Reduce jitter from uneven SincResampler buffer size requests.

media/base/audio_converter_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include <cmath>
 
 #include "base/command_line.h"
@@ skipping 187 matching lines @@
       base::Time::kMicrosecondsPerSecond / input_sample_rate);
 
   int expected_last_delay_milliseconds =
       fill_count * input_parameters.frames_per_buffer() *
       input_frame_duration.InMillisecondsF();
 
   EXPECT_EQ(expected_last_delay_milliseconds,
             callback.last_audio_delay_milliseconds());
 }
 
+// InputCallback that zero's out the provided AudioBus.  Used for benchmarking.
+class NullInputProvider : public AudioConverter::InputCallback {
+ public:
+  NullInputProvider() {}
+  virtual ~NullInputProvider() {}
+
+  virtual double ProvideInput(AudioBus* audio_bus,
+                              base::TimeDelta buffer_delay) OVERRIDE {
+    audio_bus->Zero();
+    return 1;
+  }
+};
+
 // Benchmark for audio conversion.  Original benchmarks were run with
 // --audio-converter-iterations=50000.
 TEST(AudioConverterTest, ConvertBenchmark) {
   int benchmark_iterations = kDefaultIterations;
   std::string iterations(CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
       kBenchmarkIterations));
   base::StringToInt(iterations, &benchmark_iterations);
   if (benchmark_iterations < kDefaultIterations)
     benchmark_iterations = kDefaultIterations;
 
-  // Create input and output parameters to convert between the two most common
-  // sets of parameters (as indicated via UMA data).
-  AudioParameters input_params(
-      AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_MONO, 48000, 16, 2048);
-  AudioParameters output_params(
-      AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_STEREO, 44100, 16, 440);
-  scoped_ptr<AudioConverter> converter(
-      new AudioConverter(input_params, output_params, false));
-
-  scoped_ptr<AudioBus> output_bus = AudioBus::Create(output_params);
-  FakeAudioRenderCallback fake_input1(0.2);

[DaleCurtis, 2013/04/27 01:18:46]

Turns out these are pretty slow and vary depending on requested frame size! 
Switching to a NullInputProvider makes the benchmark a lot more useful and
faster.

-  FakeAudioRenderCallback fake_input2(0.4);
-  FakeAudioRenderCallback fake_input3(0.6);
-  converter->AddInput(&fake_input1);
-  converter->AddInput(&fake_input2);
-  converter->AddInput(&fake_input3);
+  NullInputProvider fake_input1;
+  NullInputProvider fake_input2;
+  NullInputProvider fake_input3;
 
   printf("Benchmarking %d iterations:\n", benchmark_iterations);
 
-  // Benchmark Convert() w/ FIFO.
-  base::TimeTicks start = base::TimeTicks::HighResNow();
-  for (int i = 0; i < benchmark_iterations; ++i) {
-    converter->Convert(output_bus.get());
+  {
+    // Create input and output parameters to convert between the two most common
+    // sets of parameters (as indicated via UMA data).
+    AudioParameters input_params(
+        AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_MONO,
+        48000, 16, 2048);
+    AudioParameters output_params(
+        AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_STEREO,
+        44100, 16, 440);
+    scoped_ptr<AudioBus> output_bus = AudioBus::Create(output_params);
+
+    scoped_ptr<AudioConverter> converter(
+        new AudioConverter(input_params, output_params, true));
+    converter->AddInput(&fake_input1);
+    converter->AddInput(&fake_input2);
+    converter->AddInput(&fake_input3);
+
+    // Benchmark Convert() w/ FIFO.
+    base::TimeTicks start = base::TimeTicks::HighResNow();
+    for (int i = 0; i < benchmark_iterations; ++i) {
+      converter->Convert(output_bus.get());
+    }
+    double total_time_ms =
+        (base::TimeTicks::HighResNow() - start).InMillisecondsF();
+    printf("Convert() w/ Resampling took %.2fms.\n", total_time_ms);
   }
-  double total_time_ms =
-      (base::TimeTicks::HighResNow() - start).InMillisecondsF();
-  printf("Convert() w/ FIFO took %.2fms.\n", total_time_ms);
 
-  converter.reset(new AudioConverter(input_params, output_params, true));
-  converter->AddInput(&fake_input1);
-  converter->AddInput(&fake_input2);
-  converter->AddInput(&fake_input3);
+  // Create input and output parameters to convert between common buffer sizes
+  // without any resampling for the FIFO vs no FIFO benchmarks.
+  AudioParameters input_params(
+      AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_STEREO,
+      44100, 16, 2048);
+  AudioParameters output_params(
+      AudioParameters::AUDIO_PCM_LINEAR, CHANNEL_LAYOUT_STEREO,
+      44100, 16, 440);
+  scoped_ptr<AudioBus> output_bus = AudioBus::Create(output_params);
 
-  // Benchmark Convert() w/o FIFO.
-  start = base::TimeTicks::HighResNow();
-  for (int i = 0; i < benchmark_iterations; ++i) {
-    converter->Convert(output_bus.get());
+  {
+    scoped_ptr<AudioConverter> converter(
+        new AudioConverter(input_params, output_params, false));
+    converter->AddInput(&fake_input1);
+    converter->AddInput(&fake_input2);
+    converter->AddInput(&fake_input3);
+
+    // Benchmark Convert() w/ FIFO.
+    base::TimeTicks start = base::TimeTicks::HighResNow();
+    for (int i = 0; i < benchmark_iterations; ++i) {
+      converter->Convert(output_bus.get());
+    }
+    double total_time_ms =
+        (base::TimeTicks::HighResNow() - start).InMillisecondsF();
+    printf("Convert() w/ FIFO took %.2fms.\n", total_time_ms);
   }
-  total_time_ms =
-      (base::TimeTicks::HighResNow() - start).InMillisecondsF();
-  printf("Convert() w/o FIFO took %.2fms.\n", total_time_ms);
+
+  {
+    scoped_ptr<AudioConverter> converter(
+        new AudioConverter(input_params, output_params, true));
+    converter->AddInput(&fake_input1);
+    converter->AddInput(&fake_input2);
+    converter->AddInput(&fake_input3);
+
+    // Benchmark Convert() w/o FIFO.
+    base::TimeTicks start = base::TimeTicks::HighResNow();
+    for (int i = 0; i < benchmark_iterations; ++i) {
+      converter->Convert(output_bus.get());
+    }
+    double total_time_ms =
+        (base::TimeTicks::HighResNow() - start).InMillisecondsF();
+    printf("Convert() w/o FIFO took %.2fms.\n", total_time_ms);
+  }
 }
 
 TEST_P(AudioConverterTest, NoInputs) {
   FillAudioData(1.0f);
   EXPECT_TRUE(RenderAndValidateAudioData(0.0f));
 }
 
 TEST_P(AudioConverterTest, OneInput) {
   RunTest(1);
 }
 
 TEST_P(AudioConverterTest, ManyInputs) {
   RunTest(kConvertInputs);
 }
 
 INSTANTIATE_TEST_CASE_P(
     // TODO(dalecurtis): Add test cases for channel transforms.
     AudioConverterTest, AudioConverterTest, testing::Values(
         // No resampling.
         std::tr1::make_tuple(44100, 44100, 0.00000048),
 
         // Upsampling.
         std::tr1::make_tuple(44100, 48000, 0.033),
 
         // Downsampling.
         std::tr1::make_tuple(48000, 41000, 0.042)));
 
 }  // namespace media