[FFmpeg-trac] #3393(undetermined:closed): Interlaced H.264 packets are split causing MP4 STTS

FFmpeg trac at avcodec.org
Wed May 7 13:44:10 CEST 2014

#3393: Interlaced H.264 packets are split causing MP4 STTS
             Reporter:  wim_arbor    |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  h264 mov     |               Resolution:  invalid
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  1

Comment (by cehoyos):

 Replying to [comment:7 wim_arbor]:
 > What I understand from the discussion on the mailing list is that
 merging the fields into field pairs violates the ISO specification.
 > > AVC sample: An AVC sample is an access unit as defined in ISO/IEC
 > > access unit: A set of NAL units that are consecutive in decoding order
 and contain exactly one primary coded picture. (...) The decoding of an
 access unit always results in a decoded picture.
 > Each (PAFF) field is encoded as a separate picture, so a sample in a MP4
 file may only contain a single field.

 I don't know much about H.264 but I would have expected that it needs two
 PAFF fields to get a decoded picture.

 > So software which uses the sample count in the MP4 file to determine the
 frame rate is simply wrong. This includes mediainfo, vlc, quicktime and
 gspot. The same applies to other encoders which generate such files.

 > I tested sorenson squeeze with the intel and mainconcept encoder. Both
 merged fields.

 This sounds to me as if we should do the same, particularly if there is no
 playback application that fails for such output files.

Ticket URL: <https://trac.ffmpeg.org/ticket/3393#comment:9>
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