This patch will loop through the soundcard and return a list of available devices when the AudioI...

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
===================================================================
--- media/audio/mac/audio_manager_mac.cc	(revision 106297)
+++ media/audio/mac/audio_manager_mac.cc	(working copy)
@@ -5,6 +5,7 @@
 #include <CoreAudio/AudioHardware.h>
 
 #include "base/mac/mac_util.h"
+#include "base/sys_string_conversions.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
 #include "media/audio/mac/audio_input_mac.h"
@@ -65,6 +66,100 @@
       output_device_id != kAudioObjectUnknown;
 }
 
+static void GetAudioDeviceInfo(bool is_input,
+                               media::AudioDeviceNames* device_names) {
+  DCHECK(device_names);
+

[scherkus (not reviewing), 2011/10/24 18:32:13]

nit: get rid of blank line

[no longer working on chromium, 2011/10/24 22:32:30]

Done.

+  device_names->clear();
+
+  // Query the number of total devices.
+  AudioObjectPropertyAddress property_address = {
+    kAudioHardwarePropertyDevices,  // mSelector

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Why did you add these comments? Does not say much.

[no longer working on chromium, 2011/10/24 22:32:30]

It is code/comment copied from CL http://codereview.chromium.org/210009 which
replaced the deprecated AudioHardwareGetProperty with
AudioObjectGetPropertyData. But I can remove them.

+    kAudioObjectPropertyScopeGlobal,  // mScope
+    kAudioObjectPropertyElementMaster  // mElement
+  };
+  UInt32 size = 0;
+  OSStatus result = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject,
+                                                   &property_address,
+                                                   0,
+                                                   NULL,
+                                                   &size);
+  if (result || !size)

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Assume that there are no devices if we enter this state. Perhaps add a comment?

[no longer working on chromium, 2011/10/24 22:32:30]

I think the code has been quite clear. hope it is fine here.

+    return;
+
+  int device_count = 0;
+  device_count = size / sizeof(AudioDeviceID);

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Why not:

int device_count = size / ..

[no longer working on chromium, 2011/10/24 22:32:30]

Good catch, thanks.
Done

+
+  // Get the array of device id for each device.

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Can you make this comment more clear. What does the array of device IDs
correspond to? E.g. input and output?

[no longer working on chromium, 2011/10/24 22:32:30]

Done.

The story behind this is that we need to check if the device has any input
channel or output channel, and exclude those device without any channel we are
interested in. For example, if we are looking for input device, we exclude the
device without any input channel.

+  scoped_ptr_malloc<AudioDeviceID>
+      devices(reinterpret_cast<AudioDeviceID*>(malloc(size)));
+  AudioDeviceID* device_ids = devices.get();
+  result = AudioObjectGetPropertyData(kAudioObjectSystemObject,
+                                      &property_address,
+                                      0,
+                                      NULL,
+                                      &size,
+                                      device_ids);
+  if (result)
+    return;
+
+  // Iterate each device to gather information.

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

I would say "Iterate over all available devices ...." or something like that.

[no longer working on chromium, 2011/10/24 22:32:30]

Done.

+  for (int i = 0; i < device_count; ++i) {
+    int channels = 0;

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Why declaration here?

[no longer working on chromium, 2011/10/24 22:32:30]

For each device, we need to check if it has channel we need.

+    // Get the number of input or output channels of the device, exclude
+    // those devices without any right type of channel.

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

What does "without any right type of channel" mean and to which scope does this
comment belong?

[no longer working on chromium, 2011/10/24 22:32:30]

Done.

I improved the comments a bit by separating them. 

+    AudioDeviceGetPropertyInfo(device_ids[i],
+                               0,
+                               is_input,
+                               kAudioDevicePropertyStreamConfiguration,
+                               &size,
+                               NULL);
+    scoped_ptr_malloc<AudioBufferList>
+        buffer(reinterpret_cast<AudioBufferList*>(malloc(size)));
+    AudioBufferList* buffer_list = buffer.get();
+    AudioDeviceGetProperty(device_ids[i],
+                           0,
+                           is_input,
+                           kAudioDevicePropertyStreamConfiguration,
+                           &size,
+                           buffer_list);
+
+    for (uint32 j = 0; j < buffer_list->mNumberBuffers; ++j)

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

What does this section do? 

[no longer working on chromium, 2011/10/24 22:32:30]

It just gets the buffer list about the device which contains the channel
information.

+      channels += buffer_list->mBuffers[j].mNumberChannels;
+
+    if (!channels)

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Sorry, this part is not clear. Where has it been set what a valid number of
channels is?

[no longer working on chromium, 2011/10/24 22:32:30]

Just two lines above we add to channels with the number of channels in the
buffer list.

+      continue;
+
+    // Get device UID.
+    CFStringRef uid = NULL;
+    size = sizeof(uid);
+    result = AudioDeviceGetProperty(device_ids[i],
+                                    0,
+                                    is_input,
+                                    kAudioDevicePropertyDeviceUID,
+                                    &size,
+                                    &uid);
+    if (result)
+      continue;
+
+    // Get device name.
+    CFStringRef name = NULL;
+    result = AudioDeviceGetProperty(device_ids[i],
+                                    0,
+                                    is_input,
+                                    kAudioObjectPropertyName,
+                                    &size,
+                                    &name);
+    if (result)
+      continue;
+
+    media::AudioDeviceName device_name;

[henrika (OOO until Aug 14), 2011/10/24 18:51:36]

Add comment about what you actually produce and store here.

[no longer working on chromium, 2011/10/24 22:32:30]

Done.

+    device_name.device_name = base::SysCFStringRefToUTF8(name);
+    device_name.unique_id = base::SysCFStringRefToUTF8(uid);
+    device_names->push_back(device_name);
+  }
+}
+
 AudioManagerMac::AudioManagerMac()
     : num_output_streams_(0) {
 }
@@ -82,15 +177,15 @@
 
 void AudioManagerMac::GetAudioInputDeviceNames(
     media::AudioDeviceNames* device_names) {
-  // TODO(xians): query a full list of valid devices.
-  if (HasAudioInputDevices()) {
-    // Add the default device to the list.
-    // We use index 0 to make up the unique_id to identify the
-    // default devices.
+  GetAudioDeviceInfo(true, device_names);
+  if (!device_names->empty()) {
+    // Prepend the default device to the list since we always want it to be
+    // on the top of the list for all platforms. There is no duplicate
+    // counting here since the default device has been abstracted out before.
     media::AudioDeviceName name;
     name.device_name = AudioManagerBase::kDefaultDeviceName;
     name.unique_id = "0";
-    device_names->push_back(name);
+    device_names->push_front(name);
   }
 }