Re: [FFmpeg-devel] [PATCH v2] avutil: deprecate AVRational field inside AVOption::default_val

[Zhao Zhili <quinkblack@foxmail.com>]

> 在 2023年5月2日，19:39，James Almer <jamrial@gmail.com> 写道：
> 
> On 5/2/2023 8:34 AM, Tomas Härdin wrote:
>> tis 2023-05-02 klockan 15:48 +0800 skrev Zhao Zhili:
>>> From: Zhao Zhili <zhilizhao@tencent.com>
>>> 
>>> Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
>>> ---
>>>  libavutil/opt.h     | 2 ++
>>>  libavutil/version.h | 1 +
>>>  2 files changed, 3 insertions(+)
>>> 
>>> diff --git a/libavutil/opt.h b/libavutil/opt.h
>>> index 461b5d3b6b..46915754ea 100644
>>> --- a/libavutil/opt.h
>>> +++ b/libavutil/opt.h
>>> @@ -271,8 +271,10 @@ typedef struct AVOption {
>>>          int64_t i64;
>>>          double dbl;
>>>          const char *str;
>>> +#if FF_API_AVOPTION_AVRATIONAL
>>>          /* TODO those are unused now */
>>>          AVRational q;
>>> +#endif
>> Surely rationals options are useful?
> 
> They are, but this union is where the default value is stored when you define an AVOption. At some point it seems it was decided that rational (and video_rate) type AVOptions should set dbl instead of q, which is then av_q2d()'d into an AVRational.
> 
> I'd still not remove it, as Paul said. It's harmless being there and in the future it could be used.

The field itself is harmless, but it makes big confusing. It takes me some efforts to figure out a rational type must use dbl to hold default value.

For backward compatibility, I don’t think it’s easy to switch to AVRational from dbl.

If we decide to keep it, I can add a comment to reduce the confusion.

> 
>> /Tomas
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