My DVB-T picture quality is very good, but I notice a little jerkiness with end credits etc. I've select bob interlace which has improved things a little but it's still not quite on par with a STB. It seems as if the framerate is a little low.

I'm using a Twinham DVB-T card, XP2800, R5B7 and Geforce5200

Have you ensured your harddrive has been set to have DMA optimised?

I was having trouble when I was watching on a 540p modeline, or if I was trying to scale the video down to match the GUI.
When I moved to 1080i (with the VGA/Component converter, as I wasn't able to do 1080i on DVI), I was able to get rid of the deinterlacing completely, and everything was mostly great. But I still had a little jerky problem on the 720p channels (ABC/FOX). The ticker on Good Morning America, for example, would hesitate about once/second. Very distracting to watch.
So anyway, that problem was cleared up when I switched to "separate modes for GUI vs Playback". I set the playback to 1920x1080, and now all is well. And my CPU usage is down to about 50% when watching either 1080 or 720 playback.

I've concluded that any kind of zooming or scaling of the video is going to add overhead, and cause jerky playback.

If what Thornsoft is right, you might want to make sure your modeline is right. Mine concocted modeline is:
Modeline "720x576@50.00" 26.57 720 736 808 896 576 577 580 593 -HSync +Vsync

Supposedly for a PAL-I TV at 50 Htz

I am running the latest nvidia driver with the following option


With the new automodes I just need a mode of "720x576" to get this to work correctly.

I also not occasional DVB-T jerkyness, but it isn't constant. Perhaps this is a good thred to discuss DVB-T output tuning.

A couple of other thinks

1. I have XvMC on as well
2. If I play the same file via mplayer on the command line the output is near perfect.

Steve

_________________
OpenMedia Limited
New Zealands first open source PVR based on Knoppmyth
http://www.openmedia.co.nz for details

I believe Knoppmyth enables DMA by default (I'm sure I checked it once!)

My jerkyness is constant too. It's just more noticable on end credits etc.

Only just saw this...
But when I checked my DMA, it is on, but it doesn't have all the modes as listed on the wiki.

Some pointers on checking the DMA modea might be useful.

However, I found a BIG improvement by implementing the following;

In TV playback setup - enable OpenGL vsync timing and the interlace using Bob 2x

This gives much better playback with just a very small hint of jitter if you watch very closely.

It's on the wiki.
Here's the link: (It's listed as optimising hadrdrive performance)
http://knoppmythwiki.org/index.php?page=Optimize+Hard+Drive+Performance

Lem:

Another item to look at -- If you are using either "option DisplaySize" or "option DPI" in your XF86Config-4 file make sure that the ratio between the values is 4:3. I was using a ratio of 16:9 because my HDTV is 16:9, but when I upgraded to nvidia driver version 8756 I was having aspect ratio problems with xine playback. When I modified the ratio to 4:3 xine started to play back properly and my mythplayback, which was already looking very nice, got even better...


Marc

Added the Hard drive optimisation to the things I'd done above..

Silky smooth playback! Thanks guys.

Hi Lem

I have been struggling with jerky playback on my mythbox for two months now, picture quality was a lot better if i selected xvmc but BBC1 was unwatchable as sound kept breaking up horribly. I tried half a dosen different video cards with no success also even tried a high end sound card just to try to get sound right. It all came to a head over the last couple of weeks whilst the world cup was on, as the cammera panned the picture jumped if i turned on 'use video as timebase' the players would increase speed every couple of secs to bring them in line with the picture sync.

I run top to check cpu usage no matter what i did it ony varied between 15 to 25% i could not understand why it wasnt rite. Finaly after much googleing i figured it out it wasnt the playback that was at fault it was the recording. if i played recordings back in mplayer they were perfect. i contemplated using a sym link and playing bbc1 recordings in mplayer.

Well to cut to the chase ive fixed it, after some googleing, i found a setting in the dvb-t card recording setting which fixed everything. If I check the box marked "Use hardware MPEG decoder" for the dvb-t card it only records 1 sound track. After this the sound and video play back perfectly.

I remmenber you han the dvd sound problem so i figure you probably have not got this set it may be worth you giving it a try!!!

_________________
Running:-
Intel 930 3GHz dual Core
Thermaltake Fanless CPU Cooler
Asus P5GS
Samsung 750G Sata HDD
8400 512m Video Card
2 * jetway DVB-t
1 * Haupage DVB-S2 Card
Samsung Sata 16x DVDRW
2048M Ram
1 * Netop Ion 330

Thanks Simon. I had to uncheck vsync by OpenGL, but it seems to work ok. I never had any sound issues, but it seems to have improved the picture stability a bit. I'm still using Bob deinterlace and I'm still using the Standard MPEG decoder - are you using xmvc still? (can't say I've tried it yet to see for myself!)

I have just installed the KnoppMythR5C7.iso

I am new to Mythtv and first tried to install it on an Ubuntu install but could not get it to work.
So I am now trying to use KnoppMythR5C7.

I sort of have it working but not very well.
I am having this judder / slow-motion looking TV jerkiness.
I also can not get the network to connect to the internet.

I am using:

AMD sepron 2800+ CPU
512 ram
Asrock K7VT4A Pro Motherboard

KWorld DVB-T 100 Digital TV Tuner pci card (conexant broadcast decoder chip cx23883-19)

ATI 9550 AGP graphics plugged (D-sub cable) into a
Tevion LCD (physical Resolution WXGA 1280x720)

I read the link about:

Quote:

open up /etc/init.d/bootmisc.sh
look at the section at the end titled # Enable DMA
here is what mine looks like
# enable DMA
/sbin/hdparm -qd1c1u1m16 /dev/hda
/sbin/hdparm -qd1c1u1 /dev/hdc
/sbin/hdparm -qd1c1u1m16 /dev/hdb

But how do I open up?

I am finding it a little strange as when I close the TV console and find myself in the Linux Gnome screen.
Their aren’t any hard disks or any of the normal menu.

I really should do with a very very simple “how to fix” guide for a new users .

_________________
"video killed the radio star, video killed the radio star, In my mind and in my car, we can't rewind we've gone to far.
Pictures came and broke your heart, look I'll play my VCR."

Via Chipset? You could very well be suffering from the well known Via DMA problem... http://mysettopbox.tv/phpBB2/viewtopic.php?t=6321
The Hauppauge "MOMLIST" has some things that you can try. http://www.hauppauge.com/html/lockups.htm#MOMLIST