[mythtv] [mythtv-commits] Ticket #2556: Bogus video streams in output PMT

[Stuart Auchterlonie]

On Thu, Oct 12, 2006 at 09:49:37PM +0100, Neil Murphy wrote:
> > 
> > The MHEG application selects a stream by its component tag and calls
> > SetAudioByComponentTag or SetVideoByComponentTag to do this.  The reason
> > for using component tags is that PIDs could change as a result of
> > remultiplexing so it isn't a good idea to have a PID in an MHEG app.  As
> > far as I know there is no standard numbering for the tags.  They are
> > just arbitrary values.  The streams, though, are marked as private data
> > in the PMT.  The complicated part is to present the information to
> > avformatdecoder so that SetAudioByComponentTag and
> > SetVideoByComponentTag will work.  The only way I could see to do this
> > was to try to predict which could be audio and which video within
> > mpegts.c and then include them in the available streams.  It would
> > certainly be better to drive this from the other end and only treat a
> > stream as, say, audio, once SetAudioByComponentTag was called.  I just
> > couldn't see how to do that.
> > 
> > If this is the source of the problem it could be that the problem is the
> > selection of the default video and audio streams is wrong.
> > 
> 
> It certainly seems to be. I've just tried the following hack and I now
> have channel-4 working again!

I take it that it doesn't work without this patch applied?

Stuart

> 
> fnm at saruman:/usr/src/mythtv_svn/mythtv> svn diff
> Index: libs/libmythtv/avformatdecoder.cpp
> ===================================================================
> --- libs/libmythtv/avformatdecoder.cpp  (revision 11515)
> +++ libs/libmythtv/avformatdecoder.cpp  (working copy)
> @@ -1351,9 +1351,9 @@
>                  enc->decode_cc_dvd  = decode_cc_dvd;
> 
>                  // Set the default stream to the stream
> -                // with the lowest component tag.
> +                // with the highest component tag.
>                  if (selectedVideoIndex < 0 ||
> -                    ic->streams[i]->component_tag <
> +                    ic->streams[i]->component_tag >
>                      ic->streams[selectedVideoIndex]->component_tag)
>                  {
>                      selectedVideoIndex = i;
> 
> Neil.
> 
> > >
> 
> > David.
> > 
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