[mythtv-users] Stuttery playing back BBC HD

Matthew McClement mythtv at macker.co.uk
Tue Jan 2 13:10:55 UTC 2007

Paul Fowler wrote:
> My present concerns are:
> 1) can the twinhan card handle the symbol rate which BBC-HD uses (not
> sure how to test this)
>    so far I have tried playing the recorded files (eg Planet Earth
> 8.6GB/Hour!) on various machines including a P4HT 2.8GHz and still
> cannot get the full frame rate - eg. I am not sure if the disk files are
> correct.

The filesize seems about right so I'm guessing the recordings are 
valid(1 hour 11 minute recordings from DVB-T are 10GB each).

> 2) I believe my hard disk is fast enough (although ridiculously small)
> on this test machine, but not sure if ext3 filing system is killing
> performance ?

It's probably fine for a single stream.

> 3) probably the CPU is not fast enough.

It definitely isn't.

> 4) I know XVMC is working, but not sure if it is helping me with H264
> transport streams ?

XVMC only does mpeg2 so it's not going to help here.

> Can anybody suggest an in-expensive adjustments I could make, or other
> things I could check.

I don't think it's possible to playback the current streams under Linux 
at full speed. There was someone that managed to get the CoreAVC codecs 
to work with mplayer and that'd allow fullspeed on a beefy enough 
machine, but x264 just isn't fast enough.

I think the only people that have gotten the BBC HD broadcasts to play 
back using pure CPU decode are using CoreAVC and a midrange+ C2D. And 
that's under Windows.

The only option currently in MythTV is to record and transcode the 
shows(I shift them to 720p xvids). Realtime playback isn't likely to 
happen for a while.


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