[FFmpeg-trac] #8844(avformat:open): DVB subtitles don't work without PCR any more
FFmpeg
trac at avcodec.org
Thu Aug 13 00:53:30 EEST 2020
#8844: DVB subtitles don't work without PCR any more
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Reporter: mkver | Owner:
Type: defect | Status: open
Priority: important | Component: avformat
Version: git-master | Resolution:
Keywords: mpegts | Blocked By:
regression |
Blocking: | Reproduced by developer: 1
Analyzed by developer: 1 |
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Comment (by JEEB):
I have no real preference on this. Personally, I have mostly seen such
blind mux of TS packets with DVB teletext, and not with DVB subtitles
(although thankfully this is not too popular - just something you end up
seeing every now and then).
And yes, the re-timing logic already existed and since both formats were
within that if both are affected. The reasoning to add the NOPTS logic was
to not make it so that if you first get a subtitle packet, and *then* PCR
is received, you would not suddenly have a f.ex. 8 hour time difference
between these two packets in your API client, leading to quite hilarious
results. On the other hand, NOPTS makes no promises about what the
timestamp is, and API clients seem to handle it OK (including ffmpeg.c)
That said, for the DVB subtitle parser clearly NOPTS is a special value,
and the unsetting of timestamps shouldn't be applied to it. That can
either be handled by removing DVB subtitles from the re-timing logic
(which apparently was required for some sample looking at the commit
message?), or at least excluded from the NOPTS logic.
I will for now post a patch doing the latter, and which way forward is
better can also be discussed in that thread.
Normal streams without the PCR removed are unlikely to have been affected
largely since as soon as you received PCR, the possibility of the
timestamps being NOPTS'ified would get removed.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8844#comment:4>
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