alsa-lib/doc/asoundrc.doc

PCM common fields:
type		PCM type
[comment]	Saved comments

PCM types:

- hw 		Kernel PCM
Fields:
card		Card name or number
[device]	Device number (default 0)	
[subdevice]	Subdevice number, -1 first available (default -1)

- plug		Format adjusted PCM
Fields:
sname		Slave PCM name
ttable	 	Transfer table (bidimensional compound of 
	        cchannels * schannels numbers)
  .C
    .S		route value

- linear	Linear format conversion PCM
- adpcm		IMA-ADPCM format conversion PCM
- alaw		A-Law format conversion PCM
- mulaw		Mu-Law format conversion PCM
Fields:
sformat		Slave format
sname		Slave PCM name

- rate		Rate conversion PCM
Fields:
[sformat]	Slave format (default client format)
srate		Slave rate
sname		Slave PCM name

- route		Attenuated static route PCM
Fields:
[sformat]	Slave format (default client format)
[schannels]	Slave channels (default client channels)
sname 		Slave PCM name
ttable	 	Transfer table (bidimensional compound of 
	        cchannels * schannels numbers)
  .C
    .S		route value

- multi		Linked PCMs (exclusive access to selected channels)
Fields:
slave		Slaves definitions
  .N		Slave definition
    .name	Slave PCM name
    .channels	Slave channels
binding		Bindings table
  .N		Binding for client channel N
    .sidx	Slave key for slave definition
    .schannel	Slave channel

- file		File plugin
Fields:
sname		Slave PCM name
file		File name (or fd)
[format]	File format (NYI)


- null		Null endpoint plugin (NYI)
Fields:
time		Time related or not

- shm		Shared memory client PCM
Fields:
server		Server name
sname		Slave PCM name on server

- share		Share PCM
Fields:
sname		Slave name
[schannels]	Slave channels
[sformat]	Slave format
[srate]		Slave rate
binding		Bindings table
  .N		Slave channel for client channel N

- mix		Mix PCM (NYI)
Fields:
sname		Server name
binding		Bindings table
  .N		Binding for client channel N
    .schannel	Slave channel

- droute	Attenuated dynamic route PCM (NYI)
Fields:
[sformat]	Slave format (default client format)
[schannels]	Slave channels (default client channels)
sname 		Slave PCM name
binding		Bindings table
  .N		Binding entry
    .cchannel   Client channels
      .C	Client channel
    .schannel   Slave channels
      .S	Slave channel
    .control	Control name of C * S values or C values (only if C == S)

- lbserver	Loopback server (NYI)
Fields:
name		Loopback PCM ID (useful for multiple loopback served by the
		same server)
[socket]	PF_LOCAL socket name to listen
[port]		PF_INET port number to listen
sname		Slave name


CTL common fields:
type		CTL type
[comment]	Saved comments

- hw 		Kernel CTL
Fields:
card		Card name or number

- shm		Shared memory client CTL
Fields:
server		Server name
sname		Slave CTL name on server

Other related definitions:

- pcmtype	PCM type
Fields:
[lib]		Library file
open		Open function

- ctltype	Control type
Fields:
[lib]		Library file
open		Open function

- server	Server
Fields:
host		host where the server is located (if map to local address 
		server is local, and then it may be started automatically)
[socket]	PF_LOCAL socket name to listen/connect
[port]		PF_INET port number to listen/connect

Some examples:

pcmtype.hw {
	open _snd_pcm_hw_open
}

pcmtype.plug {
	open _snd_pcm_plug_open
}

pcm.trident {
	type hw
	card 0
	device 0
}

pcm.ice1712 {
	type hw
	card 1
	device 0
}

pcm.ice1712_spdif {
	type plug
	ttable.0.8 1
	ttable.1.9 1
	sname ice1712
}