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• Capturing frames from h264 video in android froyo

  21 janvier 2013, par Grzegorz Patyn

  The problem : "How to capture image frames from video in Android api level 8"
  Description : In api level 10 there was released MediaDataRetriever class, which has method "captureFrame". It doesn't work in api level 8.
  I made many studying around a problem :
  Trying to install android-support-v13 library - fail, because it doesn't have MediaDataRetriever class.
  I tried using ffmpeg.
  I compiled ffmpeg using ndk, for arm processors in many ways. Basically You can have problem Collect2: cannot find ld in ndkr8d, so i finally compiled with ndkr8b and got ffmpeg executable file.
  Now, having executable ffmpeg from this project : https://github.com/guardianproject/android-ffmpeg-java
  there is a problem :
  The library needs root access but i don't have it. I want my app work on most android apps. In order to execute ffmpeg, i do :

      String path = ( Environment.getExternalStorageDirectory() ).getAbsolutePath();
  
  String ffmpegBin = path+"/test/ffmpeg";
  
  String komenda = ffmpegBin+" -vframes 1 -ss 10 -i video.mp4 -f image2 -vcodec mjpeg "+path+"/test/frame%d.jpg";
  
  Runtime rt = Runtime.getRuntime();
  
  try {
  
      Process proc = rt.exec("chmod 700"+ffmpegBin);
  
      rt.exec(ffmpegBin,null,null);
  
  } catch (IOException e) {
  
      // TODO Auto-generated catch block
  
      e.printStackTrace();
  
  }

  Expecting to run ffmpeg command.
  I get the following error :

     01-21 15:29:24.129: W/System.err(10051): java.io.IOException: Error running exec(). Command: [/mnt/sdcard/test/ffmpeg] Working Directory: null Environment: null
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.ProcessManager.exec(ProcessManager.java:226)
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.Runtime.exec(Runtime.java:196)
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.Runtime.exec(Runtime.java:285)
  
  01-21 15:29:24.137: W/System.err(10051):    at com.example.ff.MainActivity.onStart(MainActivity.java:50)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.Activity.performStart(Activity.java:3781)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2641)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2684)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.ActivityThread.access$2300(ActivityThread.java:126)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2038)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.os.Handler.dispatchMessage(Handler.java:99)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.os.Looper.loop(Looper.java:123)
  
  01-21 15:29:24.137: W/System.err(10051):    at android.app.ActivityThread.main(ActivityThread.java:4632)
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.reflect.Method.invokeNative(Native Method)
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.reflect.Method.invoke(Method.java:521)
  
  01-21 15:29:24.137: W/System.err(10051):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
  
  01-21 15:29:24.137: W/System.err(10051):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  
  01-21 15:29:24.137: W/System.err(10051):    at dalvik.system.NativeStart.main(Native Method)
  
  01-21 15:29:24.137: W/System.err(10051): Caused by: java.io.IOException: Permission denied
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.ProcessManager.exec(Native Method)
  
  01-21 15:29:24.137: W/System.err(10051):    at java.lang.ProcessManager.exec(ProcessManager.java:224)
  
  01-21 15:29:24.137: W/System.err(10051):    ... 17 more

  In test directory there is a video.mp4 file, which is a valid file. The directory also contains ffmpeg binary compiled for arm with ndkr8b from this source : https://github.com/guardianproject/android-ffmpeg

  Is there any way to use compiled ffmpeg in applications, can i set some permissions in AndroidManifest etc. without su ?

• Android.mk include ffmpeg and Opencv

  28 janvier 2013, par Mark

  this is my project situation : I compiled ffmpeg in windows using this tutorial and I imported the ffmpeg folder generated inside my android project (under jni folder).
  In my project I have a jni_part.cpp where I inserted my jni function to operate with opencv.
  In my Android.mk I'm using the code below to import opencv and compile the jni_part.cpp

  include $(CLEAR_VARS)
  
  include ../../sdk/native/jni/OpenCV.mk
  
  LOCAL_MODULE    := mixed_sample
  
  LOCAL_SRC_FILES := jni_part.cpp
  
  LOCAL_LDLIBS +=  -llog -ldl 
  
  LOCAL_SHARED_LIBRARY := ffmpeg-prebuilt
  
  include $(BUILD_SHARED_LIBRARY)

  But what code I should use to import also ffmpeg ? I tried to use this code :

  include $(CLEAR_VARS)
  
  LOCAL_MODULE := ffmpeg-prebuilt
  
  LOCAL_SRC_FILES := ffmpeg-0.8/android/armv7-a/libffmpeg.so
  
  LOCAL_EXPORT_C_INCLUDES := ffmpeg-0.8/android/armv7-a/include/
  
  LOCAL_EXPORT_LDLIBS := ffmpeg-0.8/android/armv7-a/libffmpeg.so
  
  LOCAL_PRELINK_MODULE := true
  
  include $(PREBUILT_SHARED_LIBRARY)

  but if from mu jni_part.cpp code I try to include the file "#include " I get this error :

  **** Build of configuration Default for project OpenCV Tutorial 4 - Mix Java+Native OpenCV ****
  
  
  
  C:\android-ndk-r8c\ndk-build.cmd 
  
  Prebuilt       : libffmpeg.so <= jni/ffmpeg-0.8/android/armv7-a/
  
  Install        : libffmpeg.so => libs/armeabi-v7a/libffmpeg.so
  
  "Compile++ thumb : mixed_sample <= jni_part.cpp
  
  jni/jni_part.cpp:24:32: fatal error: libavutil/avstring.h: No such file or directory
  
  compilation terminated.
  
  make: *** [obj/local/armeabi-v7a/objs/mixed_sample/jni_part.o] Error 1
  
  
  
  **** Build Finished ****

  Someone could help me please ? I need to do this to include ffmpeg codec with the hope to use the function cvCaptureFromAVi...
  Thanks in advance

• Opening and reading a media file in android using ffmpeg

  29 octobre 2013, par ssrp

  I am developing an android project which has to open and read a MVC video file and save the streams separately in another location. I have done the basic steps for building ffmpeg for android and calling a c function through JNI. I want to know where do I have to put media files for doing above operations to it calling a C function in the C source file where I have all the Native function's implementations.