[FFmpeg-trac] #1296(undetermined:new): Multi-thread decoding artifact for MTS H.264

[FFmpeg]

#1296: Multi-thread decoding artifact for MTS H.264
----------------------------------+----------------------------------------
             Reporter:  andreasg  |                    Owner:
                 Type:  defect    |                   Status:  new
             Priority:  normal    |                Component:  undetermined
              Version:  0.10.3    |               Resolution:
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
----------------------------------+----------------------------------------

Comment (by andreasg):

 git bisect does not seem to handle the ffmpeg git structure very well.  I
 checked by hand several revisions around the revision indicated by git
 bisect and I believe that I found the revision that introduced the
 problem.  I have no idea how support for subtitles could produce this
 problem.

 {{{
 commit d150a147dac67faeaf6b1f25a523ae330168ee1e
 Author: David Mitchell <dave at fallingcanbedeadly.com>
 Date:   Thu Jan 19 07:31:01 2012 -0800

     Improve support for PGS subtitles.

     The previous implementation assumed that a new picture would always
     supersede the previous picture. Similarly, presentation segments
     were assumed to pertain to the most-recently-read picture.

     However, each presentation segment may refer to 0 or more pictures
     by their ID. Picture IDs may repeat, and a repeated picture ID
     indicates that the old picture for that ID is no longer needed
     and may be discarded.

     The new implementation allocates a buffer with one slot for each
     possible picture ID (the picture ID is a 16-bit field) and
     properly decodes presentation segments so that all relevant
     pictures are output upon encountering a display segment.

     Given that most PGS streams are unlikely to use more than a small
     fraction of the available picture IDs, it would probably be better
     to use a more memory-efficient data structure. I'm lazy though, so
     I leave this to a more motivated individual.

     I've tested the code with MKV files in VLC (a recent revision from
     their git repo) and with HandBrake (a version that I hacked up to
     use ffmpeg's PGS subtitle decoder).

     Review-by: Hendrik Leppkes <h.leppkes at gmail.com>
     Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
 }}}

 Here are the revisions that I tested.

 {{{
 b720915be103cc8b062405bf9f7765ce3ad679d1 bad
 af21823ae0dc8f72446f9beb22563a72f485a57c bad
 0bb57f8bf029427059be21a562527dcfa0e264c9 bad
 b955d4072e3e563b230c9ab4d6575577a3dc7314 bad
 f58d67000247eb8ac5029c3f16634d5851d4dfa9 bad
 0fec2cb15cc6ff1fcc724c774ec36abadcb7b6ad good
 2aadff2e44fa27664ccd1b0a63829e61bf82e939 bad
 d150a147dac67faeaf6b1f25a523ae330168ee1e bad
 cf7c7f13cdad07a174110625f8452c8e3444717b good
 575d494de561049f36f9c5492e05c7d83dd78e75 good
 feb997577b66367a0c4269100888640699ee890d good
 9bf9c314a093db16a009829bfe874bf03ffaecc9 good
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1296#comment:4>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker