linuxaudio.org

On Mon, November 12, 2012 12:11 pm, Dan MacDonald wrote:

quoted text
> Hello LA land!

>

> I got a Startech USB audio device based on the C-Media CM6206 purely in

> the

> hope of being able to use its S/PDIF input under JACK. It runs JACK just

> fine, I just don't know how I might access the SPDIF input (or even the

> line-in, just out of interest) from under JACK?

>

> When I run alsamixer and switch to viewing the capture ports of the cm6206

> there are 4 capture channels - PCM, Line, Mic and S/PDIF In but under JACK

> I only get 2 capture ports which are the L and R analogue mic input

> channels. I can also see the light emitting from the S/PDIF out port so I

> am confident the S/PDIF should work and hopefully under JACK.

Ok, first thing to try is to make sure you can see the s/pdif inout with

alsa. audacity or arecord should be able to record audio (audacity

provides metering which may make things easier). alsamixer does not show

capture ports it shows volume controls or switches. Often you would have 3

or 4 inputs that are switched/mixed to give one stereo input. So making

sure your s/pdif channel is on/unmuted/turned up is the first step. You

may wish to mute Line and Mic while playing with it. You probably (from

what you have said) have:
Mic-------------\

                 \

Line----------| Mixer |------PCM------>ALSA-->Jack

                 /

S/PDIF----------/
Each line here would be a stereo path (two Channels).
In other words I think you will find there are only two input channels to

ALSA.
> card 2: Device [USB Sound Device], device 0: USB Audio [USB Audio]

quoted text
>   Subdevices: 1/1

>   Subdevice #0: subdevice #0

Assuming this is the device notice this doesn't shows number of channels.
>  11: [ 2- 0]: digital audio playback

quoted text
>  12: [ 2- 0]: digital audio capture

>  13: [ 2]   : control

>  33:        : timer

Or this... but they don't on my 4channel+spdif card either.
Try arecord -L

(Capital L)
It still doesn't show number of outputs directly but rather choices, There

it lists stereo as:

front:CARD=M66,DEV=0

    M Audio Delta 66, ICE1712 multi

    Front speakers

and spdif as:

iec958:CARD=M66,DEV=0

    M Audio Delta 66, ICE1712 multi

    IEC958 (S/PDIF) Digital Audio Output

To use my 4 analog inputs I would use:

surround40:CARD=M66,DEV=0

    M Audio Delta 66, ICE1712 multi

    4.0 Surround output to Front and Rear speakers

This one here _might_ be my analog inputs plus spdif:

surround51:CARD=M66,DEV=0

    M Audio Delta 66, ICE1712 multi

    5.1 Surround output to Front, Center, Rear and Subwoofer speakers

I say might be because jack actually show 12 inputs:

   1-4 are analog

   5-8 are not used but defined for the ice1712

   9-10 spdif

   11-12 monitor mixer output

So the last two inputs in 5.1 might actually be the dead inputs 5-6
--

Len Ovens

www.OvenWerks.net
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