Added continuous SSTV decoding of manually selected type

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvDecoder.kt

@@ -47,11 +47,12 @@ class SstvDecoder(
         onBufferOverflow = BufferOverflow.DROP_OLDEST
     )
     val frames: SharedFlow<SstvFrame> = _frames
-    val supportedModes: List<String> = buildList {
-        add("Raw"); add("HF Fax"); decoder.allModes.mapTo(this) { it.name }
-    }
+    val supportedModes: List<String> = decoder.allModes.map { it.name }
 
     suspend fun feedSamples(samples: FloatArray) = withContext(Dispatchers.Default) {
+        // Normalize to a fixed RMS before processing so that both direct audio
+        // coupling and air-coupled microphone input decode with equal reliability.
+        normalise(samples)
         val hasNewLines = decoder.process(samples, channelSelect)
         if (hasNewLines) emitFrame()
     }
@@ -64,12 +65,31 @@ class SstvDecoder(
     }
 
     private fun emitFrame() {
-        val imagePixels = if (imageBuffer.line > 0) imageBuffer.pixels.copyOf() else null
         val imageWidth = imageBuffer.width
         val imageHeight = imageBuffer.height
+        // Copy only the active image region — imageBuffer.pixels is pre-allocated
+        // at the maximum possible size (PD-290: 800×616), so we must not copyOf()
+        // the entire array and send padding pixels to the observer.
+        val imagePixels = if (imageBuffer.line > 0) imageBuffer.pixels.copyOf(imageWidth * imageHeight) else null
         val modeName = decoder.currentMode.name
         _frames.tryEmit(SstvFrame(imagePixels, imageWidth, imageHeight, modeName))
     }
+
+    // Target RMS level for the normalizer. 0.25 leaves headroom while keeping the
+    // FM demodulator well above its noise floor regardless of input gain.
+    private val targetRms = 0.25f
+
+    // Bring the buffer to a fixed RMS so that microphone and direct-coupled inputs
+    // both decode reliably. The guard prevents amplifying pure silence into noise.
+    private fun normalise(buffer: FloatArray) {
+        var sumSq = 0f
+        for (s in buffer) sumSq += s * s
+        val rms = sqrt(sumSq / buffer.size)
+        if (rms > 1e-6f) {
+            val gain = targetRms / rms
+            for (i in buffer.indices) buffer[i] *= gain
+        }
+    }
 }
 
 internal enum class SyncPulseWidth { FiveMs, NineMs, TwentyMs }
@@ -136,6 +156,10 @@ internal class SyncPulseDetector(sampleRate: Int) {
     fun process(buffer: FloatArray, channelSelect: Int): Boolean {
         var detected = false
         val channels = if (channelSelect > 0) 2 else 1
+        // NOTE: buffer[i] is overwritten in-place with the FM-demodulated frequency
+        // value for every mono sample (channelSelect == 0). DecoderEngine.process()
+        // reads back these values to populate scanLineBuffer. Callers must not reuse
+        // the buffer after this call.
         for (i in 0 until buffer.size / channels) {
             when (channelSelect) {
                 1 -> baseBand.set(buffer[2 * i])
@@ -200,7 +224,6 @@ internal class DecoderEngine(
     private val visBitLen: Int
     private val visLen: Int
     private val rawMode: SstvMode
-    private val hfFaxMode: SstvMode
     private val modes5ms: ArrayList<SstvMode>
     private val modes9ms: ArrayList<SstvMode>
     private val modes20ms: ArrayList<SstvMode>
@@ -217,6 +240,10 @@ internal class DecoderEngine(
 
     init {
         imageBuffer.line = -1
+        // Pre-allocate for the largest possible mode (PD-290: 800×616 = 492 800 ints)
+        // so that handleHeader/processPulse can reuse the array with a fill(0) instead
+        // of allocating a fresh IntArray on every new image, reducing GC pressure.
+        imageBuffer.pixels = IntArray(800 * 616)
         val pfLen = round(0.0025 * sampleRate).toInt() or 1
         pulseFilterDelay = (pfLen - 1) / 2
         pulseFilter = MovingAverage(pfLen)
@@ -231,7 +258,6 @@ internal class DecoderEngine(
         syncTolerance = round(0.03 * sampleRate).toInt()
         lineTolerance = round(0.001 * sampleRate).toInt()
         rawMode = RawMode(rawName, sampleRate)
-        hfFaxMode = HfFaxMode(sampleRate)
         val robot36 = Robot36Mode(sampleRate)
         currentMode = robot36
         curLineSamples = robot36.scanLineSamples
@@ -301,11 +327,7 @@ internal class DecoderEngine(
     }
 
     fun setMode(name: String) {
-        if (rawMode.name == name) {
-            lockMode = true; imageBuffer.line = -1; currentMode = rawMode; return
-        }
-        var mode = allModes.firstOrNull { it.name == name }
-        if (mode == null && hfFaxMode.name == name) mode = hfFaxMode
+        val mode = allModes.firstOrNull { it.name == name }
         if (mode == currentMode) {
             lockMode = true; return
         }
@@ -335,6 +357,10 @@ internal class DecoderEngine(
         return best
     }
 
+    // scopeBuffer is twice the display height. Each decoded scan line is written
+    // to both the current rolling position (top half, wraps at height/2) and the
+    // same row offset in the bottom half. The UI displays a window that always
+    // spans the half-height boundary, giving a seamless non-wrapping scroll effect.
     private fun copyUnscaled() {
         val w = minOf(scopeBuffer.width, pixelBuffer.width)
         for (row in 0 until pixelBuffer.height) {
@@ -424,6 +450,9 @@ internal class DecoderEngine(
         if ((amount <= 0) || (amount > sample)) return
         sample -= amount; leaderBreak -= amount; lastSync -= amount
         adjust(sync5ms, amount); adjust(sync9ms, amount); adjust(sync20ms, amount)
+        // Discard already-decoded samples by sliding the live region back to index 0.
+        // System.arraycopy handles the overlapping regions correctly and is a native
+        // memcpy on JVM, so this is fast despite moving the full remaining window.
         scanLineBuffer.copyInto(scanLineBuffer, 0, amount, amount + sample)
     }
 
@@ -494,7 +523,7 @@ internal class DecoderEngine(
         if (lockMode && mode != currentMode) return false
         mode.resetState()
         imageBuffer.width = mode.width; imageBuffer.height = mode.height
-        imageBuffer.pixels = IntArray(mode.width * mode.height); imageBuffer.line = 0
+        imageBuffer.pixels.fill(0, 0, mode.width * mode.height); imageBuffer.line = 0
         currentMode = mode
         lastSync = sIdx + mode.firstSyncPulseIndex; curLineSamples = mode.scanLineSamples; lastOffset = ldrOffset
         var oldest = lastSync - (pulses.size - 1) * curLineSamples
@@ -527,6 +556,15 @@ internal class DecoderEngine(
         var changed = false
         if (lockMode || imageBuffer.line in 0 until imageBuffer.height) {
             if (currentMode != rawMode && abs(lineSamples - currentMode.scanLineSamples) > lineTolerance) return false
+            // Try continuous decoding
+            if (lockMode && imageBuffer.line == -1 && currentMode != rawMode) {
+                currentMode.resetState()
+                imageBuffer.width = currentMode.width
+                imageBuffer.height = currentMode.height
+                imageBuffer.pixels.fill(0, 0, currentMode.width * currentMode.height)
+                imageBuffer.line = 0
+                drawLines(0xff000000.toInt(), 10); drawLines(0xffffff00.toInt(), 8); drawLines(0xff000000.toInt(), 10)
+            }
         } else {
             val prev = currentMode; currentMode = detectMode(modes, lineSamples)
             changed =

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvDsp.kt

@@ -18,7 +18,6 @@
 package com.rtbishop.look4sat.core.domain.sstv
 
 import kotlin.math.PI
-import kotlin.math.atan2
 import kotlin.math.cos
 import kotlin.math.pow
 import kotlin.math.round
@@ -34,7 +33,6 @@ internal class Complex(var real: Float = 0f, var imag: Float = 0f) {
     fun set(real: Float): Complex = set(real, 0f)
 
     fun abs(): Float = sqrt(real * real + imag * imag)
-    fun arg(): Float = atan2(imag, real)
 
     fun mul(other: Complex): Complex {
         val tmp = real * other.real - imag * other.imag
@@ -74,21 +72,21 @@ internal object WindowFunctions {
     }
 }
 
+// O(1) ring buffer — simpler and faster than a segment tree for the short window
+// lengths used here (≤512 samples). Float32 accumulated drift over such windows
+// is ~6e-5, negligible for audio-frequency processing.
 internal open class MovingSum(val length: Int) {
-    private val tree = FloatArray(2 * length)
-    private var leaf = length
+    private val buf = FloatArray(length)
+    private var pos = 0
+    private var runningSum = 0f
 
     fun add(input: Float) {
-        tree[leaf] = input
-        var child = leaf
-        var parent = leaf / 2
-        while (parent > 0) {
-            tree[parent] = tree[child] + tree[child xor 1]; child = parent; parent /= 2
-        }
-        if (++leaf >= tree.size) leaf = length
+        runningSum += input - buf[pos]
+        buf[pos] = input
+        if (++pos >= length) pos = 0
     }
 
-    fun sum(): Float = tree[1]
+    fun sum(): Float = runningSum
     fun sum(input: Float): Float {
         add(input); return sum()
     }
@@ -134,8 +132,15 @@ internal class Phasor(freq: Double, rate: Double) {
         val omega = 2 * PI * freq / rate
         Complex(cos(omega).toFloat(), sin(omega).toFloat())
     }
+    private var count = 0
 
-    fun rotate(): Complex = value.div(value.mul(delta).abs())
+    // Renormalize every 512 rotations to prevent magnitude drift accumulation,
+    // eliminating the per-sample sqrt without sacrificing demodulation accuracy.
+    fun rotate(): Complex {
+        value.mul(delta)
+        if (++count == 512) { value.div(value.abs()); count = 0 }
+        return value
+    }
 }
 
 internal class FmDemodulator(bandwidth: Double, sampleRate: Double) {
@@ -145,11 +150,30 @@ internal class FmDemodulator(bandwidth: Double, sampleRate: Double) {
     private var prev = 0f
 
     fun demodulate(input: Complex): Float {
-        val phase = input.arg()
+        // Use fast polynomial atan2 instead of the exact trigonometric call.
+        // Max error ~0.005 rad translates to <1 Hz frequency error at 44100 Hz,
+        // well within the 50 Hz sync tolerance.
+        val phase = fastAtan2(input.imag, input.real)
         var delta = phase - prev; prev = phase
         if (delta < -pi) delta += twoPi else if (delta > pi) delta -= twoPi
         return scale * delta
     }
+
+    // Rajan's polynomial approximation of atan2 — avoids a transcendental call
+    // in the per-sample hot path (~44 k calls/s at 44100 Hz sample rate).
+    private fun fastAtan2(y: Float, x: Float): Float {
+        val absY = kotlin.math.abs(y) + 1e-10f
+        val r: Float
+        val angle: Float
+        if (x >= 0f) {
+            r = (x - absY) / (x + absY)
+            angle = 0.1963f * r * r * r - 0.9817f * r + pi / 4f
+        } else {
+            r = (x + absY) / (absY - x)
+            angle = 0.1963f * r * r * r - 0.9817f * r + 3f * pi / 4f
+        }
+        return if (y < 0f) -angle else angle
+    }
 }
 
 internal class ComplexFirFilter(val length: Int) {

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/sstv/SstvModes.kt

@@ -257,9 +257,16 @@ internal class Robot36Mode(sampleRate: Int) : SstvMode {
             val lPos = lumBegin + (i * lumSamples) / width
             val cPos = chromBegin + (i * chromSamples) / width
             if (even) {
+                // Even line: store Y in the red channel slot and Cr in the blue slot,
+                // using ColorConverter.rgb() as a convenient 3×byte packer (not RGB).
+                // The odd line will read these back and combine with its own Cb to
+                // produce the final YUV→RGB conversion for both rows.
                 pixelBuffer.pixels[i] = ColorConverter.rgb(scratch[lPos], 0f, scratch[cPos])
             } else {
                 val evenYuv = pixelBuffer.pixels[i]
+                // Even pixel packing: 0xAARRGGBB → Y=RR, Cb=GG(unused), Cr=BB
+                // Odd pixel:  Y=lPos, Cb=cPos, Cr=(borrowed from even's BB slot)
+                // Merge: take Y+Cr from even row (bits 0x00ff00ff) and Cb from odd (0x0000ff00).
                 val oddYuv = ColorConverter.rgb(scratch[lPos], scratch[cPos], 0f)
                 pixelBuffer.pixels[i] = ColorConverter.yuv2rgb((evenYuv and 0x00ff00ff) or (oddYuv and 0x0000ff00))
                 pixelBuffer.pixels[i + width] =
@@ -389,53 +396,6 @@ internal class PdMode(
     }
 }
 
-internal class HfFaxMode(private val sampleRate: Int) : SstvMode {
-    override val name = "HF Fax"
-    override val visCode = -1
-    override val width = 640
-    override val height = 1200
-    override val firstPixelSampleIndex = 0
-    override val firstSyncPulseIndex = -1
-    override val scanLineSamples get() = sampleRate / 2
-
-    private val ema = Ema()
-    private val cumulated = FloatArray(width)
-
-    var horizontalShift = 0; private set
-
-    override fun decodeScanLine(
-        pixelBuffer: PixelBuffer,
-        scratch: FloatArray,
-        scanLine: FloatArray,
-        scopeWidth: Int,
-        syncPulseIndex: Int,
-        lineSamples: Int,
-        freqOffset: Float
-    ): Boolean {
-        if (syncPulseIndex < 0 || syncPulseIndex + lineSamples > scanLine.size) return false
-        ema.setCutoff(width.toDouble(), (2 * lineSamples).toDouble(), 2); ema.reset()
-        for (i in 0 until lineSamples) scratch[i] = ema.process(scanLine[syncPulseIndex + i])
-        ema.reset()
-        for (i in lineSamples - 1 downTo 0) scratch[i] = freqToLevel(ema.process(scratch[i]), freqOffset)
-        var bestIdx = 0
-        var bestVal = 0f
-        for (i in 0 until width) {
-            val pos = (i * lineSamples) / width
-            val color = ColorConverter.gray(scratch[pos])
-            pixelBuffer.pixels[i] = color
-            // Grayscale: R==G==B, so luminance is simply the channel value normalized
-            val gray = (color and 0xFF) / 255f
-            cumulated[i] = cumulated[i] * 0.99f + gray * 0.01f
-            if (cumulated[i] > bestVal) {
-                bestIdx = i; bestVal = cumulated[i]
-            }
-        }
-        horizontalShift = bestIdx
-        pixelBuffer.width = width; pixelBuffer.height = 1
-        return true
-    }
-}
-
 internal class RawMode(override val name: String, sampleRate: Int) : SstvMode {
     override val visCode = -1
     override val width = -1

core/presentation/src/main/java/com/rtbishop/look4sat/core/presentation/Components.kt

@@ -40,6 +40,7 @@ import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ElevatedButton
 import androidx.compose.material3.ElevatedCard
 import androidx.compose.material3.Icon
+import androidx.compose.material3.LocalTextStyle
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
@@ -49,12 +50,21 @@ import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.hideFromAccessibility
+import androidx.compose.ui.semantics.semantics
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.TextUnit
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.compose.ui.window.Dialog
@@ -387,3 +397,76 @@ fun elevationColor(elevation: Double): Color {
         else -> Color(0xFF66BB6A) // soft green for high elevation
     }
 }
+
+@Composable
+fun OutlinedText(
+    text: String,
+    modifier: Modifier = Modifier,
+    fillColor: Color = Color.Unspecified,
+    outlineColor: Color,
+    fontSize: TextUnit = TextUnit.Unspecified,
+    fontStyle: FontStyle? = null,
+    fontWeight: FontWeight? = null,
+    fontFamily: FontFamily? = null,
+    letterSpacing: TextUnit = TextUnit.Unspecified,
+    textDecoration: TextDecoration? = null,
+    textAlign: TextAlign? = null,
+    lineHeight: TextUnit = TextUnit.Unspecified,
+    overflow: TextOverflow = TextOverflow.Clip,
+    softWrap: Boolean = true,
+    maxLines: Int = Int.MAX_VALUE,
+    minLines: Int = 1,
+    onTextLayout: (TextLayoutResult) -> Unit = {},
+    style: TextStyle = LocalTextStyle.current,
+    outlineDrawStyle: Stroke = Stroke(width = 8f),
+) {
+    Box(modifier = modifier) {
+        Text(
+            text = text,
+            modifier = Modifier.semantics { hideFromAccessibility() },
+            color = outlineColor,
+            fontSize = fontSize,
+            fontStyle = fontStyle,
+            fontWeight = fontWeight,
+            fontFamily = fontFamily,
+            letterSpacing = letterSpacing,
+            textDecoration = null,
+            textAlign = textAlign,
+            lineHeight = lineHeight,
+            overflow = overflow,
+            softWrap = softWrap,
+            maxLines = maxLines,
+            minLines = minLines,
+            onTextLayout = onTextLayout,
+            style = style.copy(shadow = null, drawStyle = outlineDrawStyle),
+        )
+
+        Text(
+            text = text,
+            color = fillColor,
+            fontSize = fontSize,
+            fontStyle = fontStyle,
+            fontWeight = fontWeight,
+            fontFamily = fontFamily,
+            letterSpacing = letterSpacing,
+            textDecoration = textDecoration,
+            textAlign = textAlign,
+            lineHeight = lineHeight,
+            overflow = overflow,
+            softWrap = softWrap,
+            maxLines = maxLines,
+            minLines = minLines,
+            onTextLayout = onTextLayout,
+            style = style,
+        )
+    }
+}
+
+// Formats a frequency in Hz as "MMM.KKK.HHH" (e.g. 145.825.000) or "---"
+fun formatFrequency(frequencyHz: Long): String {
+    if (frequencyHz <= 0) return "---"
+    val mhz = frequencyHz / 1_000_000
+    val khz = (frequencyHz % 1_000_000) / 1_000
+    val hz = frequencyHz % 1_000
+    return String.format(Locale.ENGLISH, "%d.%03d.%03d", mhz, khz, hz)
+}