In some rare cases it has been found that Windows returns a sample-rate of 0, even though it's capa…

content/renderer/renderer_webkitplatformsupport_impl.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.
 
 #include "content/renderer/renderer_webkitplatformsupport_impl.h"
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/lazy_instance.h"
@@ skipping 615 matching lines @@
 
   return true;
 }
 
 bool RendererWebKitPlatformSupportImpl::isThreadedCompositingEnabled() {
   return !!RenderThreadImpl::current()->compositor_message_loop_proxy();
 }
 
 double RendererWebKitPlatformSupportImpl::audioHardwareSampleRate() {
   RenderThreadImpl* thread = RenderThreadImpl::current();
-  return thread->GetAudioHardwareConfig()->GetOutputSampleRate();
+  int sample_rate = thread->GetAudioHardwareConfig()->GetOutputSampleRate();
+
+  // In some rare cases it has been found that Windows returns
+  // a sample-rate of 0.
+  // Let's make sure to return a sane fallback sample-rate.
+  // http://crbug.com/222718
+  static const int kMinSampleRate = 22050;

[DaleCurtis, 2013/03/25 21:29:39]

How about calling GetAudioHardwareConfig()->GetOutputConfig().IsValid() instead?

Otherwise you'll need to duplicate the sample rate check logic using the values
from media/base/limits.h instead of these Min/Max ones you've defined.

Since an invalid hardware sample rate means we're going to fallback to a fake
audio device, it doesn't really matter if you have 44.1kHz or 48kHz here. Just
pick one.

[Chris Rogers, 2013/03/25 22:46:45]

The sample-rate limits of Web Audio aren't necessarily the same as
media/base/limits.h, so since this is glue code into WebKit I'm defining these
limits here.
I'm seeing the case where the hardware *is* actually good and set to 48KHz, and
Flash and <audio> are playing back fine.  So I wanted to have the highest
probability of guessing the correct sample-rate and have chosen the values
according to the stats we know about these platforms.

+  static const int kMaxSampleRate = 192000;
+#if defined(OS_MACOSX)
+  static const int kFallbackSampleRate = 44100;
+#else
+  static const int kFallbackSampleRate = 48000;
+#endif
+  if (sample_rate < kMinSampleRate || sample_rate > kMaxSampleRate)
+    sample_rate = kFallbackSampleRate;
+
+  return sample_rate;
 }
 
 size_t RendererWebKitPlatformSupportImpl::audioHardwareBufferSize() {
   RenderThreadImpl* thread = RenderThreadImpl::current();
   return thread->GetAudioHardwareConfig()->GetOutputBufferSize();
 }
 
 unsigned RendererWebKitPlatformSupportImpl::audioHardwareOutputChannels() {
   RenderThreadImpl* thread = RenderThreadImpl::current();
   return thread->GetAudioHardwareConfig()->GetOutputChannels();
@@ skipping 244 matching lines @@
 //------------------------------------------------------------------------------
 
 GrContext* RendererWebKitPlatformSupportImpl::sharedOffscreenGrContext() {
   if (!shared_offscreen_context_)
     return NULL;
   return shared_offscreen_context_->GrContext();
 }
 
 
 }  // namespace content