Re: [FFmpeg-devel] [PATCH] avcodec/av1dec: export pixel format even if no hardware decoder is present

[James Almer <jamrial@gmail.com>]

On 9/7/2023 5:06 AM, Andreas Rheinhardt wrote:
> James Almer:
>> And remove the AVOID_PROBING flag, given it's the last av1 decoder to be tested
>> either way.
>> This fixes a regression introduced in 1652f2492f88434010053289d946dab6a57e4d58,
>> where even if forcing the native av1 decoder, if another decoder was present,
>> like libdav1d or libaom-av1, they'd be used for probing and some fate tests
>> would have different results.
>>
>> Signed-off-by: James Almer <jamrial@gmail.com>
>> ---
>>   libavcodec/av1dec.c             | 8 ++++----
>>   tests/fate/lavf-container.mak   | 8 ++++----
>>   tests/ref/fate/av1-annexb-demux | 2 +-
>>   tests/ref/lavf-fate/av1.mkv     | 4 ++--
>>   tests/ref/lavf-fate/av1.mp4     | 4 ++--
>>   5 files changed, 13 insertions(+), 13 deletions(-)
>>
>> diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
>> index ec8401f4e0..a1e08185a7 100644
>> --- a/libavcodec/av1dec.c
>> +++ b/libavcodec/av1dec.c
>> @@ -612,6 +612,9 @@ static int get_pixel_format(AVCodecContext *avctx)
>>       if (ret < 0)
>>           return ret;
>>   
>> +    s->pix_fmt = pix_fmt;
>> +    avctx->pix_fmt = ret;
>> +
>>       /**
>>        * check if the HW accel is inited correctly. If not, return un-implemented.
>>        * Since now the av1 decoder doesn't support native decode, if it will be
>> @@ -623,9 +626,6 @@ static int get_pixel_format(AVCodecContext *avctx)
>>           return AVERROR(ENOSYS);
> 
> Is the log message here actually accurate? The get_format callback
> choosing the software pixel format does not mean that the hardware this
> is run on or the lavc binary in use do not support hardware accelerated
> AV1 decoding.

It's not, but that's also unrelated to this patch.

> (How is an API user actually supposed to know that decoding will fail if
> the software pixel format is selected?)

Other than the first returned ENOSYS, nothing. I could make it always 
return ENOSYS, same as before this patch, but anything we do will 
probably be hacky unless we add an actual software implementation.
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