VC-1 format to generate a picture having a plurality of macroblocks;

(B) combine a plurality of macroblocks having a first partition into a second partition larger than said first partition; and

(C) coding said picture into an output video stream in said MPEG-2 format using said second partition.

9. The method according to claim 8, wherein step (B) comprises the sub-step of:

combining said macroblocks having an 8×

8 partition with a VC-1 frame mode into a 16×

16 partition with an MPEG-2 frame mode.

10. The method according to claim 8, wherein step (B) comprises the sub-step of:

combining said macroblocks having an 8×

8 partition with a VC-1 field mode into a 16×

8 partition with an MPEG-2 field mode.

11. The method according to claim 8, further comprising the step of:

combining a plurality of VC-1 motion vectors from a VC-1 macroblock partition in said picture to generate a seed motion vector for an MPEG-2 partition.

12. The method according to claim 11, further comprising the step of:

using said seed motion vector as a motion compensation center for an MPEG-2 motion vector.

13. The method according to claim 11, wherein the step of said combining said VC-1 motion vectors comprises the sub-step of:

calculating a median among said VC-1 motion vectors for each of said second partitions to generate a respective MPEG-2 motion vector for each of said second partitions.

14. The method according to claim 13, wherein said median comprises one of (i) a vector median and (ii) a vertical median and a horizontal median.

15. The method according to claim 11, wherein the step of said combining said VC-1 motion vectors comprises the sub-step of:

utilizing one of said VC-1 motion vectors occupying a largest area within each of said second partitions to generate a respective MPEG-2 motion vector for each of said second partitions.

16. A method for transcoding from a VC-1 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said VC-1 format to generate a picture;

(B) determining that said picture had a VC-1 picture adaptive field/frame coding in said input video stream; and

(C) coding said picture into an output video stream in said MPEG-2 format using an MPEG-2 frame mode coding.

17. The method according to claim 16, further comprising the step of:

determining a VC-1 scan order for said picture, wherein said coding of said picture into said output video stream is seeded using said VC-1 scan order.

18. The method according to claim 16, further comprising the step of:

determining a VC-1 motion compensation mode for each of a plurality of macroblocks of said picture in said input video stream, wherein said coding of said picture into said output video stream uses an MPEG-2 motion compensation mode for each of said macroblocks in said output video stream based on a respective one of said VC-1 motion compensation modes.

19. The method according to claim 16, further comprising the step of:

calculating a plurality of seed motion vectors from a plurality of VC-1 motion vectors of said picture.

20. The method according to claim 19, further comprising the step of:

using said seed motion vectors as a plurality of motion compensation centers for a plurality of MPEG-2 motion vectors.