[FFmpeg-devel] [PATCH 17/18] lavf/dv: do not update AVCodecParameters.sample_rate while demuxing

[Anton Khirnov]

Quoting Andreas Rheinhardt (2022-08-24 16:20:35)
> Anton Khirnov:
> > Demuxers are not allowed to do this and few callers, if any, will handle
> > this correctly. Send the AV_SIDE_DATA_PARAM_CHANGE_SAMPLE_RATE side data
> > instead.
> 
> 1. One of the callers which did not handle this correctly is the mov
> demuxer: A sample rate update would not propagate to the user, because
> it uses a separate AVFormatContext for it. This should be mentioned in
> the commit message. (Btw: I don't see anything that guarantees that the
> samplerate and timebase of the inner demuxer and the sample rate and
> time base reported to the user (presumably taken from mov structures)
> coincide. Given that dv_fctx and dv_demux are part of MOVContext, they
> would also leak if it would be attempted to allocate them multiple
> times. Do you see anything that guarantees that they will not be
> allocated multiple times?)
> 2. In case of ff_add_param_change() failure, users will just interpret
> that as "no more packets available", won't they?

yes, I think so

> This might be wrong, but it is not problematic.

I agree

> 3. Have you tested this with a sample with actual parameter changes?

Yes, I made a sample by concatenating two dv files. The side data is
exported correctly, but the PCM decoder fails because it is not marked
with AV_CODEC_CAP_PARAM_CHANGE. Patches welcome.

-- 
Anton Khirnov