[FFmpeg-user] is ffmpeg using gpu???

Andy Furniss adf.lists at gmail.com
Sun Jan 11 15:00:23 CET 2015

Moritz Barsnick wrote:
> On Sun, Jan 11, 2015 at 17:22:39 +0800, Rick C. wrote:
>> Can it be used though to speed things up?  If so what command would
>> I need to use? Thanks again for the help...
> May I point you to this thread and particular mail on this list:
> https://ffmpeg.org/pipermail/ffmpeg-user/2013-August/016698.html
> It only relates to OpenCL, I don't know if ffmpeg supports any other
> methods of using a GPU.

On Linux if your GPU has h/w decode and the input file is the right type
ffmpeg can use that.

For me the command would be -

ffmpeg -hwaccel vdpau -i infile ...

It may not gain you much though as GPUs decode are designed for playing
rather than going as fast as they can, there is also mention somewhere
of having to read back the yuv reducing the gain. Maybe if you have a
slow CPU then the reduced decode load will free more for the encode.

On my 4x3.4GHz box there wasn't much difference IIRC.

Just testing GPU vs s/w for bluray decode the CPU was way faster - as
expected I guess.

> In this thread, Tom notes:
>> Generally the consensus (at least on here, as far as I can tell)
>> is that GPU assisted encoding is slow and gives crap results.
>> YMMV.

Not the same thing but there is a way to get libx264 to use some opencl, 
though I don't know
what it's like as my radeonsi opencl isn't yet a complete enough
implementation to work.

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