Added HF Fax mode

app/src/main/java/xdsopl/robot36/Decoder.java

@@ -38,6 +38,7 @@ public class Decoder {
 	private final int visCodeBitSamples;
 	private final int visCodeSamples;
 	private final Mode rawMode;
+	private final Mode hfFaxMode;
 	private final ArrayList<Mode> syncPulse5msModes;
 	private final ArrayList<Mode> syncPulse9msModes;
 	private final ArrayList<Mode> syncPulse20msModes;
@@ -95,6 +96,7 @@ public class Decoder {
 		double scanLineToleranceSeconds = 0.001;
 		scanLineToleranceSamples = (int) Math.round(scanLineToleranceSeconds * sampleRate);
 		rawMode = new RawDecoder(rawName, sampleRate);
+		hfFaxMode = new HFFax(sampleRate);
 		Mode robot36 = new Robot_36_Color(sampleRate);
 		currentMode = robot36;
 		currentScanLineSamples = robot36.getScanLineSamples();
@@ -454,6 +456,8 @@ public class Decoder {
 			mode = findMode(syncPulse9msModes, name);
 		if (mode == null)
 			mode = findMode(syncPulse20msModes, name);
+		if (mode == null && hfFaxMode.getName().equals(name))
+			mode = hfFaxMode;
 		if (mode == currentMode) {
 			lockMode = true;
 			return;

app/src/main/java/xdsopl/robot36/HFFax.java

@@ -1,22 +1,31 @@
 /*
-Raw decoder
+HF Fax mode
 
-Copyright 2024 Ahmet Inan <xdsopl@gmail.com>
+Copyright 2025 Marek Ossowski <marek0ossowski@gmail.com>
 */
 
 package xdsopl.robot36;
 
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Rect;
+
+/**
+ * HF Fax, IOC 576, 120 lines per minute
+ */
 public class HFFax extends BaseMode {
 	private final ExponentialMovingAverage lowPassFilter;
-	private final int smallPictureMaxSamples;
-	private final int mediumPictureMaxSamples;
 	private final String name;
+	private final int sampleRate;
+	private final float[] cumulated;
+	private int horizontalShift = 0;
 
-	HFFax(String name, int sampleRate) {
-		this.name = name;
-		smallPictureMaxSamples = (int) Math.round(0.125 * sampleRate);
-		mediumPictureMaxSamples = (int) Math.round(0.175 * sampleRate);
+	HFFax(int sampleRate) {
+		this.name = "HF Fax";
 		lowPassFilter = new ExponentialMovingAverage();
+		this.sampleRate = sampleRate;
+		cumulated = new float[getWidth()];
 	}
 
 	private float freqToLevel(float frequency, float offset) {
@@ -35,12 +44,12 @@ public class HFFax extends BaseMode {
 
 	@Override
 	public int getWidth() {
-		return -1;
+		return 640;
 	}
 
 	@Override
 	public int getHeight() {
-		return -1;
+		return 1200;
 	}
 
 	@Override
@@ -55,33 +64,72 @@ public class HFFax extends BaseMode {
 
 	@Override
 	public int getScanLineSamples() {
-		return -1;
+		return sampleRate / 2;
 	}
 
 	@Override
 	public void resetState() {
 	}
 
+	@Override
+	public Bitmap postProcessScopeImage(Bitmap bmp) {
+		int realWidth = 1808;
+		int realHorizontalShift = horizontalShift * realWidth / getWidth();
+		Bitmap bmpMutable = Bitmap.createBitmap(realWidth, bmp.getHeight(), Bitmap.Config.ARGB_8888);
+		Canvas canvas = new Canvas(bmpMutable);
+		if (horizontalShift > 0) {
+			canvas.drawBitmap(
+					bmp,
+					new Rect(0, 0, horizontalShift, bmp.getHeight()),
+					new Rect(realWidth - realHorizontalShift, 0, realWidth, bmp.getHeight()),
+					null);
+		}
+		canvas.drawBitmap(
+				bmp,
+				new Rect(horizontalShift, 0, getWidth(), bmp.getHeight()),
+				new Rect(0, 1, realWidth - realHorizontalShift, bmp.getHeight() + 1),
+				null);
+
+		return bmpMutable;
+	}
+
 	@Override
 	public boolean decodeScanLine(PixelBuffer pixelBuffer, float[] scratchBuffer, float[] scanLineBuffer, int scopeBufferWidth, int syncPulseIndex, int scanLineSamples, float frequencyOffset) {
 		if (syncPulseIndex < 0 || syncPulseIndex + scanLineSamples > scanLineBuffer.length)
 			return false;
-		int horizontalPixels = scopeBufferWidth;
-		if (scanLineSamples < smallPictureMaxSamples)
-			horizontalPixels /= 2;
-		if (scanLineSamples < mediumPictureMaxSamples)
-			horizontalPixels /= 2;
+		int horizontalPixels = getWidth();
 		lowPassFilter.cutoff(horizontalPixels, 2 * scanLineSamples, 2);
 		lowPassFilter.reset();
 		for (int i = 0; i < scanLineSamples; ++i)
-			scratchBuffer[i] = lowPassFilter.avg(scanLineBuffer[syncPulseIndex + i]);
+			scratchBuffer[i] = lowPassFilter.avg(scanLineBuffer[i]);
 		lowPassFilter.reset();
 		for (int i = scanLineSamples - 1; i >= 0; --i)
 			scratchBuffer[i] = freqToLevel(lowPassFilter.avg(scratchBuffer[i]), frequencyOffset);
 		for (int i = 0; i < horizontalPixels; ++i) {
 			int position = (i * scanLineSamples) / horizontalPixels;
-			pixelBuffer.pixels[i] = ColorConverter.GRAY(scratchBuffer[position]);
+			int color = ColorConverter.GRAY(scratchBuffer[position]);
+			pixelBuffer.pixels[i] = color;
+
+			//accumulate recent values, forget old
+			float decay = 0.99f;
+			cumulated[i] = cumulated[i] * decay + Color.luminance(color) * (1 - decay);
 		}
+
+		//try to detect "sync": thick white margin
+		int bestIndex = 0;
+		float bestValue = 0;
+		for (int x = 0; x < getWidth(); ++x)
+		{
+			float val = cumulated[x];
+			if (val > bestValue)
+			{
+				bestIndex = x;
+				bestValue = val;
+			}
+		}
+
+		horizontalShift = bestIndex;
+
 		pixelBuffer.width = horizontalPixels;
 		pixelBuffer.height = 1;
 		return true;

app/src/main/java/xdsopl/robot36/MainActivity.java

@@ -618,6 +618,10 @@ public class MainActivity extends AppCompatActivity {
 			setMode(R.string.raw_mode);
 			return true;
 		}
+		if (id == R.id.action_force_hffax_mode) {
+			setMode(R.string.hf_fax);
+			return true;
+		}
 		if (id == R.id.action_force_robot36_color) {
 			setMode(R.string.robot36_color);
 			return true;

app/src/main/res/menu/menu_main.xml

@@ -97,6 +97,9 @@
 								android:title="@string/wraase_sc2_180" />
 						</menu>
 					</item>
+					<item
+						android:id="@+id/action_force_hffax_mode"
+						android:title="@string/hf_fax" />
 					<item
 						android:id="@+id/action_force_raw_mode"
 						android:icon="@drawable/baseline_image_not_supported_24"

app/src/main/res/values/strings.xml

@@ -21,6 +21,7 @@
 	<string name="scottie2" translatable="false">Scottie 2</string>
 	<string name="scottie_dx" translatable="false">Scottie DX</string>
 	<string name="wraase_sc2_180" translatable="false">Wraase SC2–180</string>
+	<string name="hf_fax" translatable="false">HF Fax</string>
 	<string name="rate_8000" translatable="false">8 kHz</string>
 	<string name="rate_16000" translatable="false">16 kHz</string>
 	<string name="rate_32000" translatable="false">32 kHz</string>