diff --git a/app/src/main/java/xdsopl/robot36/Decoder.java b/app/src/main/java/xdsopl/robot36/Decoder.java
index d28bd32..b3b98b5 100644
--- a/app/src/main/java/xdsopl/robot36/Decoder.java
+++ b/app/src/main/java/xdsopl/robot36/Decoder.java
@@ -13,9 +13,9 @@ public class Decoder {
 
 	private final Demodulator demodulator;
 	private final PixelBuffer pixelBuffer;
+	private final PixelBuffer scopeBuffer;
 	private final float[] scanLineBuffer;
 	private final float[] scratchBuffer;
-	private final int[] scopePixels;
 	private final int[] last5msSyncPulses;
 	private final int[] last9msSyncPulses;
 	private final int[] last20msSyncPulses;
@@ -28,8 +28,6 @@ public class Decoder {
 	private final int scanLineReserveSamples;
 	private final int syncPulseToleranceSamples;
 	private final int scanLineToleranceSamples;
-	private final int scopeWidth;
-	private final int scopeHeight;
 	private final Mode rawMode;
 	private final ArrayList<Mode> syncPulse5msModes;
 	private final ArrayList<Mode> syncPulse9msModes;
@@ -42,11 +40,9 @@ public class Decoder {
 	private int lastScanLineSamples;
 	private float lastFrequencyOffset;
 
-	Decoder(int[] scopePixels, int scopeWidth, int scopeHeight, int sampleRate) {
-		this.scopePixels = scopePixels;
-		this.scopeWidth = scopeWidth;
-		this.scopeHeight = scopeHeight;
-		pixelBuffer = new PixelBuffer(scopeWidth, 2);
+	Decoder(PixelBuffer scopeBuffer, int sampleRate) {
+		this.scopeBuffer = scopeBuffer;
+		pixelBuffer = new PixelBuffer(scopeBuffer.width, 2);
 		demodulator = new Demodulator(sampleRate);
 		double scanLineMaxSeconds = 7;
 		int scanLineMaxSamples = (int) Math.round(scanLineMaxSeconds * sampleRate);
@@ -139,11 +135,11 @@ public class Decoder {
 		if (!okay)
 			return;
 		for (int row = 0; row < pixelBuffer.height; ++row) {
-			System.arraycopy(pixelBuffer.pixels, row * pixelBuffer.width, scopePixels, scopeWidth * curLine, pixelBuffer.width);
-			Arrays.fill(scopePixels, scopeWidth * curLine + pixelBuffer.width, scopeWidth * curLine + scopeWidth, 0);
-			System.arraycopy(pixelBuffer.pixels, row * pixelBuffer.width, scopePixels, scopeWidth * (curLine + scopeHeight), pixelBuffer.width);
-			Arrays.fill(scopePixels, scopeWidth * (curLine + scopeHeight) + pixelBuffer.width, scopeWidth * (curLine + scopeHeight) + scopeWidth, 0);
-			curLine = (curLine + 1) % scopeHeight;
+			System.arraycopy(pixelBuffer.pixels, row * pixelBuffer.width, scopeBuffer.pixels, scopeBuffer.width * curLine, pixelBuffer.width);
+			Arrays.fill(scopeBuffer.pixels, scopeBuffer.width * curLine + pixelBuffer.width, scopeBuffer.width * curLine + scopeBuffer.width, 0);
+			System.arraycopy(pixelBuffer.pixels, row * pixelBuffer.width, scopeBuffer.pixels, scopeBuffer.width * (curLine + scopeBuffer.height / 2), pixelBuffer.width);
+			Arrays.fill(scopeBuffer.pixels, scopeBuffer.width * (curLine + scopeBuffer.height / 2) + pixelBuffer.width, scopeBuffer.width * (curLine + scopeBuffer.height / 2) + scopeBuffer.width, 0);
+			curLine = (curLine + 1) % (scopeBuffer.height / 2);
 		}
 	}
 
@@ -170,7 +166,7 @@ public class Decoder {
 		boolean pictureChanged = lastMode != mode
 			|| Math.abs(lastScanLineSamples - scanLineSamples) > scanLineToleranceSamples
 			|| Math.abs(lastSyncPulseIndex + scanLineSamples - pulses[pulses.length - 1]) > syncPulseToleranceSamples;
-		pixelBuffer.width = scopeWidth;
+		pixelBuffer.width = scopeBuffer.width;
 		if (pulses[0] >= scanLineSamples && pictureChanged) {
 			int endPulse = pulses[0];
 			int extrapolate = endPulse / scanLineSamples;
@@ -224,7 +220,7 @@ public class Decoder {
 					return processSyncPulse(syncPulse20msModes, last20msFrequencyOffsets, last20msSyncPulses, last20msScanLines, syncPulseIndex);
 			}
 		} else if (lastSyncPulseIndex >= scanLineReserveSamples && curSample > lastSyncPulseIndex + (lastScanLineSamples * 5) / 4) {
-			pixelBuffer.width = scopeWidth;
+			pixelBuffer.width = scopeBuffer.width;
 			copyLines(lastMode.decodeScanLine(pixelBuffer, scratchBuffer, scanLineBuffer, lastSyncPulseIndex, lastScanLineSamples, lastFrequencyOffset));
 			lastSyncPulseIndex += lastScanLineSamples;
 			return true;
diff --git a/app/src/main/java/xdsopl/robot36/MainActivity.java b/app/src/main/java/xdsopl/robot36/MainActivity.java
index 0172722..fc6ed8e 100644
--- a/app/src/main/java/xdsopl/robot36/MainActivity.java
+++ b/app/src/main/java/xdsopl/robot36/MainActivity.java
@@ -30,9 +30,8 @@ import java.util.List;
 
 public class MainActivity extends AppCompatActivity {
 
-	private final int scopeWidth = 640, scopeHeight = 1280;
 	private Bitmap scopeBitmap;
-	private int[] scopePixels;
+	private PixelBuffer scopeBuffer;
 	private ImageView scopeView;
 	private float[] recordBuffer;
 	private AudioRecord audioRecord;
@@ -52,7 +51,7 @@ public class MainActivity extends AppCompatActivity {
 		public void onPeriodicNotification(AudioRecord audioRecord) {
 			audioRecord.read(recordBuffer, 0, recordBuffer.length, AudioRecord.READ_BLOCKING);
 			if (decoder.process(recordBuffer)) {
-				scopeBitmap.setPixels(scopePixels, scopeWidth * decoder.curLine, scopeWidth, 0, 0, scopeWidth, scopeHeight);
+				scopeBitmap.setPixels(scopeBuffer.pixels, scopeBuffer.width * decoder.curLine, scopeBuffer.width, 0, 0, scopeBuffer.width, scopeBuffer.height / 2);
 				scopeView.invalidate();
 				status.setText(decoder.lastMode.getName());
 			}
@@ -75,7 +74,7 @@ public class MainActivity extends AppCompatActivity {
 			if (audioRecord.getState() == AudioRecord.STATE_INITIALIZED) {
 				audioRecord.setRecordPositionUpdateListener(recordListener);
 				audioRecord.setPositionNotificationPeriod(recordBuffer.length);
-				decoder = new Decoder(scopePixels, scopeWidth, scopeHeight, sampleRate);
+				decoder = new Decoder(scopeBuffer, sampleRate);
 				startListening();
 			} else {
 				setStatus(R.string.audio_init_failed);
@@ -128,9 +127,11 @@ public class MainActivity extends AppCompatActivity {
 		});
 		status = findViewById(R.id.status);
 		scopeView = findViewById(R.id.scope);
+		int scopeWidth = 640;
+		int scopeHeight = 1280;
 		scopeBitmap = Bitmap.createBitmap(scopeWidth, scopeHeight, Bitmap.Config.ARGB_8888);
 		scopeView.setImageBitmap(scopeBitmap);
-		scopePixels = new int[2 * scopeWidth * scopeHeight];
+		scopeBuffer = new PixelBuffer(scopeWidth, 2 * scopeHeight);
 		List<String> permissions = new ArrayList<>();
 		if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
 			permissions.add(Manifest.permission.RECORD_AUDIO);
diff --git a/app/src/main/java/xdsopl/robot36/PixelBuffer.java b/app/src/main/java/xdsopl/robot36/PixelBuffer.java
index 55f14d3..2b29935 100644
--- a/app/src/main/java/xdsopl/robot36/PixelBuffer.java
+++ b/app/src/main/java/xdsopl/robot36/PixelBuffer.java
@@ -12,6 +12,8 @@ public class PixelBuffer {
 	public int height;
 
 	PixelBuffer(int width, int height) {
-		pixels = new int[width * height];
+		this.width = width;
+		this.height = height;
+		this.pixels = new int[width * height];
 	}
 }