[mythtv-users] VIA M787 Motherboard and mythfrontend

[Gert van der Knokke]

Thomas Kaiser wrote:
> Hi Gert
>
> After a while I was thinking I was the only crazy people who tries to run a 
> Mythtv-frontend on this MB. But now I know I am not the only one.
>
> I didn't see the "Via-XVMC decoder" setting, but I will look again, thanks.
> For what does "Via-XVMC" stands for?
>
>   
It can be found in the playback settings, I'm not sure in which language 
you have installed your Myth system (mine is in Dutch...)

 From the main menu:

Configuration -> Configuration -> TV -> Playback

There is an option to select the 'preferred MPEG-2 decoder' and here you 
can choose Standard, libmpeg2, Standard XVMC and VIA XvMC.
You need to select the last one: VIA XvMC
This decoder uses some hardware videoacceleration of  the Via videochip.
For best results on a monitor you need to enable 'deinterlace playback' 
and select Bob2x as deinterlacer.

Then keep pressing Enter (NOT ESC!!!) until you come back at the menu 
again (otherwise none of your changes are saved)

After this you can go back with ESC until you get at the main menu 
again, now try and play a recording or live TV, it should play much 
smoother and CPU use should be about 40 to 60 % with a 720x576 8Mbit 
Mpeg2 file on a 1024x768 monitor.

I run my X at 1280x720 at 50Hz on a 26" Acer LCD TV and it works OK (about 
65% CPU)
> Actually the idea was to boot of a CF card as a HD but it seems that the CF card 
> is much slower than a real HD :-(.
>
>   
That should be no problem as the frontend hardly uses the harddisk 
during playback of files from a seperate backend. The harddisk lights on 
my frontends only occasionally blink. Just put in enough RAM (256 is too 
little, 512 Mb should be enough) One of my frontends runs from a 6Gb 
2.5" laptop drive without problems.

> I installed a basic Ubuntu and added only the packages as I needed (and a little 
> more for xorg, I think). Anyway, It boots and runs, but I have still the same 
> jitter problem. When I look at the kernel messages I see that DMA gets disabled. 
> Maybe this is the problem. The CF card has no DMA :-(
> In the mythtv log I see some "prebuffer underrun" or somthing like this, I don't 
> have access to the log right now, sorry.
>   
You get the prebuffer pauses because the CPU has to do all of the 
decoding and it can not keep up. That is why you need the Via XvMC 
decoder option.

> Now, I will try to get something together which just loads form the CF card and 
> runs in ram. I did a lot of reading about "initramfs", I think this the way to 
> go, or not?
>
>   
You could try and boot of the card, then mount a root filesystem over 
the network and run the frontend from there.

> I will work on this for some time or buy some other hardware :-(
>
>   
If you are planning to go HDTV then you definitely need more horsepower.
For standard PAL/NTSC (SDTV) signals, this board will do fine and runs 
quite cool too...

Gert