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On Wednesday, 29 April 2020 16:24:31 BST Peter Humphrey wrote: |
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> On Wednesday, 29 April 2020 10:15:09 BST Peter Humphrey wrote: |
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> > I'm still puzzled at why creating an asound.conf enabled - phonon? - to |
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> > pick the right device. Alsa is not installed here, apart from alsa-lib; |
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> > no applications. |
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> |
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> Well, that was a hostage to fortune. Today, after a reboot and power cycle |
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> for maintenance work, I'm back to having no sound. |
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> |
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> I suspected the devices of having been detected in the wrong order, but |
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> /proc/ asound/cards seemed to be pointing to the right one. Besides, it |
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> seemed unlikely that a USB device would be found and set up before the |
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> device in the display controller. |
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The PCI card 0 is initialised before USB hotplugging takes place. Therefore |
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the asound.conf content would be parsed by alsa and the appropriate audio card |
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# (USB) would/should be set as the default device. However, the device |
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initialisation sequencing logic can be upset. |
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It is possible things will get messy if you have a second USB audio device, in |
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your case a webcam. I don't know if USB devices are always hotplugged in a |
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predictable order, but I guess plugging/unplugging USB devices could change |
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the order in which they are being detected and consequently their numbering. |
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Therefore your card number in asound.conf could end up referencing the other |
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USB device. |
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> Next was to blacklist all the intel* modules and reboot again. Just the one |
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> card found now, the USB device. Still no sound. |
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The fact there is no intel-snd module shows your sound problem is not related |
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to the PCI device. I expect the snd-usb-audio module was loaded though? |
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There are three kernel/alsa centric solutions I can think of, but may be more. |
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The first and simpler is to name your USB device in asound.conf not by card |
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number, but by the name it is recognised as. Run: |
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cat /proc/asound/cards |
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then look at the name enclosed in [square brackets] after the card number and |
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use that. There may be other naming conventions but unless I search for it |
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I'm not sure what to advise. Obviouisly if you have two USB devices |
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identified as "USB" this solution won't work. |
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Another way is manage the order in which the USB devices are ordered when the |
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module initialises them. Create a /etc/module.d/alsa.conf file and add this: |
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alias snd-card-0 snd-usb-audio |
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alias snd-card-1 snd-usb-audio |
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options snd-usb-audio index=0,1 vid=0xAAAA,0xBBBB pid=0xCCCC,0xDDDD |
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Where vendor and product IDs can be obtained and entered in the desired order |
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by looking at the corresponding device output of lsusb. |
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A third way is to create some udev rule(s) in /etc/udev/rules.d/ - see here |
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for syntax: |
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https://alsa.opensrc.org/Udev |
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and here for different examples: |
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https://github.com/dh1tw/remoteAudio/wiki/Persistent-USB-Mapping-of-Audio-devices-(Linux) |
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> Have I to go the PulseAudio route after all? |
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You do not *have to*, but if you find the PulseAudio server and associated |
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GUI/CLI tools are convenient for you, then you can set up USE=pulseaudio and |
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use that to mix your sound sinks and sources devices with. |
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As Canek has already posted in most cases it just works. However, I must |
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confess I had a spate of pa processes racing up to 100% CPU and annoyingly |
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respawning each time I tried to kill it. An update eventually fixed this |
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problem and it worked fine ever since. |
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