Method and apparatus for H.264 to MPEG-2 video transcoding

• US 20070030903A1
• 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, Winger, Lowell
• Granted Patent: US 7,881,384 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 an H.264 format to an MPEG-2 format is disclosed. The method generally comprises the steps of (A) decoding an input video stream in the H.264 format to generate a picture having a plurality of macroblock pairs that used an H.264 macroblock adaptive field/frame coding; (B) determining a mode indicator for each of the macroblock pairs; and (C) coding the macroblock pairs 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 mode indicators.

Claims

1. A method for transcoding from an H.264 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said H.264 format to generate a picture having a plurality of macroblock pairs that used an H.264 macroblock adaptive field/frame coding;

(B) determining a mode indicator for each of said macroblock pairs; and

(C) coding said macroblock pairs 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 mode indicators.

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

determining an H.264 scan order for each of said macroblock pairs, wherein said coding of said macroblock pairs into said output video stream is seeded using said H.264 scan orders.

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

comparing a residual vertical field activity with a residual frame activity to generate a residual indicator, wherein use of (i) said MPEG-2 field mode coding and (ii) said MPEG-2 frame mode coding is further determined by said residual indicator.

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

performing an intra-frame estimation to generate an estimation indicator, wherein use of (i) said MPEG-2 field mode coding and (ii) said MPEG-2 frame mode coding is further determined by said estimation indicator.

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

performing an intra-field estimation to generate an estimation indicator, wherein use of (i) said MPEG-2 field mode coding and (ii) said MPEG-2 frame mode coding is further determined by said estimation indicator.

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

performing an MPEG-2 discrete cosine transform scan decision to generate a discrete cosine transform indicator, wherein use of (i) said MPEG-2 field mode coding and (ii) said MPEG-2 frame mode coding is further determined by said discrete cosine transform indicator.

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

generating a plurality of MPEG-2 motion vectors for said macroblock pairs from a plurality of H.264 motion vectors for said macroblock pairs.

8. A method for transcoding from an H.264 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said H.264 format to generate a picture having a plurality of macroblocks with a plurality of H.264 motion vectors pointing to at least three reference frames;

(B) scaling said H.264 motion vectors to generate a plurality of seed motion vectors that point to at most two reference frames; and

(C) coding said macroblocks into an output video stream in said MPEG-2 format based on said seed motion vectors.

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

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

10. The method according to claim 8, wherein said input video stream has an H.264 hierarchical group of pictures, the method further comprising the step of:

coding an MPEG-2 I-frame in said output video stream wherever an H.264 I-frame is received in said input video stream.

11. The method according to claim 8, wherein said input video stream has an H.264 hierarchical group of pictures, the method further comprising the step of:

prioritizing a plurality of frames in said H.264 hierarchical group of pictures from a highest desirability to a lowest desirability for use as a plurality of MPEG-2 reference frames.

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

adjusting an MPEG-2 group of pictures to utilize a least number of lowest priority frames among said MPEG-2 reference frames.

13. The method according to claim 11, wherein a highest frame of said frames in said H.264 hierarchical group has a highest priority for use as one of said MPEG-2 reference frames.

14. The method according to claim 13, wherein said highest frame comprises a reference I-frame.

15. A method for transcoding from an H.264 format to an MPEG-2 format, comprising the steps of:

(A) decoding an input video stream in said H.264 format to generate a picture;

(B) determining that said picture had an H.264 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.

16. The method according to claim 15, further comprising the step of:

determining an H.264 scan order for said picture, wherein said coding of said picture into said output video stream is seeded using said H.264 scan order.

17. The method according to claim 15, further comprising the step of:

mapping an H.264 16×

16 macroblock partition in said picture to at least one of (i) an MPEG-2 16×

16 partition and (ii) an MPEG-2 16×

8 partition.

18. The method according to claim 15, further comprising the step of:

mapping an H.264 16×

8 macroblock partition in said picture to an MPEG-2 16×

8 partition.

19. The method according to claim 15, further comprising the step of:

combining a plurality of H.264 motion vectors from an H.264 macroblock partition in said picture to generate a seed motion vector for an MPEG-2 partition.

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

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