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Old 05-23-2004, 11:51 PM   #1
Registered: Feb 2004
Location: TX, USA
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distorted sound with tv card


my problem is this.... i have a tv card installed.... when i start it its sound is very distorted.... i have to turn down th volume to 75%.... so the problem is that the volume level is set to high....

how do i change it?.... alsaconf only list my soundblaster live and my Intel onboard card...i tried adjusting alsamixer, using alsamixer -c0 and -c1(i have two sound cards installed)......alsamixer only affects the sound card not the tv card.....i do believe it is a seperate sound there a way to see a list of soundcards and or audio tuners? there a way to find out the name of the tv card's audio device?

the tv card uses bttv is the dmesg for thsat section.....

Linux video capture interface: v1.00
i2c-core.o: i2c core module version 2.6.1 (20010830)
i2c-algo-bit.o: i2c bit algorithm module
i2c-core.o: driver i2c TV tuner driver registered.
i2c-core.o: driver i2c msp3400 driver registered.
i2c-core.o: driver tv card mixer driver registered.
tvaudio: TV audio decoder + audio/video mux driver
tvaudio: known chips: tda9840,tda9873h,tda9874h/a,tda9850,tda9855,tea6300,tea642
0,tda8425,pic16c54 (PV951),ta8874z
i2c-core.o: driver generic i2c audio driver registered.
bttv: driver version 0.7.108 loaded
bttv: using 4 buffers with 2080k (8320k total) for capture
bttv: Bt8xx card found (0).
bttv0: Bt848 (rev 18) at 02:02.0, irq: 18, latency: 32, mmio: 0xec6ff000
bttv0: using: STB, Gateway P/N 6000699 (bt848) [card=3,insmod option]
i2c-algo-bit.o: Adapter: bt848 #0 scl: 1 sda: 1 -- testing...
i2c-algo-bit.o:1 scl: 1 sda: 0
i2c-algo-bit.o:2 scl: 1 sda: 1
i2c-algo-bit.o:3 scl: 0 sda: 1
i2c-algo-bit.o:4 scl: 1 sda: 1
i2c-algo-bit.o: bt848 #0 passed test.
tuner: chip found @ 0xc6
tuner(bttv): type forced to 2 (Philips NTSC (FI1236,FM1236 and compatibles)) [in
i2c-core.o: client [Philips NTSC (FI1236,FM1236 and] registered to adapter [bt84
8 #0](pos. 0).
msp3400: chip reset failed
tvaudio: found tea6300 @ 0x80
i2c-core.o: client [tea6300] registered to adapter [bt848 #0](pos. 1).
tvaudio: found tda9850 @ 0xb6
i2c-core.o: client [tda9850] registered to adapter [bt848 #0](pos. 2).
i2c-core.o: adapter bt848 #0 registered as adapter 0.
bttv0: using tuner=2
tuner: type already set (2)
bttv0: i2c: checking for TDA9875 @ 0xb0... not found
bttv0: i2c: checking for TDA7432 @ 0x8a... not found
bttv0: PLL: 28636363 => 35468950 .. ok
bttv0: registered device video0
bttv0: registered device vbi0
bttv0: registered device radio0

any ideas on how to set that sucker????
Old 05-24-2004, 12:35 AM   #2
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Turn down only the line input level on one of the sound cards that you connected the tv tuner to. Then you should be fine. After you are done with alsamixer, run "alsactl store" as su or root.

You should never put the volume up to 100% for sound cards because they will clip (distort). Clipping causes speaker driver overload if you are not careful. Between 70% to 80% are good settings.
Old 05-24-2004, 03:22 AM   #3
Registered: Feb 2004
Location: TX, USA
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i had tried using alsamixer to fix it already....

i have to open Xawtv and turn it down in seems to be a whole other device.... how can i find the name of the device and how do i set it?...

any other ideas?
Old 05-24-2004, 03:58 AM   #4
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First of all, what is the make and model of the TV card? With that information, we could look up its specifications and find out what sound chip it uses, if in fact it does use one.

Is the TV card connected to the sound card in any way? My TV card (AIW Radeon) connects to the Line-In port of my sound card. So to adjust the volume (if my Radeon had TV-in under Linux as well as Windows, which it unfortunately does not), I would have to adjust the Line-In channel on my mixer.

If your TV card does not need to connect to the sound card in any way at all, it's a fair bet that it has its own sound chip; you might try typing lspci in a terminal to see if its listed as part of the TV card's sub-devices.

Or, there's this, in the dmesg posted above:
tvaudio: found tda9850 @ 0xb6

tda9850 appears to be the audio chipset; tvaudio appears to be the driver; seems to be part of the v4l (video 4 linux) kernel driver.

Since Xawtv (or any other TV display progam you might use) is the only program to use this device, it's not surprising that you might have to use the program itself to set the sound levels. Does Xawtv not retain its settings between uses?

However, it's quite possible that this can also be set in your mixer... have you used the right arrow key to make sure you've scrolled through all the mixer channels available to alsamixer? When you changed the mixer settings, did you reduce the PCM channel, or just the Main channel? PCM is normally the one that controls the guts of the main volume. There's also a "Video" channel, which on a system with a TV card might well control the chip in question. I've noticed that the GNOME sound mixer applet (I don't know about KDE) has tabs to reflect the mixers for different sound devices... if you use GNOME, you might want to check and see if there's a tab for tvaudio or something similar.

Hope this helps.
Old 05-24-2004, 02:19 PM   #5
Registered: Feb 2004
Location: TX, USA
Distribution: slack 9.1, 10, and 10.2
Posts: 144

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what type of card is it???....i listed the dmesg...but just in is an STB TV card...card=3 and tuner=2

like i said already...i have tried using alsa mixer to adjust does plug into my Aux on my SBLive!...but that does not turn stop the distortion, it just turns down the distortrion....all other sounds and sound channels are fine....

the TV card's audio, like i said, seems to be a seperate do i set it? thier a way to set the volume in XawTV?...maybe its config....tried it....didnt work.....maybe i got the syntax wrong?....

anybody know the answer?

come on, someons's got to know

Last edited by derfaust; 05-24-2004 at 02:21 PM.


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