Improved error handling in AUAudioInputStream::Open() for Mac OSX

media/audio/mac/audio_low_latency_input_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_low_latency_input_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
@@ skipping 96 matching lines @@
 }
 
 AUAudioInputStream::~AUAudioInputStream() {
   DVLOG(1) << "~dtor";
 }
 
 // Obtain and open the AUHAL AudioOutputUnit for recording.
 bool AUAudioInputStream::Open() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "Open";
-  // Verify that we are not already opened.
-  if (audio_unit_)
-    return false;
 
-  // Verify that we have a valid device.
-  if (input_device_id_ == kAudioObjectUnknown) {
-    NOTREACHED() << "Device ID is unknown";
+  // Verify that we are not already opened. Send appropriate error code to
+  // HandleError() to ensure that the error type is added to UMA stats where
+  // the frequency of error codes can be analyzed.
+  if (audio_unit_) {
+    HandleError(kAudioUnitErr_Initialized);

[tommi (sloooow) - chröme, 2016/02/05 12:29:30]

I'm not  sure this is a good idea.  HandleError() does more than just capture
the stats.  It actually fires an error which may close the stream.

For now though it makes sense to me to add a DCHECK at the beginning of this
function to catch programmer error:

DCHECK(!audio_unit_);

[henrika (OOO until Aug 14), 2016/02/05 12:50:51]

Done.

     return false;
   }
 
+  // Verify that we have a valid device. Send appropriate error code to
+  // HandleError() to ensure that the error type is added to UMA stats.
+  if (input_device_id_ == kAudioObjectUnknown) {
+    NOTREACHED() << "Device ID is unknown";
+    HandleError(kAudioUnitErr_InvalidElement);
+    return false;
+  }
+
   // The requested sample-rate must match the hardware sample-rate.
   int sample_rate =
       AudioManagerMac::HardwareSampleRateForDevice(input_device_id_);
   if (sample_rate != format_.mSampleRate) {
     // Add UMA stat for the case when we detect a mismatch in sample rates,
     // i.e., when the actual/current native sample rate is different from the
     // one used when constructing this object. In addition, return false since
     // the current design does not support changes in the native sample rate
     // between construction and calls to Open().
     UMA_HISTOGRAM_SPARSE_SLOWLY("Media.InputInvalidSampleRateMac", sample_rate);
     NOTREACHED() << "Requested sample-rate: " << format_.mSampleRate
                  << " must match the hardware sample-rate: " << sample_rate;
+    HandleError(kAudioUnitErr_InvalidParameter);

[henrika (OOO until Aug 14), 2016/02/05 12:16:28]

Adding one extra here since we can then see the relation (frequency) of this
error in relation to the others.

[tommi (sloooow) - chröme, 2016/02/05 12:29:30]

Acknowledged.

     return false;
   }
 
   // Start by obtaining an AudioOuputUnit using an AUHAL component description.
 
   // Description for the Audio Unit we want to use (AUHAL in this case).
   // The kAudioUnitSubType_HALOutput audio unit interfaces to any audio device.
   // The user specifies which audio device to track. The audio unit can do
   // input from the device as well as output to the device. Bus 0 is used for
   // the output side, bus 1 is used to get audio input from the device.
   AudioComponentDescription desc = {
       kAudioUnitType_Output,
       kAudioUnitSubType_HALOutput,
       kAudioUnitManufacturer_Apple,
       0,
       0
   };
 
+  // Find a component that meets the description in |desc|.
   AudioComponent comp = AudioComponentFindNext(nullptr, &desc);
   DCHECK(comp);
+  if (!comp) {
+    HandleError(kAudioComponentErr_InstanceInvalidated);
+    return false;
+  }
 
   // Get access to the service provided by the specified Audio Unit.
   OSStatus result = AudioComponentInstanceNew(comp, &audio_unit_);
   if (result) {
     HandleError(result);
     return false;
   }
 
   // Initialize the AUHAL before making any changes or using it. The audio unit
   // will be initialized once more as last operation in this method but that is
@@ skipping 754 matching lines @@
                             manager_->low_latency_input_streams());
   UMA_HISTOGRAM_COUNTS_1000("Media.Audio.NumberOfBasicInputStreamsMac",
                             manager_->basic_input_streams());
   // TODO(henrika): this value will currently always report true. It should be
   // fixed when we understand the problem better.
   UMA_HISTOGRAM_BOOLEAN("Media.Audio.AutomaticGainControlMac",
                         GetAutomaticGainControl());
 }
 
 }  // namespace media