Add audio crystalizer

src/main/java/com/annimon/ffmpegbot/commands/ffmpeg/FFmpegCommandBuilder.java

@@ -44,6 +44,14 @@ public class FFmpegCommandBuilder implements Visitor<MediaSession> {
         audioCommands.add(p.getValue());
     }
 
+    @Override
+    public void visit(AudioCrystalizer p, MediaSession input) {
+        if (discardAudio) return;
+        final String value = p.getValue();
+        if (value.isEmpty() || value.equals("0")) return;
+        audioFilters.add("crystalizer=" + value);
+    }
+
     @Override
     public void visit(AudioEffect p, MediaSession input) {
         if (discardAudio) return;

src/main/java/com/annimon/ffmpegbot/commands/ffmpeg/Visitor.java

@@ -5,6 +5,7 @@ import com.annimon.ffmpegbot.parameters.*;
 public interface Visitor<I> {
     void visit(DisableAudio p, I input);
     void visit(AudioBitrate p, I input);
+    void visit(AudioCrystalizer p, I input);
     void visit(AudioEffect p, I input);
     void visit(AudioPitch p, I input);
     void visit(AudioVolume p, I input);

src/main/java/com/annimon/ffmpegbot/parameters/AudioCrystalizer.java

@@ -0,0 +1,24 @@
+package com.annimon.ffmpegbot.parameters;
+
+import com.annimon.ffmpegbot.commands.ffmpeg.Visitor;
+import java.util.List;
+
+public class AudioCrystalizer extends StringParameter {
+    private static final List<String> VALUES = List.of(
+            "-8", "-4", "-2", "0", "2", "4", "8"
+    );
+
+    public AudioCrystalizer() {
+        super("crystalizer", "Audio crystalizer", VALUES, "0");
+    }
+
+    @Override
+    public int defaultColumnsCount() {
+        return 4;
+    }
+
+    @Override
+    public <I> void accept(Visitor<I> visitor, I input) {
+        visitor.visit(this, input);
+    }
+}

src/main/java/com/annimon/ffmpegbot/parameters/BooleanParameter.java

@@ -3,13 +3,13 @@ package com.annimon.ffmpegbot.parameters;
 import java.util.List;
 
 public abstract class BooleanParameter extends Parameter<Boolean> {
-    public BooleanParameter(String id, String name, Boolean value) {
+    protected BooleanParameter(String id, String name, Boolean value) {
         super(id, name, List.of(false, true), value);
     }
 
     @Override
     public String describeValue(Boolean value) {
-        if (value) {
+        if (value != null && value) {
             return "ON";
         } else {
             return "OFF";

src/main/java/com/annimon/ffmpegbot/parameters/StringParameter.java

@@ -3,7 +3,7 @@ package com.annimon.ffmpegbot.parameters;
 import java.util.List;
 
 public abstract class StringParameter extends Parameter<String> {
-    public StringParameter(String id, String name, List<String> possibleValues, String value) {
+    protected StringParameter(String id, String name, List<String> possibleValues, String value) {
         super(id, name, possibleValues, value);
     }
 }

src/main/java/com/annimon/ffmpegbot/parameters/resolvers/AudioResolver.java

@@ -20,6 +20,7 @@ public class AudioResolver implements ParametersResolver {
             disableAudioParam(parameters, fileInfo.fileType());
             parameters.addAll(List.of(
                     new AudioBitrate(),
+                    new AudioCrystalizer(),
                     new AudioEffect(),
                     new AudioPitch(),
                     new AudioVolume()