On VAAPI vs libx264

[Sreerenj Balachandran]

On Fri, Jul 22, 2016 at 10:31 AM, Víctor M. Jáquez L. <vjaquez at igalia.com>
wrote:

> On 07/22/16 at 02:43am, Ezequiel Garcia wrote:
> > Currently, I am using libx264 to encode analog videos on a video server
> product.
> > I'm near the CPU limit, so I was considering switching to vaapi-based
> encoding.
> > My initial experiments were *very* promising, as my CPU went down like a
> sack
> > of potatoes
> >
> > The only issue I found so far is that file size is greatly increased
> > (around 4 times bigger!), yet I'm unable to tune vaapih264enc
> > to match libx264.
>
> Sree can give more details about this than me, but as far as I know,
> gstreamer-vaapi generates a lot of I frames with small GOP and that is
> because
> on how gstreamer-vaapi encoders were written originally.
>
> But Sree right now  is working to improve this.
>





Unfortunately We don't have rich set of tuning options like x264 , but we
will improve this in future.

For GOP adjustments, currently we only have "max-bframes" property.You
might have already experimented with it :)

There are few options to reduce the file size,
-- enable cabac (no need if you are using git master of gstreamer-vaapi
where cabac enabled by default)
-- increase max-bframes value
-- increase the init-qp value

Some works to add hierachical encode is on going:
https://cgit.freedesktop.org/~sree/gstreamer-vaapi/log/?h=svc


>
> vmjl
>
> >
> > Before I start diving into the encoder internals, I was wondering:
> >
> > Is this an intrinsic limitaion of the hardware encoder, or should
> > I dig into libva parameters? For example, I haven't found a way to
> > change the GOP size to improve compression (while keeping quality).
> >
> > Maybe we need to add extra knobs in the gstreamer frontend?
> >
> > Thanks!
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>



-- 
Regards,

Sreerenj Balachandran
Intel Open Source Technology Center
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