Move audio compatibility check

The compatibility depends on the capture constraints, not the encoding.

This will allow to add a new capture implementation with different
constraints.

PR Genymobile#5102 <Genymobile#5102>

server/src/main/java/com/genymobile/scrcpy/audio/AudioCapture.java

@@ -121,6 +121,13 @@ private void startRecording() throws AudioCaptureException {
         recorder.startRecording();
     }
 
+    public void checkCompatibility() throws AudioCaptureException {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.R) {
+            Ln.w("Audio disabled: it is not supported before Android 11");
+            throw new AudioCaptureException();
+        }
+    }
+
     public void start() throws AudioCaptureException {
         if (Build.VERSION.SDK_INT == Build.VERSION_CODES.R) {
             startWorkaroundAndroid11();

server/src/main/java/com/genymobile/scrcpy/audio/AudioEncoder.java

@@ -187,6 +187,8 @@ private void encode() throws IOException, ConfigurationException, AudioCaptureEx
 
         boolean mediaCodecStarted = false;
         try {
+            capture.checkCompatibility(); // throws an AudioCaptureException on error
+
             Codec codec = streamer.getCodec();
             mediaCodec = createMediaCodec(codec, encoderName);