Added WSPRProcessor

Author: consuelita

…foundation/audiocoder/WsprFileManager.kt …foundation/audiocoder/WSPRFileManager.ktAudioCoder/src/main/java/org/operatorfoundation/audiocoder/WsprFileManager.kt renamed to AudioCoder/src/main/java/org/operatorfoundation/audiocoder/WSPRFileManager.kt AudioCoder/src/main/java/org/operatorfoundation/audiocoder/WsprFileManager.kt renamed to AudioCoder/src/main/java/org/operatorfoundation/audiocoder/WSPRFileManager.kt

@@ -11,7 +11,7 @@ import java.nio.ByteBuffer
 import java.util.Date
 import java.util.Locale
 
-class WsprFileManager(private val context: Context)
+class WSPRFileManager(private val context: Context)
 {
     companion object
     {

AudioCoder/src/main/java/org/operatorfoundation/audiocoder/WSPRProcessor.kt

@@ -0,0 +1,134 @@
+package org.operatorfoundation.audiocoder
+
+class WSPRProcessor
+{
+    companion object
+    {
+        // WSPR Audio Format Constants
+        private const val WSPR_SAMPLE_RATE_HZ = 12000 // WSPR uses 12kHz sample rate
+        private const val BYTES_PER_SHORT = 2
+        private const val BYTE_MASK = 0xFF
+        private const val BITS_PER_BYTE = 8
+
+        // WSPR Protocol Constants
+        private const val WSPR_SYMBOL_DURATION_SECONDS = 0.683f //Each symbol is ~0.683 seconds
+        private const val WSPR_SYMBOLS_PER_MESSAGE = 162 // WSPR messages have 162 symbols
+        private const val WSPR_TRANSMISSION_DURATION_SECONDS = WSPR_SYMBOL_DURATION_SECONDS * WSPR_SYMBOLS_PER_MESSAGE // ~110.6 seconds
+
+        // Buffer Timing Constants
+        private const val MINIMUM_DECODE_SECONDS = 120f // Minimum for decode attempt
+        private const val RECOMMENDED_BUFFER_SECONDS = 180f // Recommended buffer for reliable decode (3 minutes for overlap)
+        private const val BUFFER_OVERLAP_SECONDS = RECOMMENDED_BUFFER_SECONDS - WSPR_TRANSMISSION_DURATION_SECONDS // ~60 seconds overlap
+
+        // Buffer Size Calculations
+        private const val MAXIMUM_BUFFER_SAMPLES = (WSPR_SAMPLE_RATE_HZ * RECOMMENDED_BUFFER_SECONDS).toInt()
+        private const val MINIMUM_DECODE_SAMPLES = (WSPR_SAMPLE_RATE_HZ * MINIMUM_DECODE_SECONDS).toInt()
+
+        // Default WSPR Frequencies
+        private const val DEFAULT_WSPR_20M_FREQUENCY_MHZ = 14.097
+        private const val DEFAULT_WSPR_40M_FREQUENCY_MHZ = 7.040
+        private const val DEFAULT_WSPR_80M_FREQUENCY_MHZ = 3.593
+    }
+
+    private val audioBuffer = mutableListOf<Short>()
+
+    /**
+     * Adds audio samples to the WSPR processing buffer.
+     */
+    fun addSamples(samples: ShortArray)
+    {
+        audioBuffer.addAll(samples.toList())
+
+        // Maintain buffer size within limits
+        if (audioBuffer.size > MAXIMUM_BUFFER_SAMPLES)
+        {
+            val samplesToRemove = audioBuffer.size - MAXIMUM_BUFFER_SAMPLES
+
+            // TODO: Consider saving these to a different buffer
+            repeat(samplesToRemove)
+            {
+                audioBuffer.removeAt(0)
+            }
+        }
+    }
+
+    /**
+     * Gets the current buffer duration in seconds.
+     */
+    fun getBufferDurationSeconds(): Float
+    {
+        return audioBuffer.size.toFloat() / WSPR_SAMPLE_RATE_HZ
+    }
+
+    /**
+     * Checks if buffer has enough data for a WSPR decode
+     */
+    fun isReadyForDecode(): Boolean
+    {
+        return audioBuffer.size >= MINIMUM_DECODE_SAMPLES
+    }
+
+    /**
+     * Decodes WSPR from buffered audio data.
+     */
+    fun decodeBufferedWSPR(
+        dialFrequencyMHz: Double = DEFAULT_WSPR_20M_FREQUENCY_MHZ,
+        useLowerSideband: Boolean = false
+    ): Array<WSPRMessage>?
+    {
+        if (!isReadyForDecode()) { return null }
+
+        val audioBytes = convertShortsToBytes(audioBuffer.toShortArray())
+        return CJarInterface.WSPRDecodeFromPcm(audioBytes, dialFrequencyMHz, useLowerSideband)
+    }
+
+    /**
+     * Clears the audio buffer
+     */
+    fun clearBuffer()
+    {
+        audioBuffer.clear()
+    }
+
+    /**
+     * Gets recommended buffer duration for optimal WSPR decoding.
+     */
+    fun getRecommendedBufferSeconds(): Float = RECOMMENDED_BUFFER_SECONDS
+
+    /**
+     * Gets minimum buffer duration for WSPR decode attempts.
+     */
+    fun getMinimumBufferSeconds(): Float = MINIMUM_DECODE_SECONDS
+
+    /**
+     * Gets the actual WSPR transmission duration
+     */
+    fun getWSPRTransmissionSeconds(): Float = WSPR_TRANSMISSION_DURATION_SECONDS
+
+    /**
+     * Gets the buffer overlap duration (extra buffering beyond transmission time)
+     */
+    fun getBufferOverlapSeconds(): Float = BUFFER_OVERLAP_SECONDS
+
+    /**
+     * Converts 16-bit samples to byte array for AudioCoder processing
+     */
+    private fun convertShortsToBytes(samples: ShortArray): ByteArray
+    {
+        val bytes = ByteArray(samples.size * BYTES_PER_SHORT)
+
+        for (sampleIndex in samples.indices)
+        {
+            val sample = samples[sampleIndex].toInt()
+            val byteIndex = sampleIndex * BYTES_PER_SHORT
+
+            // Little Endian Byte order
+            bytes[byteIndex] = (sample and BYTE_MASK).toByte()
+            bytes[byteIndex + 1] = ((sample shr BITS_PER_BYTE) and BYTE_MASK).toByte()
+        }
+
+        return bytes
+    }
+
+
+}