[FFmpeg-devel] [PATCH 2/2] avcodec/jpeg2000dec: jpeg2000 has its own lowres option

[James Almer]

On 6/24/2023 5:46 PM, Tomas Härdin wrote:
> lör 2023-06-24 klockan 19:54 +0200 skrev Paul B Mahol:
>> On Sat, Jun 24, 2023 at 12:53 PM Tomas Härdin <git at haerdin.se> wrote:
>>
>>> lör 2023-06-10 klockan 20:31 +0200 skrev Michael Niedermayer:
>>>> jpeg2000 overrides the global lowres variable with a lowres field
>>>> called reduction_factor
>>>> ffmpeg -lowres X causes the reduction_factor to be set
>>>> ffplay -lowres X causes both lowres and the reduction_factor to
>>>> be
>>>> set
>>>> ossfuss sets only lowres
>>>
>>> Why does jpeg2000dec have its own -lowres? Does lavc reset it
>>> somewhere
>>> to where the decoder can't make use of the avctx-level setting?
>>>
>>>
>> Libav removed lowres from avctx, but same was not done here.
>>
>> IMHO lowres is codec-specific thing and only codecs supporting it
>> should
>> have private option to change it.
> 
> Enough codecs support lowres that marking support for it in codec caps
> may be worthwhile. Something to consider for the future.

There's AVCodec.max_lowres, which when not zero it means the decoder 
supports lowres.

> 
> /Tomas
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