Take latency and current time into account for visualization

Buffer more data, and return the data that is currently being
output from the audio output, to ensure that visualizations are
smooth and responsive even when the audio output has a large
latency and/or large buffers.
b/6522728

Change-Id: I401637f01be7600b3c594a55c869036c13b206c0

1 files changed, 63 insertions, 34 deletions

diff --git a/media/libeffects/visualizer/EffectVisualizer.cpp b/media/libeffects/visualizer/EffectVisualizer.cpp
index 44d05cd..d3c69f4 100644
--- a/media/libeffects/visualizer/EffectVisualizer.cpp
+++ b/media/libeffects/visualizer/EffectVisualizer.cpp
@@ -52,6 +52,8 @@ enum visualizer_state_e {
 // that the framework has stopped playing audio and we must start returning silence
 #define MAX_STALL_TIME_MS 1000
 
+#define CAPTURE_BUF_SIZE 65536 // "64k should be enough for everyone"
+
 struct VisualizerContext {
     const struct effect_interface_s *mItfe;
     effect_config_t mConfig;
@@ -59,10 +61,10 @@ struct VisualizerContext {
     uint32_t mCaptureSize;
     uint32_t mScalingMode;
     uint8_t mState;
-    uint8_t mCurrentBuf;
-    uint8_t mLastBuf;
+    uint8_t mLastCaptureIdx;
+    uint32_t mLatency;
     struct timespec mBufferUpdateTime;
-    uint8_t mCaptureBuf[2][VISUALIZER_CAPTURE_SIZE_MAX];
+    uint8_t mCaptureBuf[CAPTURE_BUF_SIZE];
 };
 
 //
@@ -72,11 +74,10 @@ struct VisualizerContext {
 void Visualizer_reset(VisualizerContext *pContext)
 {
     pContext->mCaptureIdx = 0;
-    pContext->mCurrentBuf = 0;
-    pContext->mLastBuf = 1;
+    pContext->mLastCaptureIdx = 0;
     pContext->mBufferUpdateTime.tv_sec = 0;
-    memset(pContext->mCaptureBuf[0], 0x80, VISUALIZER_CAPTURE_SIZE_MAX);
-    memset(pContext->mCaptureBuf[1], 0x80, VISUALIZER_CAPTURE_SIZE_MAX);
+    pContext->mLatency = 0;
+    memset(pContext->mCaptureBuf, 0x80, CAPTURE_BUF_SIZE);
 }
 
 //----------------------------------------------------------------------------
@@ -316,25 +317,25 @@ int Visualizer_process(
 
     uint32_t captIdx;
     uint32_t inIdx;
-    uint8_t *buf = pContext->mCaptureBuf[pContext->mCurrentBuf];
+    uint8_t *buf = pContext->mCaptureBuf;
     for (inIdx = 0, captIdx = pContext->mCaptureIdx;
-         inIdx < inBuffer->frameCount && captIdx < pContext->mCaptureSize;
+         inIdx < inBuffer->frameCount;
          inIdx++, captIdx++) {
+        if (captIdx >= CAPTURE_BUF_SIZE) {
+            // wrap around
+            captIdx = 0;
+        }
         int32_t smp = inBuffer->s16[2 * inIdx] + inBuffer->s16[2 * inIdx + 1];
         smp = smp >> shift;
         buf[captIdx] = ((uint8_t)smp)^0x80;
     }
-    pContext->mCaptureIdx = captIdx;
 
-    // go to next buffer when buffer full
-    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;
-        }
+    // XXX the following two should really be atomic, though it probably doesn't
+    // matter much for visualization purposes
+    pContext->mCaptureIdx = captIdx;
+    // update last buffer update time stamp
+    if (clock_gettime(CLOCK_MONOTONIC, &pContext->mBufferUpdateTime) < 0) {
+        pContext->mBufferUpdateTime.tv_sec = 0;
     }
 
     if (inBuffer->raw != outBuffer->raw) {
@@ -464,6 +465,10 @@ int Visualizer_command(effect_handle_t self, uint32_t cmdCode, uint32_t cmdSize,
             pContext->mScalingMode = *((uint32_t *)p->data + 1);
             ALOGV("set mScalingMode = %d", pContext->mScalingMode);
             break;
+        case VISUALIZER_PARAM_LATENCY:
+            pContext->mLatency = *((uint32_t *)p->data + 1);
+            ALOGV("set mLatency = %d", pContext->mLatency);
+            break;
         default:
             *(int32_t *)pReplyData = -EINVAL;
         }
@@ -481,13 +486,9 @@ int Visualizer_command(effect_handle_t self, uint32_t cmdCode, uint32_t cmdSize,
             return -EINVAL;
         }
         if (pContext->mState == VISUALIZER_STATE_ACTIVE) {
-            memcpy(pReplyData,
-                   pContext->mCaptureBuf[pContext->mCurrentBuf ^ 1],
-                   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) &&
-                    (pContext->mBufferUpdateTime.tv_sec != 0)) {
+            int32_t latencyMs = pContext->mLatency;
+            uint32_t deltaMs = 0;
+            if (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;
@@ -496,17 +497,45 @@ int Visualizer_command(effect_handle_t self, uint32_t cmdCode, uint32_t cmdSize,
                         --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);
+                    deltaMs = secs * 1000 + nsec / 1000000;
+                    latencyMs -= deltaMs;
+                    if (latencyMs < 0) {
+                        latencyMs = 0;
                     }
                 }
             }
-            pContext->mLastBuf = pContext->mCurrentBuf;
+            uint32_t deltaSmpl = pContext->mConfig.inputCfg.samplingRate * latencyMs / 1000;
+
+            int32_t capturePoint = pContext->mCaptureIdx - pContext->mCaptureSize - deltaSmpl;
+            int32_t captureSize = pContext->mCaptureSize;
+            if (capturePoint < 0) {
+                int32_t size = -capturePoint;
+                if (size > captureSize) {
+                    size = captureSize;
+                }
+                memcpy(pReplyData,
+                       pContext->mCaptureBuf + CAPTURE_BUF_SIZE + capturePoint,
+                       size);
+                pReplyData += size;
+                captureSize -= size;
+                capturePoint = 0;
+            }
+            memcpy(pReplyData,
+                   pContext->mCaptureBuf + capturePoint,
+                   captureSize);
+
+
+            // if audio framework has stopped playing audio although the effect is still
+            // active we must clear the capture buffer to return silence
+            if ((pContext->mLastCaptureIdx == pContext->mCaptureIdx) &&
+                    (pContext->mBufferUpdateTime.tv_sec != 0)) {
+                if (deltaMs > MAX_STALL_TIME_MS) {
+                    ALOGV("capture going to idle");
+                    pContext->mBufferUpdateTime.tv_sec = 0;
+                    memset(pReplyData, 0x80, pContext->mCaptureSize);
+                }
+            }
+            pContext->mLastCaptureIdx = pContext->mCaptureIdx;
         } else {
             memset(pReplyData, 0x80, pContext->mCaptureSize);
         }