[FFmpeg-devel] [FFmpeg-user] BUG in use of extradata and extradata_size with dvb subtitles and teletext

[Andriy Lysnevych]

Hi,

We are almost done with patch that fixes DVB subtitles and teletext issues.

We are doing 2 things in this patch:

1) Removing dependency on extradata. All the values that currently stored
in extradatata will be generated from metadata. For example in case of DVB
subtitles metadata will hold the following values:

language
subtitling_type
composition_page_id
ancillary_page_id

This values will be used for correct PMT generation. The values can be
comma separated because one DVB subtitle stream can carry few subtitle
substreams of different language, type, etc.

a) In case of copy scenario the values will be copied from metadata of
MPEGTS demuxer subtitle stream to metadata of MPEGTS muxer subtitle stream.

b) In case when you generate subtitles (i.e. using FFmpeg libraries and DVB
subtitles encoder) you should set the fields in metadata correctly for
output subtitles stream of MPEGTS muxer otherwise default values will be
used.

2) Currently there 2 different formats of DVB subtitles payload in
AVPacket.data. Fore details you can read this thread
https://trac.ffmpeg.org/ticket/2989

We are fixing FFmpeg so only one common format of DVB subtitles will be
used across all the components. AVPacket payload of DVB subtitles will
contain all the fields from standard:

data_identifier 8bit - always set to 0x20
subtitle_stream_id 8bit - always set to 0x00
subtitling_segments - actual payload
end_of_PES_data_field_makrer 8bit - always set to 0xFF

Feel free to ask any questions.

Regards,
Andriy Lysnevich