[FFmpeg-devel] [FFmpeg-cvslog] lavc/qsvenc: add VDENC support for H264

[Carl Eugen Hoyos]

2019-01-11 4:42 GMT+01:00, Li, Zhong <zhong.li at intel.com>:

>> >> 2019-01-10 14:51 GMT+01:00, Linjie Fu <git at videolan.org>:
>> >>
>> >> > +#if QSV_HAVE_VDENC
>> >> > +    { "low_power", "enable low power mode(experimental: many
>> >> > +limitations by
>> >> > mfx version, BRC modes, etc.)", OFFSET(qsv.low_power),
>> >> > AV_OPT_TYPE_BOOL, {
>> >> > .i64 =  0 }, 0, 1, VE},
>> >> > +#endif
>> >>
>> >> This seems wrong to me: The visibility of an option should probably
>> >> not depend on configuration details (the effect can of course depend
>> >> on many details).
>> >
>> > That's is just a remind that this feature has some limitations. The
>> > configures are just to make driver to support this feature.
>> > In ffmpeg level, the only thing we should do IMHO is to query
>> > MSDK/Driver capability and report an error message if not supported.
>> > And it was done:
>> >
>> https://github.com/FFmpeg/FFmpeg/blob/395e8a53fa0266f26581f3e9752b
>> 0dbc
>> > 93998a90/libavcodec/qsvenc.c#L376
>>
>> That is probably helpful, but the issue I try to explain is unrelated to
>> the brokenness of the option:
>> Now, in some cases FFmpeg shows the option and in other cases
>> it does not.
>> I believe that instead, the option should always be shown, even
>> if it does not work.
>
> That is a big topic since I see many components are doing this. E.g;
> we can find some options of libx264 and nvenc are hided too.

Which libx264 option is / can be hidden?

> Personally speaking I like current way: if the implementation of an
> option is not built-in, it is not necessary to show the option, else it
> is really confusing that this option can't work at any case.

Isn't it more confusing for a user who reads about a documented
option and wants to use if it isn't there instead of a message shown?

(You don't have to fix every existing issue, avoiding to add new
ones is a plus though.)

Carl Eugen