commit 411cb8e45442d16d983a38722c7c7bce487bde6b
author Andy Hung <hunga@google.com> Tue May 27 12:32:17 2014 -0700
committer Andy Hung <hunga@google.com> Wed May 28 14:20:23 2014 -0700
tree e819e73fe603393fa8f80dc0c12be7e2434cd43b
parent 498692535c7ceecb3434a99c47e4c90ba3fdd90e

Update dynamic resampler buffer fetching

Make the criteria tight for fetching to avoid storing
excessive frame data internal to the resampler.
This should reduce jitter in frame delivery computation.

Bug: 14962343
Change-Id: I7adaf714d11c272696ccdbf218bda994c7217477

services/audioflinger/AudioResamplerDyn.cpp

diff --git a/services/audioflinger/AudioResamplerDyn.cpp b/services/audioflinger/AudioResamplerDyn.cpp
index 3abe8fd..a4446a4 100644
--- a/services/audioflinger/AudioResamplerDyn.cpp
+++ b/services/audioflinger/AudioResamplerDyn.cpp
@@ -455,12 +455,13 @@
     const Constants& c(mConstants);
     const TC* const coefs = mConstants.mFirCoefs;
     TI* impulse = mInBuffer.getImpulse();
-    size_t inputIndex = mInputIndex;
+    size_t inputIndex = 0;
     uint32_t phaseFraction = mPhaseFraction;
     const uint32_t phaseIncrement = mPhaseIncrement;
     size_t outputIndex = 0;
     size_t outputSampleCount = outFrameCount * 2;   // stereo output
-    size_t inFrameCount = getInFrameCountRequired(outFrameCount);
+    size_t inFrameCount = getInFrameCountRequired(outFrameCount) + (phaseFraction != 0);
+    ALOG_ASSERT(0 < inFrameCount && inFrameCount < (1U << 31));
     const uint32_t phaseWrapLimit = c.mL << c.mShift;
 
     // NOTE: be very careful when modifying the code here. register
@@ -474,11 +475,13 @@
         // buffer is empty, fetch a new one
         while (mBuffer.frameCount == 0) {
             mBuffer.frameCount = inFrameCount;
+            ALOG_ASSERT(inFrameCount > 0);
             provider->getNextBuffer(&mBuffer,
                     calculateOutputPTS(outputIndex / 2));
             if (mBuffer.raw == NULL) {
                 goto resample_exit;
             }
+            inFrameCount -= mBuffer.frameCount;
             if (phaseFraction >= phaseWrapLimit) { // read in data
                 mInBuffer.template readAdvance<CHANNELS>(
                         impulse, c.mHalfNumCoefs,
@@ -487,7 +490,7 @@
                 while (phaseFraction >= phaseWrapLimit) {
                     inputIndex++;
                     if (inputIndex >= mBuffer.frameCount) {
-                        inputIndex -= mBuffer.frameCount;
+                        inputIndex = 0;
                         provider->releaseBuffer(&mBuffer);
                         break;
                     }
@@ -535,15 +538,22 @@
 done:
         // often arrives here when input buffer runs out
         if (inputIndex >= frameCount) {
-            inputIndex -= frameCount;
+            inputIndex = 0;
             provider->releaseBuffer(&mBuffer);
-            // mBuffer.frameCount MUST be zero here.
+            ALOG_ASSERT(mBuffer.frameCount == 0);
         }
     }
 
 resample_exit:
+    // Release frames to avoid the count being inaccurate for pts timing.
+    // TODO: Avoid this extra check by making fetch count exact. This is tricky
+    // due to the overfetching mechanism which loads unnecessarily when
+    // mBuffer.frameCount == 0.
+    if (inputIndex) {
+        mBuffer.frameCount = inputIndex;
+        provider->releaseBuffer(&mBuffer);
+    }
     mInBuffer.setImpulse(impulse);
-    mInputIndex = inputIndex;
     mPhaseFraction = phaseFraction;
 }