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DVB Picture Jerkiness?
http://forums.linhes.org/viewtopic.php?f=15&t=9696		 Page 1 of 2
Author:  Lem [ Wed Apr 19, 2006 9:31 am ]
Post subject:  DVB Picture Jerkiness?
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
Author:  tophee [ Wed Apr 19, 2006 9:58 am ]
Post subject: 
Have you ensured your harddrive has been set to have DMA optimised?
Author:  thornsoft [ Wed Apr 19, 2006 10:05 am ]
Post subject: 
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.
Author:  tophee [ Wed Apr 19, 2006 11:11 am ]
Post subject: 
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
Author:  steven_ellis [ Thu Apr 20, 2006 12:57 am ]
Post subject: 
I am running the latest nvidia driver with the following option
Code:
Option         "TVStandard" "HD576i"


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
Author:  Lem [ Tue Apr 25, 2006 6:26 am ]
Post subject: 
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.
Author:  tophee [ Wed Apr 26, 2006 9:48 am ]
Post subject: 
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.
Author:  Lem [ Fri Apr 28, 2006 6:55 am ]
Post subject: 
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.
Author:  tophee [ Fri Apr 28, 2006 7:36 am ]
Post subject: 
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
Author:  marc.aronson [ Sat Apr 29, 2006 5:56 pm ]
Post subject: 
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
Author:  Lem [ Mon May 08, 2006 4:40 am ]
Post subject: 
Added the Hard drive optimisation to the things I'd done above..

Silky smooth playback! Thanks guys.
Author:  simonf [ Thu Jun 22, 2006 3:31 pm ]
Post subject:  Just Another thing to try (fixed it for me)
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!!!

:lol:
Author:  Lem [ Thu Jun 29, 2006 1:39 am ]
Post subject: 
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!)
Author:  studiodaz [ Tue Aug 15, 2006 11:09 am ]
Post subject: 
:?:
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 . :?:
Author:  tjc [ Tue Aug 15, 2006 6:29 pm ]
Post subject: 
Quote:
ASRock K7VT4A Pro Motherboard
(Sempron/Athlon/XP, Socket A, VIA KT400A/VIA 8237, ATX, 2GB DDR, 333MHz FSB - MPN: K7VT4APRO)

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
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