modify the volume of audio

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

@@ -78,7 +78,7 @@ class AudioHandleActivity : BaseActivity() {
                         txtProgress!!.visibility = View.VISIBLE
                         txtProgress!!.text = String.format(Locale.getDefault(), "%d%%", progress)
                     } else {
-                        txtProgress!!.visibility = View.INVISIBLE
+                        txtProgress!!.visibility = View.GONE
                     }
                 }
                 MSG_INFO -> {
@@ -119,7 +119,8 @@ class AudioHandleActivity : BaseActivity() {
                 R.id.btn_audio_echo,
                 R.id.btn_audio_tremolo,
                 R.id.btn_audio_denoise,
-                R.id.btn_audio_silence
+                R.id.btn_audio_silence,
+                R.id.btn_audio_volume
         )
     }
 
@@ -250,15 +251,21 @@ class AudioHandleActivity : BaseActivity() {
                 val tremoloPath = PATH + File.separator + "tremolo.mp3"
                 commandLine = FFmpegUtil.audioTremolo(srcFile, frequency, depth, tremoloPath)
             }
-            R.id.btn_audio_denoise
+            R.id.btn_audio_denoise //audio denoise
             -> {
                 val noisePath = PATH + File.separator + "denoise.mp3"
                 commandLine = FFmpegUtil.audioDenoise(srcFile, noisePath)
             }
-            R.id.btn_audio_silence
+            R.id.btn_audio_silence //silence detect
             -> {
                 commandLine = FFmpegUtil.audioSilenceDetect(srcFile)
             }
+            R.id.btn_audio_volume // modify volume
+            -> {
+                val volume = 0.5f // 0.0-1.0
+                val volumePath = PATH + File.separator + "volume.mp3"
+                commandLine = FFmpegUtil.audioVolume(srcFile, volume, volumePath)
+            }
             else -> {
             }
         }

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

@@ -146,6 +146,20 @@ public class FFmpegUtil {
         return silenceCmd.split(" ");
     }
 
+    /**
+     * Change volume of a chunk of audio
+     *
+     * @param inputPath  input file
+     * @param volume     volume
+     * @param outputPath output file
+     */
+    public static String[] audioVolume(String inputPath, float volume, String outputPath) {
+        // output_volume = volume * input_volume
+        String volumeCmd = "ffmpeg -i %s -af volume=%f %s";
+        volumeCmd = String.format(Locale.getDefault(), volumeCmd, inputPath, volume, outputPath);
+        return volumeCmd.split(" ");
+    }
+
     /**
      * mux audio and video together
      *

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

@@ -106,6 +106,13 @@
             android:text="@string/audio_silence"
             android:layout_marginTop="10dp" />
 
+        <Button
+            android:id="@+id/btn_audio_volume"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/audio_volume"
+            android:layout_marginTop="10dp" />
+
     </LinearLayout>
 
     <include

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

@@ -13,6 +13,8 @@
     <string name="audio_tremolo">Tremolo effect</string>
     <string name="audio_denoise">Audio denoise</string>
     <string name="audio_silence">Silence detect</string>
+    <string name="audio_volume">Audio volume</string>
+    <string name="audio_add_equalizer">Add equalizer</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

@@ -13,6 +13,8 @@
     <string name="audio_tremolo">惊悚效果</string>
     <string name="audio_denoise">音频降噪</string>
     <string name="audio_silence">静音检测</string>
+    <string name="audio_volume">修改音量</string>
+    <string name="audio_add_equalizer">均衡器+</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>