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

• US 20070030904A1
• 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 8,155,194 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 19/51 Motion estimation or motion compensation
• 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 MPEG-2 format to an H.264 format is disclosed. The method generally comprises the steps of (A) decoding an input video stream in the MPEG-2 format to generate a plurality of macroblocks; (B) determining a plurality of indicators from a pair of the macroblocks, the pair of the macroblocks being vertically adjoining; and (C) coding the pair of the macroblocks into an output video stream in the H.264 format using one of (i) a field mode coding and (ii) a frame mode coding as determined from the indicators.

Claims

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

(A) decoding an input video stream in said MPEG-2 format to generate a plurality of macroblocks;

(B) determining a plurality of indicators from a pair of said macroblocks, said pair of said macroblocks being vertically adjoining; and

(C) coding said pair of said macroblocks into an output video stream in said H.264 format using one of (i) a field mode coding and (ii) a frame mode coding as determined from said indicators.

2. The method according to claim 1, wherein said indicators comprise (i) a first motion compensation mode for a top macroblock of said pair and (ii) a second motion compensation mode for a bottom macroblock of said pair.

3. The method according to claim 1, wherein said indicators comprise (i) a first coefficient scan order of a top macroblock of said pair and (ii) a second coefficient scan order of a bottom macroblock of said pair.

4. The method according to claim 1, wherein said pair of said macroblocks are coded into said output video stream in said H.264 format using said field mode coding where said indicators show that at least one macroblock of said pair used said field mode coding in said MPEG-2 format.

5. The method according to claim 1, wherein said pair of said macroblocks are coded into said output video stream in said H.264 format using said field mode coding where said indicators show that at least one macroblock of said pair used a field coefficient scan in said MPEG-2 format and contained a plurality of non-zero coefficients.

6. The method according to claim 1, wherein said pair of said macroblocks are coded into said output video stream in said H.264 format using said frame mode coding where said indicators show that both macroblocks of said pair used said frame mode coding in said MPEG-2 format.

7. The method according to claim 1, wherein said pair of said macroblocks are coded into said output video stream in said H.264 format using said frame mode coding where said indicators show that both macroblocks of said pair used a frame coefficient scan in said MPEG-2 format.

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

(A) decoding a first macroblock in a first row of a picture within an input video stream in said MPEG-2 format;

(B) decoding a second macroblock in a second row of said picture; and

(C) coding said first macroblock and said second macroblock together into an output video stream in said H.264 format using an H.264 macroblock adaptive field/frame coding.

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

detecting an MPEG-2 startcode for said first row before decoding said first macroblock.

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

storing a first position in said input video stream marking said first macroblock as decoded.

11. The method according to claim 10, further comprising the step of:

detecting said MPEG-2 startcode for said second row before completing decoding of said first row.

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

storing a second position in said input video stream marking said second macroblock as decoded.

13. The method according to claim 12, further comprising the steps of:

decoding a third macroblock sequentially following said first position; and

decoding a fourth macroblock sequentially following said second position.

14. The method according to claim 13, further comprising the step of:

coding said third macroblock and said fourth macroblock together into said output video stream using said H.264 macroblock adaptive field/frame coding.

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

(A) decoding an input video stream in said MPEG-2 format to generate a plurality of macroblocks;

(B) determining at least one item from a first of said macroblocks; and

(C) coding said first macroblock into an output video stream in said H.264 format using said at least one item to refine an H.264 motion vector for said first macroblock.

16. The method according to claim 15, wherein said at least one item is an MPEG-2 motion vector for said first macroblock, the method further comprising the step of:

generating an H.264 motion vector for said first macroblock using said MPEG-2 motion vector as a center of a motion compensation search.

17. The method according to claim 15, wherein (i) said first macroblock is decoded from an MPEG-2 I-frame and coded into an H.264 P-frame and (ii) said at least one item is an MPEG-2 intra frame concealment motion vector used as a starting point for finding said H.264 motion vector.

18. The method according to claim 15, wherein said at least one item comprises an MPEG-2 fcode, the method further comprising the step of:

determining a size for said refine of said H.264 motion vector based on said MPEG-2 fcode.

19. The method according to claim 15, wherein said at least one item comprises an MPEG-2 fcode, the method further comprising the step of:

determining one of (i) a spatial direct mode and (ii) a temporal direct mode for said first macroblock based on said MPEG-2 fcode.

20. The method according to claim 15, further comprising the steps of:

determining an MPEG-2 quantization parameter for said first macroblock;

controlling an encoder rate for said output video stream using said quantization parameter as an H.264 macroblock complexity indicator.