[Libva] (H264) Reference Picture selection

[Zhao Yakui]

On Fri, 2014-05-09 at 03:06 -0600, Yuan, Feng wrote:
> Hi,
> 
> >>> I have a scheme where the decoder ack's received frames - With this
> >>> information I could resync without an IDR by carefully selecting the
> >>> reference frame(s).
> >
> >> Will you please describe your idea in detail?
> >
> >>> long term references would typically be employed as well, but it
> >>> seems ref-pic-marking was removed may'13?
> >
> >> Why do you hope to use the long-term reference? As you know, the
> >> current encoding is based on hardware-acceleration. When more the
> >> reference frames can be selected, the driver will be more complex and
> >> then the encoding speed is also affected.
> >
> >It's for implementing Cisco's clearpath technology
> >(http://www.cisco.com/c/dam/en/us/td/docs/telepresence/endpoint/softwa
> >re/clearpath/clearpath_whitepaper.pdf)
> >Basically one would  periodically mark a P frame as long term reference, in
> >case of packet loss one can thus refer to this one instead of restarting the
> >stream with an idr.
> >
> >
> >I'm not too concerned about the encoding speed as long as it's above
> >realtime (60fps 1920x1080)
> 
> Maybe it's more convenient If libva can have a switch for slice_header made between driver and app. Then some specially cases(ref-reorder, long-term-ref) may let app to manage slice-header.

Thanks for your suggestion. If the slice-header info is also generated
by the app and then be passed to the driver, it can be easy to do the
operation of "re-order and long-term-ref"

But this will depend on the policy how the slice header info is
generated. (by app or the driver). Now this is exported by querying the
capability of the driver. If we move this into the app, the
infrastructure will be changed a lot.

Another problem is that it is possible that one frame has multiple
slices. In such case the user should pass the multiple slice header
info.  

Thanks.
    Yakui