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

[Baptiste Coudurier]

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.

-- 
Baptiste COUDURIER
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