[FFmpeg-devel] About xvmc_acceleration

Michael Niedermayer michaelni
Fri Feb 13 13:13:22 CET 2009

avOn Fri, Feb 13, 2009 at 12:41:49PM +0200, Ivan Kalvachev wrote:
> On 2/13/09, Reimar D?ffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> > On Fri, Feb 13, 2009 at 09:59:04AM +0100, Gwenole Beauchesne wrote:
> >> Is some xvmc_acceleration different than 2 used nowadays? I wonder because
> >>
> >> I'd like to replace xvmc_acceleration by an hwaccel_id = {HWACCEL_ID_NONE,
> >>
> >
> > What exactly would be the purpose of this?
> > I do not like having a global, user modifiable variable that exactly
> > duplicates the information in pix_fmt.
> > The XvMC case is just checking against two different PIX_FMTs,
> > the codec-specific checks for VDPAU can be replaced by 1 or two pix_fmt
> > checks, too, and the stuff in the common code IMO would be much nicer if
> > it used a check against a appropriately named flag, e.g.
> > CODEC_FLAG_SKIP_DECODE (actually this should be used in the codec
> > specific parts, too, where it is appropriate).
> > Admittedly that assumes that the different API will mostly need to skip
> > mostly the same parts of the code, and mostly the codec-specific packing
> > into AVFrames/slices will need to differ between the APIs.
> It is speed enhancement.
> xvmc_accel/hdaccel_id having value of 0, is sure indication that
> we are in full software mode and there is no need to mandatory
> check 4-5 different pixfmt values to figure out that.
> These checks could cause significant speed loos if used in inner loops

but this is no argument to place xvmc_accel in AVCodecContext instead of

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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