ALSA & Python - Capturing multiple mono audio inputs

Question

I'm using the python audio alsa library to interact with my M-Audio Delta 1010LT PCI audio interface. This audio interface has 8 analog inputs. I'd like to analyze the signal of one specific mono input. The card is being recognized:

cat /proc/asound/cards 0 [M1010LT        ]: ICE1712 - M Audio Delta 1010LT
                  M Audio Delta 1010LT at 0xa000, irq 18

After that I listed all device names (showing input ADCs here) with the command "amixer"

...
Simple mixer control 'ADC',0
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 142 [87%] [7.50dB]
Simple mixer control 'ADC',1
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',2
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',3
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',4
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',5
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',6
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
Simple mixer control 'ADC',7
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 164
Mono: 164 [100%] [18.50dB]
...

After that I listed the recording harware devices using the command "arecord -l"

arecord -l**** List of CAPTURE Hardware Devices ****
card 0: M1010LT [M Audio Delta 1010LT], device 0: ICE1712 multi [ICE1712 multi]
Subdevices: 1/1
Subdevice #0: subdevice #0

Am I right? Is this displaying only 1 recording subdevice? Shouln't it be showing 8?

I also installed Mudita24 - an envy24 visual mixer. With this one I can adjust and monitor the level of all input channels flawlessly.

After that I made a little test using GStreamer which worked also quite well:

gst-launch-0.10 alsasrc card-name=0 device-name='ADC 0' ! queue ! alsasink card-name=0 device-name='DAC 0'

But I'm having troubles to address a certain mono channel in python's alsa using the following card and device descriptors:

'default'  // This one get's me channel 1 & 2 MIXED (I'd like to get them as seperated mono inputs)
'hw:0,0'   // recognizes device but the input value is 0
'hw:0,0,0' // returns same as hw:0,0
'hw:0,0,1' // Device or resource busy (pretty much every other value than 0 returns this)
'hw:0,1'   // No such file or directory

How do I address a specific mono input channel using ALSA? This is the python library I'm using: link

This is how I'm trying to create a device for each channel:

pcm.one_channel {
@args [ CHANNEL ]
@args.CHANNEL { type integer }
type dsnoop
ipc_key 20130206
slave {
    pcm "hw:0"
    channels 12
    rate 44000
}
bindings [ $CHANNEL ]
}

pcm.two_channel {
    @args [ CHANNEL ]
    @args.CHANNEL { type integer }
    type dsnoop
    ipc_key 20130206
    slave {
        pcm "hw:0"
        channels 12
        rate 44000
    }
    bindings [ $CHANNEL ]
}

pcm.three_channel {
    @args [ CHANNEL ]
    @args.CHANNEL { type integer }
    type dsnoop
    ipc_key 20130206
    slave {
        pcm "hw:0"
        channels 12
        rate 44000
    }
    bindings [ $CHANNEL ]
}

pcm.four_channel {
    @args [ CHANNEL ]
    @args.CHANNEL { type integer }
    type dsnoop
    ipc_key 20130206
    slave {
        pcm "hw:0"
        channels 12
        rate 44000
    }
    bindings [ $CHANNEL ]
}

pcm.five_channel {
    @args [ CHANNEL ]
    @args.CHANNEL { type integer }
    type dsnoop
    ipc_key 20130206
    slave {
        pcm "hw:0"
        channels 12
        rate 44000
    }
    bindings [ $CHANNEL ]
}

Did I interpret your advice correctly? I've been also looking around the web for this and found two other .asoundrc for this card (which unfortunately also do not work).

#
# M-Audio Delta 1010
#

pcm.ice1712_capture {
    type dsnoop
    ipc_key 1024
    slave {
        pcm "hw:0"
        period_size 0
        buffer_size 65536
        rate 44100
        channels 10
        format "S16_LE"
    }
}

pcm.ice1712_playback {
    type dsnoop
    ipc_key 1024
    slave {
        pcm "hw:0"
        period_size 0
        buffer_size 65536
        rate 44100
        channels 10
        format "S16_LE"
    }
}

pcm.ice1712_duplex {
    type asym
    playback.pcm ice1712_playback
    capture.pcm ice1712_capture
}

pcm.ch1 {
    type plug
    ttable.0.0 1
    slave.pcm ice1712_duplex
}

pcm.ch2 {
    type plug
    ttable.1.1 1
    slave.pcm ice1712_duplex
}

pcm.ch3 {
    type plug
    ttable.0.2 1
    slave.pcm ice1712_duplex
}

pcm.ch4 {
    type plug
    ttable.1.3 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch5 {
    type plug
    ttable.0.4 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch6 {
    type plug
    ttable.1.5 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch7 {
    type plug
    ttable.0.6 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch8 {
    type plug
    ttable.1.7 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch9 {
    type plug
    ttable.0.8 1
    slave.pcm ice1712_duplex
}

pcm.ice1712_ch10 {
    type plug
    ttable.1.9 1
    slave.pcm ice1712_duplex
}

and here another one:

pcm.multi_capture {
    type multi
    slaves.a.pcm hw:0 
    slaves.a.channels 12

# First 8 channels of first soundcard (capture)
    bindings.0.slave a
    bindings.0.channel 0
    bindings.1.slave a
    bindings.1.channel 1
    bindings.2.slave a
    bindings.2.channel 2
    bindings.3.slave a
    bindings.3.channel 3
    bindings.4.slave a
    bindings.4.channel 4
    bindings.5.slave a
    bindings.5.channel 5
    bindings.6.slave a
    bindings.6.channel 6
    bindings.7.slave a
    bindings.7.channel 7

# S/PDIF section. Uncomment bindings if required.

# S/PDIF first soundcard (capture)
    #bindings.16.slave a
    #bindings.16.channel 8
    #bindings.17.slave a
    #bindings.17.channel 9
}

ctl.multi_capture {
    type hw
    card 0
}

pcm.multi_playback {
    type multi
    slaves.a.pcm hw:0
    slaves.a.channels 10

# First 8 channels of first soundcard (playback)
    bindings.0.slave a
    bindings.0.channel 0
    bindings.1.slave a
    bindings.1.channel 1
    bindings.2.slave a
    bindings.2.channel 2
    bindings.3.slave a
    bindings.3.channel 3
    bindings.4.slave a
    bindings.4.channel 4
    bindings.5.slave a
    bindings.5.channel 5
    bindings.6.slave a
    bindings.6.channel 6
    bindings.7.slave a
    bindings.7.channel 7

# S/PDIF section. Uncomment bindings if required.

# S/PDIF first soundcard (playback)
    #bindings.16.slave a
    #bindings.16.channel 8
    #bindings.17.slave a
    #bindings.17.channel 9
}

ctl.multi_playback {
    type hw
    card 0
}

CL. CL. · Accepted Answer · 2013-02-06T10:11:14

The amixer tool does not show device names but mixer controls.

The ICE1712 chip indeed has only one capture device (with exactly 12 channels).

To get virtual devices for individual channels, try to add something like the following to your ~/.asoundrc or /etc/asound.conf:

pcm.one_channel {
    @args [ CHANNEL ]
    @args.CHANNEL { type integer }
    type dsnoop
    ipc_key 20130206
    slave {
        pcm "hw:0"
        channels 12
        rate 48000
    }
    bindings [ $CHANNEL ]
}

and then use device names like one_channel:0, one_channel:1, etc.

ALSA & Python - Capturing multiple mono audio inputs

1 Answers