Increase the buffer size in AudioRendererImpl to fix muted playback rate

media/audio/audio_util.cc

Index: media/audio/audio_util.cc
diff --git a/media/audio/audio_util.cc b/media/audio/audio_util.cc
index b4b8751885b570b2ebdabb30ae78f6122e7ca20a..8caced5204243dd7e1ee1337f6a6e5e7ce9dd386 100644
--- a/media/audio/audio_util.cc
+++ b/media/audio/audio_util.cc
@@ -14,9 +14,11 @@
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/shared_memory.h"
+#include "base/time.h"
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
 #endif
+#include "media/audio/audio_parameters.h"
 #include "media/audio/audio_util.h"
 #if defined(OS_MACOSX)
 #include "media/audio/mac/audio_low_latency_input_mac.h"
@@ -436,4 +438,29 @@ void Crossfade(int bytes_to_crossfade, int number_of_channels,
   }
 }
 
+// The minimum number of samples in a hardware packet.
+// This value is selected so that we can handle down to 5khz sample rate.
+static const int kMinSamplesPerHardwarePacket = 1024;
+
+// The maximum number of samples in a hardware packet.
+// This value is selected so that we can handle up to 192khz sample rate.
+static const int kMaxSamplesPerHardwarePacket = 64 * 1024;
+
+// This constant governs the hardware audio buffer size, this value should be
+// chosen carefully.
+// This value is selected so that we have 8192 samples for 48khz streams.
+static const int kMillisecondsPerHardwarePacket = 170;
+
+uint32 SelectSamplesPerPacket(int sample_rate) {
+  // Select the number of samples that can provide at least
+  // |kMillisecondsPerHardwarePacket| worth of audio data.
+  int samples = kMinSamplesPerHardwarePacket;
+  while (samples <= kMaxSamplesPerHardwarePacket &&
+         samples * base::Time::kMillisecondsPerSecond <
+         sample_rate * kMillisecondsPerHardwarePacket) {
+    samples *= 2;
+  }
+  return samples;
+}
+

[Chris Rogers, 2012/02/22 23:08:53]

It would be great to put this function in
content/renderer/media/audio_hardware.h

because this seems to be where it belongs.  We already have a function called
GetOutputBufferSize(), so maybe this function should be re-named
"GetHighLatencyOutputBufferSize() or something like that?

People using AUDIO_PCM_LINEAR would call GetHighLatencyOutputBufferSize()
People using AUDIO_PCM_LOW_LATENCY would call GetOutputBufferSize()

It seems kind of confusing to split these two similar types of functions into
two different header files with different naming conventions...

Also, see comment in audio_renderer_host.cc so we can remove the need to call
from there...

 }  // namespace media