From 5a264c24313fec8378cea7aa61a7ae560ce564d5 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <xdsopl@gmail.com>
Date: Wed, 1 May 2024 14:11:13 +0200
Subject: [PATCH] don't change the mode until end on header detection

---
 app/src/main/java/xdsopl/robot36/Decoder.java | 20 +++++++++++--------
 .../java/xdsopl/robot36/MainActivity.java     |  1 -
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/app/src/main/java/xdsopl/robot36/Decoder.java b/app/src/main/java/xdsopl/robot36/Decoder.java
index 38af30b..c79b6b3 100644
--- a/app/src/main/java/xdsopl/robot36/Decoder.java
+++ b/app/src/main/java/xdsopl/robot36/Decoder.java
@@ -54,6 +54,7 @@ public class Decoder {
 	Decoder(PixelBuffer scopeBuffer, PixelBuffer imageBuffer, int sampleRate) {
 		this.scopeBuffer = scopeBuffer;
 		this.imageBuffer = imageBuffer;
+		imageBuffer.line = -1;
 		pixelBuffer = new PixelBuffer(scopeBuffer.width, 2);
 		demodulator = new Demodulator(sampleRate);
 		double syncPulseFilterSeconds = 0.0025;
@@ -347,10 +348,14 @@ public class Decoder {
 		if (scanLineStdDev(lines, mean) > scanLineToleranceSamples)
 			return false;
 		float frequencyOffset = (float) frequencyOffsetMean(freqOffs);
-		Mode mode = detectMode(modes, scanLineSamples);
-		boolean pictureChanged = lastMode != mode
-			|| Math.abs(lastScanLineSamples - scanLineSamples) > scanLineToleranceSamples
-			|| Math.abs(lastSyncPulseIndex + scanLineSamples - pulses[pulses.length - 1]) > syncPulseToleranceSamples;
+		boolean pictureChanged = false;
+		if (imageBuffer.line < 0 || imageBuffer.line >= imageBuffer.height) {
+			Mode prevMode = lastMode;
+			lastMode = detectMode(modes, scanLineSamples);
+			pictureChanged = lastMode != prevMode
+				|| Math.abs(lastScanLineSamples - scanLineSamples) > scanLineToleranceSamples
+				|| Math.abs(lastSyncPulseIndex + scanLineSamples - pulses[pulses.length - 1]) > syncPulseToleranceSamples;
+		}
 		if (pictureChanged) {
 			drawLines(0xff000000, 10);
 			drawLines(0xff00ffff, 8);
@@ -361,15 +366,14 @@ public class Decoder {
 			int extrapolate = endPulse / scanLineSamples;
 			int firstPulse = endPulse - extrapolate * scanLineSamples;
 			for (int pulseIndex = firstPulse; pulseIndex < endPulse; pulseIndex += scanLineSamples)
-				copyLines(mode.decodeScanLine(pixelBuffer, scratchBuffer, scanLineBuffer, scopeBuffer.width, pulseIndex, scanLineSamples, frequencyOffset));
+				copyLines(lastMode.decodeScanLine(pixelBuffer, scratchBuffer, scanLineBuffer, scopeBuffer.width, pulseIndex, scanLineSamples, frequencyOffset));
 		}
 		for (int i = pictureChanged ? 0 : lines.length - 1; i < lines.length; ++i)
-			copyLines(mode.decodeScanLine(pixelBuffer, scratchBuffer, scanLineBuffer, scopeBuffer.width, pulses[i], lines[i], frequencyOffset));
-		lastMode = mode;
+			copyLines(lastMode.decodeScanLine(pixelBuffer, scratchBuffer, scanLineBuffer, scopeBuffer.width, pulses[i], lines[i], frequencyOffset));
 		lastSyncPulseIndex = pulses[pulses.length - 1];
 		lastScanLineSamples = scanLineSamples;
 		lastFrequencyOffset = frequencyOffset;
-		shiftSamples(lastSyncPulseIndex + mode.getBegin());
+		shiftSamples(lastSyncPulseIndex + lastMode.getBegin());
 		return true;
 	}
 
diff --git a/app/src/main/java/xdsopl/robot36/MainActivity.java b/app/src/main/java/xdsopl/robot36/MainActivity.java
index 0210450..28bc2ad 100644
--- a/app/src/main/java/xdsopl/robot36/MainActivity.java
+++ b/app/src/main/java/xdsopl/robot36/MainActivity.java
@@ -363,7 +363,6 @@ public class MainActivity extends AppCompatActivity {
 		peakMeterBuffer = new PixelBuffer(1, 16);
 		createPeakMeter();
 		imageBuffer = new PixelBuffer(640, 496);
-		imageBuffer.line = -1;
 		List<String> permissions = new ArrayList<>();
 		if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
 			permissions.add(Manifest.permission.RECORD_AUDIO);