Enable pinning stream output routing for webapp request on ChromeOS

media/audio/cras/cras_unified.cc

Index: media/audio/cras/cras_unified.cc
diff --git a/media/audio/cras/cras_unified.cc b/media/audio/cras/cras_unified.cc
index 929854497c3987671e9c1f0a17147a7771055db8..346aa1e46010270ee1f542a56d6a667198e56265 100644
--- a/media/audio/cras/cras_unified.cc
+++ b/media/audio/cras/cras_unified.cc
@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/strings/string_number_conversions.h"
 #include "media/audio/cras/audio_manager_cras.h"
 
 namespace media {
@@ -52,7 +53,8 @@ namespace media {
 // of audio.
 
 CrasUnifiedStream::CrasUnifiedStream(const AudioParameters& params,
-                                     AudioManagerCras* manager)
+                                     AudioManagerCras* manager,
+                                     const std::string& device_id)
     : client_(NULL),
       stream_id_(0),
       params_(params),
@@ -61,11 +63,17 @@ CrasUnifiedStream::CrasUnifiedStream(const AudioParameters& params,
       volume_(1.0),
       manager_(manager),
       source_callback_(NULL),
-      stream_direction_(CRAS_STREAM_OUTPUT) {
+      stream_direction_(CRAS_STREAM_OUTPUT),
+      pin_device_(NO_DEVICE) {
   DCHECK(manager_);
   DCHECK_GT(params_.channels(), 0);
 
   output_bus_ = AudioBus::Create(params);
+  if (!manager_->IsDefault(device_id, false)) {
+    uint64_t cras_node_id;
+    base::StringToUint64(device_id, &cras_node_id);
+    pin_device_ = dev_index_of(cras_node_id);
+  }
 }
 
 CrasUnifiedStream::~CrasUnifiedStream() {
@@ -196,8 +204,9 @@ void CrasUnifiedStream::Start(AudioSourceCallback* callback) {
   bytes_per_frame_ = cras_client_format_bytes_per_frame(audio_format);
 
   // Adding the stream will start the audio callbacks requesting data.
-  if (cras_client_add_stream(client_, &stream_id_, stream_params) < 0) {
-    LOG(WARNING) << "Failed to add the stream";
+  if (cras_client_add_pinned_stream(client_, pin_device_, &stream_id_,
+                                    stream_params)) {
+    LOG(WARNING) << "Failed to add the stream.";

[dgreid, 2016/11/30 01:45:08]

How does this work when the Chrome OS UI switches the device?  What about when a
device is unplugged?

I was expecting this to set a pinned device when needed, but add a default
stream otherwise.

[Qiang(Joe) Xu, 2016/11/30 02:08:44]

The expectation can be satisfied. When GetUserMedia is called, audio manager
(AudioManagerCras here) MakeOutputStream, depending on the device_id (Default
choice or device that wants to be pinned to), pin_device_ will be initialized in
line 72-76. If 'Default' label is chosen, pin_device_ == NO_DEVICE, which will
be the default stream, otherwise pin_device_ is a dev_idx.

cras_client_add_pinned_stream(client_, NO_DEVICE, &stream_id_, stream_params) is
equal to cras_client_add_stream(client_, &stream_id_, stream_params)

When ChromeOS UI switches the device, it matters when the choice is 'Default',
but it doesn't matter for other choices.

When a device is unplugged, all I can think of is if this device is doing
pinning stream, it can no longer fill or read audio datas anymore... my cl
doesn't handle this. It will possibly notify stream error, and stop or destroy
the stream? If this device is not doing pinning stream, I think it is fine. The
next mediaDevices.enumerateDevices call will not show the unplugged device.

     callback->OnError(this);
     cras_audio_format_destroy(audio_format);
     cras_client_stream_params_destroy(stream_params);