[Simoo]

Hi,

I feel I have hit a brick wall with MythTV at the moment which is so frustrating because I am so close to having a working system! I am unable to get smooth playback. I am comparing it directly to an 'off the shelf' digibox so I know the signal is alright.

I have an AMD 64 3000+ with 1 gig RAM and a PCI-E Nvidia graphics board. MythTV version - 0.20.2_p14324 & Nvidia driver version - 100.14.09 Running Gentoo. The capture card is A Nova-T DVB-T and I run live TV in a resolution of 720x576 from the SVIDEO TV out on the Nvidia to a SD TV.

It is quite subtle but especially noticeable when a camera 'pans', it appears to be dropping frames. I have tried various deinterlace/filter options with no luck and opengl vsync seems to make things worse. I also tried enabling XvMC but get this error:

...
VideoOutputXv Error: XvMC output requested, but
is not supported by display.
Xlib: extension "XVideo-MotionCompensation" missing on display ":0.0".
Xlib: extension "XVideo-MotionCompensation" missing on display ":0.0".
Xlib: extension "XVideo-MotionCompensation" missing on display ":0.0".
Xlib: extension "XVideo-MotionCompensation" missing on display ":0.0".
...

I have a couple of other smaller problems which may be linked so any help would be most appreciated

Thanks,

Simon

[Edster]

The system should have more than enough power to do that. You should have perfect quality pictues (well as good as your signal anyway).

Run 'top' in the background in a terminal window and see if anything is eating up the cpu.
Stop any services you do not need. If you are on Gentoo hopefully you do not have any extras sitting doing nothing in the back ground as you would have had to install them unlike most distros that give you services to do just about everything just in case you want to connect your pc to a tooth brush or a microwave etc etc etc

[Simoo]

Hi, thanks for the reply,

top shows my cpu about 7% when watching live TV and now with the gig of RAM there should be no problems.

You said "well as good as your signal anyway"

I have been doing quite a lot of searching on this and may have a little understanding of what is happening. Would I be right in saying that while using a graphics card to output to a TV you can never achieve perfectly smooth movement?

I think some other piece of hardware is needed? eg. The TV out on a PVR 350 or using an Xbox as a front end?

I could be completely wrong and if you have any other ideas please let me know

Thanks

Simon

[Edster]

when I said 'as good as your signal'
I was talking about picture compression. In order to squeeze all that video and audio into as little data flow as possible (so they can bundle more channels into each frequency space) they use compression.
One place you will see this is in big slowly changing colour areas. For example if you are looking at a big wall that takes most of the screen and due to lighting it goes from pink to red (it could be any colour). In order to save colours it will pick nearest colours for the compression and you will see areas or stripes of colour instead of a smooth fade.
The other place you see this is when you get fast moving items. As pixels have to change quickly to new colours and it doesn't like doing that it often gets very blocky on diagnal lines. A great place to see this is watching car racing (I love the F1 races)

But that is all just chatter and doesn't fix your problem...

Every time you have to move the picture from one place to another you are leaving an area where any delay will cause a dropped frame or a tear in the picture. If you had an old pc that was lacking memory or running other things that would fill up the cpu I would say that was your problem. But you are not.
A PVR350 card would probably help as it has hardware encoding chips but you would still be moving data in and out of the pc as mythtv works in software mode and doesn't use the full features of these chips (I use VDR and the TV data does not leave the card it just goes through the chips and straight out the tv out socket )

Try one other thing before you go shopping for new cards - Open up your box and make sure the tv card is at one end of the bus. If it already is try the other end. One of the slots is sometimes called the bus master and is in control of the interrupts and timing signals. It would always be best if this was the tv card as it has lots of data to ship and it sets the timing signal not another card. When you boot go into your BIOS. Look for settings about 'bus mastering' make sure it is enabled. Test the different settings if it has them. Also check the interrupts (IRQ) settings. If you have a list of cards like Network, Audio, video, Media card) try to make sure video and media (your tv card) are not sharing irqs with other things. Maybe get network and audio to share instead etc.
It is free so try this first. I've seen it do wonders for data shifting problems.

[Simoo]

Thanks so much for all that info, great stuff. I'm gunna have a play with lots of things. I tried moving the TV card up to the top PCI slot, although I didn't find anything in the BIOS about a 'BUS Mastering'.

I have a feeling it is not a problem with data transfer through the system. It maybe more to do with outputting to the TV at the correct rates.

I was interested to read about VDR... it looks tempting... as I am still stuck really...

Thanks again, I'll post up if anything happens.

Simon