commit 03c48d5afcb3dfc1e43df93e1f3b3b3e9292e148
author Glenn Kasten <gkasten@google.com> Wed Jan 27 17:25:17 2016 -0800
committer Glenn Kasten <gkasten@google.com> Mon Feb 01 11:11:51 2016 -0800
tree 14e38bde5515cc54b0295faf92c13c37097f53e7
parent 16558ea318c3cf25a945fc1771572f489763527e

Add limiter for mono blend

Bug: 26904791
Change-Id: I76b16e70871cd9fc0a9b8badc66f27069fabe1cb

services/audioflinger/FastMixer.cpp

diff --git a/services/audioflinger/FastMixer.cpp b/services/audioflinger/FastMixer.cpp
index cc9acff..1446d19 100644
--- a/services/audioflinger/FastMixer.cpp
+++ b/services/audioflinger/FastMixer.cpp
@@ -416,7 +416,7 @@
         }
 
         if (mMasterMono.load()) {  // memory_order_seq_cst
-            mono_blend(mMixerBuffer, mMixerBufferFormat, Format_channelCount(mFormat), frameCount);
+            mono_blend(mMixerBuffer, mMixerBufferFormat, Format_channelCount(mFormat), frameCount, true /*limit*/);
         }
         // prepare the buffer used to write to sink
         void *buffer = mSinkBuffer != NULL ? mSinkBuffer : mMixerBuffer;

services/audioflinger/Threads.cpp

diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 8ae798c..7a29cce 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -2917,8 +2917,8 @@
                 // mono blend occurs for mixer threads only (not direct or offloaded)
                 // and is handled here if we're going directly to the sink.
                 if (requireMonoBlend() && !mEffectBufferValid) {
-                    mono_blend(
-                            mMixerBuffer, mMixerBufferFormat, mChannelCount, mNormalFrameCount);
+                    mono_blend(mMixerBuffer, mMixerBufferFormat, mChannelCount, mNormalFrameCount,
+                               true /*limit*/);
                 }
 
                 memcpy_by_audio_format(buffer, format, mMixerBuffer, mMixerBufferFormat,
@@ -2958,7 +2958,8 @@
             //ALOGV("writing effect buffer to sink buffer format %#x", mFormat);
 
             if (requireMonoBlend()) {
-                mono_blend(mEffectBuffer, mEffectBufferFormat, mChannelCount, mNormalFrameCount);
+                mono_blend(mEffectBuffer, mEffectBufferFormat, mChannelCount, mNormalFrameCount,
+                           true /*limit*/);
             }
 
             memcpy_by_audio_format(mSinkBuffer, mFormat, mEffectBuffer, mEffectBufferFormat,

services/audioflinger/Threads.h

diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index fa047fa..ae8bbb9 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -927,6 +927,8 @@
                                }
                            }
                 // the FastMixer performs mono blend if it exists.
+                // Blending with limiter is not idempotent,
+                // and blending without limiter is idempotent but inefficient to do twice.
     virtual     bool       requireMonoBlend() { return mMasterMono.load() && !hasFastMixer(); }
 };