add the echo effect

app/src/main/java/com/frank/ffmpeg/activity/AudioHandleActivity.kt

@@ -102,7 +102,8 @@ class AudioHandleActivity : BaseActivity() {
                 R.id.btn_play_opensl,
                 R.id.btn_audio_encode,
                 R.id.btn_pcm_concat,
-                R.id.btn_audio_speed
+                R.id.btn_audio_speed,
+                R.id.btn_audio_echo
         )
     }
 
@@ -220,6 +221,12 @@ class AudioHandleActivity : BaseActivity() {
                 val speedPath = PATH + File.separator + "speed.mp3"
                 commandLine = FFmpegUtil.changeAudioSpeed(srcFile, speedPath, speed)
             }
+            R.id.btn_audio_echo//setting echo effect
+            -> {
+                val echo = 1000 // echo effect, range from 0 to 90000
+                val echoPath = PATH + File.separator + "echo.mp3"
+                commandLine = FFmpegUtil.audioEcho(srcFile, echo, echoPath)
+            }
             else -> {
             }
         }

app/src/main/java/com/frank/ffmpeg/util/FFmpegUtil.java

@@ -85,6 +85,24 @@ public class FFmpegUtil {
     }
     //mixing formula: value = sample1 + sample2 - (sample1 * sample2 / (pow(2, 16-1) - 1))
 
+    /**
+     * Set echo and delay effect
+     *
+     * @param inputPath  input file
+     * @param delay      delay to play
+     * @param outputPath output file
+     * @return mix success or not
+     */
+    public static String[] audioEcho(String inputPath, int delay, String outputPath) {
+        // in_gain (0, 1], Default is 0.6
+        // out_gain (0, 1], Default is 0.3
+        // delays (0 - 90000]. Default is 1000
+        // decays (0 - 1.0]. Default is 0.5
+        String echoCmd = "ffmpeg -i %s -af aecho=0.8:0.8:%d:0.5 %s";
+        echoCmd = String.format(Locale.getDefault(), echoCmd, inputPath, delay, outputPath);
+        return echoCmd.split(" ");
+    }
+
     /**
      * mux audio and video together
      *

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

@@ -65,7 +65,8 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/pcm_concat"
-            android:layout_marginTop="10dp" />
+            android:layout_marginTop="10dp"
+            android:visibility="gone"/>
 
         <Button
             android:id="@+id/btn_audio_speed"
@@ -74,6 +75,13 @@
             android:text="@string/audio_speed"
             android:layout_marginTop="10dp" />
 
+        <Button
+            android:id="@+id/btn_audio_echo"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/audio_echo"
+            android:layout_marginTop="10dp" />
+
     </LinearLayout>
 
     <include

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

@@ -9,6 +9,7 @@
     <string name="audio_encode">PCM encode</string>
     <string name="pcm_concat">PCM concat</string>
     <string name="audio_speed">Audio speed</string>
+    <string name="audio_echo">Echo effect</string>
     <string name="audio_effect">Audio effect</string>
     <string name="audio_equalizer">Audio equalizer:</string>
     <string name="audio_style">Audio style:</string>

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

@@ -9,6 +9,7 @@
     <string name="audio_encode">PCM编码</string>
     <string name="pcm_concat">PCM合并</string>
     <string name="audio_speed">音频速度</string>
+    <string name="audio_echo">空灵效果</string>
     <string name="audio_effect">音乐均衡器</string>
     <string name="audio_equalizer">均衡器:</string>
     <string name="audio_style">风格:</string>