Documentation/sound/cards/audigy-mixer.rst

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Documentation/sound/cards/audigy-mixer.rst
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=============================================
Sound Blaster Audigy mixer / default DSP code
=============================================

This is based on sb-live-mixer.rst.

The EMU10K2 chips have a DSP part which can be programmed to support 
various ways of sample processing, which is described here.
(This article does not deal with the overall functionality of the 
EMU10K2 chips. See the manuals section for further details.)

The ALSA driver programs this portion of chip by default code
(can be altered later) which offers the following functionality:


Digital mixer controls
======================

These controls are built using the DSP instructions. They offer extended
functionality. Only the default built-in code in the ALSA driver is described
here. Note that the controls work as attenuators: the maximum value is the 
neutral position leaving the signal unchanged. Note that if the same destination
is mentioned in multiple controls, the signal is accumulated and can be clipped
(set to maximal or minimal value without checking for overflow).


Explanation of used abbreviations:

DAC
	digital to analog converter
ADC
	analog to digital converter
I2S
	one-way three wire serial bus for digital sound by Philips Semiconductors
	(this standard is used for connecting standalone D/A and A/D converters)
LFE
	low frequency effects (used as subwoofer signal)
AC97
	a chip containing an analog mixer, D/A and A/D converters
IEC958
	S/PDIF
FX-bus
	the EMU10K2 chip has an effect bus containing 64 accumulators.
	Each of the synthesizer voices can feed its output to these accumulators
	and the DSP microcontroller can operate with the resulting sum.

name='PCM Front Playback Volume',index=0
----------------------------------------
This control is used to attenuate samples from left and right front PCM FX-bus
accumulators. ALSA uses accumulators 8 and 9 for left and right front PCM 
samples for 5.1 playback. The result samples are forwarded to the front speakers.

name='PCM Surround Playback Volume',index=0
-------------------------------------------
This control is used to attenuate samples from left and right surround PCM FX-bus
accumulators. ALSA uses accumulators 2 and 3 for left and right surround PCM 
samples for 5.1 playback. The result samples are forwarded to the surround (rear)
speakers.

name='PCM Side Playback Volume',index=0
---------------------------------------
This control is used to attenuate samples from left and right side PCM FX-bus
accumulators. ALSA uses accumulators 14 and 15 for left and right side PCM
samples for 7.1 playback. The result samples are forwarded to the side speakers.

name='PCM Center Playback Volume',index=0
-----------------------------------------
This control is used to attenuate samples from center PCM FX-bus accumulator.
ALSA uses accumulator 6 for center PCM samples for 5.1 playback. The result
samples are forwarded to the center speaker.

Annotation

Implementation Notes