[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
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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
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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
14496‐10
>
> > 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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