[FFmpeg-devel] [PATCH v4 1/2] libavcodec/libaomenc.c: Support gray input

[James Almer]

On 4/14/2020 9:26 PM, James Zern wrote:
> On Tue, Apr 14, 2020 at 3:57 AM Ryo Hirafuji <ryo.hirafuji at link-u.co.jp> wrote:
>>
>> Thanks for the review!
>>
>> This should bump the micro version number in libavcodec/version.h.
>>
>>
>> OK, I will bump up the version when the problem below is solved.
>>
> 
> If we want to go for compatibility with different versions of the
> library we could move forward with the patch as is, though it would be
> simpler to just treat this as a bug fix in libaom.

Once a new version of libaom is tagged (Hopefully soon, since it's been
almost two years since 1.0.0), we could set it as the minimum
requirement and forget about 1.0.0, since that version is by now
essentially unusable.

> 
>>
>>> That's annoying. I filed a bug to track [1]. The monochrome flag
>>> itself seems unnecessary for the library rather than just an image
>>> format, but that's another discussion.
>>>
>>
>>  Thanks for creating the issue.
>>
>> You might be right.
>> I just need this line to set  the monochrome flag to 1 in Sequence Header
>> OBU:
>>> enccfg->monochrome = 1u;
>>
>> This reads a little strangely to me, maybe something like: U and V
>>> information is ignored, but must point to valid buffers...?
>>> [1] https://crbug.com/aomedia/2639
>>
>>
>> I pasted the stack trace when V plane and U plane are NULL and ffmpeg
>> crashes:
>> https://bugs.chromium.org/p/aomedia/issues/detail?id=2639#c1
>> (ryoh at ... is also my account)
>>
> 
> Thanks for adding the detail.
> 
>> If we allocate aom_image with aom_img_alloc function, allocated V plane and
>> U plane are filled with 0 (not 128, 512 or 2048).
>> And I don't have to fill them to 128 to obtain a gray image.
>> (I tried it in https://github.com/link-u/cavif )
>> So I think these planes are just ignored (but not sure).
>>
> 
> They should be. From the stack trace it looks like a simple fix when
> dealing with border extension, though that may uncover other issues.
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