CR-Client: CoreAudio additions to detect when device isn't receiving data

Modified by: bobclarkreal.com
Date: 12/5/06
Project: Mac OS X
Bug Number: internal PR 183844, PR 183850, PR 183834

Synopsis: Additions to the CoreAudio audio device code to
detect when 
there's not enough data making it to CoreAudio.

Overview:

The OS X CoreAudio device implementation is described here:

http://lists.helixcommunity.org/piperma
il/audio-dev/2006-July/000745.html

But it wasn't detecting dryness -- when there wasn't enough
data making it 
into CoreAudio.

These changes note when more data is required than exists,
and halts the 
timeline until more audio data arrives.

Files Modified:
audio/device/pub/platform/mac/osxaudio.h
audio/device/platform/mac/osxaudio.cpp

Image Size and Heap Use impact (Client -Only): negligible

Platforms and Profiles Affected: OS X only

Platforms and Profiles Build Verified: OS X

Platforms and Profiles Functionality verified: OS X

Branch: HEAD and 150Cay

Copyright assignment: I am a RealNetworks employee

Index: pub/platform/mac/osxaudio.h
============================================================
=======
RCS file:
/cvsroot/audio/device/pub/platform/mac/osxaudio.h,v
retrieving revision 1.2
diff -u -w -r1.2 osxaudio.h
--- pub/platform/mac/osxaudio.h 30 Aug 2006 20:54:10 -0000  
   1.2
+++ pub/platform/mac/osxaudio.h 5 Dec 2006 20:16:25 -0000
 -116,6
+116,8 
      UInt64      mResetTimeNanos;
      UInt64      mElapsedNanos;
      UInt64      mElapsedNanosAtPause;
+    UInt64      mNanoSecondsThatCoreAudioDrynessOccurred;
+    UInt64      mAccumulatedNanoSecondsOfCoreAudioDryness;
      double      mCurrentVolume;

      static      HXMutex* zm_pMutex;

Index: platform/mac/osxaudio.cpp
============================================================
=======
RCS file: /cvsroot/audio/device/platform/mac/osxaudio.cpp,v
retrieving revision 1.2
diff -u -w -r1.2 osxaudio.cpp
--- platform/mac/osxaudio.cpp   30 Aug 2006 20:54:10 -0000  
   1.2
+++ platform/mac/osxaudio.cpp   5 Dec 2006 20:16:25 -0000
 -57,9
+57,12 
   , mDeviceNumberOfChannels(0)
   , mInputNumberOfChannels(0)
   , mStaleBytesInFirstBuffer(0)
+ , mCurrentTime(0)
   , mResetTimeNanos(0)
   , mElapsedNanos(0)
   , mElapsedNanosAtPause(0)
+ , mNanoSecondsThatCoreAudioDrynessOccurred(0)
+ , mAccumulatedNanoSecondsOfCoreAudioDryness(0)
   , mCurrentVolume(75.0)
  {
      OSStatus err = noErr;
 -199,6
+202,8 
      mResetTimeNanos -= mElapsedNanosAtPause;
      mCurrentTime = mElapsedNanosAtPause;
      mElapsedNanosAtPause = 0;
+    mNanoSecondsThatCoreAudioDrynessOccurred = 0;
+    mAccumulatedNanoSecondsOfCoreAudioDryness = 0;

      // This is important!
      OnTimeSync();
 -225,6
+230,8 
      mResetTimeNanos = 
::AudioConvertHostTimeToNanos(::AudioGetCurrentHostTime());
      mElapsedNanos = 0;
      mElapsedNanosAtPause = 0;
+    mNanoSecondsThatCoreAudioDrynessOccurred = 0;
+    mAccumulatedNanoSecondsOfCoreAudioDryness = 0;
      return HXR_OK;
  }

 -378,7
+385,35 
      }

      UInt64 inNano =
::AudioConvertHostTimeToNanos(inCurTime->mHostTime);
-    mCurrentTime = inNano;
+
+    if (outOutputData->mBuffers[0].mDataByteSize >
bytesWritten)
+    {
+        // we're experiencing dryness
+
+        UInt64 bytesPerSecond =
(UInt64)(m_AudioFmt.uBitsPerSample/8)
+                                *
(UInt64)(m_AudioFmt.uChannels) * 
(UInt64)(m_AudioFmt.ulSamplesPerSec);
+
+        UInt64 nanoSecondsPlayed = (UInt64)bytesWritten * 
(UInt64)1000000000 / bytesPerSecond;
+
+        if (!mNanoSecondsThatCoreAudioDrynessOccurred)
+        {
+            mNanoSecondsThatCoreAudioDrynessOccurred =
mCurrentTime + 
nanoSecondsPlayed;
+        }
+
+        mCurrentTime += nanoSecondsPlayed; // estimate
timeline 
progression since this chunk may only be "partly
dry"
+    }
+    else
+    {
+        if (mNanoSecondsThatCoreAudioDrynessOccurred)
+        {
+            // we're just coming out of "dry
mode"
+            mAccumulatedNanoSecondsOfCoreAudioDryness =
inNano - 
mNanoSecondsThatCoreAudioDrynessOccurred;
+            mNanoSecondsThatCoreAudioDrynessOccurred = 0;
+        }
+
+        mCurrentTime = inNano -
mAccumulatedNanoSecondsOfCoreAudioDryness;
+    }
+
      return noErr;
  }

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CR-Client: CoreAudio additions to detect when device isn't receiving data

Thread: CR-Client: CoreAudio additions to detect when device isn't receiving data