With 'hw=1.0' the first number is the sound card, and the second the
device on the sound card. Each device can have a number of sub-devices,
which are the actual physical outputs.
For example, my computer has two soundcards. An onboard intel ALC
horrible thing (hw=0) and a Gina20 (hw=1).
It looks like this:
$cat /proc/asound/pcm
00-00: ALC883 Analog : ALC883 Analog : playback 1 : capture 1
00-01: ALC883 Digital : ALC883 Digital : playback 1 : capture 1
00-02: ALC883 Analog : ALC883 Analog : capture 1
01-00: Analog PCM : Gina20 : playback 8 : capture 2
01-01: Digital PCM : Gina20 : playback 2 : capture 2
The Gina20 (card 1, device 0)(ANALOG OUTS) looks like this:
$ cat /proc/asound/card1/pcm0p/info
card: 1
device: 0
subdevice: 0
stream: PLAYBACK
id: Analog PCM
name: Gina20
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 8
subdevices_avail: 8
The Gina20 (card 1, device 1)(SPDIF OUTS) looks like this:
$ cat /proc/asound/card1/pcm1p/info
card: 1
device: 1
subdevice: 0
stream: PLAYBACK
id: Digital PCM
name: Gina20
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 2
subdevices_avail: 2
So, the first Gina20 device (1.0) has 8 sub-devices, and corresponds to
the eight analog audio outs.
The second Gina20 device (1.1) has 2 sub-devices, and corresponds to the
stereo SPDIF outputs.
SPDIF connections are treated as their own device as they have some
unique properties (emphasis, clocking etc) compared to the analog outs.
Really though, you should not be addressing the 'hw:0' stuff directly.
It's better to do all this using a GUI interface and sound servers,
unless you are troubleshooting something. One of the reasons for this is
that the sound card order (which soundcard is hw:0 or hw:1) is *not
fixed* and will change depending on the order you plug the cards in. The
other reason is that if a sound card has no digital gain controls, then
ALSA will not show any. The desktop sound servers will insert software
gain controls.
To summarise: Avoid all the above. For general Linux audio it's easier to
right-click on the little speaker icon on the desktop and select a sound
card than to mess with ALSA. :)
If you are doing music recording though, it is nice to be sure there is
no unnecessary latency, sample rate conversion or software mixing/gain
controls in the audio path. This is where Jack comes in.