[FFmpeg-devel] [PATCH v4 0/9] avformat: wav-s337m support + new probe_stream option

[Nicolas Gaullier]

>> Because of the dependencies, I had to group all the patches in a serie, but they are 3 functional parts :
>> * patch 1 is necessary to fix dolby_e pts that will be part of the 
>> test in patch 8
>> * patch 2,3,4,5,6,7,8 : s337m support in wav
>>     this is a rework of a precedent serie 
>> (https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=106)
>
>Sorry if this is not related at all but isn't dolby-e mostly found in some dvb streams?
dolby_e is a "professional" codec, it is not used for distribution and not supported by end user chips, so the most common formats are :
- contribution: mpegts (or dvb for satt etc.) with s302m data -> s337m (this could be interesting for ffmpeg to support it)
- broadcast muxers: mxf, mov, gxf, lxf : in s337m, within stereo tracks or most commonly sadly split into mono tracks (limited support for a simple case such as mxf stereo would still be welcome). There is also a newer form with AMWA-AS 11 with audio samples not encoded, but with single separated audio metadata bistream in VANC : this is not strictly "dolby E", just the metadata part of it (dialnorm et.), and currently dolby_e.c does not support parsing these metadata.
- wav

>> * patch 9 : AVOption to disable codec auto-detect : it seems it is a 
>> general request from many users, and it is also critical here for dolby_e as many broadcasters will still need to just pass-through dolby_e data as they already do.
>> Thus, the patchset 2,3,4,5,6,7 should not be applied without the last patch 9 applied quickly behind...
>
>As said, this surprises me, please elaborate.
>
>Carl Eugen
Most of the time, broadcast users just want to pass-through dolby E: typically they mux m2v/wav essence files to an mxf file. Downstream broadcast hardwares or applications can probe the stream and transcode the detected dolby_e stream to an ac-3 stream which can be distributed. Without an option to disable dolby_e stream probing, it would be strictly impossible to do this. In the future, one can imagine that broadcast muxers mxf/wav/.. would be able to support dolby_e by automatically submuxing to s337m with correct guard-band/phase, and that could be interesting to repair a bad s337m submux, but this is a long way...
Apart from that, it seems some users would like to be able to disable stream probing, so it seems it is an opportunity to add this AVOption right now.

Nicolas