cx88: white noise with audio cable; no sound with cx88-alsa

cx88: white noise with audio cable; no sound with cx88-alsa

[Steve S]

Hi all.

This is my first post, so please be gentle :)

I have a WinTV PCI card with a cx88 chip.

--------------------------------------------
00:0f.0 Multimedia video controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder (rev 03)
00:0f.1 Multimedia controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder [Audio Port] (rev 03)

--------------------------------------------
$ cat /proc/asound/cards
 0 [V8235          ]: VIA8233 - VIA 8235
                      VIA 8235 with ALC650E at 0xe000, irq 19
 1 [CX8811         ]: CX88x - Conexant CX8811
                      Conexant CX8811 at 0xd2000000

--------------------------------------------
/etc/asound.names:

ctl {
	alsactl1 {
		name hw:0
		comment 'Physical Device - VIA 8235 with ALC650E at 0xe000, irq 19'
	}
	alsactl2 {
		name hw:1
		comment 'Physical Device - Conexant CX8811 at 0xd2000000'
	}
}
[...]

--------------------------------------------

I have 2 issues:

1) Right now, I'm capturing the sound using the analog audio cable that's
plugged into my onboard soundcard line-in (the VIA chip). At boot, I hear white
(static) noise coming from the line out of the TV card. If I start my TV app
(tvtime), the noise is replaced by the normal TV sound. When I close the TV
app, the noise is gone.

2) After a lot of searching the net, I was not able to track this issue down.
So I thought I try to capture the sound in another way.  According to [1,2], I
should be also able to capture the sound via the cx88-alsa module. The only
difference seems to be that I have rev 3, not rev 5.  I've read a lot about
redirecting the sound from the TV card but I feel a bit lost here. I tried

    $ sox -c 2 -t alsa hw:1 -t alsa hw:0    
    $ arecord -D hw:1 -c 2 -r 48000 -f S16_LE -t wav | aplay -

They all play nothing but silence. So, is this even possible with my card? 

My system: Debian testing, kernel compiled from from Debian kernel sources
(linux-source-2.6.24-6).

If you need more information, please say so. I'd be happy to provide as much as
I can, I just don't know where to start :) Many thanks!

steve

[1] http://www.linuxtv.org/v4lwiki/index.php/Cx88_devices_(cx2388x)
[2] http://www.mythtv.org/wiki/index.php/PCI_TV_audio

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Re: cx88: white noise with audio cable; no sound with cx88-alsa

[Steve S]

On May 23 13:17, Steve S wrote:

[...]

> I have a WinTV PCI card with a cx88 chip.
> 
> --------------------------------------------
> 00:0f.0 Multimedia video controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder (rev 03)
> 00:0f.1 Multimedia controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder [Audio Port] (rev 03)
> 
> --------------------------------------------
> $ cat /proc/asound/cards
>  0 [V8235          ]: VIA8233 - VIA 8235
>                       VIA 8235 with ALC650E at 0xe000, irq 19
>  1 [CX8811         ]: CX88x - Conexant CX8811
>                       Conexant CX8811 at 0xd2000000
> 
> --------------------------------------------
> /etc/asound.names:
> 
> ctl {
> 	alsactl1 {
> 		name hw:0
> 		comment 'Physical Device - VIA 8235 with ALC650E at 0xe000, irq 19'
> 	}
> 	alsactl2 {
> 		name hw:1
> 		comment 'Physical Device - Conexant CX8811 at 0xd2000000'
> 	}
> }
> [...]
> 
> --------------------------------------------
> 
> I have 2 issues:
> 
> 1) Right now, I'm capturing the sound using the analog audio cable that's
> plugged into my onboard soundcard line-in (the VIA chip). At boot, I hear white
> (static) noise coming from the line out of the TV card. If I start my TV app
> (tvtime), the noise is replaced by the normal TV sound. When I close the TV
> app, the noise is gone.
>
> 2) After a lot of searching the net, I was not able to track this issue down.
> So I thought I try to capture the sound in another way.  According to [1,2], I
> should be also able to capture the sound via the cx88-alsa module. The only
> difference seems to be that I have rev 3, not rev 5.  I've read a lot about
> redirecting the sound from the TV card but I feel a bit lost here. I tried
> 
>     $ sox -c 2 -t alsa hw:1 -t alsa hw:0    
>     $ arecord -D hw:1 -c 2 -r 48000 -f S16_LE -t wav | aplay -
> 
> They all play nothing but silence. So, is this even possible with my card? 

update:

I was able to capture the TV sound with cx88-alsa using mplayer like so:

    $ mplayer tv:// -tv driver=v4l2:alsa:adevice=hw.1:amode=1:audiorate=48000:volume=100:immediatemode=0:norm=PAL-BG:mjpeg

So, my card can do that. I still haven't found out why the other two
possibilities above don't work, though. Also, I read that these solutions can
cause the video and audio streams to go out of sync. So, maybe this isn't a
promising route to go anyway.

Now, I've observed something else: If I keep the loopback cable plugged into
the onboard soudcard and close mplayer, the white noise/buzzing sound over the
loopback cable starts again until I start tvtime, which stops it. Can anybody
explain this? I'd really like to know why I hear white noise over the loopback
cable (or direct at the TV card's line-out).  If anybody can give me a hint,
that would be highly appreciated.

[...]

> [1] http://www.linuxtv.org/v4lwiki/index.php/Cx88_devices_(cx2388x)
> [2] http://www.mythtv.org/wiki/index.php/PCI_TV_audio
> 

steve

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[SOLVED] cx88: white noise with audio cable; no sound with cx88-alsa

[Steve S]

On May 23 13:17 +0200, Steve S  wrote:
> Hi all.
> 
> This is my first post, so please be gentle :)
> 
> I have a WinTV PCI card with a cx88 chip.
> 
> --------------------------------------------
> 00:0f.0 Multimedia video controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder (rev 03)
> 00:0f.1 Multimedia controller: Conexant CX23880/1/2/3 PCI Video and Audio Decoder [Audio Port] (rev 03)
> 
> --------------------------------------------
> $ cat /proc/asound/cards
>  0 [V8235          ]: VIA8233 - VIA 8235
>                       VIA 8235 with ALC650E at 0xe000, irq 19
>  1 [CX8811         ]: CX88x - Conexant CX8811
>                       Conexant CX8811 at 0xd2000000
> 
> --------------------------------------------
> /etc/asound.names:
> 
> ctl {
> 	alsactl1 {
> 		name hw:0
> 		comment 'Physical Device - VIA 8235 with ALC650E at 0xe000, irq 19'
> 	}
> 	alsactl2 {
> 		name hw:1
> 		comment 'Physical Device - Conexant CX8811 at 0xd2000000'
> 	}
> }
> [...]
> 
> --------------------------------------------
> 

[...]

>
> 1) Right now, I'm capturing the sound using the analog audio cable that's
> plugged into my onboard soundcard line-in (the VIA chip). At boot, I hear white
> (static) noise coming from the line out of the TV card. If I start my TV app
> (tvtime), the noise is replaced by the normal TV sound. When I close the TV
> app, the noise is gone.

Solution: Mute the Line In at shutdown and reboot.

At boot, the TV card sound gets activated, even if there is no need to (related
to the post by Daniel Gimpelevich: "[PATCH] Implement proper cx88
deactivation"?).  This produces white noise at the Line In. At shutdown or
reboot, /etc/init.d/alsa (/etc/rc{0,6}.d/K<NN>alsa) stores the current mixer
status, and here esspecially the Line In volume. I had to add a script 
/etc/init.d/foo (/etc/rc{0,6}.d/K<MM>foo), which mutes the Line In (`amixer set
Line mute`) *before* the ALSA K scripts are called. So, at boot, the card audio is
still active, but Line In is silent. Yeah!

best,
steve

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