[FFmpeg-devel] [PATCH v2] avformat/ifv: added support for ifv cctv files

[Carl Eugen Hoyos]

Am So., 5. Mai 2019 um 21:59 Uhr schrieb Reimar Döffinger
<Reimar.Doeffinger at gmx.de>:

> > +    avio_skip(s->pb, 0x5c);
>
> If for any of these skips you have any idea what data they
> contain, it would be nice to document it.

Iirc, all values we understood are used now.

> > +    if (aud_magic == MKTAG('G','R','A','W')) {
> > +        ifv->is_audio_present = 1;
> > +    } else if (aud_magic == MKTAG('P','C','M','U')) {
> > +        ifv->is_audio_present = 0;
> > +    } else {
> > +        avpriv_request_sample(s, "Unknown audio codec %x\n", aud_magic);
> > +    }
>
> Why does PCMU mean "no audio"?

We have several files with "PCMU" and several files with "GRAW".
All files with GRAW contain audio data, none of the files with PCMU
contain audio data.
I originally thought that the two bytes at 0x40/0x41 (iirc) show number
of streams but a test with the proprietary player confirmed that this
is not correct.
Another test would be to overwrite GRAW with PCMU to find out if
audio is still played...

Thank you for your comments, Carl Eugen