Provide a mechanism to hint for correct duration.

For cases where duration can't be calculated accurately

StreamingKit/StreamingKit/STKDataSource.h

@@ -48,6 +48,7 @@
 @property (readonly) SInt64 position;
 @property (readonly) SInt64 length;
 @property (readonly) BOOL hasBytesAvailable;
+@property (nonatomic, readwrite, assign) double durationHint;
 @property (readwrite, unsafe_unretained) id<STKDataSourceDelegate> delegate;
 
 -(BOOL) registerForEvents:(NSRunLoop*)runLoop;

StreamingKit/StreamingKit/STKQueueEntry.h

@@ -28,6 +28,7 @@
     volatile int processedPacketsCount;
 	volatile int processedPacketsSizeTotal;
     AudioStreamBasicDescription audioStreamBasicDescription;
+    double durationHint;
 }
 
 @property (readonly) UInt64 audioDataLengthInBytes;

StreamingKit/StreamingKit/STKQueueEntry.m

@@ -23,6 +23,7 @@
         self.dataSource = dataSourceIn;
         self.queueItemId = queueItemIdIn;
         self->lastFrameQueued = -1;
+        self->durationHint = dataSourceIn.durationHint;
     }
     
     return self;
@@ -60,6 +61,8 @@
 
 -(double) duration
 {
+    if (durationHint > 0.0) return durationHint;
+    
     if (self->sampleRate <= 0)
     {
         return 0;