[pulseaudio-discuss] cracks and pops with intelHDA

Erik Slagter erik at slagter.name
Sun Jan 13 02:59:09 PST 2008

Lennart Poettering wrote:
> On Sat, 12.01.08 12:35, Erik Slagter (erik at slagter.name) wrote:

>> I had posted here a few weeks ago. I have an amplifier with USB terminal 
>> (and accompanying DAC) that removes the USB DAC (power down) when powered 
>> down. This is a problem for me because I need to supply both the amplifier 
>> and the internal soundcard with audio 24/7. When the amplifier 's USB DAC 
>> goes away, the device is removed by alsa, which most programs don't like. 
>> My thought was to use PulseAudio to solve this, but PulseAudio does indeed 
>> notice that the USB DAC goes away, and actually even re-enables it when it 
>> comes back, but never inserts it back into the "combined" device.
> This is a bug as it appears. Please provide me with an output of
> pulseaudio -vv when this happens an module-combine doesn't recognize
> the USB hw again when it is plugged in.

Purged the packages... I will try to explain things in detail.

Setup: one intel-hda alsa device and a USB sound device, these are fed 
by an mp3 player 24/7 and should work continuously, with the USB device 
either powered up or down.

Config option 1: using the hal-detect module. I noted the sink names 
that are dynamically assigned to the two alsa devices (these are 
_long_!) First problem is that hal doensn't always produce the same 
identifiers. This is a problem with combine module as I need to specify 
the sink names (according to the docs?!) Most of the time the id's are 
identical though, so I was able to do some testing. I started pulseaudio 
when the USB device was already up, and had the combine module combine 
the two sinks. Initially this works, until the USB device is removed and 
inserted back. I do get a new alsa "hal-detected" device, but it doesn't 
get back into the combined device.

Config option 2: using static configuration. Created two alsa devices 
and linked these together using combine. When I remove the USB device, 
the sink and module disappear, but when the USB is reinserted, it isn't 
detected at all. It looks like some "stick around" option is needed for 
device specific modules.
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