show frequency plot

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

@@ -32,6 +32,7 @@ import androidx.core.view.ViewCompat;
 import androidx.core.view.WindowInsetsCompat;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 public class MainActivity extends AppCompatActivity {
@@ -39,6 +40,9 @@ public class MainActivity extends AppCompatActivity {
 	private Bitmap scopeBitmap;
 	private PixelBuffer scopeBuffer;
 	private ImageView scopeView;
+	private Bitmap freqPlotBitmap;
+	private PixelBuffer freqPlotBuffer;
+	private ImageView freqPlotView;
 	private float[] recordBuffer;
 	private AudioRecord audioRecord;
 	private Decoder decoder;
@@ -65,16 +69,39 @@ public class MainActivity extends AppCompatActivity {
 		public void onPeriodicNotification(AudioRecord audioRecord) {
 			audioRecord.read(recordBuffer, 0, recordBuffer.length, AudioRecord.READ_BLOCKING);
 			if (decoder.process(recordBuffer, recordChannel)) {
+				processScope();
+				processFreqPlot();
+				setStatus(decoder.lastMode.getName());
+			}
+		}
+	};
+
+	private void processFreqPlot() {
+		int width = freqPlotBitmap.getWidth();
+		int height = freqPlotBitmap.getHeight();
+		int stride = freqPlotBuffer.width;
+		int line = stride * freqPlotBuffer.line;
+		int channels = recordChannel > 0 ? 2 : 1;
+		Arrays.fill(freqPlotBuffer.pixels, line, line + stride, 0);
+		for (int i = 0; i < recordBuffer.length / channels; ++i) {
+			int x = Math.min(Math.max(Math.round((recordBuffer[i] + 3) * stride / 6), 0), stride - 1);
+			freqPlotBuffer.pixels[line + x] = tint;
+		}
+		System.arraycopy(freqPlotBuffer.pixels, line, freqPlotBuffer.pixels, line + stride * (freqPlotBuffer.height / 2), stride);
+		freqPlotBuffer.line = (freqPlotBuffer.line + 1) % (freqPlotBuffer.height / 2);
+		int offset = stride * (freqPlotBuffer.line + freqPlotBuffer.height / 2 - height);
+		freqPlotBitmap.setPixels(freqPlotBuffer.pixels, offset, stride, 0, 0, width, height);
+		freqPlotView.invalidate();
+	}
+
+	private void processScope() {
 		int width = scopeBitmap.getWidth();
 		int height = scopeBitmap.getHeight();
 		int stride = scopeBuffer.width;
 		int offset = stride * (scopeBuffer.line + scopeBuffer.height / 2 - height);
 		scopeBitmap.setPixels(scopeBuffer.pixels, offset, stride, 0, 0, width, height);
 		scopeView.invalidate();
-				setStatus(decoder.lastMode.getName());
 	}
-		}
-	};
 
 	private void initAudioRecord() {
 		boolean rateChanged = true;
@@ -280,6 +307,10 @@ public class MainActivity extends AppCompatActivity {
 		scopeView = findViewById(R.id.scope);
 		scopeBuffer = new PixelBuffer(640, 2 * 1280);
 		createScope(getResources().getConfiguration());
+		freqPlotView = findViewById(R.id.freq_plot);
+		freqPlotBuffer = new PixelBuffer(640, 2 * 640);
+		freqPlotBitmap = Bitmap.createBitmap(freqPlotBuffer.width, freqPlotBuffer.height / 2, Bitmap.Config.ARGB_8888);
+		freqPlotView.setImageBitmap(freqPlotBitmap);
 		List<String> permissions = new ArrayList<>();
 		if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
 			permissions.add(Manifest.permission.RECORD_AUDIO);

app/src/main/res/layout/activity_main.xml

@@ -3,9 +3,9 @@
 	xmlns:app="http://schemas.android.com/apk/res-auto"
 	xmlns:tools="http://schemas.android.com/tools"
 	android:id="@+id/main"
-	android:keepScreenOn="true"
 	android:layout_width="match_parent"
 	android:layout_height="match_parent"
+	android:keepScreenOn="true"
 	tools:context=".MainActivity">
 
 	<ImageView
@@ -14,9 +14,17 @@
 		android:layout_height="0dp"
 		android:contentDescription="@string/scope_description"
 		app:layout_constraintBottom_toBottomOf="parent"
-		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintEnd_toStartOf="@+id/freq_plot"
 		app:layout_constraintStart_toStartOf="parent"
 		app:layout_constraintTop_toTopOf="parent" />
 
-
+	<ImageView
+		android:id="@+id/freq_plot"
+		android:layout_width="0dp"
+		android:layout_height="0dp"
+		android:contentDescription="@string/freq_plot_description"
+		app:layout_constraintBottom_toBottomOf="parent"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toEndOf="@+id/scope"
+		app:layout_constraintTop_toTopOf="parent" />
 </androidx.constraintlayout.widget.ConstraintLayout>

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

@@ -24,7 +24,8 @@
 	<string name="audio_setup_failed">Audio setup failed</string>
 	<string name="audio_permission_denied">Audio permission denied</string>
 	<string name="audio_recording_error">Audio recording error</string>
-	<string name="scope_description">Visualization of audio signal</string>
+	<string name="scope_description">Decoded SSTV picture</string>
+	<string name="freq_plot_description">Frequency plot</string>
 	<string name="night_mode">Night Mode</string>
 	<string name="enable">Enable</string>
 	<string name="disable">Disable</string>