[FFmpeg-devel] [PATCH] lavc/qsvdec: allow qsv decoders to use initialized device

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> Mark Thompson
> Sent: Wednesday, September 2, 2020 9:38 PM
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH] lavc/qsvdec: allow qsv decoders to use
> initialized device
> 
> On 02/09/2020 15:36, Rogozhkin, Dmitry V wrote:
> > On Wed, 2020-09-02 at 14:21 +0000, Rogozhkin, Dmitry V wrote:
> >> On Wed, 2020-09-02 at 08:41 +0000, Soft Works wrote:
> >>> ...
> >
> > Small suggestion: let's move discussion around -qsv_device and
> > -hwaccel_device options entirely to the "ffmpeg_qsv: use
> > -hwaccel_device to specify a device for VAAPI backend" thread and a
> > return focus on the original patch which is not about -qsv_device, but
> > about this command line:
> >
> > ffmpeg -init_hw_device vaapi=va:/dev/dri/renderD129 -init_hw_device
> > qsv=hw at va -c:v h264_qsv -i input.h264 -c:v hevc_qsv -y output.h264
> 
> I wouldn't recommend doing this; using the appropriate acceleration API is
> preferred to messing with the vendor-specific full-offload decoders:
> 
> ffmpeg -init_hw_device vaapi:/dev/dri/renderD129 -hwaccel vaapi -i
> input.h264 -vf hwmap=derive_device=qsv -c:v hevc_qsv -y output.h264
> 
> (Or ... -init_hw_device dxva2:1 -hwaccel dxva2 ...)

Hi Mark,

In the latter case I have to disagree. We've gone through so many 
Tests and the QSV decoders have almost always resulted in better 
overall performance compared to their DXVA2 and D3D11VA counterparts,
when using a full hw pipeline qsv_dec > qsv_vpp > qsv_enc.

Also, capabilities may differ (supported color formats, resolutions,
profiles..)

Kind regards,
softworkz