[mythtv] avcodec_dual_language flips on one channel (ticket #4976)

[Robert Johnston]

Markus Schulz wrote:
> hello,
>
> i have a problem with understanding the avcodec_dual_language switch. On 
> one channel (ARD at Astra 19.2E) it flips regular and perhaps randomly?
>
> for each pass from avformatdecoder.cpp:3372 mainloop (CODEC_TYPE_AUDIO 
> switch) it looks like:
> avcodec_dual_language =0
> avcodec_dual_language =0
> avcodec_dual_language =1
> avcodec_dual_language =0
> avcodec_dual_language =1
> avcodec_dual_language =0
> avcodec_dual_language =0
> avcodec_dual_language =0
> avcodec_dual_language =1
> avcodec_dual_language =0
> avcodec_dual_language =0
> avcodec_dual_language =0
> avcodec_dual_language =1
> avcodec_dual_language =0
> avcodec_dual_language =0
>
> this results in splitting or not splitting to an additional stream and 
> selecting a stream after them (for example the AC3 one) was impossible 
> (without my hack, see ticket #4976).
>
> Starting the stream gives the following AFD output:
> -----------------------
> 2008-06-21 12:56:47.304 AFD: Opened codec 0x8ba8590, id(MPEG2VIDEO) 
> type(Video)
> 2008-06-21 12:56:47.304 AFD: codec MP3 has 2 channels
> 2008-06-21 12:56:47.304 AFD: Opened codec 0x837f010, id(MP3) type(Audio)
> NO SPLITTING
> 2008-06-21 12:56:47.304 AFD: codec MP3 has 2 channels
> 2008-06-21 12:56:47.304 AFD: Opened codec 0xa33fe00, id(MP3) type(Audio)
> SPLITTING
> 2008-06-21 12:56:47.305 AFD: codec AC3 has 2 channels
> No accelerated IMDCT transform found
> 2008-06-21 12:56:47.305 AFD: Opened codec 0xa2d32c0, id(AC3) type(Audio)
> NO SPLITTING
> -----------------------
> SPLITTING means that AvFormatDecoder::ScanStreams splits the stream 
> based on avcodec_dual_language.
>
> Any ideas? A bug in ffmpeg or the stream from this channel was crap? 
> What can we do in the latter case?
>   

I got no idea, but out of interest, was this during a program, or was it 
during commercials? I'm thinking that different commercials have 
different soundtracks, and as each is played the stream is re-set for 
that soundtrack.

Just a thoery.
-- 
Robert Johnston