[FFmpeg-devel] avformat/mpegts: respect program number when merging streams

merge_pmt_versions was not usable if multiple programs were present because
when it was searching for candidate streams it did not make sure that the PMT was
of the same program. This caused the streams of all programs to get merged into
a single (garbled) program.

This patch makes sure that the program number (service ID) is also matching
with the old streams when parsing the PMT making the feature useful for multi
program streams.

This change might cause issues for single program streams if the program number
changes as well, but I think it is acceptable because the goal of the option is
to make the parsing resilient to PID changes, and that is still working as
expected.

Signed-off-by: Marton Balint <cus@passwd.hu>
---
 libavformat/mpegts.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

On Tue, Jul 9, 2019 at 2:07 PM Marton Balint <cus@passwd.hu> wrote:

> merge_pmt_versions was not usable if multiple programs were present because
> when it was searching for candidate streams it did not make sure that the
> PMT was
> of the same program. This caused the streams of all programs to get merged
> into
> a single (garbled) program.
>
> This patch makes sure that the program number (service ID) is also matching
> with the old streams when parsing the PMT making the feature useful for
> multi
> program streams.
>
> This change might cause issues for single program streams if the program
> number
> changes as well, but I think it is acceptable because the goal of the
> option is
> to make the parsing resilient to PID changes, and that is still working as
> expected.
>

Patch looks good to me. Thanks for catching this!

Aman


>
> Signed-off-by: Marton Balint <cus@passwd.hu>
> ---
>  libavformat/mpegts.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index 8a84e5cc19..47d8d5f877 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -2130,7 +2130,7 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc,
> AVStream *st, int stream_type
>      return 0;
>  }
>
> -static AVStream *find_matching_stream(MpegTSContext *ts, int pid,
> +static AVStream *find_matching_stream(MpegTSContext *ts, int pid,
> unsigned int programid,
>                                        int stream_identifier, int
> pmt_stream_idx)
>  {
>      AVFormatContext *s = ts->stream;
> @@ -2139,6 +2139,8 @@ static AVStream *find_matching_stream(MpegTSContext
> *ts, int pid,
>
>      for (i = 0; i < s->nb_streams; i++) {
>          AVStream *st = s->streams[i];
> +        if (st->program_num != programid)
> +            continue;
>          if (stream_identifier != -1) { /* match based on "stream
> identifier descriptor" if present */
>              if (st->stream_identifier == stream_identifier+1) {
>                  found = st;
> @@ -2309,7 +2311,7 @@ static void pmt_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
>          if (ts->pids[pid] && ts->pids[pid]->type == MPEGTS_PES) {
>              pes = ts->pids[pid]->u.pes_filter.opaque;
>              if (ts->merge_pmt_versions && !pes->st) {
> -                st = find_matching_stream(ts, pid, stream_identifier, i);
> +                st = find_matching_stream(ts, pid, h->id,
> stream_identifier, i);
>                  if (st) {
>                      pes->st = st;
>                      pes->stream_type = stream_type;
> @@ -2331,7 +2333,7 @@ static void pmt_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
>                  mpegts_close_filter(ts, ts->pids[pid]); // wrongly added
> sdt filter probably
>              pes = add_pes_stream(ts, pid, pcr_pid);
>              if (ts->merge_pmt_versions && pes && !pes->st) {
> -                st = find_matching_stream(ts, pid, stream_identifier, i);
> +                st = find_matching_stream(ts, pid, h->id,
> stream_identifier, i);
>                  if (st) {
>                      pes->st = st;
>                      pes->stream_type = stream_type;
> @@ -2353,7 +2355,7 @@ static void pmt_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
>                  st = ts->stream->streams[idx];
>              }
>              if (ts->merge_pmt_versions && !st) {
> -                st = find_matching_stream(ts, pid, stream_identifier, i);
> +                st = find_matching_stream(ts, pid, h->id,
> stream_identifier, i);
>              }
>              if (!st) {
>                  st = avformat_new_stream(ts->stream, NULL);
> --
> 2.16.4
>
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On Tue, 9 Jul 2019, Aman Gupta wrote:

> On Tue, Jul 9, 2019 at 2:07 PM Marton Balint <cus@passwd.hu> wrote:
>
>> merge_pmt_versions was not usable if multiple programs were present because
>> when it was searching for candidate streams it did not make sure that the
>> PMT was
>> of the same program. This caused the streams of all programs to get merged
>> into
>> a single (garbled) program.
>>
>> This patch makes sure that the program number (service ID) is also matching
>> with the old streams when parsing the PMT making the feature useful for
>> multi
>> program streams.
>>
>> This change might cause issues for single program streams if the program
>> number
>> changes as well, but I think it is acceptable because the goal of the
>> option is
>> to make the parsing resilient to PID changes, and that is still working as
>> expected.
>>
>
> Patch looks good to me. Thanks for catching this!

Thanks, applied.

Regards,
Marton