[FFmpeg-user] Faster codec with alpha

[Fred Perie]

2016-12-02 17:38 GMT+01:00 Joshua Grauman <jnfo at grauman.com>:
>
> Thanks guys, I'll look into these ideas!
>
> Josh
>
>
> On Fri, 2 Dec 2016, Paul B Mahol wrote:
>
>> On 12/2/16, Joshua Grauman <jnfo at grauman.com> wrote:
>>>
>>> Hello all,
>>>
>>> I am using the following command successfully to generate a screencast.
>>> The video comes from my program 'gen-vid' which outputs the raw frames
>>> with alpha channel. The resulting .avi has alpha channel as well which
is
>>> my goal. It all works great except that my computer can't handle doing
it
>>> real-time. So I am wondering if there is a different vcodec I could use
to
>>> achieve the same result that was less demaning on the cpu? I am willing
to
>>> sacrifice some compression for more speed, but would prefer not to have
to
>>> store all the raw frames without any compression. Storing the alpha
>>> channel is also a must. It is preferable if the compression is lossless.
>>> Does anyone have any other suggestions for compression other than png
that
>>> may be faster? Thanks!
>>
>>
>> utvideo, huffyuv, ffvhuff
>>
>>>
>>> ./gen-vid | ffmpeg -f rawvideo -pixel_format bgra -video_size 1920x1080
>>> -framerate 30 -i - -vcodec png over.avi
>>>
>>> Josh
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>>
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Hi Joshua
I regularly use ffv1 with pix_fmt bgra
If speed is really a problem when reading/decoding, you can  also consider
having two files one containing the alpha channel codec ffv1 pix_fmt gray8
and the color using a codec like H264
I don't know how to do this with the ffmpeg command. I use the ffmpeg
libraries and a specific program.

Fred



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