[FFmpeg-devel] [PATCH] avformat/apngenc: use the stream parameters extradata if no updated one is made available

Hendrik Leppkes h.leppkes at gmail.com
Wed Nov 2 22:10:20 EET 2016

On Wed, Nov 2, 2016 at 8:13 PM, Andreas Cadhalpun
<andreas.cadhalpun at googlemail.com> wrote:
> On 01.11.2016 23:10, Hendrik Leppkes wrote:
>> Am 01.11.2016 17:17 schrieb "Andreas Cadhalpun" <
>> andreas.cadhalpun at googlemail.com>:
>>> Not again, but instead, as the extradata is then only transferred as side data.
>>> That way it is again consistent between demuxer/decoder and encoder/muxer.
>> I don't think thats a good idea. Demuxers should fill the extradata field
>> if any is present and required for decoding - some other decoder might want
>> extradata for init or something, and that way you can accommodate it
>> without having to wait for the first packet.
> Is this documented somewhere?

What documented? This seems quite logical. If you have extradata, set
extradata in codecpar

>> That's basically how all demuxers work, will extradata and if it can and
>> does change just send an update notice.
> Requiring to use codecpar->extradata for passing this from demuxer to decoder,
> while at the same time requiring to use AV_PKT_DATA_NEW_EXTRADATA side data
> to pass this from muxer to encoder seems quite strange to me.

encoders should also be able to just set extradata and the muxer read
that, this is how many other encoders work.
I don't know how the apng muxer works, but maybe it also just pretends
to be special.

- Hendrik

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