[FFmpeg-devel] [PATCH]lavc/avcodec: Allow libavcodec to overwrite profile and level

[Hendrik Leppkes]

On Fri, Nov 24, 2017 at 5:42 PM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> On Fri, Nov 24, 2017 at 12:47:16AM +0100, Carl Eugen Hoyos wrote:
>> 2017-11-23 22:58 GMT+01:00 Michael Niedermayer <michael at niedermayer.cc>:
>> > On Thu, Nov 23, 2017 at 04:01:06PM +0100, Carl Eugen Hoyos wrote:
>> >> Hi!
>> >>
>> >> The (external) encoders may overwrite level and profile because of
>> >> requested encoding properties, allowing libavcodec to (also) overwrite
>> >> them in the context makes sense (and is already done in some cases
>> >> afaict).
>> >>
>> >> Please comment, Carl Eugen
>> >
>> > If a user needs to generate a file with a specific profile/level
>> > for example because its for broadcast, some specification or a hw
>> > decoder.
>> > How could he after this patch ensure that exactly the needed profile
>> > is used?
>>
>> Afair, x264 does change profile and / or level depending on properties
>> set by the user. Currently there is no way for the libavcodec user to
>> know that libx264 changed something.
>> With this change the user can know that he does not get the
>> requested values.
>>
>> Or am I wrong and libx264 never overwrites requested values
>> for level and / or profile?
>
> IIUC (someone please correct me if iam wrong) libx264 can change
> the profile/level to a compatible one.
>
> The proposed API would allow any change.
> That would add a requirement to the user apps to check if the actual
> profile/level is compatible to the users requirements. And that would
> make this require special treatment in many user apps, not just pass
> user options to ffmpeg
>

But this change doesn't actually change behavior. If you want to
propose a different wording to allow encoders to slightly adjust the
value in a compatible manner, we're all ears. :)

- Hendrik