Delay delivery of audio input data.

The AudioQueue API may use a large internal buffer and repeatedly call us
back to back once that internal buffer is filled.  When this happens the
renderer client does not have enough time to read data back from the
shared memory before the next write comes along.  If HandleInputBuffer()
is called too frequently, Sleep() to simulate realtime input and ensure
the shared memory doesn't get trampled.

BUG=157613
TEST=Playback works on older style Mac units.

Review URL: https://codereview.chromium.org/11482002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171681 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 24 insertions, 2 deletions

diff --git a/media/audio/mac/audio_input_mac.cc b/media/audio/mac/audio_input_mac.cc
index fd2d9be..69791cf 100644
--- a/media/audio/mac/audio_input_mac.cc
+++ b/media/audio/mac/audio_input_mac.cc
@@ -192,12 +192,31 @@ void PCMQueueInAudioInputStream::HandleInputBuffer(
     return;
   }
 
-  if (audio_buffer->mAudioDataByteSize)
+  if (audio_buffer->mAudioDataByteSize) {
+    // The AudioQueue API may use a large internal buffer and repeatedly call us
+    // back to back once that internal buffer is filled.  When this happens the
+    // renderer client does not have enough time to read data back from the
+    // shared memory before the next write comes along.  If HandleInputBuffer()
+    // is called too frequently, Sleep() to simulate realtime input and ensure
+    // the shared memory doesn't get trampled.
+    // TODO(dalecurtis): This is a HACK.  Long term the AudioQueue path is going
+    // away in favor of the AudioUnit based AUAudioInputStream().  Tracked by
+    // http://crbug.com/161383
+    base::TimeDelta elapsed = base::Time::Now() - last_fill_;
+    base::TimeDelta buffer_length = base::TimeDelta::FromMilliseconds(
+       audio_buffer->mAudioDataByteSize * base::Time::kMillisecondsPerSecond /
+       static_cast<float>(format_.mBytesPerFrame * format_.mSampleRate));
+    if (elapsed < buffer_length)
+      base::PlatformThread::Sleep(buffer_length - elapsed);
+
     callback_->OnData(this,
                       reinterpret_cast<const uint8*>(audio_buffer->mAudioData),
                       audio_buffer->mAudioDataByteSize,
                       audio_buffer->mAudioDataByteSize,
                       0.0);
+
+    last_fill_ = base::Time::Now();
+  }
   // Recycle the buffer.
   OSStatus err = QueueNextBuffer(audio_buffer);
   if (err != noErr) {
diff --git a/media/audio/mac/audio_input_mac.h b/media/audio/mac/audio_input_mac.h
index ddef40f..1f9856f1 100644
--- a/media/audio/mac/audio_input_mac.h
+++ b/media/audio/mac/audio_input_mac.h
@@ -9,6 +9,7 @@
 #include <AudioToolbox/AudioFormat.h>
 
 #include "base/compiler_specific.h"
+#include "base/time.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
 
@@ -62,7 +63,7 @@ class PCMQueueInAudioInputStream : public AudioInputStream {
                          UInt32 num_packets,
                          const AudioStreamPacketDescription* packet_desc);
 
-  static const int kNumberBuffers = 1;
+  static const int kNumberBuffers = 3;
 
   // Manager that owns this stream, used for closing down.
   AudioManagerBase* manager_;
@@ -76,6 +77,8 @@ class PCMQueueInAudioInputStream : public AudioInputStream {
   uint32 buffer_size_bytes_;
   // True iff Start() has been called successfully.
   bool started_;
+  // Used to determine if we need to slow down |callback_| calls.
+  base::Time last_fill_;
 
   DISALLOW_COPY_AND_ASSIGN(PCMQueueInAudioInputStream);
 };