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, 5 deletions

diff --git a/firmware/export/config/ondavx747.h b/firmware/export/config/ondavx747.h
index d303ea5925..8499c15ce9 100644
--- a/firmware/export/config/ondavx747.h
+++ b/firmware/export/config/ondavx747.h
@@ -132,11 +132,6 @@
 /* has no volume control, so we use the software ones */
 #define HAVE_SW_VOLUME_CONTROL
 
-/* software controlled volume ranges from -73 -> 0 dB, other than that
-   is controlled by hardware */
-#define SW_VOLUME_MIN   -73
-#define SW_VOLUME_MAX   0
-
 /* define the bitmask of hardware sample rates */
 #define HW_SAMPR_CAPS   (SAMPR_CAP_48 | SAMPR_CAP_44 | SAMPR_CAP_32 | \
                          SAMPR_CAP_24 | SAMPR_CAP_22 | SAMPR_CAP_16 | \