[mythtv-users] bad frame concealment ffmpeg vs VDPAU

Christopher Kerr mythtv at theseekerr.com
Mon Sep 19 04:11:32 UTC 2011


On Mon, Sep 19, 2011 at 6:00 AM, Wil <nodenet at hotmail.com> wrote:
> A while ago after switching to VDPAU I noticed that the decoder does not
> seem to make any attempt to conceal bad frames in mpeg-2 video streams.
> Essentially you normally get a nice sneeze or similar effect whenever there
> is a problem with the transmission i.e. bad frames are not concealed.
>
> Various A/B comparisons I performed with ffmpeg also seemed to confirm this
> when using VDPAU on other hardware. I'm currently running 0.24.1-Fixes but
> noticed this back on 0.22. The issue has remained in effect regardless of
> the mythtv revision or the version of the nvidia drivers that are utilised.
> I suspect that this is just a shortcoming of the VDPAU decoder. As such I do
> not use it for SD material any longer.
>
> Has anyone else spotted this

Your experience matches mine - VDPAU doesn't seem to conceal bad
frames at all. Given that decoding is performed by a dedicated ASIC,
I'm not sure it's even possible for nVidia to correct this on existing
hardware.

Personally, it doesn't bother me - putting up with one or two
"hiccups" per show is far outweighed by the superior deinterlacing.

- Chris


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