Implement universal in-PCM-driver software volume control.

Implements double-buffered volume, balance and prescaling control in
the main PCM driver when HAVE_SW_VOLUME_CONTROL is defined ensuring
that all PCM is volume controlled and level changes are low in latency.

Supports -73 to +6 dB using a 15-bit factor so that no large-integer
math is needed.

Low-level hardware drivers do not have to implement it themselves but
parameters can be changed (currently defined in pcm-internal.h) to work
best with a particular SoC or to provide different volume ranges.

Volume and prescale calls should be made in the codec driver. It should
appear as a normal hardware interface. PCM volume calls expect .1 dB
units.

Change-Id: Idf6316a64ef4fb8abcede10707e1e6c6d01d57db
Reviewed-on: http://gerrit.rockbox.org/423
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested-by: Michael Sevakis <jethead71@rockbox.org>

1 files changed, 0 insertions, 3 deletions

diff --git a/lib/rbcodec/dsp/pga.h b/lib/rbcodec/dsp/pga.h
index f0c4c4717f..c05265873b 100644
--- a/lib/rbcodec/dsp/pga.h
+++ b/lib/rbcodec/dsp/pga.h
@@ -28,9 +28,6 @@ enum pga_gain_ids
 {
     PGA_EQ_PRECUT = 0,
     PGA_REPLAYGAIN,
-#ifdef HAVE_SW_VOLUME_CONTROL
-    PGA_VOLUME,
-#endif
     PGA_NUM_GAINS,
 };