[mythtv-users] Imperfect skip with FreeviewHD -> PCTV 290e -> nVidia ION

Paul Gardiner lists at glidos.net
Tue Nov 8 13:17:57 UTC 2011

On 08/11/2011 13:02, phipps-hutton at sky.com wrote:
> Hi All,
> I've been recoding FreeviewHD for a little while now and it is going
> great except for one thing. It looks like skipping isn't going to a
> keyframe some of the time. Sometimes it works and sometimes not. When
> it doesn't I get to see the usual pattern of macroblocks from previous
> frames in the wrong places. Looking in the recordedseek table shows
> marks at around 0.9s intervals and appears to match how long it takes
> to get a good picture. There is not much on the logs that is different
> when it works and fails. There are some of these:
> 2011-11-07 23:21:59.804 [h264_vdpau @ 0xb4c92f60]mmco: unref short failure
> 2011-11-07 23:21:59.889 Player(6): Waited 100ms for video buffers
> Does anyone else have a similar set up and perfect skipping?

As far as I know it is not possible, at least with BBC HD and
BBC 1 HD. h264 has several methods for creating clean starting
points, but the BBC streams don't contain these. There are
regular I-frames, but h264 allows use of references across an
I-frame, which BBC streams exploit.

I've recently added an option to mythtranscode denoted by --cleancut
to perform cuts partly by throwing away frames, so at least
you don't see any brokenness after transcoding. --cleancut
works only in fifodir mode.


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