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On board AC97 audio problem. - scratchy audio / with pops
http://forum.linhes.org/viewtopic.php?f=2&t=12696		 Page 1 of 1
Author:  kravaholic [ Thu Nov 23, 2006 7:34 am ]
Post subject:  On board AC97 audio problem. - scratchy audio / with pops
I am having a problem with my on board AC97 audio. My problem is that both live TV and anything recorded off live TV has scratchy audio it is discernable but still very annoying. I’ve searched here and at the Wiki but haven’t found much regarding this type of problem.

This is what I have tried so far.

Alsamixer – ran live TV went out to prompt but I could still hear the audio. Adjusted all settings trying to improve the sound quality but nothing worked. My audio source is an external satellite box with the audio going into my Happ. 150 it then runs out to my TV from the audio out on the onboard line out.

I have the follow configured in Myth Settings.

In myth settings screen:

Audio Output Device: /dev/dsp - (I’ve tried dsp0 with no improvement)

Enable AC3 to SPDIF pass-through: on
Enable DTS to SPDIF pass-through: on
Use internal volume controls: on

Mixer Device: /dev/mixer
Mixer Controls: PCM

I have ALSAmixer ver. 1.0.12rc1

The only thing that seems to show any signs of improvement is turning the input level down on Master Volume the only problem is that. I have to set it so low that you can’t really hear it. The audio distortion seems to be with voice dialogue only. Special effects and background noise appear unaffected.

Is there some sort of equalizer available that would allow me to adjust certain frequency ranges? If so I am certain that I could clean it up. Unless this is a Happ. 150 problem in which case I would have to some how clean it up before it is recorded.

I haven’t tried to copy a recording and play it in another device to see if the problem carries over to the recording. So I guess it is possible that it is a problem with the capture card.

Any help would be appreciated.

Thank you.
Author:  kravaholic [ Fri Nov 24, 2006 5:18 pm ]
Post subject: 
Updated the 1.0.12rc1 alsa driver to the new 1.0.13 driver. This made some improvement. However I still have the same problem.

Any ideas?
Author:  kravaholic [ Mon Nov 27, 2006 10:06 pm ]
Post subject:  Scratchy audio
Well I have the digital out working now. However my problem is still not solved. The problem is now more intermittent. When you enter MythTV sometimes the audio is perfect. If you exit and go right back in the audio is scratchy. May have to enter and exit MythTV up to 10 or 12 times to get it back to perfect.

Does anyone have any ideas on what I might do about this?
Author:  zitroneneis [ Thu Nov 30, 2006 9:27 pm ]
Post subject: 
hi.
I think I have had the same problem like you.
The sound output in music, video and DVD Module was clear
even the music in TV Mode sounded quite good,
but the Voices sounded pretty scratchy which was very disturbing.

So I tried around a long time and finally solved the problem (for me)
First of all I changed the Mythconfig and told the System that I would use an external Volume Control, as I prefer doing it directly at my Amplifier (I dont know if this step has to be done)

What did the Trick for me was running
"alsamixer -V all"

Setting:

Master to 81%
PCM to 71%
Line (seems to be unimportant)
Capture (at the very end and this is the most important) down to 30%

everything more than 30 % resultet in this scraty voices.

Tip: Run Live TV (Talkshow :-) ) on your Mythtv Box and log into your PVR machine from a remote Laptop via SSL and run Alsamixer from there. Like this you can here the results of your experiments live. (Makes it a lot easier)
Hope this helps you too -
Atleast I can enjoy watching TV finally
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