audio policy: volume in dBs

Volumes are now stored and exchanged in dBs to be
consistent with the volume tables.

They are converted if needed when applied to the target
gain controller.

Change-Id: I916cbb0bbe65c916444b8c65a2bdca9645c58399

3 files changed, 26 insertions, 4 deletions

diff --git a/services/audiopolicy/common/include/Volume.h b/services/audiopolicy/common/include/Volume.h
index a4cc759..4205589 100755
--- a/services/audiopolicy/common/include/Volume.h
+++ b/services/audiopolicy/common/include/Volume.h
@@ -18,6 +18,10 @@
 
 #include <system/audio.h>
 #include <utils/Log.h>
+#include <math.h>
+
+// Absolute min volume in dB (can be represented in single precision normal float value)
+#define VOLUME_MIN_DB (-758)
 
 class VolumeCurvePoint
 {
@@ -32,7 +36,7 @@ public:
     /**
      * 4 points to define the volume attenuation curve, each characterized by the volume
      * index (from 0 to 100) at which they apply, and the attenuation in dB at that index.
-     * we use 100 steps to avoid rounding errors when computing the volume in volIndexToAmpl()
+     * we use 100 steps to avoid rounding errors when computing the volume in volIndexToDb()
      *
      * @todo shall become configurable
      */
@@ -134,4 +138,20 @@ public:
         }
     }
 
+    static inline float DbToAmpl(float decibels)
+    {
+        if (decibels <= VOLUME_MIN_DB) {
+            return 0.0f;
+        }
+        return exp( decibels * 0.115129f); // exp( dB * ln(10) / 20 )
+    }
+
+    static inline float AmplToDb(float amplification)
+    {
+        if (amplification == 0) {
+            return VOLUME_MIN_DB;
+        }
+        return 20 * log10(amplification);
+    }
+
 };
diff --git a/services/audiopolicy/common/managerdefinitions/include/AudioOutputDescriptor.h b/services/audiopolicy/common/managerdefinitions/include/AudioOutputDescriptor.h
index c6bb975..f1aee46 100644
--- a/services/audiopolicy/common/managerdefinitions/include/AudioOutputDescriptor.h
+++ b/services/audiopolicy/common/managerdefinitions/include/AudioOutputDescriptor.h
@@ -74,7 +74,7 @@ public:
     audio_patch_handle_t mPatchHandle;
     uint32_t mRefCount[AUDIO_STREAM_CNT]; // number of streams of each type using this output
     nsecs_t mStopTime[AUDIO_STREAM_CNT];
-    float mCurVolume[AUDIO_STREAM_CNT];   // current stream volume
+    float mCurVolume[AUDIO_STREAM_CNT];   // current stream volume in dB
     int mMuteCount[AUDIO_STREAM_CNT];     // mute request counter
     bool mStrategyMutedByDevice[NUM_STRATEGIES]; // strategies muted because of incompatible
                                         // device selection. See checkDeviceMuteStrategies()
diff --git a/services/audiopolicy/common/managerdefinitions/src/AudioOutputDescriptor.cpp b/services/audiopolicy/common/managerdefinitions/src/AudioOutputDescriptor.cpp
index 0837a54..596aa1d 100644
--- a/services/audiopolicy/common/managerdefinitions/src/AudioOutputDescriptor.cpp
+++ b/services/audiopolicy/common/managerdefinitions/src/AudioOutputDescriptor.cpp
@@ -21,6 +21,7 @@
 #include "AudioOutputDescriptor.h"
 #include "IOProfile.h"
 #include "AudioGain.h"
+#include "Volume.h"
 #include "HwModule.h"
 #include <media/AudioPolicy.h>
 
@@ -354,11 +355,12 @@ bool SwAudioOutputDescriptor::setVolume(float volume,
     if (changed) {
         // Force VOICE_CALL to track BLUETOOTH_SCO stream volume when bluetooth audio is
         // enabled
+        float volume = Volume::DbToAmpl(mCurVolume[stream]);
         if (stream == AUDIO_STREAM_BLUETOOTH_SCO) {
             mClientInterface->setStreamVolume(
-                    AUDIO_STREAM_VOICE_CALL, mCurVolume[stream], mIoHandle, delayMs);
+                    AUDIO_STREAM_VOICE_CALL, volume, mIoHandle, delayMs);
         }
-        mClientInterface->setStreamVolume(stream, mCurVolume[stream], mIoHandle, delayMs);
+        mClientInterface->setStreamVolume(stream, volume, mIoHandle, delayMs);
     }
     return changed;
 }