[FFmpeg-devel] MPEGTS stream auto-guessed before PMT is read

[Stephen D'Angelo]

On 11/19/2010 1:54:49 AM, Baptiste Coudurier wrote:
> To: FFmpeg development discussions and patches
> Subject: Re: [FFmpeg-devel] MPEGTS stream auto-guessed before PMT is 
> read
> 
> Hi,
> 
> On 11/18/10 8:53 AM, Stephen D'Angelo wrote:
> > Hello,
> > 
> > I have encountered transport streams where the AVStreams
> created are
> > not properly associated with the AVPrograms.  I'm no expert on the 
> > current mpegts.c code, but I believe it is happening
> because of the following:
> > 
> > - The PMT for the stream's program is not read in
> mpegts_read_header
> > before auto_guess is turned on (line 1401)
> > - During av_find_stream_info, the pes stream is added to
> ts->pids in
> > handle_packet because auto_guess is true (line 1196)
> > - The PMT is read later and in pmt_cb the pes stream in found in
> > ts->pids, but pes->st has not been set yet, causing pmt_cb to return
> > (line 936)
> > - The AVStream for the pes stream is then added later in 
> > mpegts_push_data (line 693), but it is not properly associated with 
> > its AVProgram
> > 
> > The following patch fixes the problem by creating an
> AVStream for the
> > pes stream if it doesn't have one, and then the subsequent call to 
> > ff_program_add_stream_index properly associates the
> AVStream with the
> > AVProgram.
> > 
> > Index: libavformat/mpegts.c
> > ===================================================================
> > --- libavformat/mpegts.c        (revision 25762)
> > +++ libavformat/mpegts.c        (working copy)
> > @@ -926,6 +926,8 @@
> >          if (ts->pids[pid] && ts->pids[pid]->type == MPEGTS_PES) {
> >              pes = ts->pids[pid]->u.pes_filter.opaque;
> >              st = pes->st;
> > +            if (!st)
> > +                st = pes->st = av_new_stream(pes->stream,
> pes->pid);
> >          } else {
> >              if (ts->pids[pid]) mpegts_close_filter(ts,
> > ts->pids[pid]); //wrongly added sdt filter probably
> >              pes = add_pes_stream(ts, pid, pcr_pid);
> > 
> > Would it instead make more sense to "add_pid_to_pmt" before
> checking
> > that there is no AVStream (line 936) and "continue" if there is no 
> > AVStream (line 937) so that all of the pes streams are
> associated with
> > the program and then after calling av_new_stream in
> mpegts_push_data,
> > call ff_program_add_stream_index to associate the AVStream with its 
> > AVProgram?  If it's done that way, the AVStream will not have the 
> > proper language information that's added in pmt_cb.
> 
> Thanks for the patch.
> I believe it is correct and that's the good approach. PMT is the 
> reference.
> 
> Can you please submit a file which shows this problem ?
> 
> Thanks.

Sorry about that, this message flew past me.  I'll blame Outlook's
message threading.  This also explains your question as to whether I
read the mailing list.

I have uploaded a sample to
/MPlayer/incoming/mpegts_autoguess_before_pmt

Like the previous sample, I've noted that it is copyrighted material.

Thanks,

 - Stephen