On Tue, Apr 19, 2022 at 11:06 PM Marton Balint <c...@passwd.hu> wrote: > > > > On Tue, 19 Apr 2022, Jan Ekström wrote: > > > On Tue, Apr 19, 2022 at 1:13 PM Jan Ekström <jee...@gmail.com> wrote: > >> > >> On Tue, Apr 19, 2022 at 3:00 AM Marton Balint <c...@passwd.hu> wrote: > >> > > >> > > >> > > >> > On Thu, 14 Apr 2022, Jan Ekström wrote: > >> > > >> > > On Mon, Apr 11, 2022 at 1:50 PM Jan Ekström <jee...@gmail.com> wrote: > >> > >> > >> > >> From: Jan Ekström <jan.ekst...@24i.com> > >> > >> > >> > >> Additionally, they should not be probed, as this is essentially > >> > >> various types of binary data. > >> > >> > >> > >> Signed-off-by: Jan Ekström <jan.ekst...@24i.com> > >> > >> --- > >> > > > >> > > Ping. > >> > > > >> > > Basically this checks if we have an unknown stream with a private > >> > > stream type still at the end of the per-stream loop in PMT parsing, > >> > > and then cancels the stop of parsing that usually occurs as a PMT is > >> > > hit. Instead the logic will continue parsing further. When an SDT is > >> > > then found and a PMT for that program has already been received, it > >> > > will then stop header reading at that point. > >> > > >> > But why does it matter when the initial parsing is stopped? I mean it > >> > stops at the first PMT right now, nobody expects it to find all the > >> > programs and all the streams or all the stream codecs/parameters. > >> > > >> > I am saying, that ideally, the ts->stop_parse magic should not be needed > >> > to be changed to fix your issue and when an SDT is detected with the > >> > broadcast descriptor that should stop any existing data stream parsing. > >> > Do > >> > you know why it does not work like that? > >> > > >> > >> If the codec is unknown after header parsing, the general parsing > >> logic is utilized to probe which codec is possibly in that unknown > >> stream, and thus more data is read from that stream, which can cause > >> further delays. > >> > >> If the codec is known as data, it leads to no such result. > >> > >> Basically, the idea is to figure out whether a stream is a data stream > >> or not during header parsing, if possible. > >> > > > > Just double-checked and the difference is whether > > max_stream_analyze_duration gets utilized in > > libavformat/demux.c::avformat_find_stream_info . > > > > If a stream is marked as unknown, it will get checked for longer. If > > it is marked as a known "codec" it gets through quicker. > > The part of the patch which parses the SDT and sets the codec is fine. > But the fact that you have to set the codec during mpegts_read_header > to make it stop parsing definitely looks like some bug in some code > somewhere. It should be enough to set the codec sometime later in > mpegts_read_packet() (which is called during avformat_find_stream_info()) > > Or to make it even more strange: comment out handle_packets() in > mpegts_read_header. And it will work just fine. So if nothing is parsed > in mpegts_read_header then it works. If something is parsed, then it does > not. Kind of unexpected... > > Regards, > Marton
Hi, So I poked at this again and did the changes you requested. The result is that if the "continue parsing until SDT if you have these sorts of streams in-band" logic is removed, it leads to the FATE test ending up with the result of "codec_name=unknown". Which makes the test rather useless as it doesn't actually show that the stream is noted as a data stream. Additionally, I thought the logic made sense since as much as I dislike having information outside of PMT being utilized for PMT purposes, that is effectively what this SDT descriptor is utilized for. Given I specifically limited this logic to unknown streams within a specific stream identifier range, the effect of this change would have been far-from-global as well. I have a hunch that information is copied from the lavf-internal codec context to codecpar at one point, and then no further synchronization is attempted. As for the results being different without any packets being actually demuxed, codec_info_nb_frames is possibly a variable which has some relevance to it, although most checks against it seem to be of the > 1 type, instead of > 0. 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".
