Bug 901633 - Part 1 - Implement a generic audio packetizer. r=jesup

dom/media/AudioPacketizer.h

@@ -0,0 +1,186 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef AudioPacketizer_h_
+#define AudioPacketizer_h_
+
+#include <mozilla/PodOperations.h>
+#include <mozilla/Assertions.h>
+#include <nsAutoPtr.h>
+#include <AudioSampleFormat.h>
+
+// Enable this to warn when `Output` has been called but not enough data was
+// buffered.
+// #define LOG_PACKETIZER_UNDERRUN
+
+namespace mozilla {
+/**
+ * This class takes arbitrary input data, and returns packets of a specific
+ * size. In the process, it can convert audio samples from 16bit integers to
+ * float (or vice-versa).
+ *
+ * Input and output, as well as length units in the public interface are
+ * interleaved frames.
+ *
+ * Allocations of output buffer are performed by this class.  Buffers can simply
+ * be delete-d.  This is because packets are intended to be sent off to
+ * non-gecko code using normal pointers/length pairs
+ *
+ * The implementation uses a circular buffer using absolute virtual indices.
+ */
+template <typename InputType, typename OutputType>
+class AudioPacketizer
+{
+public:
+  AudioPacketizer(uint32_t aPacketSize, uint32_t aChannels)
+    : mPacketSize(aPacketSize)
+    , mChannels(aChannels)
+    , mReadIndex(0)
+    , mWriteIndex(0)
+    // Start off with a single packet
+    , mStorage(new InputType[aPacketSize * aChannels])
+    , mLength(aPacketSize * aChannels)
+  {
+     MOZ_ASSERT(aPacketSize > 0 && aChannels > 0,
+       "The packet size and the number of channel should be strictly positive");
+  }
+
+  void Input(InputType* aFrames, uint32_t aFrameCount)
+  {
+    uint32_t inputSamples = aFrameCount * mChannels;
+    // Need to grow the storage. This should rarely happen, if at all, once the
+    // array has the right size.
+    if (inputSamples > EmptySlots()) {
+      // Calls to Input and Output are roughtly interleaved
+      // (Input,Output,Input,Output, etc.), or balanced
+      // (Input,Input,Input,Output,Output,Output), so we update the buffer to
+      // the exact right size in order to not waste space.
+      uint32_t newLength = AvailableSamples() + inputSamples;
+      uint32_t toCopy = AvailableSamples();
+      nsAutoPtr<InputType> oldStorage = mStorage;
+      mStorage = new InputType[newLength];
+      // Copy the old data at the beginning of the new storage.
+      if (WriteIndex() >= ReadIndex()) {
+        PodCopy(mStorage.get(),
+                oldStorage.get() + ReadIndex(),
+                AvailableSamples());
+      } else {
+        uint32_t firstPartLength = mLength - ReadIndex();
+        uint32_t secondPartLength = AvailableSamples() - firstPartLength;
+        PodCopy(mStorage.get(),
+                oldStorage.get() + ReadIndex(),
+                firstPartLength);
+        PodCopy(mStorage.get() + firstPartLength,
+                oldStorage.get(),
+                secondPartLength);
+      }
+      mWriteIndex = toCopy;
+      mReadIndex = 0;
+      mLength = newLength;
+    }
+
+    if (WriteIndex() + inputSamples <= mLength) {
+      PodCopy(mStorage.get() + WriteIndex(), aFrames, aFrameCount * mChannels);
+    } else {
+      uint32_t firstPartLength = mLength - WriteIndex();
+      uint32_t secondPartLength = inputSamples - firstPartLength;
+      PodCopy(mStorage.get() + WriteIndex(), aFrames, firstPartLength);
+      PodCopy(mStorage.get(), aFrames + firstPartLength, secondPartLength);
+    }
+
+    mWriteIndex += inputSamples;
+  }
+
+  OutputType* Output()
+  {
+    uint32_t samplesNeeded = mPacketSize * mChannels;
+    OutputType* out = new OutputType[samplesNeeded];
+
+    // Under-run. Pad the end of the buffer with silence.
+    if (AvailableSamples() < samplesNeeded) {
+#ifdef LOG_PACKETIZER_UNDERRUN
+      char buf[256];
+      snprintf(buf, 256,
+               "AudioPacketizer %p underrun: available: %u, needed: %u\n",
+               this, AvailableSamples(), samplesNeeded);
+      NS_WARNING(buf);
+#endif
+      uint32_t zeros = samplesNeeded - AvailableSamples();
+      PodZero(out + AvailableSamples(), zeros);
+      samplesNeeded -= zeros;
+    }
+    if (ReadIndex() + samplesNeeded <= mLength) {
+      ConvertAudioSamples<InputType,OutputType>(mStorage.get() + ReadIndex(),
+                                                out,
+                                                samplesNeeded);
+    } else {
+      uint32_t firstPartLength = mLength - ReadIndex();
+      uint32_t secondPartLength = samplesNeeded - firstPartLength;
+      ConvertAudioSamples<InputType, OutputType>(mStorage.get() + ReadIndex(),
+                                                 out,
+                                                 firstPartLength);
+      ConvertAudioSamples<InputType, OutputType>(mStorage.get(),
+                                                 out + firstPartLength,
+                                                 secondPartLength);
+    }
+    mReadIndex += samplesNeeded;
+
+    return out;
+  }
+
+  uint32_t PacketsAvailable() const {
+    return AvailableSamples() / mChannels / mPacketSize;
+  }
+
+  bool Empty() const {
+   return mWriteIndex == mReadIndex;
+  }
+
+  bool Full() const {
+    return mWriteIndex - mReadIndex == mLength;
+  }
+
+  uint32_t PacketSize() const {
+    return mPacketSize;
+  }
+
+  uint32_t Channels() const {
+    return mChannels;
+  }
+
+private:
+  uint32_t ReadIndex() const {
+    return mReadIndex % mLength;
+  }
+
+  uint32_t WriteIndex() const {
+    return mWriteIndex % mLength;
+  }
+
+  uint32_t AvailableSamples() const {
+    return mWriteIndex - mReadIndex;
+  }
+
+  uint32_t EmptySlots() const {
+    return mLength - AvailableSamples();
+  }
+
+  // Size of one packet of audio, in frames
+  uint32_t mPacketSize;
+  // Number of channels of the stream flowing through this packetizer
+  uint32_t mChannels;
+  // Two virtual index into the buffer: the read position and the write
+  // position.
+  uint64_t mReadIndex;
+  uint64_t mWriteIndex;
+  // Storage for the samples
+  nsAutoPtr<InputType> mStorage;
+  // Length of the buffer, in samples
+  uint32_t mLength;
+};
+
+} // mozilla
+
+#endif // AudioPacketizer_h_

dom/media/compiledtest/TestAudioPacketizer.cpp

@@ -0,0 +1,172 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdint.h>
+#include <assert.h>
+#include "../AudioPacketizer.h"
+
+using namespace mozilla;
+
+template<typename T>
+class AutoBuffer
+{
+public:
+  AutoBuffer(size_t aLength)
+  {
+    mStorage = new T[aLength];
+  }
+  ~AutoBuffer() {
+    delete [] mStorage;
+  }
+  T* Get() {
+    return mStorage;
+  }
+private:
+  T* mStorage;
+};
+
+int16_t Sequence(int16_t* aBuffer, uint32_t aSize, uint32_t aStart = 0)
+{
+  uint32_t i;
+  for (i = 0; i < aSize; i++) {
+    aBuffer[i] = aStart + i;
+  }
+  return aStart + i;
+}
+
+void IsSequence(int16_t* aBuffer, uint32_t aSize, uint32_t aStart = 0)
+{
+  for (uint32_t i = 0; i < aSize; i++) {
+    if (aBuffer[i] != static_cast<int64_t>(aStart + i)) {
+      fprintf(stderr, "Buffer is not a sequence at offset %u\n", i);
+      assert(false);
+    }
+  }
+  assert("Buffer is a sequence.");
+}
+
+void Zero(int16_t* aBuffer, uint32_t aSize)
+{
+  for (uint32_t i = 0; i < aSize; i++) {
+    if (aBuffer[i] != 0) {
+      fprintf(stderr, "Buffer is not null at offset %u\n", i);
+      assert(false);
+    }
+  }
+}
+
+double sine(uint32_t aPhase) {
+ return sin(aPhase * 2 * M_PI * 440 / 44100);
+}
+
+int main() {
+  for (int16_t channels = 1; channels < 2; channels++) {
+    // Test that the packetizer returns zero on underrun
+    {
+      AudioPacketizer<int16_t, int16_t> ap(441, channels);
+      for (int16_t i = 0; i < 10; i++) {
+        int16_t* out = ap.Output();
+        Zero(out, 441);
+        delete out;
+      }
+    }
+    // Simple test, with input/output buffer size aligned on the packet size,
+    // alternating Input and Output calls.
+    {
+      AudioPacketizer<int16_t, int16_t> ap(441, channels);
+      int16_t seqEnd = 0;
+      for (int16_t i = 0; i < 10; i++) {
+        AutoBuffer<int16_t> b(441 * channels);
+        int16_t prevEnd = seqEnd;
+        seqEnd = Sequence(b.Get(), channels * 441, prevEnd);
+        ap.Input(b.Get(), 441);
+        int16_t* out = ap.Output();
+        IsSequence(out, 441 * channels, prevEnd);
+        delete out;
+      }
+    }
+    // Simple test, with input/output buffer size aligned on the packet size,
+    // alternating two Input and Output calls.
+    {
+      AudioPacketizer<int16_t, int16_t> ap(441, channels);
+      int16_t seqEnd = 0;
+      for (int16_t i = 0; i < 10; i++) {
+        AutoBuffer<int16_t> b(441 * channels);
+        AutoBuffer<int16_t> b1(441 * channels);
+        int16_t prevEnd0 = seqEnd;
+        seqEnd = Sequence(b.Get(), 441 * channels, prevEnd0);
+        int16_t prevEnd1 = seqEnd;
+        seqEnd = Sequence(b1.Get(), 441 * channels, seqEnd);
+        ap.Input(b.Get(), 441);
+        ap.Input(b1.Get(), 441);
+        int16_t* out = ap.Output();
+        int16_t* out2 = ap.Output();
+        IsSequence(out, 441 * channels, prevEnd0);
+        IsSequence(out2, 441 * channels, prevEnd1);
+        delete out;
+        delete out2;
+      }
+    }
+    // Input/output buffer size not aligned on the packet size,
+    // alternating two Input and Output calls.
+    {
+      AudioPacketizer<int16_t, int16_t> ap(441, channels);
+      int16_t prevEnd = 0;
+      int16_t prevSeq = 0;
+      for (int16_t i = 0; i < 10; i++) {
+        AutoBuffer<int16_t> b(480 * channels);
+        AutoBuffer<int16_t> b1(480 * channels);
+        prevSeq = Sequence(b.Get(), 480 * channels, prevSeq);
+        prevSeq = Sequence(b1.Get(), 480 * channels, prevSeq);
+        ap.Input(b.Get(), 480);
+        ap.Input(b1.Get(), 480);
+        int16_t* out = ap.Output();
+        int16_t* out2 = ap.Output();
+        IsSequence(out, 441 * channels, prevEnd);
+        prevEnd += 441 * channels;
+        IsSequence(out2, 441 * channels, prevEnd);
+        prevEnd += 441 * channels;
+        delete out;
+        delete out2;
+      }
+      printf("Available: %d\n", ap.PacketsAvailable());
+    }
+
+    // "Real-life" test case: streaming a sine wave through a packetizer, and
+    // checking that we have the right output.
+    // 128 is, for example, the size of a Web Audio API block, and 441 is the
+    // size of a webrtc.org packet when the sample rate is 44100 (10ms)
+    {
+      AudioPacketizer<int16_t, int16_t> ap(441, channels);
+      AutoBuffer<int16_t> b(128 * channels);
+      uint32_t phase = 0;
+      uint32_t outPhase = 0;
+      for (int16_t i = 0; i < 1000; i++) {
+        for (int32_t j = 0; j < 128; j++) {
+          for (int32_t c = 0; c < channels; c++) {
+            // int16_t sinewave at 440Hz/44100Hz sample rate
+            b.Get()[j * channels + c] = (2 << 14) * sine(phase);
+          }
+          phase++;
+        }
+        ap.Input(b.Get(), 128);
+        while (ap.PacketsAvailable()) {
+          int16_t* packet = ap.Output();
+          for (uint32_t k = 0; k < ap.PacketSize(); k++) {
+            for (int32_t c = 0; c < channels; c++) {
+              assert(packet[k * channels + c] ==
+                     static_cast<int16_t>(((2 << 14) * sine(outPhase))));
+            }
+            outPhase++;
+          }
+          delete [] packet;
+        }
+      }
+    }
+  }
+
+  printf("OK\n");
+  return 0;
+}

dom/media/compiledtest/moz.build

@@ -6,7 +6,8 @@
 
 GeckoCppUnitTests([
     'TestAudioBuffers',
-    'TestAudioMixer'
+    'TestAudioMixer',
+    'TestAudioPacketizer'
 ])
 
 LOCAL_INCLUDES += [

dom/media/moz.build

@@ -101,6 +101,7 @@ EXPORTS += [
     'AudioChannelFormat.h',
     'AudioCompactor.h',
     'AudioMixer.h',
+    'AudioPacketizer.h',
     'AudioSampleFormat.h',
     'AudioSegment.h',
     'AudioStream.h',