[FFmpeg-devel] [PATCH] avformat/mpegtsenc: private_stream_1 is not asynchronous KLV

[zheng qian]

On Tue, Apr 20, 2021 at 12:44 AM Mao Hata <xt4ubq at gmail.com> wrote:
>
> The reason I created the patch was to fix the problem: when I transcode
> a transport stream based on ARIB-STD-B24, the PTS/DTS is removed from
> private_stream_1 streams, and, conversely, it is added to private_stream_2.
> "ISO/IEC 13818-1 Table 2-17 - PES packet" (sorry, the table number may
> have been shifted) defines the conditions under which PTS/DTS can exist
> as follows:
>
>  >if (stream_id != program_stream_map
>  > && stream_id != padding_stream
>  > && stream_id != private_stream_2
>  > && stream_id != ECM
>  > && stream_id != EMM
>  > && stream_id != program_stream_directory
>  > && stream_id != DSMCC_stream
>  > && stream_id != ITU-T Rec. H.222.1 type E stream) {
>
> So, private_stream_2 can not insert PTS/DTS. In addition, "ARIB-STD-B24,
> VOLUME3, Chapter5" defines private_stream_1 as "Synchronized PES"
> (mainly used for subtitles, with PTS/DTS inserted) and
> private_stream_2 as "Asynchronous PES" (mainly used for superinpose, no
> PTS/DTS inserted).

I'm working on ARIB related patches for mpegtsenc.c and later
I would like to provide a patch to fix the bug of private_stream_2.

In current situation, mpegts_write_pes() incorrectly writes
private_stream_2 with actually a private_stream_1-like PES header
that shouldn't appear according to the ISO/IEC 13818-1 standard.

Regards,
zheng

>  From these things, I misunderstood like that " PTS/DTS is generally
> inserted for private_stream_1, so the `if (stream_id ==
> STREAM_ID_PRIVATE_STREAM_1)` statement (I patched) must be a mistake! " ...
>
> Anyway, as I read the related code, I now understand that the problem
> should be solved specifically for ARIB-based transport stream (at
> "mpegts.c" or so.).
> Thank you again.
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