Fix ringbuffer handling

Explicitly keep track of the number of samples in the ring buffer,
rather than inferring it from the difference between the read and
write pointer, since the latter cannot distinguish between a
completely full and a completely empty buffer.

Bug: 17582331

Change-Id: I24d16ce96710209b7457ffad7c4c60201451980f

1 files changed, 17 insertions, 23 deletions

diff --git a/media/libstagefright/codecs/aacdec/SoftAAC2.cpp b/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
index 863b908..fb27dca 100644
--- a/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
+++ b/media/libstagefright/codecs/aacdec/SoftAAC2.cpp
@@ -137,6 +137,7 @@ status_t SoftAAC2::initDecoder() {
     mOutputDelayRingBuffer = new short[mOutputDelayRingBufferSize];
     mOutputDelayRingBufferWritePos = 0;
     mOutputDelayRingBufferReadPos = 0;
+    mOutputDelayRingBufferFilled = 0;
 
     if (mAACDecoder == NULL) {
         ALOGE("AAC decoder is null. TODO: Can not call aacDecoder_SetParam in the following code");
@@ -411,6 +412,10 @@ bool SoftAAC2::outputDelayRingBufferPutSamples(INT_PCM *samples, int32_t numSamp
     if (numSamples == 0) {
         return true;
     }
+    if (outputDelayRingBufferSpaceLeft() < numSamples) {
+        ALOGE("RING BUFFER WOULD OVERFLOW");
+        return false;
+    }
     if (mOutputDelayRingBufferWritePos + numSamples <= mOutputDelayRingBufferSize
             && (mOutputDelayRingBufferReadPos <= mOutputDelayRingBufferWritePos
                     || mOutputDelayRingBufferReadPos > mOutputDelayRingBufferWritePos + numSamples)) {
@@ -422,10 +427,6 @@ bool SoftAAC2::outputDelayRingBufferPutSamples(INT_PCM *samples, int32_t numSamp
         if (mOutputDelayRingBufferWritePos >= mOutputDelayRingBufferSize) {
             mOutputDelayRingBufferWritePos -= mOutputDelayRingBufferSize;
         }
-        if (mOutputDelayRingBufferWritePos == mOutputDelayRingBufferReadPos) {
-            ALOGE("RING BUFFER OVERFLOW");
-            return false;
-        }
     } else {
         ALOGV("slow SoftAAC2::outputDelayRingBufferPutSamples()");
 
@@ -435,16 +436,19 @@ bool SoftAAC2::outputDelayRingBufferPutSamples(INT_PCM *samples, int32_t numSamp
             if (mOutputDelayRingBufferWritePos >= mOutputDelayRingBufferSize) {
                 mOutputDelayRingBufferWritePos -= mOutputDelayRingBufferSize;
             }
-            if (mOutputDelayRingBufferWritePos == mOutputDelayRingBufferReadPos) {
-                ALOGE("RING BUFFER OVERFLOW");
-                return false;
-            }
         }
     }
+    mOutputDelayRingBufferFilled += numSamples;
     return true;
 }
 
 int32_t SoftAAC2::outputDelayRingBufferGetSamples(INT_PCM *samples, int32_t numSamples) {
+
+    if (numSamples > mOutputDelayRingBufferFilled) {
+        ALOGE("RING BUFFER WOULD UNDERRUN");
+        return -1;
+    }
+
     if (mOutputDelayRingBufferReadPos + numSamples <= mOutputDelayRingBufferSize
             && (mOutputDelayRingBufferWritePos < mOutputDelayRingBufferReadPos
                     || mOutputDelayRingBufferWritePos >= mOutputDelayRingBufferReadPos + numSamples)) {
@@ -463,10 +467,6 @@ int32_t SoftAAC2::outputDelayRingBufferGetSamples(INT_PCM *samples, int32_t numS
         ALOGV("slow SoftAAC2::outputDelayRingBufferGetSamples()");
 
         for (int32_t i = 0; i < numSamples; i++) {
-            if (mOutputDelayRingBufferWritePos == mOutputDelayRingBufferReadPos) {
-                ALOGE("RING BUFFER UNDERRUN");
-                return -1;
-            }
             if (samples != 0) {
                 samples[i] = mOutputDelayRingBuffer[mOutputDelayRingBufferReadPos];
             }
@@ -476,22 +476,15 @@ int32_t SoftAAC2::outputDelayRingBufferGetSamples(INT_PCM *samples, int32_t numS
             }
         }
     }
+    mOutputDelayRingBufferFilled -= numSamples;
     return numSamples;
 }
 
 int32_t SoftAAC2::outputDelayRingBufferSamplesAvailable() {
-    int32_t available = mOutputDelayRingBufferWritePos - mOutputDelayRingBufferReadPos;
-    if (available < 0) {
-        available += mOutputDelayRingBufferSize;
-    }
-    if (available < 0) {
-        ALOGE("FATAL RING BUFFER ERROR");
-        return 0;
-    }
-    return available;
+    return mOutputDelayRingBufferFilled;
 }
 
-int32_t SoftAAC2::outputDelayRingBufferSamplesLeft() {
+int32_t SoftAAC2::outputDelayRingBufferSpaceLeft() {
     return mOutputDelayRingBufferSize - outputDelayRingBufferSamplesAvailable();
 }
 
@@ -658,7 +651,7 @@ void SoftAAC2::onQueueFilled(OMX_U32 /* portIndex */) {
 
             AAC_DECODER_ERROR decoderErr;
             do {
-                if (outputDelayRingBufferSamplesLeft() <
+                if (outputDelayRingBufferSpaceLeft() <
                         (mStreamInfo->frameSize * mStreamInfo->numChannels)) {
                     ALOGV("skipping decode: not enough space left in ringbuffer");
                     break;
@@ -1032,6 +1025,7 @@ void SoftAAC2::onReset() {
     mOutputDelayCompensated = 0;
     mOutputDelayRingBufferWritePos = 0;
     mOutputDelayRingBufferReadPos = 0;
+    mOutputDelayRingBufferFilled = 0;
     mEndOfInput = false;
     mEndOfOutput = false;
     mBufferTimestamps.clear();