Audio commands
Tutorials on Linux commands can be found everywhere on the internet.
http://www.linuxcommand.org/
http://tldp.org/LDP/intro-linux/html/index.html
Sound cards
ALSA numbers the sound cards starting with 0.
A card can have more then one device, again numbering starts at 0.
You refer to a soundcard with (card, device)
hw:0,0 refers to the first card and the first device of this card.
You can use hw or plughw
If you use the "plughw" interface, you need not care much about the sound hardware. If your soundcard does not support the sample rate or sample format you specify, your data will be automatically converted. This also applies to the access type and the number of channels. With the "hw" interface, you have to check whether your hardware supports the configuration you would like to use.
Commands
The following commands works in Ubuntu, a Debian distro.
asoundconf
Utility to read and change the user's ALSA library configuration
asoundconf set-default-card B10
Makes B10 (USB DAC) the default sound card, see cat to get the name of the soundcard.
aplay
A native ALSA wav player.
Can be used for some testing as well.
More ALSA utils
cat
Concatenates files, an easy way to list your audio devices in the terminal
cat /proc/asound/cards
0 [Intel ]: HDA-Intel - HDA Intel
HDA Intel at 0xb0000000 irq 16
1 [B10 ]: USB-Audio - Benchmark 1.0
Texas Instruments Benchmark 1.0 at usb-0000:00:1d.0-1, full speed
cat /proc/asound/devices
2: : timer
3: : sequencer
4: [ 0- 0]: digital audio playback
5: [ 0- 0]: digital audio capture
6: [ 0] : control
7: [ 1- 0]: digital audio playback
8: [ 1] : control
cat /proc/asound/hwdep
cat /proc/asound/modules
0 snd_hda_intel
1 snd_usb_audio
vincent@vincent-ubuntu:~$ cat /proc/asound/pcm
00-00: ALC260 Analog : ALC260 Analog : playback 1 : capture 1
01-00: USB Audio : USB Audio : playback 1
cat /proc/asound/timers
G0: system timer : 4000.000us (10000000 ticks)
P0-0-0: PCM playback 0-0-0 : SLAVE
P0-0-1: PCM capture 0-0-1 : SLAVE
P1-0-0: PCM playback 1-0-0 : SLAVE
cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version 1.0.17.
cat /proc/asound/card1/stream0
Shows you the properties of the audio stream.
Momentary freq tells you what Alsa is sending to the device.
This allows you to check if resampling is applied.
Texas Instruments Benchmark 1.0 at usb-0000:00:1d.0-1, full speed : USB Audio
Playback:
Status: Running
Interface = 1
Altset = 1
URBs = 2 [ 3 3 ]
Packet Size = 576
Momentary freq = 44100 Hz (0x2c.199a)
Interface 1
Altset 1
Format: 0x20
Channels: 2
Endpoint: 1 OUT (ADAPTIVE)
Rates: 44100, 48000, 88200, 96000
lspci
shows you all the PCI devices.
A very useful one is GREP, it filters the output.
lspci | grep –i audio
shows devices with audio in their name only, use –i to ignore upper/lower case
00:1b.0 Audio device: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller (rev 03)
lsusb
list all USB devices.
lsusb -2 002 -v list all properties of the USB-DAC
Bus 002 Device 002: ID 04d8:feea Microchip Technology, Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x04d8 Microchip Technology, Inc.
idProduct 0xfeea
bcdDevice 1.00
iManufacturer 1 Texas Instruments
iProduct 2 Benchmark 1.0
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 109
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
bInterfaceProtocol 0
iInterface 0
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 1.00
wTotalLength 30
bInCollection 1
baInterfaceNr( 0) 1
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 5
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bNrChannels 2
wChannelConfig 0x0003
Left Front (L)
Right Front (R)
iChannelNames 0
iTerminal 0
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 8
wTerminalType 0x0301 Speaker
bAssocTerminal 0
bSourceID 5
iTerminal 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
AudioStreaming Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 5
bDelay 1 frames
wFormatTag 1 PCM
AudioStreaming Interface Descriptor:
bLength 20
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 2
bSubframeSize 3
bBitResolution 24
bSamFreqType 4 Discrete
tSamFreq[ 0] 44100
tSamFreq[ 1] 48000
tSamFreq[ 2] 88200
tSamFreq[ 3] 96000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 9
Transfer Type Isochronous
Synch Type Adaptive
Usage Type Data
wMaxPacketSize 0x0240 1x 576 bytes
bInterval 1
bRefresh 0
bSynchAddress 0
AudioControl Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x01
Sampling Frequency
bLockDelayUnits 0 Undefined
wLockDelay 0 Undefined
Device Status: 0x0000
(Bus Powered)
ps
List processes.
ps -edalf | grep -i dsp
List processes using dsp
Specifying an audio device
hw:0,0
This means go directly to the hardware, card0, device 0. (the left number is the card, the right number is the device). If the device has a name you can use that as well.
hw talks directly to the hardware, no conversions whatsoever are performed.
If the DAC is 24 bits and you are playing a 16 bits file it won't play.
In this case, use the "plug" interface. Plug will do simple conversions such as bit differences and sample rate conversions as necessary.
You talk to the plug interface the same way as to hw.