Provide fake audio parameters when devices don't exist.

media/audio/mac/audio_manager_mac.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 "media/audio/mac/audio_manager_mac.h"
 
 #include <CoreAudio/AudioHardware.h>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 383 matching lines @@
 }
 
 void AudioManagerMac::GetAudioOutputDeviceNames(
     media::AudioDeviceNames* device_names) {
   DCHECK(device_names->empty());
   GetAudioDeviceInfo(false, device_names);
 }
 
 AudioParameters AudioManagerMac::GetInputStreamParameters(
     const std::string& device_id) {
-  // Due to the sharing of the input and output buffer sizes, we need to choose
-  // the input buffer size based on the output sample rate.  See
-  // http://crbug.com/154352.
-  const int buffer_size = ChooseBufferSize(
-      AUAudioOutputStream::HardwareSampleRate());
-
   AudioDeviceID device = GetAudioDeviceIdByUId(true, device_id);
   if (device == kAudioObjectUnknown) {
     DLOG(ERROR) << "Invalid device " << device_id;
-    return AudioParameters();
+    return AudioParameters(
+        AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
+        kFallbackSampleRate, 16, ChooseBufferSize(kFallbackSampleRate));
   }
 
   int channels = 0;
   ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   if (GetDeviceChannels(device, kAudioDevicePropertyScopeInput, &channels) &&
       channels <= 2) {
     channel_layout = GuessChannelLayout(channels);
   } else {
     DLOG(ERROR) << "Failed to get the device channels, use stereo as default "
                 << "for device " << device_id;
   }
 
   int sample_rate = HardwareSampleRateForDevice(device);
   if (!sample_rate)
     sample_rate = kFallbackSampleRate;
 
+  // Due to the sharing of the input and output buffer sizes, we need to choose
+  // the input buffer size based on the output sample rate.  See
+  // http://crbug.com/154352.
+  const int buffer_size = ChooseBufferSize(sample_rate);
+
   // TODO(xians): query the native channel layout for the specific device.
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
       sample_rate, 16, buffer_size);
 }
 
 std::string AudioManagerMac::GetAssociatedOutputDeviceID(
     const std::string& input_device_id) {
   AudioDeviceID device = GetAudioDeviceIdByUId(true, input_device_id);
   if (device == kAudioObjectUnknown)
@@ skipping 199 matching lines @@
 
   return stream;
 }
 
 AudioParameters AudioManagerMac::GetPreferredOutputStreamParameters(
     const std::string& output_device_id,
     const AudioParameters& input_params) {
   AudioDeviceID device = GetAudioDeviceIdByUId(false, output_device_id);
   if (device == kAudioObjectUnknown) {
     DLOG(ERROR) << "Invalid output device " << output_device_id;
-    return AudioParameters();
+    return input_params.IsValid() ? input_params : AudioParameters(
+        AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
+        kFallbackSampleRate, 16, ChooseBufferSize(kFallbackSampleRate));
   }
 
   int hardware_channels = 2;
   if (!GetDeviceChannels(device, kAudioDevicePropertyScopeOutput,
                          &hardware_channels)) {
     // Fallback to stereo.
     hardware_channels = 2;
   }
 
   ChannelLayout channel_layout = GuessChannelLayout(hardware_channels);
@@ skipping 85 matching lines @@
   }
 
   return buffer_size;
 }
 
 AudioManager* CreateAudioManager(AudioLogFactory* audio_log_factory) {
   return new AudioManagerMac(audio_log_factory);
 }
 
 }  // namespace media