Podcast recording on OSX fixed. Details:

The threading logic was changed somewhat. UBQuickTimeFile's run()
function no longer handles enqueuing the video/audio samples in a while
loop. Instead, it runs once, and uses Apple's Dispatch Queues to handle
enqueuing samples.
One dispatch queue was thus added for each input to the AssetWriter.
Each input is associated to one queue, and the requestMediaDataWhenReady
function insures that the inputs go and fetch any available samples when
they are able to write them.

As tested (for short podcasts, repeatedly), this solves all the problems
encountered earlier, such as the program hanging due to one input not
being ready, or corrupt files due (presumably) to missing samples.

src/podcast/quicktime/UBAudioQueueRecorder.cpp

@@ -257,7 +257,8 @@ bool UBAudioQueueRecorder::init(const QString& waveInDeviceName)
 
     int nbBuffers = 6;
     mSampleBufferSize = sAudioFormat.mSampleRate *  sAudioFormat.mChannelsPerFrame
-                * sAudioFormat.mChannelsPerFrame * mBufferLengthInMs / 1000; // 44.1 Khz * stereo * 16bit * buffer length
+                * sAudioFormat.mBitsPerChannel / 8 * mBufferLengthInMs / 1000; 
+        // BufferSize [bytes] = Length [s] * 44100 frames per second [Fr./s] * channels per frame [Ch./Fr.] * bytes per channel [bytes/Ch.]
 
     for (int i = 0; i < nbBuffers; i++)
     {

src/podcast/quicktime/UBQuickTimeFile.h

@@ -89,12 +89,13 @@ class UBQuickTimeFile : public QThread
     signals:
         void audioLevelChanged(quint8 level);
         void compressionSessionStarted();
+        void compressionFinished();
 
     protected:
         void run();
 
     private slots:
-        void appendAudioBuffer(void* pBuffer, long pLength);
+        void enqueueAudioBuffer(void* pBuffer, long pLength);
 
     private:
 
@@ -102,7 +103,7 @@ class UBQuickTimeFile : public QThread
         void setLastErrorMessage(const QString& error);
 
         void appendVideoFrame(CVPixelBufferRef pixelBuffer, long msTimeStamp);
-
+        bool appendSampleBuffer(CMSampleBufferRef sampleBuffer);
         
         QSize mFrameSize;
         QString mVideoFileName;
@@ -125,12 +126,16 @@ class UBQuickTimeFile : public QThread
         volatile bool mShouldStopCompression;
         volatile bool mCompressionSessionRunning;
 
-        
-
         QString mLastErrorMessage;
-
         QString mAudioRecordingDeviceName;
 
+        dispatch_queue_t mVideoDispatchQueue;
+        dispatch_queue_t mAudioDispatchQueue;
+
+        static QQueue<CMSampleBufferRef> audioQueue;
+        static QMutex audioQueueMutex;
+
+        static QMutex audioWriterMutex;
 };
 
 #endif /* UBQUICKTIMEFILE_H_ */

src/podcast/quicktime/UBQuickTimeFile.mm

@@ -41,16 +41,25 @@ QQueue<UBQuickTimeFile::VideoFrame> UBQuickTimeFile::frameQueue;
 QMutex UBQuickTimeFile::frameQueueMutex;
 QWaitCondition UBQuickTimeFile::frameBufferNotEmpty;
 
+
+QQueue<CMSampleBufferRef> UBQuickTimeFile::audioQueue;
+QMutex UBQuickTimeFile::audioQueueMutex;
+QMutex UBQuickTimeFile::audioWriterMutex;
+
 UBQuickTimeFile::UBQuickTimeFile(QObject * pParent)
     : QThread(pParent)
     , mVideoWriter(0)
     , mVideoWriterInput(0)
     , mAdaptor(0)
+    , mAudioWriterInput(0)
+    , mWaveRecorder(0)
     , mTimeScale(1000)
     , mRecordAudio(true)
     , mShouldStopCompression(false)
     , mCompressionSessionRunning(false)
 {
+    mVideoDispatchQueue = dispatch_queue_create("org.oef.VideoDispatchQueue", NULL);
+    mAudioDispatchQueue = dispatch_queue_create("org.oef.AudioDispatchQueue", NULL);
 }
 
 
@@ -66,6 +75,7 @@ bool UBQuickTimeFile::init(const QString& pVideoFileName, const QString& pProfil
     mFrameSize = pFrameSize;
     mVideoFileName = pVideoFileName;
     mRecordAudio = pRecordAudio;
+    //mRecordAudio = false;
 
     if (mRecordAudio)
         mAudioRecordingDeviceName = audioRecordingDevice;
@@ -90,33 +100,36 @@ void UBQuickTimeFile::run()
     mCompressionSessionRunning = true;
     emit compressionSessionStarted();
 
-    do {
+    [mVideoWriterInput requestMediaDataWhenReadyOnQueue:mVideoDispatchQueue
-        // Video
+        usingBlock:^{
             frameQueueMutex.lock();
+            //frameBufferNotEmpty.wait(&UBQuickTimeFile::frameQueueMutex); // TODO: monitor performance with and without this
 
-        frameBufferNotEmpty.wait(&UBQuickTimeFile::frameQueueMutex);
+            if (!mShouldStopCompression && 
-
+                !frameQueue.isEmpty() &&
-        if (!frameQueue.isEmpty()) {
+                [mVideoWriterInput isReadyForMoreMediaData]) 
-            QQueue<VideoFrame> localQueue = frameQueue;
+            {
-            frameQueue.clear();
+                    VideoFrame frame = frameQueue.dequeue();
-
-            frameQueueMutex.unlock();
-
-            while (!localQueue.isEmpty()) {
-                if ([mVideoWriterInput isReadyForMoreMediaData]) {
-                    VideoFrame frame = localQueue.dequeue();
                     appendVideoFrame(frame.buffer, frame.timestamp);
             }
-                else
+
-                    usleep(10000);
-            }
-        }
-        else
             frameQueueMutex.unlock();
             
-    } while(!mShouldStopCompression);
+    }];
     
-    endSession();
+    if (mRecordAudio) {
+        [mAudioWriterInput requestMediaDataWhenReadyOnQueue:mAudioDispatchQueue
+            usingBlock:^{
+                audioQueueMutex.lock();
+                if (!audioQueue.isEmpty() && 
+                    [mAudioWriterInput isReadyForMoreMediaData]) 
+                {
+                        appendSampleBuffer(audioQueue.dequeue());
+                }
+                audioQueueMutex.unlock();
+
+            }];
+    }
 
 }
 
@@ -197,7 +210,7 @@ bool UBQuickTimeFile::beginSession()
 
         if(mWaveRecorder->init(mAudioRecordingDeviceName)) {
             connect(mWaveRecorder, &UBAudioQueueRecorder::newWaveBuffer,
-                    this, &UBQuickTimeFile::appendAudioBuffer);
+                    this, &UBQuickTimeFile::enqueueAudioBuffer);
 
             connect(mWaveRecorder, SIGNAL(audioLevelChanged(quint8)),
                     this, SIGNAL(audioLevelChanged(quint8)));
@@ -223,7 +236,7 @@ bool UBQuickTimeFile::beginSession()
             AVFormatIDKey         : [NSNumber numberWithUnsignedInt:kAudioFormatMPEG4AAC],
             AVEncoderBitRateKey   : [NSNumber numberWithInteger:128000],
             AVSampleRateKey       : [NSNumber numberWithInteger:44100],
-            AVChannelLayoutKey    : channelLayoutAsData,
+            //AVChannelLayoutKey    : channelLayoutAsData,
             AVNumberOfChannelsKey : [NSNumber numberWithUnsignedInteger:1]
         };
 
@@ -232,8 +245,6 @@ bool UBQuickTimeFile::beginSession()
 
         NSCParameterAssert([mVideoWriter canAddInput:mAudioWriterInput]);
         [mVideoWriter addInput:mAudioWriterInput];
-
-        qDebug() << "audio writer input created and added";
     }
 
 
@@ -252,14 +263,20 @@ bool UBQuickTimeFile::beginSession()
  */
 void UBQuickTimeFile::endSession()
 {
+    //qDebug() << "Ending session";
+
+
     [mVideoWriterInput markAsFinished];
-    [mVideoWriter finishWritingWithCompletionHandler:^{}];
 
+    [mVideoWriter finishWritingWithCompletionHandler:^{
         [mAdaptor release];
         [mVideoWriterInput release];
-    [mVideoWriter release];
+
+        if (mAudioWriterInput != 0)
             [mAudioWriterInput release];
         
+        [mVideoWriter release];
+
         mAdaptor = nil;
         mVideoWriterInput = nil;
         mVideoWriter = nil;
@@ -270,6 +287,10 @@ void UBQuickTimeFile::endSession()
             mWaveRecorder->deleteLater();
         }
 
+
+        emit compressionFinished();
+    }];
+
 }
 
 /**
@@ -277,12 +298,22 @@ void UBQuickTimeFile::endSession()
  */
 void UBQuickTimeFile::stop()
 {
+    //qDebug() << "requested end of recording";
     mShouldStopCompression = true;
+
+
+    frameQueueMutex.lock();
+    audioQueueMutex.lock();
+    endSession();
+    frameQueueMutex.unlock();
+    audioQueueMutex.unlock();
 }
 
 
 /**
- * \brief Create a CVPixelBufferRef from the input adaptor's CVPixelBufferPool
+ * \brief Create and return a CVPixelBufferRef 
+ *
+ * The CVPixelBuffer is created from the input adaptor's CVPixelBufferPool
  */
 CVPixelBufferRef UBQuickTimeFile::newPixelBuffer()
 {
@@ -305,6 +336,7 @@ CVPixelBufferRef UBQuickTimeFile::newPixelBuffer()
  */
 void UBQuickTimeFile::appendVideoFrame(CVPixelBufferRef pixelBuffer, long msTimeStamp)
 {
+    //qDebug() << "appending video frame";
     CMTime t = CMTimeMake((msTimeStamp * mTimeScale / 1000.0), mTimeScale);
 
     bool added = [mAdaptor appendPixelBuffer: pixelBuffer
@@ -329,10 +361,11 @@ void UBQuickTimeFile::appendVideoFrame(CVPixelBufferRef pixelBuffer, long msTime
  * (implemented in the UBAudioQueueRecorder class) and the recording, handled
  * by the AVAssetWriterInput instance mAudioWriterInput.
  */
-void UBQuickTimeFile::appendAudioBuffer(void* pBuffer,
+void UBQuickTimeFile::enqueueAudioBuffer(void* pBuffer,
                                         long pLength)
 {
-    if(!mRecordAudio)
+    
+    if(!mRecordAudio || mShouldStopCompression)
         return;
 
 
@@ -370,31 +403,37 @@ void UBQuickTimeFile::appendAudioBuffer(void* pBuffer,
                                                     NULL,
                                                     &sampleBuffer);
 
+    //qDebug() << "enqueueAudioBuffer, timeStamp = " << timeStamp.value << " / " << timeStamp.timescale;
 
-    // Wait until the AssetWriterInput is ready, but no more than 100ms
-    // (bit of a duct tape solution; cleaner solution would be to use a QQueue,
-    // similar to the VideoWriter)
-    int waitTime = 0;
-    while(![mAudioWriterInput isReadyForMoreMediaData] && waitTime < 100) {
-        waitTime += 10;
-        usleep(10000);
-    }
     
-    if ([mAudioWriterInput isReadyForMoreMediaData]) {
+    audioQueueMutex.lock();
-        if(![mAudioWriterInput appendSampleBuffer:sampleBuffer])
+    audioQueue.enqueue(sampleBuffer);
+    audioQueueMutex.unlock();
+    
+    //qDebug() << "buffer enqueued";
+    
+
+
+}
+
+
+bool UBQuickTimeFile::appendSampleBuffer(CMSampleBufferRef sampleBuffer)
+{
+    bool success = [mAudioWriterInput appendSampleBuffer:sampleBuffer];
+    
+    if (!success)
         setLastErrorMessage(QString("Failed to append sample buffer to audio input"));
-    }
-    else
-        setLastErrorMessage(QString("AudioWriterInput not ready. Buffer dropped."));
     
 
+    CMBlockBufferRef blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer);
 
     CFRelease(sampleBuffer);
     CFRelease(blockBuffer);
 
-    // The audioQueueBuffers are all freed when UBAudioQueueRecorder::close() is called
+    return success;
 }
 
+
 /**
  * \brief Print an error message to the terminal, and store it
  */

src/podcast/quicktime/UBQuickTimeVideoEncoder.cpp

@@ -68,7 +68,7 @@ bool UBQuickTimeVideoEncoder::start()
         return false;
     }
 
-    connect(&mQuickTimeCompressionSession, SIGNAL(finished()), this, SLOT(compressionFinished()));
+    connect(&mQuickTimeCompressionSession, SIGNAL(compressionFinished()), this, SLOT(compressionFinished()));
     connect(&mQuickTimeCompressionSession, SIGNAL(audioLevelChanged(quint8)), this, SIGNAL(audioLevelChanged(quint8)));
 
     mQuickTimeCompressionSession.start();
@@ -79,10 +79,7 @@ bool UBQuickTimeVideoEncoder::start()
 
 bool UBQuickTimeVideoEncoder::stop()
 {
-    if (mQuickTimeCompressionSession.isRunning())
-    {
     mQuickTimeCompressionSession.stop();
-    }
 
     UBQuickTimeFile::frameBufferNotEmpty.wakeAll();