diff --git a/src/main/java/mpo/dayon/assisted/capture/CaptureEngine.java b/src/main/java/mpo/dayon/assisted/capture/CaptureEngine.java
index a6e68403..918864c5 100644
--- a/src/main/java/mpo/dayon/assisted/capture/CaptureEngine.java
+++ b/src/main/java/mpo/dayon/assisted/capture/CaptureEngine.java
@@ -2,7 +2,6 @@
 
 import java.awt.*;
 import java.util.Arrays;
-import java.util.Objects;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import mpo.dayon.common.capture.Capture;
@@ -132,7 +131,7 @@ private void mainLoop() throws InterruptedException {
             fireOnRawCaptured(captureId, pixels); // debugging purpose (!)
             final CaptureTile[] dirty = computeDirtyTiles(captureId, pixels, captureFactory.getDimension());
 
-            if (!Arrays.stream(dirty).allMatch(Objects::isNull)) {
+            if (dirty != null) {
                 final Capture capture = new Capture(captureId, reset.get(), skipped, 0, captureFactory.getDimension(), TILE_DIMENSION, dirty);
                 fireOnCaptured(capture); // might update the capture (i.e., merging with previous not sent yet)
                 updatePreviousCapture(capture);
@@ -184,7 +183,7 @@ private CaptureTile[] computeDirtyTiles(int captureId, byte[] capture, Dimension
             previousCapture = new long[length];
             resetPreviousCapture();
         }
-        CaptureTile[] dirty = new CaptureTile[length];
+        CaptureTile[] dirty = null;
         int tileId = 0;
         for (int ty = 0; ty < captureDimension.height; ty += TILE_DIMENSION.height) {
             final int th = min(captureDimension.height - ty, TILE_DIMENSION.height);
@@ -194,6 +193,9 @@ private CaptureTile[] computeDirtyTiles(int captureId, byte[] capture, Dimension
                 final byte[] tileData = createTile(capture, captureDimension.width, offset, tw, th);
                 final long cs = CaptureTile.computeChecksum(tileData, 0, tileData.length);
                 if (cs != previousCapture[tileId]) {
+                    if (dirty == null) {
+                        dirty = new CaptureTile[length];
+                    }
                     dirty[tileId] = new CaptureTile(captureId, tileId, cs, new Position(tx, ty), tw, th, tileData);
                 }
                 ++tileId;
diff --git a/src/main/java/mpo/dayon/common/buffer/MemByteBuffer.java b/src/main/java/mpo/dayon/common/buffer/MemByteBuffer.java
index 068dde57..83ffd708 100644
--- a/src/main/java/mpo/dayon/common/buffer/MemByteBuffer.java
+++ b/src/main/java/mpo/dayon/common/buffer/MemByteBuffer.java
@@ -127,8 +127,4 @@ private void increaseBuffer(int newCount) {
 			buffer = Arrays.copyOf(buffer, Math.max(buffer.length << 1, newCount));
 		}
 	}
-
-	public final MemByteBuffer copy() {
-		return new MemByteBuffer(buffer);
-	}
 }
diff --git a/src/main/java/mpo/dayon/common/capture/Capture.java b/src/main/java/mpo/dayon/common/capture/Capture.java
index 653eefc1..288fea95 100644
--- a/src/main/java/mpo/dayon/common/capture/Capture.java
+++ b/src/main/java/mpo/dayon/common/capture/Capture.java
@@ -43,8 +43,8 @@ public Capture(int captureId, boolean reset, int skipped, int merged, Dimension
 		this.reset = reset;
 		this.skipped = new AtomicInteger(skipped);
 		this.merged = new AtomicInteger(merged);
-		this.captureDimension = new Dimension(captureDimension);
-		this.tileDimension = new Dimension(tileDimension);
+		this.captureDimension = captureDimension;
+		this.tileDimension = tileDimension;
 		this.dirty = dirty.clone();
 	}
 
diff --git a/src/main/java/mpo/dayon/common/capture/CaptureTile.java b/src/main/java/mpo/dayon/common/capture/CaptureTile.java
index 778a5253..38b9629f 100644
--- a/src/main/java/mpo/dayon/common/capture/CaptureTile.java
+++ b/src/main/java/mpo/dayon/common/capture/CaptureTile.java
@@ -68,7 +68,7 @@ public CaptureTile(int captureId, int id, XYWH xywh, MemByteBuffer capture) {
 		this.position = new Position(xywh.x, xywh.y);
 		this.width = xywh.w;
 		this.height = xywh.h;
-		this.capture = capture.copy();
+		this.capture = capture;
 		if (width * height != capture.size()) {
 			throw new IllegalArgumentException("Ouch!");
 		}
@@ -149,7 +149,7 @@ public int getHeight() {
 	}
 
 	public MemByteBuffer getCapture() {
-		return capture.copy();
+		return capture;
 	}
 
 	/**
diff --git a/src/main/java/mpo/dayon/common/compressor/CompressorEngineConfiguration.java b/src/main/java/mpo/dayon/common/compressor/CompressorEngineConfiguration.java
index ff3d3332..2b6ddea2 100644
--- a/src/main/java/mpo/dayon/common/compressor/CompressorEngineConfiguration.java
+++ b/src/main/java/mpo/dayon/common/compressor/CompressorEngineConfiguration.java
@@ -31,11 +31,7 @@ public class CompressorEngineConfiguration extends Configuration {
      */
     public CompressorEngineConfiguration() {
         final Preferences prefs = Preferences.getPreferences();
-
-        // Note: did not exist in version = 0 => no migration is required.
-
-        this.method = prefs.getEnumPreference(PREF_METHOD, CompressionMethod.XZ, CompressionMethod.values());
-
+        this.method = prefs.getEnumPreference(PREF_METHOD, CompressionMethod.ZIP, CompressionMethod.values());
         this.useCache = prefs.getBooleanPreference(PREF_USE_CACHE, true);
         this.maxSize = prefs.getIntPreference(PREF_CACHE_MAX_SIZE, RegularTileCache.DEFAULT_MAX_SIZE);
         this.purgeSize = prefs.getIntPreference(PREF_CACHE_PURGE_SIZE, RegularTileCache.DEFAULT_PURGE_SIZE);
diff --git a/src/main/java/mpo/dayon/common/network/message/NetworkCaptureMessage.java b/src/main/java/mpo/dayon/common/network/message/NetworkCaptureMessage.java
index c7e9addb..b85fa0a7 100644
--- a/src/main/java/mpo/dayon/common/network/message/NetworkCaptureMessage.java
+++ b/src/main/java/mpo/dayon/common/network/message/NetworkCaptureMessage.java
@@ -98,7 +98,7 @@ public static NetworkCaptureMessage unmarshall(ObjectInputStream in) throws IOEx
 	}
 
 	public MemByteBuffer getPayload() {
-		return payload.copy();
+		return payload;
 	}
 
 	public String toString() {
diff --git a/src/main/java/mpo/dayon/common/squeeze/XzZipper.java b/src/main/java/mpo/dayon/common/squeeze/XzZipper.java
index 67e1cf48..4ce644bd 100644
--- a/src/main/java/mpo/dayon/common/squeeze/XzZipper.java
+++ b/src/main/java/mpo/dayon/common/squeeze/XzZipper.java
@@ -6,10 +6,21 @@
 import java.io.*;
 
 public class XzZipper implements Zipper {
-	@Override
+
+	private final FilterOptions options;
+
+    XzZipper() {
+        try {
+            options = new LZMA2Options(3);
+        } catch (UnsupportedOptionsException e) {
+            throw new IllegalArgumentException(e);
+        }
+    }
+
+    @Override
     public MemByteBuffer zip(MemByteBuffer unCompressed) throws IOException {
 		try (MemByteBuffer compressed = new MemByteBuffer()) {
-			try (XZOutputStream xzOutputStream = new XZOutputStream(compressed, new LZMA2Options(6))) {
+			try (XZOutputStream xzOutputStream = new XZOutputStream(compressed, options)) {
 				xzOutputStream.write(unCompressed.getInternal(), 0, unCompressed.size());
 				xzOutputStream.flush();
 			}