Therefore, on Android, I got Working Directory: NULL Environment: NULL Error.

try {
    Process p = Runtime.getRuntime().exec("/data/data/com.example.foo/files/ffmpeg -f image2 -i "
+ Environment.getExternalStorageDirectory().getAbsolutePath() + "/img/b%d.jpg " 
+ Environment.getExternalStorageDirectory().getAbsolutePath() + "/DCIM/Camera/a444.mp4");   
} catch (IOException e)  { 
    e . printStackTrace ( ) ; 
}

Error log

04-09 01:50:45.683: I/Adreno-EGL(18393): <qeglDrvAPI_eglInitialize:320>: EGL 1.4 QUALCOMM Build: I0404c4692afb8623f95c43aeb6d5e13ed4b30ddbDate: 11/06/13
04-09 01:50:45.713: D/OpenGLRenderer(18393): Enabling debug mode 0
04-09 01:53:56.487: D/dalvikvm(18551): Trying to load lib /data/app-lib/com.example.sodeneme-1/libffmpeg.so 0x423d7d00
04-09 01:53:56.487: D/dalvikvm(18551): Added shared lib /data/app-lib/com.example.sodeneme-1/libffmpeg.so 0x423d7d00
04-09 01:53:56.487: D/dalvikvm(18551): No JNI_OnLoad found in /data/app-lib/com.example.sodeneme-1/libffmpeg.so 0x423d7d00, skipping init
04-09 01:53:56.537: W/System.err(18551): java.io.IOException: Error running exec(). Command: [/data/data/com.example.sodeneme/files/ffmpeg, -f, image2, -i, /storage/emulated/0/img/b%d.jpg, /storage/emulated/0/DCIM/Camera/a444.mp4] Working Directory: null Environment: null
04-09 01:53:56.537: W/System.err(18551):    at java.lang.ProcessManager.exec(ProcessManager.java:211)
04-09 01:53:56.537: W/System.err(18551):    at java.lang.Runtime.exec(Runtime.java:173)
04-09 01:53:56.537: W/System.err(18551):    at java.lang.Runtime.exec(Runtime.java:246)
04-09 01:53:56.537: W/System.err(18551):    at java.lang.Runtime.exec(Runtime.java:189)
04-09 01:53:56.537: W/System.err(18551):    at com.example.sodeneme.MainActivity.onCreate(MainActivity.java:40)
04-09 01:53:56.537: W/System.err(18551):    at android.app.Activity.performCreate(Activity.java:5231)
04-09 01:53:56.537: W/System.err(18551):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-09 01:53:56.537: W/System.err(18551):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-09 01:53:56.537: W/System.err(18551):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-09 01:53:56.537: W/System.err(18551):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-09 01:53:56.537: W/System.err(18551):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-09 01:53:56.537: W/System.err(18551):    at android.os.Handler.dispatchMessage(Handler.java:102)
04-09 01:53:56.537: W/System.err(18551):    at android.os.Looper.loop(Looper.java:136)
04-09 01:53:56.537: W/System.err(18551):    at android.app.ActivityThread.main(ActivityThread.java:5017)
04-09 01:53:56.537: W/System.err(18551):    at java.lang.reflect.Method.invokeNative(Native Method)
04-09 01:53:56.537: W/System.err(18551):    at java.lang.reflect.Method.invoke(Method.java:515)
04-09 01:53:56.537: W/System.err(18551):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-09 01:53:56.537: W/System.err(18551):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-09 01:53:56.537: W/System.err(18551):    at dalvik.system.NativeStart.main(Native Method)
04-09 01:53:56.547: W/System.err(18551): Caused by: java.io.IOException: No such file or directory
04-09 01:53:56.547: W/System.err(18551):    at java.lang.ProcessManager.exec(Native Method)
04-09 01:53:56.547: W/System.err(18551):    at java.lang.ProcessManager.exec(ProcessManager.java:209)
04-09 01:53:56.547: W/System.err(18551):    ... 18 more
04-09 01:53:56.577: I/Adreno-EGL(18551): <qeglDrvAPI_eglInitialize:320>: EGL 1.4 QUALCOMM Build: I0404c4692afb8623f95c43aeb6d5e13ed4b30ddbDate: 11/06/13
04-09 01:53:56.607: D/OpenGLRenderer(18551): Enabling debug mode 0

Authority

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />

How to Solve this error:

Maybe you need to add this permission to your AndroidManifest.xml file :

android.permission.WRITE_EXTERNAL_STORAGE