commit b4605663882a9472b2e8915c851de899b14a27a5
author Eric Laurent <elaurent@google.com> Fri Mar 23 15:35:48 2012 -0700
committer Eric Laurent <elaurent@google.com> Mon Mar 26 11:05:25 2012 -0700
tree 7b1afad2be9db1f46821f0f76881b75babbc3331
parent 2e842a58ebbc3a8a0599dfb0c19d7cda7ed21e5f

fix visualizer inactivity detection

Current method implemented by the visualizer to detect that audioflinger has
stopped providing audio buffers does not work if the application
reads pcm captures too fast.

The fix consist in implementing a method based on real time measurement only.
One drawback is that the new method makes use of system calls that add some
overhead to the process and capture functions.

Change-Id: I53bd596b856f1cc7f0f47e08413af3335227100b

media/libeffects/visualizer/EffectVisualizer.cpp

diff --git a/media/libeffects/visualizer/EffectVisualizer.cpp b/media/libeffects/visualizer/EffectVisualizer.cpp
index 51c8b68..bdb1a1c 100644
--- a/media/libeffects/visualizer/EffectVisualizer.cpp
+++ b/media/libeffects/visualizer/EffectVisualizer.cpp
@@ -21,6 +21,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <new>
+#include <time.h>
 #include <audio_effects/effect_visualizer.h>
 
 
@@ -47,9 +48,9 @@
     VISUALIZER_STATE_ACTIVE,
 };
 
-// maximum number of reads from same buffer before resetting capture buffer. This means
+// maximum time since last capture buffer update before resetting capture buffer. This means
 // that the framework has stopped playing audio and we must start returning silence
-#define MAX_STALL_COUNT 10
+#define MAX_STALL_TIME_MS 1000
 
 struct VisualizerContext {
     const struct effect_interface_s *mItfe;
@@ -59,7 +60,7 @@
     uint8_t mState;
     uint8_t mCurrentBuf;
     uint8_t mLastBuf;
-    uint8_t mStallCount;
+    struct timespec mBufferUpdateTime;
     uint8_t mCaptureBuf[2][VISUALIZER_CAPTURE_SIZE_MAX];
 };
 
@@ -72,7 +73,7 @@
     pContext->mCaptureIdx = 0;
     pContext->mCurrentBuf = 0;
     pContext->mLastBuf = 1;
-    pContext->mStallCount = 0;
+    pContext->mBufferUpdateTime.tv_sec = 0;
     memset(pContext->mCaptureBuf[0], 0x80, VISUALIZER_CAPTURE_SIZE_MAX);
     memset(pContext->mCaptureBuf[1], 0x80, VISUALIZER_CAPTURE_SIZE_MAX);
 }
@@ -321,6 +322,11 @@
     if (pContext->mCaptureIdx == pContext->mCaptureSize) {
         pContext->mCurrentBuf ^= 1;
         pContext->mCaptureIdx = 0;
+
+        // update last buffer update time stamp
+        if (clock_gettime(CLOCK_MONOTONIC, &pContext->mBufferUpdateTime) < 0) {
+            pContext->mBufferUpdateTime.tv_sec = 0;
+        }
     }
 
     if (inBuffer->raw != outBuffer->raw) {
@@ -453,16 +459,25 @@
                    pContext->mCaptureSize);
             // if audio framework has stopped playing audio although the effect is still
             // active we must clear the capture buffer to return silence
-            if (pContext->mLastBuf == pContext->mCurrentBuf) {
-                if (pContext->mStallCount < MAX_STALL_COUNT) {
-                    if (++pContext->mStallCount == MAX_STALL_COUNT) {
+            if ((pContext->mLastBuf == pContext->mCurrentBuf) &&
+                    (pContext->mBufferUpdateTime.tv_sec != 0)) {
+                struct timespec ts;
+                if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
+                    time_t secs = ts.tv_sec - pContext->mBufferUpdateTime.tv_sec;
+                    long nsec = ts.tv_nsec - pContext->mBufferUpdateTime.tv_nsec;
+                    if (nsec < 0) {
+                        --secs;
+                        nsec += 1000000000;
+                    }
+                    uint32_t deltaMs = secs * 1000 + nsec / 1000000;
+                    if (deltaMs > MAX_STALL_TIME_MS) {
+                        ALOGV("capture going to idle");
+                        pContext->mBufferUpdateTime.tv_sec = 0;
                         memset(pContext->mCaptureBuf[pContext->mCurrentBuf ^ 1],
                                 0x80,
                                 pContext->mCaptureSize);
                     }
                 }
-            } else {
-                pContext->mStallCount = 0;
             }
             pContext->mLastBuf = pContext->mCurrentBuf;
         } else {