[FFmpeg-devel] [PATCH] Try to make new VDPAU usable by adding context to callback.

Reimar Döffinger Reimar.Doeffinger at gmx.de
Thu Aug 8 19:26:58 CEST 2013

On Thu, Aug 08, 2013 at 11:28:53AM +0200, wm4 wrote:
> On Thu, 8 Aug 2013 03:53:33 +0200
> Reimar Döffinger <Reimar.Doeffinger at gmx.de> wrote:
> > I have no idea what you propose.
> > How does any of this allow me to free the old resources, create the new decoder and call the decode function again within the decode function?
> The new API doesn't allow you to free old resources (AVFrame references
> inside the decoder embed vdpau surface handles), but maybe it doesn't
> matter too much: vdpau preemption implicitly marks all allocated vdpau
> objects as deallocated/invalid.

Sure it does, you just have to store a generation counter in the
opaque pointer of the AVFrame. When the generation counter is behind
you know you need to update the surface.
Of course it's even simpler if you ignore what it was "supposed" to be
and just pass an array index instead of the actual surface number to
FFmpeg. You then just need to update all the surfaces in your array once
to handle preemption.

> You have a point about calling the decode function, but that helps only
> if the preemption is for a short moment. Preemption recovery can take a
> longer period of time, for example when switching away from X. At least
> in my tests vdpau will refuse to reinitialize until you switch back to
> X, so what you want to do would block the player completely. Moreover,
> calling the real decode function again will not make much sense, since
> the surface contents are lost anyway.

Huh? I don't know what happens to the reference frames, but even if they
should be destroyed that is not an issue for e.g. intra-only content.

> > How would I even be able to handle the return value of the render function in general, no matter the cause of error? (if you don't care about losing more frames than necessary I guess you coukd handle preemption outside the decode loop, but that seems at least suboptimal).
> > lavc ignores the return value, and any wrapper would have nowhere to store it.
> Maybe lavc should check the return value, and return it from the
> libavcodec decoding function?

Remapping all possible VDPAU errors to FFmpeg ones? That's going to be

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