[alsa-devel] [PATCH 1/2] ALSA: add LaCie Firewire Speakers/Griffin FireWave surround driver

[Stefan Richter]

On Feb 08 Clemens Ladisch wrote:
> Stefan Richter wrote:
> > Next test:  Plugged the Speakers in, unloaded snd_hda_intel, loaded
> > firewire-ohci, snd_firewire_speakers now gets bound to devie right away.
> > Started xine and played a file.  No complaint.  (Hmm, I wonder whether I
> > had an operator error in my earlier session with FireWave.)  There is the
> > same problem as in the first KDE4 control panel test:  Playback starts
> > with an Autechre remix during the first few seconds. ;-)

I cannot reproduce the noise (clicks) at the start.  But clicks or pops
during playback are fully reproducible with the FireWave.  I am not 100%
sure but I think the Speakers are not affected.

These clicks or pops occur at a fast rate whenever there is a louder
passage in the sound stream.  The pitch and rate of clicks or pops
apparently depends on the spectrum of of the sound stream.  They happen
alongside the normal expected sound.

> If it is the same with both devices, the problem is probably not a wrong
> number of channels.
> 
> Choppy sound could indicate a wrong sample rate.  Jay used speaker-test,
> which uses 48 kHz by default, but most music files are 44.1 kHz, so it
> looks as if switching the sample rate does not work correctly.
> 
> > Alas the missing mixer makes the whole affair not quite usable yet:  The
> > LaCie FireWire Speakers are very loud; too loud for the desk or living
> > room.  On OS X, I had their volume pulled down to the lowest mark.
> 
> Attached are .conf files that enable software volume emulation for
> devices "default", "front", "surround40", and "surround51", but not "hw".
> Put them into /usr/share/alsa/cards/ (or wherever your distribution puts
> them).

This works indeed... most of the time.  Eventually (after device replugs
or driver reloading), somehow this software mixer/ volume control was not
found anymore.  It was back again in a later session.

But I learned that Audacious has an option to add such a software mixer/
volume control itself.

The effect of either way of volume control on the Speakers is that they
become usable (as far as desktop speakers can be considered usable).

The effect on the FireWave is that above mentioned clicks or pops are
avoided if the volume is turned down far enough.  However, at this state
the right channel puts out a high-frequency tone, close to what I suspect
is the upper frequency of the hearing capability of a well-maintained ear.
The left channel doesn't do that.

Furthermore, the muffled sound that the C/S port (the S channel) puts out
under OS X by Apple's stock driver¹ does not occur under Linux.

¹) as if it was driven as a 2.1 system, but it is probably just accidental
because it is too quiet and there are occasional pops on this channel
-- 
Stefan Richter
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