resampler: add Fastest quality

It will use a bi-linear interpolation.
Also cleanup FullDuplexEcho

8 files changed, 38 insertions, 31 deletions

diff --git a/apps/OboeTester/app/src/main/cpp/FullDuplexEcho.cpp b/apps/OboeTester/app/src/main/cpp/FullDuplexEcho.cpp
index 30511a4b..0da2d002 100644
--- a/apps/OboeTester/app/src/main/cpp/FullDuplexEcho.cpp
+++ b/apps/OboeTester/app/src/main/cpp/FullDuplexEcho.cpp
@@ -29,32 +29,21 @@ oboe::DataCallbackResult FullDuplexEcho::onBothStreamsReady(
         void *outputData,
         int   numOutputFrames) {
     // FIXME only handles matching stream formats.
-    // TODO use array of delays
     // TODO Add delay node
     // TODO use flowgraph to handle format conversion
     int32_t framesToEcho = std::min(numInputFrames, numOutputFrames);
     float *inputFloat = (float *)inputData;
     float *outputFloat = (float *)outputData;
+    // zero out entire output array
+    memset(outputFloat, 0, numOutputFrames * getOutputStream()->getBytesPerFrame());
+
     int32_t inputStride = getInputStream()->getChannelCount();
     int32_t outputStride = getOutputStream()->getChannelCount();
     float delayFrames = mDelayTimeSeconds * getOutputStream()->getSampleRate();
-    if (outputStride == 1) {
-        while (framesToEcho-- > 0) {
-            *outputFloat++ = mDelayLine->process(delayFrames, *inputFloat); // mono delay
-            inputFloat += inputStride;
-        }
-    } else if (outputStride == 2) {
-        while (framesToEcho-- > 0) {
-            *outputFloat++ = mDelayLine->process(delayFrames, *inputFloat); // mono delay
-            *outputFloat++ = 0.0f;
-            inputFloat += inputStride;
-        }
-    } // else TODO
-
-    // zero out remainder of output array
-    int32_t framesLeft = numOutputFrames - numInputFrames;
-    if (framesLeft > 0) {
-        memset(outputFloat, 0, framesLeft * getOutputStream()->getBytesPerFrame());
+    while (framesToEcho-- > 0) {
+        *outputFloat = mDelayLine->process(delayFrames, *inputFloat); // mono delay
+        inputFloat += inputStride;
+        outputFloat += outputStride;
     }
     return oboe::DataCallbackResult::Continue;
 };
diff --git a/apps/OboeTester/app/src/main/cpp/flowunits/LinearShape.h b/apps/OboeTester/app/src/main/cpp/flowunits/LinearShape.h
index 694f9a74..2ea97e15 100644
--- a/apps/OboeTester/app/src/main/cpp/flowunits/LinearShape.h
+++ b/apps/OboeTester/app/src/main/cpp/flowunits/LinearShape.h
@@ -29,7 +29,7 @@ public:
 
     int32_t onProcess(int numFrames) override;
 
-    float getMinimum() const { // TODO create sweep base class
+    float getMinimum() const {
         return mMinimum;
     }
 
diff --git a/apps/OboeTester/app/src/main/java/com/google/sample/oboe/manualtest/StreamConfiguration.java b/apps/OboeTester/app/src/main/java/com/google/sample/oboe/manualtest/StreamConfiguration.java
index 733e9560..915dcdbd 100644
--- a/apps/OboeTester/app/src/main/java/com/google/sample/oboe/manualtest/StreamConfiguration.java
+++ b/apps/OboeTester/app/src/main/java/com/google/sample/oboe/manualtest/StreamConfiguration.java
@@ -48,10 +48,11 @@ public class StreamConfiguration {
     public static final int PERFORMANCE_MODE_LOW_LATENCY = 12; // must match AAUDIO
 
     public static final int RATE_CONVERSION_QUALITY_NONE = 0; // must match Oboe
-    public static final int RATE_CONVERSION_QUALITY_LOW = 1; // must match Oboe
-    public static final int RATE_CONVERSION_QUALITY_MEDIUM = 2; // must match Oboe
-    public static final int RATE_CONVERSION_QUALITY_HIGH = 3; // must match Oboe
-    public static final int RATE_CONVERSION_QUALITY_BEST = 4; // must match Oboe
+    public static final int RATE_CONVERSION_QUALITY_FASTEST = 1; // must match Oboe
+    public static final int RATE_CONVERSION_QUALITY_LOW = 2; // must match Oboe
+    public static final int RATE_CONVERSION_QUALITY_MEDIUM = 3; // must match Oboe
+    public static final int RATE_CONVERSION_QUALITY_HIGH = 4; // must match Oboe
+    public static final int RATE_CONVERSION_QUALITY_BEST = 5; // must match Oboe
 
     private int mNativeApi;
     private int mBufferCapacityInFrames;
@@ -67,7 +68,7 @@ public class StreamConfiguration {
     private boolean mChannelConversionAllowed = true;
     private int mRateConversionQuality = RATE_CONVERSION_QUALITY_HIGH;
 
-    private int mFramesPerBurst = 29; // TODO review
+    private int mFramesPerBurst = 0;
     private boolean mMMap = false;
 
     public StreamConfiguration() {
diff --git a/apps/OboeTester/app/src/main/res/values/strings.xml b/apps/OboeTester/app/src/main/res/values/strings.xml
index 53c3bea0..72d3cba1 100644
--- a/apps/OboeTester/app/src/main/res/values/strings.xml
+++ b/apps/OboeTester/app/src/main/res/values/strings.xml
@@ -120,6 +120,7 @@
     <string name="src_prompt">SRC:</string>
     <string-array name="conversion_qualities">
         <item>None</item>
+        <item>Fastest</item>
         <item>Low</item>
         <item>Medium</item>
         <item>High</item>
diff --git a/include/oboe/AudioStreamBuilder.h b/include/oboe/AudioStreamBuilder.h
index 092d1773..4e1dad74 100644
--- a/include/oboe/AudioStreamBuilder.h
+++ b/include/oboe/AudioStreamBuilder.h
@@ -341,12 +341,13 @@ public:
     }
 
     /**
-     * If set to None then Oboe will not do sample rate conversion. But the underlying APIs
-     * might do sample rate conversion. Unfortunately sample rate conversion in Android typically
-     * prevents one from getting a low latency stream. So we can do the conversion in Android
-     * and still get a low latency stream.
+     * Specify the quality of the sample rate converter in Oboe.
      *
-     * Default is SampleRateConversionType::Sinc. TODO currently Linear
+     * If set to None then Oboe will not do sample rate conversion. But then the underlying APIs
+     * might do sample rate conversion, which can prevent one from getting a low latency stream.
+     * If we do the conversion in Oboe then we can still get a low latency stream.
+     *
+     * Default is SampleRateConversionQuality::None
      */
     AudioStreamBuilder *setSampleRateConversionQuality(SampleRateConversionQuality quality) {
         mSampleRateConversionQuality = quality;
diff --git a/include/oboe/Definitions.h b/include/oboe/Definitions.h
index 29fd55d1..b1ea7f13 100644
--- a/include/oboe/Definitions.h
+++ b/include/oboe/Definitions.h
@@ -228,18 +228,26 @@ namespace oboe {
     };
 
     /**
-     * The algorithm used to perform sample rate conversion.
+     * Specifies the quality of the sample rate conversion performed by Oboe.
      * Higher quality will require more CPU load.
+     * Higher quality conversion will probably be implemented using a sinc based resampler.
      */
     enum class SampleRateConversionQuality : int32_t {
         /**
          * No conversion by Oboe. Underlying APIs may still do conversion.
          */
         None,
-
+        /**
+         * Fastest conversion but may not sound great.
+         * This may be implemented using bilinear interpolation.
+         */
+        Fastest,
         Low,
         Medium,
         High,
+        /**
+         * Highest quality conversion, which may be expensive in terms of CPU.
+         */
         Best,
     };
 
diff --git a/src/flowgraph/resampler/MultiChannelResampler.cpp b/src/flowgraph/resampler/MultiChannelResampler.cpp
index c35cf04f..c54ca758 100644
--- a/src/flowgraph/resampler/MultiChannelResampler.cpp
+++ b/src/flowgraph/resampler/MultiChannelResampler.cpp
@@ -54,6 +54,9 @@ MultiChannelResampler *MultiChannelResampler::make(int32_t channelCount,
 
     // TODO benchmark and review these numTaps
     switch (quality) {
+        case Quality::Fastest:
+            builder.setNumTaps(2);
+            break;
         case Quality::Low:
             builder.setNumTaps(4);
             break;
@@ -77,6 +80,9 @@ MultiChannelResampler *MultiChannelResampler::make(int32_t channelCount,
 }
 
 MultiChannelResampler *MultiChannelResampler::Builder::build() {
+    if (getNumTaps() == 2) {
+        return new LinearResampler(*this);
+    }
     IntegerRatio ratio(getInputRate(), getOutputRate());
     ratio.reduce();
     bool usePolyphase = (getNumTaps() * ratio.getDenominator()) <= kMaxCoefficients;
diff --git a/src/flowgraph/resampler/MultiChannelResampler.h b/src/flowgraph/resampler/MultiChannelResampler.h
index 31ff2c0b..3e6bb438 100644
--- a/src/flowgraph/resampler/MultiChannelResampler.h
+++ b/src/flowgraph/resampler/MultiChannelResampler.h
@@ -39,6 +39,7 @@ class MultiChannelResampler {
 public:
 
     enum class Quality : int32_t {
+        Fastest,
         Low,
         Medium,
         High,