[FFmpeg-devel] [PATCH] libvpx: Enable vp9 alpha encoding

Ivan Kalvachev ikalvachev at gmail.com
Sat Jul 2 10:04:46 CEST 2016


On 7/2/16, Vignesh Venkatasubramanian <vigneshv-at-google.com at ffmpeg.org> wrote:
> On Fri, Jul 1, 2016 at 12:48 PM, Ronald S. Bultje <rsbultje at gmail.com>
> wrote:
>> Hi,
>>
>> On Fri, Jul 1, 2016 at 3:29 PM, Ronald S. Bultje <rsbultje at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> On Fri, Jul 1, 2016 at 3:12 PM, Vignesh Venkatasubramanian <
>>> vigneshv-at-google.com at ffmpeg.org> wrote:
>>>
>>>> On Fri, Jul 1, 2016 at 11:06 AM, James Almer <jamrial at gmail.com> wrote:
>>>> > On 7/1/2016 2:53 PM, Ronald S. Bultje wrote:
>>>> >> Hi,
>>>> >>
>>>> >> On Fri, Jul 1, 2016 at 1:40 PM, James Zern <
>>>> jzern-at-google.com at ffmpeg.org>
>>>> >> wrote:
>>>> >>
>>>> >>> On Fri, Jul 1, 2016 at 10:07 AM, Carl Eugen Hoyos <cehoyos at ag.or.at>
>>>> >>> wrote:
>>>> >>>>> Do we have decoder support (for either vp8 or vp9) for these
>>>> >>>>> files?
>>>> >>>>
>>>> >>>> No, only encoding and muxing.
>>>> >>>
>>>> >>> Seems like a feature request, but no reason to block this one if the
>>>> >>> vp8 one is here.
>>>> >>
>>>> >>
>>>> >> I'm not sure I have an opinion on this... But it feels strange to
>>>> >> allow
>>>> >> encoding of content we cannot decode. Being ffmpeg, how do we
>>>> >> recommend
>>>> >> people handle the files created with this feature, if not by using
>>>> ffmpeg
>>>> >> itself?
>>>>
>>>> One plausible reason is that Chrome can decode this. So it will be
>>>> useful for people who already have ffmpeg in their pipelines and want
>>>> to create such files. And like James Almer mentioned, this isn't a
>>>> first. VP8 Alpha has been this way too.
>>>
>>>
>>> The fact that something is the way it is, does not prove that it is
>>> therefore right, or that we should therefore continue doing it that way
>>> in
>>> other cases.
>>>
>>> So you're suggesting that it is perfectly fine for people to use Chrome
>>> as
>>> decoder if FFmpeg is the encoder. What if people don't have Chrome
>>> installed? Or what if they want a way of UI-less batch-processing such
>>> files, e.g. what if a service like Youtube/Vimeo wants to allow upload of
>>> vp8a/vp9a files without invoking Chrome for decoding?
>>>
>>
>> Additional evidence in [1], [2].
>>
>> There absolutely seems to be interest in support for vp8a/vp9a decoding
>> outside Chrome. I'm not saying you should implement it in all multimedia
>> frameworks ever created in human history, but doing it in one of them
>> (e.g.
>> ffmpeg, since it already supports encoding) certainly sounds helpful?
>>
>
> I'm not saying alpha decoder shouldn't ever be implemented in ffmpeg.
> I'm just saying that it shouldn't be a reason to block this patch. :)
> Sorry if i wasn't clear before.

The libvpx is used for both encoding and decoding,
so it should be able to decode alpha planes and
provide them to ffmpeg.

Do you have idea how hard is adding decoding support this way?
Can you do it?


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