audioflinger: fix effect problem during underrun

When an audio track underruns, the input buffer of the
corresponding effect chain (if any) must be cleared, otherwise
audio from previous mixer run will be fed again to the effect process
function.

Bug 6551652.

Change-Id: I5cd02196745f756c85af82d6937e9dc54369b37f

2 files changed, 37 insertions, 2 deletions

diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 57d70891..eea3cd22 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -3147,6 +3147,13 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::MixerThread::prepareTrac
                 mixerStatus = MIXER_TRACKS_READY;
             }
         } else {
+            // clear effect chain input buffer if an active track underruns to avoid sending
+            // previous audio buffer again to effects
+            chain = getEffectChain_l(track->sessionId());
+            if (chain != 0) {
+                chain->clearInputBuffer();
+            }
+
             //ALOGV("track %d u=%08x, s=%08x [NOT READY] on thread %p", name, cblk->user, cblk->server, this);
             if ((track->sharedBuffer() != 0) || track->isTerminated() ||
                     track->isStopped() || track->isPaused()) {
@@ -3661,6 +3668,12 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::DirectOutputThread::prep
             mActiveTrack = t;
             mixerStatus = MIXER_TRACKS_READY;
         } else {
+            // clear effect chain input buffer if an active track underruns to avoid sending
+            // previous audio buffer again to effects
+            if (!mEffectChains.isEmpty()) {
+                mEffectChains[0]->clearInputBuffer();
+            }
+
             //ALOGV("track %d u=%08x, s=%08x [NOT READY]", track->name(), cblk->user, cblk->server);
             if (track->isTerminated() || track->isStopped() || track->isPaused()) {
                 // We have consumed all the buffers of this track.
@@ -8978,6 +8991,25 @@ sp<AudioFlinger::EffectModule> AudioFlinger::EffectChain::getEffectFromType_l(
     return 0;
 }
 
+void AudioFlinger::EffectChain::clearInputBuffer()
+{
+    Mutex::Autolock _l(mLock);
+    sp<ThreadBase> thread = mThread.promote();
+    if (thread == 0) {
+        ALOGW("clearInputBuffer(): cannot promote mixer thread");
+        return;
+    }
+    clearInputBuffer_l(thread);
+}
+
+// Must be called with EffectChain::mLock locked
+void AudioFlinger::EffectChain::clearInputBuffer_l(sp<ThreadBase> thread)
+{
+    size_t numSamples = thread->frameCount() * thread->channelCount();
+    memset(mInBuffer, 0, numSamples * sizeof(int16_t));
+
+}
+
 // Must be called with EffectChain::mLock locked
 void AudioFlinger::EffectChain::process_l()
 {
@@ -9002,8 +9034,7 @@ void AudioFlinger::EffectChain::process_l()
             // if no track is active and the effect tail has not been rendered,
             // the input buffer must be cleared here as the mixer process will not do it
             if (tracksOnSession || mTailBufferCount > 0) {
-                size_t numSamples = thread->frameCount() * thread->channelCount();
-                memset(mInBuffer, 0, numSamples * sizeof(int16_t));
+                clearInputBuffer_l(thread);
                 if (mTailBufferCount > 0) {
                     mTailBufferCount--;
                 }
diff --git a/services/audioflinger/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index 51cbae73..19390b1a 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -1717,6 +1717,8 @@ mutable Mutex               mLock;      // mutex for process, commands and handl
         void checkSuspendOnEffectEnabled(const sp<EffectModule>& effect,
                                               bool enabled);
 
+        void clearInputBuffer();
+
         status_t dump(int fd, const Vector<String16>& args);
 
     protected:
@@ -1744,6 +1746,8 @@ mutable Mutex               mLock;      // mutex for process, commands and handl
         // types or implementations from the suspend/restore mechanism.
         bool isEffectEligibleForSuspend(const effect_descriptor_t& desc);
 
+        void clearInputBuffer_l(sp<ThreadBase> thread);
+
         wp<ThreadBase> mThread;     // parent mixer thread
         Mutex mLock;                // mutex protecting effect list
         Vector< sp<EffectModule> > mEffects; // list of effect modules