aja: Fix memory overrun on aja-source

When too many audio frames are captured and at the same time the ring
buffer on the card is wrapped, memory overrun was not captured before
DMA transfer, which resulted in corruption of memory contents. This
commit moves the overrun check before the DMA transfer.

plugins/aja/aja-source.cpp

@@ -293,11 +293,28 @@ void AJASource::CaptureThread(AJAThread *thread, void *data)
 				audioOverrun = true;
 			}
 
-			if (!audioOverrun) {
+			if (!audioOverrun)
 				card->DMAReadAudio(audioSystem,
 						   ajaSource->mAudioBuffer,
 						   offsets.lastAddress,
 						   offsets.bytesRead);
+
+			if (!audioOverrun &&
+			    offsets.currentAddress - offsets.readOffset >
+				    ajaSource->mAudioBuffer.GetByteCount() -
+					    offsets.bytesRead) {
+				blog(LOG_DEBUG,
+				     "AJASource::CaptureThread: Audio overrun (2)! Buffer Size: %d, Bytes Captured: %d",
+				     ajaSource->mAudioBuffer.GetByteCount() -
+					     offsets.bytesRead,
+				     offsets.currentAddress -
+					     offsets.readOffset);
+				ResetAudioBufferOffsets(card, audioSystem,
+							offsets);
+				audioOverrun = true;
+			}
+
+			if (!audioOverrun) {
 				card->DMAReadAudio(
 					audioSystem,
 					reinterpret_cast<ULWord *>(
@@ -311,16 +328,6 @@ void AJASource::CaptureThread(AJAThread *thread, void *data)
 						     offsets.readOffset;
 			}
 
-			if (offsets.bytesRead >
-			    ajaSource->mAudioBuffer.GetByteCount()) {
-				blog(LOG_DEBUG,
-				     "AJASource::CaptureThread: Audio overrun (2)! Buffer Size: %d, Bytes Captured: %d",
-				     ajaSource->mAudioBuffer.GetByteCount(),
-				     offsets.bytesRead);
-				ResetAudioBufferOffsets(card, audioSystem,
-							offsets);
-				audioOverrun = true;
-			}
 		} else {
 			offsets.bytesRead =
 				offsets.currentAddress - offsets.lastAddress;