Fix resampler to allow output of single frame
Bug: 13073201
Change-Id: If7818a3389a191a37277bbd8e96a59ef8ce68509
Signed-off-by: Andy Hung <hunga@google.com>
diff --git a/services/audioflinger/AudioResampler.cpp b/services/audioflinger/AudioResampler.cpp
index b206116..ca98f16 100644
--- a/services/audioflinger/AudioResampler.cpp
+++ b/services/audioflinger/AudioResampler.cpp
@@ -341,7 +341,7 @@
uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2;
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
// ALOGE("starting resample %d frames, inputIndex=%d, phaseFraction=%d, phaseIncrement=%d",
// outFrameCount, inputIndex, phaseFraction, phaseIncrement);
@@ -439,7 +439,7 @@
uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2;
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
// ALOGE("starting resample %d frames, inputIndex=%d, phaseFraction=%d, phaseIncrement=%d",
// outFrameCount, inputIndex, phaseFraction, phaseIncrement);
diff --git a/services/audioflinger/AudioResampler.h b/services/audioflinger/AudioResampler.h
index dc33f29..0592855 100644
--- a/services/audioflinger/AudioResampler.h
+++ b/services/audioflinger/AudioResampler.h
@@ -110,6 +110,38 @@
uint64_t mLocalTimeFreq;
int64_t mPTS;
+ // returns the inFrameCount required to generate outFrameCount frames.
+ //
+ // Placed here to be a consistent for all resamplers.
+ //
+ // Right now, we use the upper bound without regards to the current state of the
+ // input buffer using integer arithmetic, as follows:
+ //
+ // (static_cast<uint64_t>(outFrameCount)*mInSampleRate + (mSampleRate - 1))/mSampleRate;
+ //
+ // The double precision equivalent (float may not be precise enough):
+ // ceil(static_cast<double>(outFrameCount) * mInSampleRate / mSampleRate);
+ //
+ // this relies on the fact that the mPhaseIncrement is rounded down from
+ // #phases * mInSampleRate/mSampleRate and the fact that Sum(Floor(x)) <= Floor(Sum(x)).
+ // http://www.proofwiki.org/wiki/Sum_of_Floors_Not_Greater_Than_Floor_of_Sums
+ //
+ // (so long as double precision is computed accurately enough to be considered
+ // greater than or equal to the Floor(x) value in int32_t arithmetic; thus this
+ // will not necessarily hold for floats).
+ //
+ // TODO:
+ // Greater accuracy and a tight bound is obtained by:
+ // 1) subtract and adjust for the current state of the AudioBufferProvider buffer.
+ // 2) using the exact integer formula where (ignoring 64b casting)
+ // inFrameCount = (mPhaseIncrement * (outFrameCount - 1) + mPhaseFraction) / phaseWrapLimit;
+ // phaseWrapLimit is the wraparound (1 << kNumPhaseBits), if not specified explicitly.
+ //
+ inline size_t getInFrameCountRequired(size_t outFrameCount) {
+ return (static_cast<uint64_t>(outFrameCount)*mInSampleRate
+ + (mSampleRate - 1))/mSampleRate;
+ }
+
private:
const src_quality mQuality;
diff --git a/services/audioflinger/AudioResamplerCubic.cpp b/services/audioflinger/AudioResamplerCubic.cpp
index 1f9714b..8f14ff9 100644
--- a/services/audioflinger/AudioResamplerCubic.cpp
+++ b/services/audioflinger/AudioResamplerCubic.cpp
@@ -60,7 +60,7 @@
uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2;
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
// fetch first buffer
if (mBuffer.frameCount == 0) {
@@ -128,7 +128,7 @@
uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2;
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
// fetch first buffer
if (mBuffer.frameCount == 0) {
diff --git a/services/audioflinger/AudioResamplerDyn.cpp b/services/audioflinger/AudioResamplerDyn.cpp
index 54c2309..939b128 100644
--- a/services/audioflinger/AudioResamplerDyn.cpp
+++ b/services/audioflinger/AudioResamplerDyn.cpp
@@ -466,7 +466,7 @@
const uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2; // stereo output
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
const uint32_t phaseWrapLimit = c.mL << c.mShift;
// NOTE: be very careful when modifying the code here. register
diff --git a/services/audioflinger/AudioResamplerSinc.cpp b/services/audioflinger/AudioResamplerSinc.cpp
index 207f26b..d0a7a58 100644
--- a/services/audioflinger/AudioResamplerSinc.cpp
+++ b/services/audioflinger/AudioResamplerSinc.cpp
@@ -540,7 +540,7 @@
uint32_t phaseIncrement = mPhaseIncrement;
size_t outputIndex = 0;
size_t outputSampleCount = outFrameCount * 2;
- size_t inFrameCount = (outFrameCount*mInSampleRate)/mSampleRate;
+ size_t inFrameCount = getInFrameCountRequired(outFrameCount);
while (outputIndex < outputSampleCount) {
// buffer is empty, fetch a new one