Limit OnData() callbacks to every 5ms for mac audio input.

media/audio/mac/audio_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_input_mac.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
 #include "media/audio/audio_manager_base.h"
@@ skipping 179 matching lines @@
     // This can happen if Stop() was called without start.
     DCHECK_EQ(0U, audio_buffer->mAudioDataByteSize);
     return;
   }
 
   if (audio_buffer->mAudioDataByteSize) {
     // The AudioQueue API may use a large internal buffer and repeatedly call us
     // back to back once that internal buffer is filled.  When this happens the
     // renderer client does not have enough time to read data back from the
     // shared memory before the next write comes along.  If HandleInputBuffer()
-    // is called too frequently, Sleep() to simulate realtime input and ensure
-    // the shared memory doesn't get trampled.
+    // is called too frequently, Sleep() at least 5ms to ensure the shared
+    // memory doesn't get trampled.
     // TODO(dalecurtis): This is a HACK.  Long term the AudioQueue path is going
     // away in favor of the AudioUnit based AUAudioInputStream().  Tracked by
-    // http://crbug.com/161383
+    // http://crbug.com/161383.
     base::TimeDelta elapsed = base::Time::Now() - last_fill_;
-    base::TimeDelta buffer_length = base::TimeDelta::FromMilliseconds(
-       audio_buffer->mAudioDataByteSize * base::Time::kMillisecondsPerSecond /
-       static_cast<float>(format_.mBytesPerFrame * format_.mSampleRate));
-    if (elapsed < buffer_length)
-      base::PlatformThread::Sleep(buffer_length - elapsed);
+    const base::TimeDelta kMinDelay = base::TimeDelta::FromMilliseconds(5);
+    if (elapsed < kMinDelay)
+      base::PlatformThread::Sleep(kMinDelay - elapsed);
 
     callback_->OnData(this,
                       reinterpret_cast<const uint8*>(audio_buffer->mAudioData),
                       audio_buffer->mAudioDataByteSize,
                       audio_buffer->mAudioDataByteSize,
                       0.0);
 
     last_fill_ = base::Time::Now();
   }
   // Recycle the buffer.
   OSStatus err = QueueNextBuffer(audio_buffer);
   if (err != noErr) {
     if (err == kAudioQueueErr_EnqueueDuringReset) {
       // This is the error you get if you try to enqueue a buffer and the
       // queue has been closed. Not really a problem if indeed the queue
       // has been closed.
       // TODO(joth): PCMQueueOutAudioOutputStream uses callback_ to provide an
       // extra guard for this situation, but it seems to introduce more
       // complications than it solves (memory barrier issues accessing it from
       // multiple threads, looses the means to indicate OnClosed to client).
       // Should determine if we need to do something equivalent here.
       return;
     }
     HandleError(err);
   }
 }
 
 }  // namespace media