At Mon, 7 May 2007 14:10:18 -0700, John L. Utz III wrote: > > Hello; > > the CMI8738 allows for 4 channel output by providing a second DAC, but > sadly the hardware has no volume control for said second DAC. > > A review of /usr/share/alsa/cards/CMI8738-MC6.conf shows that the > implementor of said file was aware of the need to fix the problem: > > # 2nd DAC > # FIXME: we need a volume attenuator for rear channel. > CMI8738-MC6.pcm.rear.0 { > @args [ CARD ] > @args.CARD { > type string > } > type hw > card $CARD > device 1 > } > > > > I'd really like to fix this! > > Is it fixable by creating a softvol plugin? > > http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html#pcm_plugins > > so, if i have to invoke speaker test with -Dhw:0,1 to get 4 channel > out, what does that tell me about how i need to configure a softvol for > this item? > > Or am i missing the point and it's actually the *driver* that needs to > be doctored up to provide a softvol implementation. If so, how? For using the rear PCM defined in the above, you must use "rear" PCM as it's named, not hw:0,1, such as % aplay -Drear foo.wav The softvol implementation is easy. See CMI8738-MC8.conf as a reference. Note that you should use a different mixer name instead of "PCM Playback Volume". If an existing control name is specified, softvol will be skipped automatically. Use "Rear Playback Volume" instead, for example. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel