[linux-dvb] Strange problem on 1 channel only (UK)

Chris Audley chris at navaho.co.uk
Mon Jan 9 16:27:58 CET 2006

On Mon, 09 Jan, James Pattinson wrote:
> Hi All
> I'm using a Freecom DVB-T USB interface in the UK, and it's working well 
> except for one channel, BBC ONE. On this channel only, the audio breaks 
> up and the video seems choppy.
> The thing I can't understand is that other channels on the same 
> multiplex are fine, like BBC TWO etc...  so that suggests it's not a 
> signal strength issue. What could possibly be different about this stream?
> I'm using MythTV and i've tried the tuner in both PS and TS mode with 
> the same results.
> I don't get any messages in the kernel log about this. I'm running 
> kernel 2.6.14-gentoo-r5 on a P4 system that also has a TechniSat SkyStar 
> 2 PCI card installed for DVB-S.
> Any ideas would be appreciated!

I've just upgraded my Myth system and run into this exact problem. If you are using XvMC acceleration in Myth, try setting "Use hardware MPEG decoder" in the DVB card setup.

AFAICT the problem is actually to do with the number of audio channels in the stream - too many and the XvMC decoder starts stuttering. I believe turning on the MPEG decoder option in myth strips out the extra streams - but don't quote me on that, I couldn't find a definitve answer on the net and haven't had a chance to browse the src yet.

Note, this will only affect _new_ recordings made after you have enabled the hardware decoder option - your old recordings will still stutter.

Chris Audley                                       mailto:chris at navaho.co.uk
Technical Director                                    sip:chris at navaho.co.uk
Navaho Technologies Ltd.                              tel:02380000010 ext110
Fairchild House, Southampton Street, SO15 2ED, UK    http://www.navaho.co.uk

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