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

FFmpeg trac at avcodec.org
Fri Mar 21 08:57:06 CET 2014

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

Comment (by 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.

 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.

Ticket URL: <https://trac.ffmpeg.org/ticket/3393#comment:7>
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