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mdcclxv

Member

Registered: 2022-04-26

Posts: 207

[SOLVED] Questions about aplay -l output

Hi again,

I can't find any article explaining in detail the output of aplay -l.
My system has a built in sound card with analog & digital outputs and also a Radeon graphics card with three ports: DisplayPort, HDMI and DVI. On each port I have a monitor connected, both HDMI & DP monitors with integrated speakers. The monitor on the DVI port is connected via a DVI to HDMI adapter. I know DVI does not support audio, I'm just mentioning the DVI part here for the sake of clarity.

So here is the output of "aplay -l" on my system:

**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA ATI HDMI], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 8: HDMI 2 [U32R59x]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 9: HDMI 3 [HS160PC]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA ATI HDMI], device 10: HDMI 4 [HDMI 4]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Generic [HD-Audio Generic], device 0: ALC1220 Analog [ALC1220 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 1: Generic [HD-Audio Generic], device 1: ALC1220 Digital [ALC1220 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

What I understand from the listing:
- I have two sound cards, card 0 and card 1
- on card 0 I have five devices
- on card 1 I have two devices, device 0 the analog output and device 1 the digital output

What I don't understand:
1. Why do I have 5 HDMI devices listed? I was expecting just two.
2. Why do the devices have non-successive IDs (0,1,3,7,8,9,10) and should I make of the missing ones (2,4,5,6)?
3. What's the meaning of the x/y numbers listed on the Subdevices lines?

Thanks in advance.

Last edited by mdcclxv (2022-07-26 13:23:41)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,266

Re: [SOLVED] Questions about aplay -l output

1. The devices for HDMI are per output port of the graphics card, you always have them regardless of whether you have an actual monitor attached.  You might have more here because the card is specced for more but only "visibly" exposes 3

2. Nothing, that has always/is the case with HDMI devices, I'm not entirely sure why that is the way it is for HDMI in particular but it has always been the case

3. the subdevice line tells you whether that device is "in active use" or not. In ALSA land you can only have one single application have an audio stream open per subdevice and 1/1 means the device is still available (so nothing is currently playing back/using it) and 0/1 means the device is currently "blocked/in use" by something. For most "modern" purposes the application that takes control and handles the audio device is a sound server like pipewire or pulseaudio and they in turn make sure that multiple applications are able to play back at the same time (because they combine all different sources into one and then open the card with it.

   Back in the days of sound cards that had multiple HW mixers you might have more subdevices and the card itself is able to mix multiple applications, but you don't really see those anymore in standard consumer cards, maybe in some pro audio offerings but for the vast majority of cases you have one device and leave mixing multiple application streams to the OS

Last edited by V1del (2022-07-25 12:35:14)

mdcclxv

Member

Registered: 2022-04-26

Posts: 207

Re: [SOLVED] Questions about aplay -l output

@V1del: thanks for the elaborate answer, really helpful.