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

1 files changed, 24 insertions, 9 deletions

diff --git a/media/libeffects/visualizer/EffectVisualizer.cpp b/media/libeffects/visualizer/EffectVisualizer.cpp
index 51c8b68354e8..bdb1a1cd969c 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 @@ enum visualizer_state_e {
     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 @@ struct VisualizerContext {
     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 @@ void Visualizer_reset(VisualizerContext *pContext)
     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 @@ int Visualizer_process(
     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 @@ int Visualizer_command(effect_handle_t self, uint32_t cmdCode, uint32_t cmdSize,
                    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 {