Re: [FFmpeg-devel] [PATCH 4/6] avformat/wavdec: s337m support

From: "Tomas Härdin" <git@haerdin.se>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 4/6] avformat/wavdec: s337m support
Date: Tue, 21 Feb 2023 10:53:09 +0100
Message-ID: <d673c68374b32dd48522cd9a45aa4f484b0660b0.camel@haerdin.se> (raw)
In-Reply-To: <MR1P264MB2483EACEA0088A53BBCB3E809BA19@MR1P264MB2483.FRAP264.PROD.OUTLOOK.COM>

fre 2023-02-17 klockan 10:30 +0000 skrev Nicolas Gaullier:
> > > +#if CONFIG_S337M_DEMUXER
> > > +    {"non_pcm_mode", "Chooses what to do with s337m",
> > > OFFSET(non_pcm_mode), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, DEC, 
> > > "non_pcm_mode"},
> > > +    {"copy"        , "Pass s337m through unchanged", 0,
> > > AV_OPT_TYPE_CONST, {.i64 = 0}, 0, 1, DEC, "non_pcm_mode"},
> > > +    {"demux"       , "Demux s337m"                 , 0,
> > > AV_OPT_TYPE_CONST, {.i64 = 1}, 0, 1, DEC, "non_pcm_mode"},
> > > +#endif
> > >      { NULL },
> > >  };
> > 
> > So default is to demux? Sounds OK and probably avoids eardrum
> > destruction
> 
> Well, to be honest, I am not very comfortable with that.
> The fact is, I fear that many users have scripts to mux wav/dolby_e
> into mxf outputs and they will be affected...

This is why it is better to demand that these things be explicitly
signalled. At the same time a lot of users expect ffmpeg to Just Work,
but that is not always possible. Perhaps we should should put this in
the manual and tell spdif/s377m/dolby-e users to RTFM?

> And another point here in this latest edition on my patch serie is
> that the use of an existing AVOption makes it possible for users
> to upgrade their command lines just now by adding the option :
> ignored in previous version, it will take effect the day they upgrade
> their ffmpeg version,
> so the transition can be smooth...

Assuming users read the documentation of course..

> 
> > > +                            } else {
> > > +                                av_log(s, AV_LOG_INFO, "Passing
> > > through S337M data: codec will not be reported\n");
> > > +                            }
> > 
> > Perhaps the user should also be informed when S337m is demuxed
> > rather than passed through?
> 
> I could add a debug message if you think that could be helpful ?
> I think I cannot add an INFO log as spdif and other probe-mecanisms
> are not verbose in current code.

Nah, it was more a rhetorical question

/Tomas

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