gstmpegdemux: subtitle pads not created

[Tim Müller]

On Wed, 2016-05-11 at 15:27 +0200, Sachs Jürgen wrote:

Hi Jürgen,

> I've a problem decoding files using gstmpegdemux (MPEG PES streams,
> VOB files). When I launch gst-play, gst-launch etc. with some of this
> kind of files, I do not get the subtitle tracks. (Indeed I do not
> want to use gst-play & co - I'm maintaining a GStreamer application)
> 
> The reason for this is that the demux "looks for substreams" for ~2s
> and then sending the "no-more-pads" message. After the message the
> demux does not create new pads. Unfortunately the subtitles start
> later in the stream...
> 
> Is there a recommended way how to handle such situations on
> application level? 
>  * I found similary issue in https://bugzilla.gnome.org/show_bug.cgi?
> id=747616, is there a workaround available
>  * possibly I can check something using pad probes or other "tricks"
> every some seconds and reconstruct the pipeline in case of subtitles
> are to be decoded?
> 
> Thanks for any hints and ideas that can help

If you know in advance what streams will exist, you could send a custom
event to the demuxer like the dvdreadsrc does, but that's not exactly
ideal of course.

There's also some work ongoing [*] that will make this kind of
situation easier to handle properly in GStreamer and which will
hopefully land in master soon.

Cheers
 -Tim

[*] https://bugzilla.gnome.org/show_bug.cgi?id=758960

-- 
Tim Müller, Centricular Ltd - http://www.centricular.com