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Mythtv quality of Live TV
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Author:  board_tester [ Fri Oct 01, 2004 4:47 am ]
Post subject:  Mythtv quality of Live TV
Hi,

I use the TV-out of my graphic card to use Mythtv on my TV. If I watch a recorded movie the picture ist great and there are no interrupts during watching. But if I watch Live TV the picture is not sharp and at fast movements you can see a shadow. There are some interrupts during Live TV.
I guess there is no problem with the harddrive, because if I record a movie in the background and watch a recorded movie at the same time I have no problems an the picture quality is very good.
Does anybody know a solution?

Thanks a lot

ce ya, Andre
Author:  tjc [ Fri Oct 01, 2004 9:47 am ]
Post subject: 
1) Details of your hardware would help us answer your question.

2) Since you didn't provide these, my advice witll be to "search the forum!"

3) - Have you checked your DMA?
- Have you looked at the MythTV how to? http://www.mythtv.org/modules.php?name=MythInstall
- Have you looked at the MythTV and KnoppMyth wikis? http://www.mythtv.info/
http://knoppmythwiki.homelinux.org/
- Did you compare the recording profiles in setup, particularly default vs. live?
Author:  board_tester [ Mon Oct 04, 2004 1:28 am ]
Post subject: 
1) I guess I have a Intel Celeron with 2,7 GHz, 512 MB Ram,
GForce2 MX -TV-Out, 3 Harddrives, Hauppauge PVR 250 and
a Hauppauge WinTV.
Installed System is Debian, Kernel 2.6.7, Mythtv 0.16, IVTV I´m not sure
0.11 ?!
The quality issue is only at the 250 PVR, the other TV-card I use only for
nxtvepg.

2) I searched this forum twice, I didn´t find a solution.

3) I checked DMA, it is activated.(hdparm option -t says, the transferate is about 40 MB/s I guess this should be enough?) I have my swap-partition and my Mythtv-cache on drive hdc, which is the same model than hdb. Checking the transfertate with hdparm -t, hdb is about 5 - 6 MB/s faster than hdc. (hdd is my cdrom drive).
The profile entries for LiveTV and for Default are the same.

I have some transcode problems as well, after transcode the movie is without the commercials but it isn´t smaller (minus the commercial) than the original. I checked the MPEG4 entrie and it looks ok.

Thank for the rapide respond

ce ya, Andre
Author:  tjc [ Mon Oct 04, 2004 2:24 pm ]
Post subject: 
The CPU should be fast enough, and that's a good amount of RAM. The PVR-250 should be keeping the CPU load fairly low during recording. The transfer rates look OK, although you generally want to avoid putting an optical drive on the same IDE channel as an HD since everything on a channel is limited to the speed of the slowest device.

Not so sure about the GForce2. Also what is the chipset on your motherboard?

Your IVTV version should be 0.1.9 (default) or possibly one of the 0.1.10-pre2-ck-100 series (t or z) if you compiled it yourself.
Author:  ceenvee703 [ Mon Oct 04, 2004 4:03 pm ]
Post subject: 
The only thing I can chime in about is the transcoding. The default is to transcode MPEG2 to Motion JPEG, which will indeed be a lot larger than the MPEG2 input file. You'll need to change that to transcoding to MPEG4 if you want a smaller file.
Author:  board_tester [ Tue Oct 05, 2004 1:30 am ]
Post subject: 
The GeForce2 MX should be fast enough, because watching Video (Xine or MPlayer) is very good. Only the interrupts during watching live tv.
I guess it is a intel chipset. I compiled my ivtv by myself.
I set the priority of the myth-backend,the X-server and the mythfrontend to -5, and know it looks better ( no interrupts for the first 30 minutes).

I not able to watch as a usual user anymore, only looking for some interrupts ;-).

Do I have to change the transcode settings in the section recording setup, where all my tv-cards are listed, and i can choose between Default, Live TV,High Quality ......Do I have to change there the entries for Default in the section RJMPEG/MPG4 ?
Author:  tjc [ Tue Oct 05, 2004 6:06 pm ]
Post subject: 
Why I suspect your video is that other than that I generally have SLOWER hardware and don't have any trouble at all.
Code:
/dev/hda:
 Timing buffer-cache reads:   128 MB in  0.34 seconds =376.47 MB/sec
 Timing buffered disk reads:  64 MB in  1.20 seconds = 53.33 MB/sec

/dev/hdb:
 Timing buffer-cache reads:   128 MB in  0.34 seconds =376.47 MB/sec
 Timing buffered disk reads:  64 MB in  1.11 seconds = 57.66 MB/sec


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