Re: [FFmpeg-devel] [PATCH v1] avcodec/libaomdec: don't set aspect ratio when it's not yet known

[James Almer <jamrial@gmail.com>]

On 10/8/2023 9:45 AM, Steven Liu wrote:
> James Almer <jamrial@gmail.com>于2023年10月8日 周日20:08写道：
> 
>> On 10/8/2023 8:57 AM, Steven Liu wrote:
>>> Makes the output of the libaom av1 decoder consistent with external
>> decoders like
>>> libdav1d.
>>>
>>> reference commit: 1652f2492f88434010053289d946dab6a57e4d58
>>
>> But it is known at this point. picture->sample_aspect_ratio is set
>> directly above.
>>
>> What needs to be done is initializing the decoder in aom_init() using
>> the extradata, so lavf will not attempt to decode frames in order to get
>> stream info, which is what i assume is happening here and why you want
>> SAR to be 0/1.
> 
> i want fate pass

It will if you parse extradata during init().
This change is not ok given it's removing SAR altogether, meaning if a 
sample has render dimensions that are not the same as the coded 
dimensions, this information will not be propagated and players will 
display the frames with the wrong aspect ratio.

> 
>>
>>
>>>
>>> Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
>>> ---
>>>    libavcodec/libaomdec.c | 1 -
>>>    1 file changed, 1 deletion(-)
>>>
>>> diff --git a/libavcodec/libaomdec.c b/libavcodec/libaomdec.c
>>> index 695d901051..ff4137bfc6 100644
>>> --- a/libavcodec/libaomdec.c
>>> +++ b/libavcodec/libaomdec.c
>>> @@ -204,7 +204,6 @@ static int aom_decode(AVCodecContext *avctx, AVFrame
>> *picture,
>>>                      picture->height * img->r_w,
>>>                      picture->width * img->r_h,
>>>                      INT_MAX);
>>> -        ff_set_sar(avctx, picture->sample_aspect_ratio);
>>>
>>>            if ((img->fmt & AOM_IMG_FMT_HIGHBITDEPTH) && img->bit_depth ==
>> 8)
>>>                ff_aom_image_copy_16_to_8(picture, img);
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