Remove AudioBuffer::set_duration(), instead base on frames.

media/base/audio_buffer_unittest.cc

 // Copyright 2013 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.
 
-#include "base/strings/string_util.h"
-#include "base/strings/stringprintf.h"
 #include "media/base/audio_buffer.h"
 #include "media/base/audio_bus.h"
 #include "media/base/test_helpers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace media {
 
-const static int kSampleRate = 44100;
+static const int kSampleRate = 48000;
 
-static void VerifyResult(float* channel_data,
-                         int frames,
-                         float start,
-                         float increment) {
-  for (int i = 0; i < frames; ++i) {
-    SCOPED_TRACE(base::StringPrintf(
-        "i=%d/%d start=%f, increment=%f", i, frames, start, increment));
-    ASSERT_EQ(channel_data[i], start);
-    start += increment;
+static void VerifyBus(AudioBus* bus, int frames, float start, float increment) {
+  for (int ch = 0; ch < bus->channels(); ++ch) {
+    const float v = start + ch * bus->frames() * increment;
+    for (int i = 0; i < frames; ++i) {
+      ASSERT_FLOAT_EQ(v + i * increment, bus->channel(ch)[i]) << "i=" << i
+                                                              << ", ch=" << ch;
+    }
   }
 }
 
 TEST(AudioBufferTest, CopyFrom) {
-  const ChannelLayout channel_layout = CHANNEL_LAYOUT_MONO;
-  const int frames = 8;
-  const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
-  scoped_refptr<AudioBuffer> buffer =
+  const ChannelLayout kChannelLayout = CHANNEL_LAYOUT_MONO;
+  scoped_refptr<AudioBuffer> original_buffer =
       MakeAudioBuffer<uint8>(kSampleFormatU8,
-                             channel_layout,
-                             ChannelLayoutToChannelCount(channel_layout),
+                             kChannelLayout,
+                             ChannelLayoutToChannelCount(kChannelLayout),
                              kSampleRate,
                              1,
                              1,
-                             frames,
-                             start_time,
-                             duration);
-  EXPECT_EQ(frames, buffer->frame_count());
-  EXPECT_EQ(buffer->timestamp(), start_time);
-  EXPECT_EQ(buffer->duration().InSeconds(), frames);
-  EXPECT_FALSE(buffer->end_of_stream());
+                             kSampleRate / 100,
+                             base::TimeDelta());
+  scoped_refptr<AudioBuffer> new_buffer =
+      AudioBuffer::CopyFrom(kSampleFormatU8,
+                            original_buffer->channel_layout(),
+                            original_buffer->channel_count(),
+                            original_buffer->sample_rate(),
+                            original_buffer->frame_count(),
+                            &original_buffer->channel_data()[0],
+                            original_buffer->timestamp());
+  EXPECT_EQ(original_buffer->frame_count(), new_buffer->frame_count());
+  EXPECT_EQ(original_buffer->timestamp(), new_buffer->timestamp());
+  EXPECT_EQ(original_buffer->duration(), new_buffer->duration());
+  EXPECT_EQ(original_buffer->sample_rate(), new_buffer->sample_rate());
+  EXPECT_EQ(original_buffer->channel_count(), new_buffer->channel_count());
+  EXPECT_EQ(original_buffer->channel_layout(), new_buffer->channel_layout());
+  EXPECT_FALSE(original_buffer->end_of_stream());
 }
 
 TEST(AudioBufferTest, CreateEOSBuffer) {
   scoped_refptr<AudioBuffer> buffer = AudioBuffer::CreateEOSBuffer();
   EXPECT_TRUE(buffer->end_of_stream());
 }
 
 TEST(AudioBufferTest, FrameSize) {
   const uint8 kTestData[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
                               15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
                               27, 28, 29, 30, 31 };
-  const base::TimeDelta kTimestampA = base::TimeDelta::FromMicroseconds(1337);
-  const base::TimeDelta kTimestampB = base::TimeDelta::FromMicroseconds(1234);
+  const base::TimeDelta kTimestamp = base::TimeDelta::FromMicroseconds(1337);
 
   const uint8* const data[] = { kTestData };
   scoped_refptr<AudioBuffer> buffer =
       AudioBuffer::CopyFrom(kSampleFormatU8,
                             CHANNEL_LAYOUT_STEREO,
                             2,
                             kSampleRate,
                             16,
                             data,
-                            kTimestampA,
-                            kTimestampB);
+                            kTimestamp);
   EXPECT_EQ(16, buffer->frame_count());  // 2 channels of 8-bit data
 
   buffer = AudioBuffer::CopyFrom(kSampleFormatF32,
                                  CHANNEL_LAYOUT_4_0,
                                  4,
                                  kSampleRate,
                                  2,
                                  data,
-                                 kTimestampA,
-                                 kTimestampB);
+                                 kTimestamp);
   EXPECT_EQ(2, buffer->frame_count());  // now 4 channels of 32-bit data
 }
 
 TEST(AudioBufferTest, ReadU8) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_4_0;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
-  const int frames = 4;
+  const int frames = 10;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer = MakeAudioBuffer<uint8>(kSampleFormatU8,
                                                              channel_layout,
                                                              channels,
                                                              kSampleRate,
                                                              128,
                                                              1,
                                                              frames,
-                                                             start_time,
-                                                             duration);
+                                                             start_time);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
+  buffer->ReadFrames(frames, 0, 0, bus.get());
+  VerifyBus(bus.get(), frames, 0, 1.0f / 127.0f);
 
-  // Read all 4 frames from the buffer. Data is interleaved, so ch[0] should be
-  // 128, 132, 136, 140, other channels similar. However, values are converted
-  // from [0, 255] to [-1.0, 1.0] with a bias of 128. Thus the first buffer
-  // value should be 0.0, then 1/127, 2/127, etc.
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
-  buffer->ReadFrames(frames, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), frames, 0.0f, 4.0f / 127.0f);
-  VerifyResult(bus->channel(1), frames, 1.0f / 127.0f, 4.0f / 127.0f);
-  VerifyResult(bus->channel(2), frames, 2.0f / 127.0f, 4.0f / 127.0f);
-  VerifyResult(bus->channel(3), frames, 3.0f / 127.0f, 4.0f / 127.0f);
+  // Now read the same data one frame at a time.
+  bus->Zero();
+  for (int i = 0; i < frames; ++i)
+    buffer->ReadFrames(1, i, i, bus.get());
+  VerifyBus(bus.get(), frames, 0, 1.0f / 127.0f);
 }
 
 TEST(AudioBufferTest, ReadS16) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
   const int frames = 10;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer = MakeAudioBuffer<int16>(kSampleFormatS16,
                                                              channel_layout,
                                                              channels,
                                                              kSampleRate,
                                                              1,
                                                              1,
                                                              frames,
-                                                             start_time,
-                                                             duration);
-
-  // Read 6 frames from the buffer. Data is interleaved, so ch[0] should be 1,
-  // 3, 5, 7, 9, 11, and ch[1] should be 2, 4, 6, 8, 10, 12. Data is converted
-  // to float from -1.0 to 1.0 based on int16 range.
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
-  buffer->ReadFrames(6, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 6, 1.0f / kint16max, 2.0f / kint16max);
-  VerifyResult(bus->channel(1), 6, 2.0f / kint16max, 2.0f / kint16max);
+                                                             start_time);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
+  buffer->ReadFrames(frames, 0, 0, bus.get());
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
 
   // Now read the same data one frame at a time.
-  bus = AudioBus::Create(channels, 100);
-  for (int i = 0; i < frames; ++i) {
+  bus->Zero();
+  for (int i = 0; i < frames; ++i)
     buffer->ReadFrames(1, i, i, bus.get());
-  }
-  VerifyResult(bus->channel(0), frames, 1.0f / kint16max, 2.0f / kint16max);
-  VerifyResult(bus->channel(1), frames, 2.0f / kint16max, 2.0f / kint16max);
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
 }
 
 TEST(AudioBufferTest, ReadS32) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
-  const int frames = 6;
+  const int frames = 20;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer = MakeAudioBuffer<int32>(kSampleFormatS32,
                                                              channel_layout,
                                                              channels,
                                                              kSampleRate,
                                                              1,
                                                              1,
                                                              frames,
-                                                             start_time,
-                                                             duration);
+                                                             start_time);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
+  buffer->ReadFrames(frames, 0, 0, bus.get());
+  VerifyBus(bus.get(), frames, 1.0f / kint32max, 1.0f / kint32max);
 
-  // Read 6 frames from the buffer. Data is interleaved, so ch[0] should be 1,
-  // 3, 5, 7, 9, 11, and ch[1] should be 2, 4, 6, 8, 10, 12. Data is converted
-  // to float from -1.0 to 1.0 based on int32 range.
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
-  buffer->ReadFrames(frames, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), frames, 1.0f / kint32max, 2.0f / kint32max);
-  VerifyResult(bus->channel(1), frames, 2.0f / kint32max, 2.0f / kint32max);
-
-  // Now read 2 frames starting at frame offset 3. ch[0] should be 7, 9, and
-  // ch[1] should be 8, 10.
-  buffer->ReadFrames(2, 3, 0, bus.get());
-  VerifyResult(bus->channel(0), 2, 7.0f / kint32max, 2.0f / kint32max);
-  VerifyResult(bus->channel(1), 2, 8.0f / kint32max, 2.0f / kint32max);
+  // Read second 10 frames.
+  bus->Zero();
+  buffer->ReadFrames(10, 10, 0, bus.get());
+  VerifyBus(bus.get(), 10, 11.0f / kint32max, 1.0f / kint32max);
 }
 
 TEST(AudioBufferTest, ReadF32) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
   const int frames = 20;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer = MakeAudioBuffer<float>(kSampleFormatF32,
                                                              channel_layout,
                                                              channels,
                                                              kSampleRate,
                                                              1.0f,
                                                              1.0f,
                                                              frames,
-                                                             start_time,
-                                                             duration);
-
-  // Read first 10 frames from the buffer. F32 is interleaved, so ch[0] should
-  // be 1, 3, 5, ... and ch[1] should be 2, 4, 6, ...
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
+                                                             start_time);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
   buffer->ReadFrames(10, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 10, 1.0f, 2.0f);
-  VerifyResult(bus->channel(1), 10, 2.0f, 2.0f);
+  VerifyBus(bus.get(), 10, 1, 1);
 
   // Read second 10 frames.
-  bus = AudioBus::Create(channels, 100);
+  bus->Zero();
   buffer->ReadFrames(10, 10, 0, bus.get());
-  VerifyResult(bus->channel(0), 10, 21.0f, 2.0f);
-  VerifyResult(bus->channel(1), 10, 22.0f, 2.0f);
+  VerifyBus(bus.get(), 10, 11, 1);
 }
 
 TEST(AudioBufferTest, ReadS16Planar) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
   const int frames = 20;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer =
       MakeAudioBuffer<int16>(kSampleFormatPlanarS16,
                              channel_layout,
                              channels,
                              kSampleRate,
                              1,
                              1,
                              frames,
-                             start_time,
-                             duration);
-
-  // Read 6 frames from the buffer. Data is planar, so ch[0] should be 1, 2, 3,
-  // 4, 5, 6, and ch[1] should be 21, 22, 23, 24, 25, 26. Data is converted to
-  // float from -1.0 to 1.0 based on int16 range.
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
-  buffer->ReadFrames(6, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 6, 1.0f / kint16max, 1.0f / kint16max);
-  VerifyResult(bus->channel(1), 6, 21.0f / kint16max, 1.0f / kint16max);
+                             start_time);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
+  buffer->ReadFrames(10, 0, 0, bus.get());
+  VerifyBus(bus.get(), 10, 1.0f / kint16max, 1.0f / kint16max);
 
   // Read all the frames backwards, one by one. ch[0] should be 20, 19, ...
-  bus = AudioBus::Create(channels, 100);
-  for (int i = 0; i < frames; ++i) {
-    buffer->ReadFrames(1, frames - i - 1, i, bus.get());
-  }
-  VerifyResult(bus->channel(0), frames, 20.0f / kint16max, -1.0f / kint16max);
-  VerifyResult(bus->channel(1), frames, 40.0f / kint16max, -1.0f / kint16max);
+  bus->Zero();
+  for (int i = frames - 1; i >= 0; --i)
+    buffer->ReadFrames(1, i, i, bus.get());
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
 
   // Read 0 frames with different offsets. Existing data in AudioBus should be
   // unchanged.
   buffer->ReadFrames(0, 0, 0, bus.get());
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
   buffer->ReadFrames(0, 0, 10, bus.get());
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
   buffer->ReadFrames(0, 10, 0, bus.get());
-  VerifyResult(bus->channel(0), frames, 20.0f / kint16max, -1.0f / kint16max);
-  VerifyResult(bus->channel(1), frames, 40.0f / kint16max, -1.0f / kint16max);
+  VerifyBus(bus.get(), frames, 1.0f / kint16max, 1.0f / kint16max);
 }
 
 TEST(AudioBufferTest, ReadF32Planar) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_4_0;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
   const int frames = 100;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer =
       MakeAudioBuffer<float>(kSampleFormatPlanarF32,
                              channel_layout,
                              channels,
                              kSampleRate,
                              1.0f,
                              1.0f,
                              frames,
-                             start_time,
-                             duration);
+                             start_time);
 
   // Read all 100 frames from the buffer. F32 is planar, so ch[0] should be 1,
   // 2, 3, 4, ..., ch[1] should be 101, 102, 103, ..., and so on for all 4
   // channels.
   scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
   buffer->ReadFrames(frames, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), frames, 1.0f, 1.0f);
-  VerifyResult(bus->channel(1), frames, 101.0f, 1.0f);
-  VerifyResult(bus->channel(2), frames, 201.0f, 1.0f);
-  VerifyResult(bus->channel(3), frames, 301.0f, 1.0f);
+  VerifyBus(bus.get(), frames, 1, 1);
 
   // Now read 20 frames from the middle of the buffer.
-  bus = AudioBus::Create(channels, 100);
+  bus->Zero();
   buffer->ReadFrames(20, 50, 0, bus.get());
-  VerifyResult(bus->channel(0), 20, 51.0f, 1.0f);
-  VerifyResult(bus->channel(1), 20, 151.0f, 1.0f);
-  VerifyResult(bus->channel(2), 20, 251.0f, 1.0f);
-  VerifyResult(bus->channel(3), 20, 351.0f, 1.0f);
+  VerifyBus(bus.get(), 20, 51, 1);
 }
 
 TEST(AudioBufferTest, EmptyBuffer) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_4_0;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
-  const int frames = 100;
+  const int frames = kSampleRate / 100;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
   scoped_refptr<AudioBuffer> buffer = AudioBuffer::CreateEmptyBuffer(
-      channel_layout, channels, kSampleRate, frames, start_time, duration);
+      channel_layout, channels, kSampleRate, frames, start_time);
   EXPECT_EQ(frames, buffer->frame_count());
   EXPECT_EQ(start_time, buffer->timestamp());
-  EXPECT_EQ(frames, buffer->duration().InSeconds());
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(10), buffer->duration());
   EXPECT_FALSE(buffer->end_of_stream());
 
   // Read all 100 frames from the buffer. All data should be 0.
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
   buffer->ReadFrames(frames, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), frames, 0.0f, 0.0f);
-  VerifyResult(bus->channel(1), frames, 0.0f, 0.0f);
-  VerifyResult(bus->channel(2), frames, 0.0f, 0.0f);
-  VerifyResult(bus->channel(3), frames, 0.0f, 0.0f);
+  VerifyBus(bus.get(), frames, 0, 0);
 }
 
 TEST(AudioBufferTest, Trim) {
   const ChannelLayout channel_layout = CHANNEL_LAYOUT_4_0;
   const int channels = ChannelLayoutToChannelCount(channel_layout);
-  const int frames = 100;
+  const int frames = kSampleRate / 10;
   const base::TimeDelta start_time;
-  const base::TimeDelta duration = base::TimeDelta::FromSeconds(frames);
+  const base::TimeDelta duration = base::TimeDelta::FromMilliseconds(100);
   scoped_refptr<AudioBuffer> buffer =
       MakeAudioBuffer<float>(kSampleFormatPlanarF32,
                              channel_layout,
                              channels,
                              kSampleRate,
-                             1.0f,
+                             0.0f,
                              1.0f,
                              frames,
-                             start_time,
-                             duration);
+                             start_time);
   EXPECT_EQ(frames, buffer->frame_count());
   EXPECT_EQ(start_time, buffer->timestamp());
-  EXPECT_EQ(frames, buffer->duration().InSeconds());
+  EXPECT_EQ(duration, buffer->duration());
 
-  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, 100);
-  buffer->ReadFrames(20, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 20, 1.0f, 1.0f);
+  const int ten_ms_of_frames = kSampleRate / 100;
+  const base::TimeDelta ten_ms = base::TimeDelta::FromMilliseconds(10);
 
-  // Trim off 10 frames from the start.
-  buffer->TrimStart(10);
-  EXPECT_EQ(buffer->frame_count(), frames - 10);
-  EXPECT_EQ(buffer->timestamp(), start_time + base::TimeDelta::FromSeconds(10));
-  EXPECT_EQ(buffer->duration(), base::TimeDelta::FromSeconds(90));
-  buffer->ReadFrames(20, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 20, 11.0f, 1.0f);
+  scoped_ptr<AudioBus> bus = AudioBus::Create(channels, frames);
+  buffer->ReadFrames(buffer->frame_count(), 0, 0, bus.get());
+  VerifyBus(bus.get(), buffer->frame_count(), 0.0f, 1.0f);
 
-  // Trim off 10 frames from the end.
-  buffer->TrimEnd(10);
-  EXPECT_EQ(buffer->frame_count(), frames - 20);
-  EXPECT_EQ(buffer->timestamp(), start_time + base::TimeDelta::FromSeconds(10));
-  EXPECT_EQ(buffer->duration(), base::TimeDelta::FromSeconds(80));
-  buffer->ReadFrames(20, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 20, 11.0f, 1.0f);
+  // Trim off 10ms of frames from the start.
+  buffer->TrimStart(ten_ms_of_frames);
+  EXPECT_EQ(start_time + ten_ms, buffer->timestamp());
+  EXPECT_EQ(frames - ten_ms_of_frames, buffer->frame_count());
+  EXPECT_EQ(duration - ten_ms, buffer->duration());
+  buffer->ReadFrames(buffer->frame_count(), 0, 0, bus.get());
+  VerifyBus(bus.get(), buffer->frame_count(), ten_ms_of_frames, 1.0f);
 
-  // Trim off 50 more from the start.
-  buffer->TrimStart(50);
-  EXPECT_EQ(buffer->frame_count(), frames - 70);
-  EXPECT_EQ(buffer->timestamp(), start_time + base::TimeDelta::FromSeconds(60));
-  EXPECT_EQ(buffer->duration(), base::TimeDelta::FromSeconds(30));
-  buffer->ReadFrames(10, 0, 0, bus.get());
-  VerifyResult(bus->channel(0), 10, 61.0f, 1.0f);
+  // Trim off 10ms of frames from the end.
+  buffer->TrimEnd(ten_ms_of_frames);
+  EXPECT_EQ(start_time + ten_ms, buffer->timestamp());
+  EXPECT_EQ(frames - 2 * ten_ms_of_frames, buffer->frame_count());
+  EXPECT_EQ(duration - 2 * ten_ms, buffer->duration());
+  buffer->ReadFrames(buffer->frame_count(), 0, 0, bus.get());
+  VerifyBus(bus.get(), buffer->frame_count(), ten_ms_of_frames, 1.0f);
 
-  // Trim off the last 30 frames.
-  buffer->TrimEnd(30);
-  EXPECT_EQ(buffer->frame_count(), 0);
-  EXPECT_EQ(buffer->timestamp(), start_time + base::TimeDelta::FromSeconds(60));
-  EXPECT_EQ(buffer->duration(), base::TimeDelta::FromSeconds(0));
+  // Trim off 40ms more from the start.
+  buffer->TrimStart(4 * ten_ms_of_frames);
+  EXPECT_EQ(start_time + 5 * ten_ms, buffer->timestamp());
+  EXPECT_EQ(frames - 6 * ten_ms_of_frames, buffer->frame_count());
+  EXPECT_EQ(duration - 6 * ten_ms, buffer->duration());
+  buffer->ReadFrames(buffer->frame_count(), 0, 0, bus.get());
+  VerifyBus(bus.get(), buffer->frame_count(), 5 * ten_ms_of_frames, 1.0f);
+
+  // Trim off the final 40ms from the end.
+  buffer->TrimEnd(4 * ten_ms_of_frames);
+  EXPECT_EQ(0, buffer->frame_count());
+  EXPECT_EQ(start_time + 5 * ten_ms, buffer->timestamp());
+  EXPECT_EQ(base::TimeDelta(), buffer->duration());
 }
 
 }  // namespace media