Fix muted audio when playback rate != 1.0 or 0.0

content/renderer/media/audio_hardware.cc

 // Copyright (c) 2011 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 "content/renderer/media/audio_hardware.h"
 
 #include "base/logging.h"
 #include "content/common/view_messages.h"
 #include "content/renderer/render_thread_impl.h"
 
@@ skipping 31 matching lines @@
     uint32 buffer_size = 0;
     RenderThreadImpl::current()->Send(
         new ViewHostMsg_GetHardwareBufferSize(&buffer_size));
     output_buffer_size = buffer_size;
   }
 
   return output_buffer_size;
 }
 
 size_t GetHighLatencyOutputBufferSize(int sample_rate) {
-  // 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 size_t kMinSamplesPerHardwarePacket = 1024;
+  // kNominalBufferSize has been tested on Windows, Mac OS X, and Linux
+  // using the low-latency audio codepath (SyncSocket implementation

[Chris Rogers, 2012/02/23 23:39:54]

Sorry for causing all the confusion with the double-meaning of "low-latency" vs.
"high-latency".  I know that some time ago you removed the old (non-sync-socket)
code-paths which we were calling high-latency at the time.

I'm just calling this out now because the actual function name has the word
"HighLatency" in it, but in the comment we say "low-latency"

I'm not sure what the best approach is:
1) rename the function
2) change the comment to simply not mention "low-latency" codepath, since
that's all we have now anyways

but it seems like we have to do something

[vrk (LEFT CHROMIUM), 2012/02/27 18:19:13]

Oh good catch! I opted for 2. Thanks!

+  // with the AUDIO_PCM_LINEAR flag.
+  const size_t kNominalBufferSize = 2048;
 
-  // 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 size_t kMaxSamplesPerHardwarePacket = 64 * 1024;
+  if (sample_rate <= 48000)
+    return kNominalBufferSize;
+  else if (sample_rate <= 96000)
+    return kNominalBufferSize * 2;
 
-  // 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 size_t kMillisecondsPerHardwarePacket = 170;
-
-  // Select the number of samples that can provide at least
-  // |kMillisecondsPerHardwarePacket| worth of audio data.
-  size_t samples = kMinSamplesPerHardwarePacket;
-  while (samples <= kMaxSamplesPerHardwarePacket &&
-         samples * base::Time::kMillisecondsPerSecond <
-         sample_rate * kMillisecondsPerHardwarePacket) {
-    samples *= 2;
-  }
-  return samples;
+  return kNominalBufferSize * 4;
 }
 
 uint32 GetInputChannelCount() {
   DCHECK(RenderThreadImpl::current() != NULL);
 
   if (!input_channel_count) {
     uint32 channels = 0;
     RenderThreadImpl::current()->Send(
         new ViewHostMsg_GetHardwareInputChannelCount(&channels));
     input_channel_count = channels;
   }
 
   return input_channel_count;
 }
 
 void ResetCache() {
   DCHECK(RenderThreadImpl::current() != NULL);
 
   output_sample_rate = 0.0;
   input_sample_rate = 0.0;
   output_buffer_size = 0;
   input_channel_count = 0;
 }
 
 }  // namespace audio_hardware