[alsa-devel] Incorrect name of PCM

Christopher Head alsa at chead.ca
Sun Jul 22 17:38:50 CEST 2018


Hi folks,
I have an Asus P8H77-I motherboard. On board is an Intel HDA connected
to a Via VT1708S codec. There are a number of analogue ports. In
addition to them, on the back panel are an HDMI port (from an
integrated GPU) and a TOSLINK port. The motherboard manual isn’t totally
clear on whether the HDMI port can also carry sound or only video, but
Windows claims to be able to send sound there, so probably yes. I don’t
use the integrated GPU, though.

Here’s the problem:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: VT1708S Analog [VT1708S Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 2: VT1708S Alt Analog [VT1708S Alt
Analog] Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: VT1708S Digital [VT1708S Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 9: HDMI 3 [HDMI 3]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

OK, a little bit unexpected that there is only one digital device
listed rather than two. The codec datasheet says it should have two
digital output widgets. Maybe it’s due to the integrated GPU being
disabled though.

$ aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
default:CARD=PCH
    HDA Intel PCH, VT1708S Analog
    Default Audio Device
sysdefault:CARD=PCH
    HDA Intel PCH, VT1708S Analog
    Default Audio Device
front:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    Front speakers
surround21:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
hdmi:CARD=PCH,DEV=0
    HDA Intel PCH, VT1708S Digital
    HDMI Audio Output
hdmi:CARD=NVidia,DEV=0
    HDA NVidia, HDMI 0
    HDMI Audio Output
hdmi:CARD=NVidia,DEV=1
    HDA NVidia, HDMI 1
    HDMI Audio Output
hdmi:CARD=NVidia,DEV=2
    HDA NVidia, HDMI 2
    HDMI Audio Output
hdmi:CARD=NVidia,DEV=3
    HDA NVidia, HDMI 3
    HDMI Audio Output

Why is this wrong? Because when I play to the “hdmi” PCM, at least with
the S/PDIF switch turned on in mixer controls, the sound comes out the
TOSLINK port! It seems that the PCM naming is wrong. This is all
without any configuration file. Everything works fine, just the name is
wrong.

I don’t know whether turning off the S/PDIF switch results in the sound
coming out the HDMI port instead; maybe it does (I don’t have anything
that speaks HDMI and can also play sound to test with). Either way,
seems like it should be called either “spdif” (if it’s only the TOSLINK
port) or some combination of the two (if it’s both and switchable by
the mixer switch).

If replying, please note that I’m not subscribed.

Thanks!
-- 
Christopher Head
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