On Thu, Aug 13, 2020 at 10:34 AM Marton Balint <c...@passwd.hu> wrote: > > > > On Thu, 13 Aug 2020, Jan Ekström wrote: > > > While having the possibility of non-NOPTS values that can suddenly > > jump in time due to adjustments to match PCR is not nice for DVB > > subtitles, apparently the parser for this format bases its behavior on > > whether the packets' timestamps are NOPTS or not. > > Actually what matters is that the parser separates packets which have > different PTS values. Having a DVB subtitle packet with no PTS is not even > valid based on what I read from the specs: > > "Each PES header shall carry a PTS, associated with all the subtitle data > contained within that PES packet. " > > So I guess current code assumes that if a packet has no PTS then it is > also part of the previous packet, but this also seems like a workaround > for bad streams... >
Yup, it's layers upon layers of fun :) Just like a box of chocolates or an onion. I posted this patch to get a discussion rolling, as I was highlighted on the parser being broken with NOPTS. > > Thus while we can adjust timestamps, we should exclude DVB subtitles > > from the timestamp unsetting logic. > > Ok, but to be frank the timestamp setting logic (even when it is > used with PCR) also breaks the parser, because it might assign different > PTS to PES packets which have the same PTS... > Yup. Cascades of things and all that jazz are fun. I just addressed the most obvious bit which I caused by my unsetting of timestamps (which in turn was to make sure that the time line doesn't suddenly jump X hours back or so). On trac reverting http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=42aa02418e43802b4ebcca373d2413ab63a0307e was mentioned, but that seems to have been a case fixing https://trac.ffmpeg.org/ticket/4200 . The ticket lacks exact details, but I expect there to be a bad mux with the subtitle timestamps not matching the general time line according to PCR. > > > > Fixes #8844 > > --- > > libavformat/mpegts.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c > > index f71f18a57d..50d4d5e9bc 100644 > > --- a/libavformat/mpegts.c > > +++ b/libavformat/mpegts.c > > @@ -1343,7 +1343,8 @@ skip: > > } > > } > > > > - if (!pcr_found) { > > + if (pes->st->codecpar->codec_id == > > AV_CODEC_ID_DVB_TELETEXT && > > + !pcr_found) { > > av_log(pes->stream, AV_LOG_VERBOSE, > > "Forcing DTS/PTS to be unset for a " > > "non-trustworthy PES packet for PID %d as " > > Patch LGTM, I am just saying that the problems lies more deep... > Thanks. Unless people have a better idea of how to go forward with this, I'll apply this patch. Jan _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
