#11462: Cannot embed .scc file into .mp4 using -c:s copy
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Reporter: Zach | Owner: (none)
Type: enhancement | Status: new
Priority: important | Component:
| undetermined
Version: git-master | Resolution:
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by Devin Heitmueller):
Ok, so a few comments.
The MP4 format can certainly do a dedicated 608 track (i.e. it doesn't
have to be embedded in SEI). In fact, the MP4 muxer (movenc.c) supports
this, although looking at the code I wouldn't say it's very robust. Also,
I've implemented correct output of 608 with decklink when the file source
is MP4 and it has a c608 track.
So in terms of the various standards, it's definitely possible to embed a
608 stream in an MP4 without it being in the H.264 SEI.
See the following link from Apple on the cdat atom:
https://developer.apple.com/documentation/quicktime-file-
format/closed_captioning_sample_data
The cc_fifo mechanism I wrote for ffmpeg was never intended arbitrary 608
padding if not present in the source stream. It just ensures the 608
tuples are embedded with the proper rate control assuming it's already
present in the source. That said, it wouldn't be hard to have the cc_fifo
insert padding.
My suggestion would be we should add a BSF which takes in the 608 stream
from the SCC, reformats the 608 tuples to have the proper rate, and then
feeds into the MP4 mux. We already have the vf_ccrepack filter which
operates on AVFrames, but we would need to create a BSF equivalent which
works on C608 AVPackets.
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Ticket URL: <https://trac.ffmpeg.org/ticket/11462#comment:23>
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