     PaDeviceIndex outputDevice;
 } UserOptions;
-#define BIG_BUFFER_SIZE  (sizeof(float) * 2 * 2048)
+#define BIG_BUFFER_SIZE  (sizeof(float) * 2 * 2 * 1024)
 static unsigned char g_ReadWriteBuffer[BIG_BUFFER_SIZE];
-static unsigned char g_ConversionBuffer[BIG_BUFFER_SIZE];
+#define MAX_CONVERSION_SAMPLES   (2 * 32 * 1024)
+#define CONVERSION_BUFFER_SIZE  (sizeof(float) * 2 * MAX_CONVERSION_SAMPLES)
+static unsigned char g_ConversionBuffer[CONVERSION_BUFFER_SIZE];
 /*******************************************************************/
 static int RecordAndPlaySinesCallback( const void *inputBuffer, void *outputBuffer,
                         unsigned long framesPerBuffer,
     {
         int channelsPerFrame = loopbackContext->test->inputParameters.channelCount;
         float *in = (float *)inputBuffer;
         PaSampleFormat inFormat = loopbackContext->test->inputParameters.sampleFormat;
         if( inFormat != paFloat32 )
         {
+            int samplesToConvert = framesPerBuffer * channelsPerFrame;
             in = (float *) g_ConversionBuffer;
-            PaQa_ConvertToFloat( inputBuffer, framesPerBuffer * channelsPerFrame, inFormat, (float *) g_ConversionBuffer );
+            if( samplesToConvert > MAX_CONVERSION_SAMPLES )
+            {
+                // Hack to prevent buffer overflow.
+                // @todo Loop with small buffer instead of failing.
+                printf("Format conversion buffer too small!\n");
+                return paComplete;
+            }
+            PaQa_ConvertToFloat( inputBuffer, samplesToConvert, inFormat, (float *) g_ConversionBuffer );
         }
         // Read each channel from the buffer.
         if( outFormat != paFloat32 )
         {
+            int samplesToConvert = framesPerBuffer * channelsPerFrame;
+            if( samplesToConvert > MAX_CONVERSION_SAMPLES )
+            {
+                printf("Format conversion buffer too small!\n");
+                return paComplete;
+            }
             PaQa_ConvertFromFloat( out, framesPerBuffer * channelsPerFrame, outFormat, outputBuffer );
         }
         printf( "OK" );
     }
-    printf( ", %d/%d/%d/%d ",
+    printf( ", %d/%d,%d/%d ",
            loopbackContext.inputOverflowCount,
            loopbackContext.inputUnderflowCount,
            loopbackContext.outputOverflowCount,
     const char *sampleFormatNames[] = { "paUInt8", "paInt8", "paInt16", "paInt32" };
     int numSampleFormats = (sizeof(sampleFormats)/sizeof(PaSampleFormat));
-    printf( "=============== Analysing Loopback %d to %d ====================\n", outputDevice, inputDevice  );
+    printf( "=============== Analysing Loopback %d to %d =====================\n", outputDevice, inputDevice  );
     printf( "    Devices: %s => %s\n", outputDeviceInfo->name, inputDeviceInfo->name);
     PaQa_SetDefaultTestParameters( &testParams, inputDevice, outputDevice );
         testParams.flags = flagSettings[iFlags];
         printf( "\n************ Mode = %s ************\n",
                (( testParams.flags & 1 ) ? s_FlagOnNames[0] : s_FlagOffNames[0]) );
-        printf("|-   requested  -|- measured ----------------------------------------------->\n");
+        printf("|-   requested  -|- measured ------------------------------\n");
-        printf("|-sRate-|-fr/buf-|- frm/buf -|-latency-|-channel results-------------------->\n");
+        printf("|-sRate-|-fr/buf-|- frm/buf -|-latency-|- channel results -\n");
         // Loop though various sample rates.
         if( userOptions->sampleRate < 0 )
     PaQa_SetupLoopbackContext( &loopbackContext, &testParams );
-    testParams.flags = PAQA_FLAG_TWO_STREAMS;
+    if( inputDevice == outputDevice )
+    {
+        // Use full duplex if checking for loopback on one device.
+        testParams.flags &= ~PAQA_FLAG_TWO_STREAMS;
+    }
+    else
+    {
+        // Use half duplex if checking for loopback on two different device.
+        testParams.flags = PAQA_FLAG_TWO_STREAMS;
+    }
     err = PaQa_RunLoopback( &loopbackContext );
     QA_ASSERT_TRUE("loopback detection callback did not run", (loopbackContext.callbackCount > 1) );