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Problem with sound on saa7134 card
http://forum.linhes.org/viewtopic.php?f=2&t=6775		 Page 1 of 1
Author:  gravety [ Fri Nov 04, 2005 6:28 pm ]
Post subject:  Problem with sound on saa7134 card
Hi,

I had this working with the last version of KnoppMyth I had installed (R5A10) by editing one of the driver source files - either the saa7134 or tda9887, I can't remember which.

The problem: From the install the sound exhibits two bursts of static noise when changing TV channel (this is to do with the driver scanning for the correct audio freq.). This can be fixed by adding the following command to a boot script:
Code:
/usr/bin/v4lctl /dev/video0 setnorm PAL-I

However, this doesn't fix the issue with sound quality. Audio when watching TV (or recording a program) sometimes turns to heavy static.

You can still hear the audio but it sounds really distorted. Changing channel will usually sort it out.

Anyone else come across this problem and have a solution/suggestion?
Author:  gravety [ Wed Nov 09, 2005 2:51 pm ]
Post subject: 
The double burst of static noise was fixed by compiling the latest (video4linux-20051011.tar.gz) source for video4linx. You can find this here: http://www.linuxtv.org/downloads/video4linux/

It appears that they have fixed the driver so that it still does the audio scan but without outputting the results to the soundcard. This gives a slight delay before the sound kicks in.

I needed to add the following to /home/mythtv/.fluxbox/apps
Code:
[startup] {/usr/bin/v4lctl -c <devicename>  volume mute off}
to un-mute the audio card (which wasn't needed previously). I also added
Code:
[startup] {/usr/bin/v4lctl -c <devicename>  setnorm PAL-I}
for good measure (though I haven't bothered to experiment as to whether this made a difference!).

You will now find that the audio should be noise burst free! The solution mentioned in the 1st post (just adding the setnorm command and using the R5A22 drivers) still left noise bursts on recordings.

Note: The other noise distortions (again mentioned in the 1st post) were due to a poor signal that day and too high CPU load!

There was an alternative solution (if u don't feel like getting your hands dirty compiling) posted by lel http://mysettopbox.tv/phpBB2/viewtopic.php?t=5965.

Hope this helped someone!!

Regards, Graham
Author:  lel [ Sun Nov 13, 2005 6:54 am ]
Post subject: 
I should mention that my script you link to did not make things 100% perfekt. For some reason the sound would sometimes become very echoing and tinny. It could happen in the middle of a show. Even if that was better than the complete static nosie I got before using my script, it was really annoying.

To fix it I changed from grabbing audio over PCI to using a loopcable to line-in. I adjusted the script to mute recording by changing line-in source of the normal /dev/mixer0 (rather than the tv-cards /dev/mixer1) during channel change.

I have yet not had a singel recording with strange or destroyed sound!
Author:  gravety [ Mon Nov 21, 2005 4:59 pm ]
Post subject: 
Yeah, after testing I have found that the audio (sometimes) suffers from 'pops' in my case. These are quite noticable and occur every 5 secs or so... :(

I have also noticed audio corruption (really bad) which sounds like the audio is being sent through water!? At first I thought this was to do with CPU load but last time it occured the CPU usage was at 40-50%...

I am going to try hooking up one card through the CD analogue line in connector on the MB. This is not ideal (it just wouldn't scale with more TV cards) but should work ok and hopefully solve the audio issues.

Will post back with results.

BTW: I never noticed this with my previous KM R5A10 install...
Author:  gravety [ Wed Nov 23, 2005 2:39 pm ]
Post subject: 
Hmm, I have tried a card hooked up through the analogue lead and I still had distorted audio (on occasion). Even if it had worked it would mean installing another sound card (impossible in my pundit-r!) for two TV cards...

I have turned debug on for the tda9887 module and it is always selecting the correct tvnorm. Also, there are no errors reported in the myth backend log.

I will try some other driver snapshots when I get some time.
Author:  zaphod24 [ Wed Nov 23, 2005 7:57 pm ]
Post subject: 
I've got an Asus Digimatrix with an SAA7134 tv card. I've noticed that sometimes I get mute or distorted audio when changing channels and watching live tv. If I exit back to the menu and then go back to watch live tv again, the distortion goes away. If the audio is muted, I can just change channels up or down and then back to the original channel and it's unmuted. Is this maybe a driver problem? The latest kernel(and therefore video4linux) did fix some tuning problems I was having with channel 49. Sure love to get this fixed because the wife gets irritated when 1 show in 20 has no sound or bad sound.

Fedora Core 4 2.6.14-1.1637_FC4
Digimatrix BIOS 1006
Intel P4 2.66Ghz
FlyTV mini with LG NTSC (TALN mini series) tuner (saa7134)
1024MB PC3200 RAM
300 GB Western Digital 8MB Cache 7200rpm IDE
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