app/src/main/java/com/example/babyphone/MainActivity.java

@@ -27,7 +27,7 @@ import java.util.List;
 
 public class MainActivity extends AppCompatActivity {
 
-    private static final int SAMPLE_RATE = 44100;
+    private static final int SAMPLE_RATE = 8000;
     private static final int PORT = 50005;
     private boolean isStreaming = false;
     private Thread recordingThread;
@@ -97,8 +97,9 @@ public class MainActivity extends AppCompatActivity {
         clientListenerThread.start();
 
         // Thread: Audio aufnehmen und an alle Clients senden (mit µ-law)
+// Thread: Audio aufnehmen und an alle Clients senden (µ-Law, 8kHz)
         recordingThread = new Thread(() -> {
-            int minBufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE,
+            int minBufferSize = AudioRecord.getMinBufferSize(8000, // neue Sample-Rate
                     AudioFormat.CHANNEL_IN_MONO,
                     AudioFormat.ENCODING_PCM_16BIT);
 
@@ -114,7 +115,7 @@ public class MainActivity extends AppCompatActivity {
             try {
                 recorder = new AudioRecord(
                         MediaRecorder.AudioSource.MIC,
-                        SAMPLE_RATE,
+                        44100, // Aufnahme weiterhin mit nativer Rate
                         AudioFormat.CHANNEL_IN_MONO,
                         AudioFormat.ENCODING_PCM_16BIT,
                         minBufferSize
@@ -127,23 +128,37 @@ public class MainActivity extends AppCompatActivity {
             byte[] pcmBuffer = new byte[minBufferSize];
             recorder.startRecording();
 
+            // Buffer für Resampling
+            short[] pcmSamples = new short[minBufferSize / 2];
+
             while (isStreaming) {
                 int read = recorder.read(pcmBuffer, 0, pcmBuffer.length);
                 if (read > 0) {
-                    // PCM → µ-Law konvertieren
-                    byte[] muLawData = pcm16ToMuLaw(pcmBuffer, read);
+                    // PCM Byte-Array → short[]
+                    ByteBuffer.wrap(pcmBuffer, 0, read).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(pcmSamples, 0, read / 2);
 
+                    // Resample 44.1kHz -> 8kHz (einfaches Downsampling, z.B. jede 5.5. Probe nehmen)
+                    short[] downsampled = new short[(int) (pcmSamples.length * 8000f / 44100f)];
+                    for (int i = 0; i < downsampled.length; i++) {
+                        downsampled[i] = pcmSamples[(int) (i * 44100f / 8000f)];
+                    }
+
+                    // PCM → µ-Law
+                    byte[] muLawData = new byte[downsampled.length];
+                    for (int i = 0; i < downsampled.length; i++) {
+                        muLawData[i] = linearToMuLawSample(downsampled[i]);
+                    }
+
+                    // Senden an alle Clients
                     synchronized (clients) {
                         Iterator<Socket> iterator = clients.iterator();
                         while (iterator.hasNext()) {
                             Socket client = iterator.next();
                             try {
                                 OutputStream out = client.getOutputStream();
-                                out.write(muLawData, 0, muLawData.length);
+                                out.write(muLawData);
                             } catch (IOException e) {
-                                try {
-                                    client.close();
-                                } catch (IOException ignored) {}
+                                try { client.close(); } catch (IOException ignored) {}
                                 iterator.remove();
                                 showToast("Client getrennt");
                             }
@@ -156,6 +171,7 @@ public class MainActivity extends AppCompatActivity {
             recorder.release();
         });
 
+
         recordingThread.start();
     }