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• Apply sound effects on a video file

  31 mars 2013, par talhamalik22

  I am a little miss guided here and it seems i am totally lost. I am developing an android app and its core idea is to develop a video recorder and video player that applies some sound effects on the voice of the people or any sound that it records. Sound effect means that if i make a video of a person who is giving some speech then there should be no effect on video but his/her voice should appear like voice in talking tom cat app. I hope you understand the idea. Similar app is Helium Booth you can check it here. I am trying to use libraries like libSonic, libpd and tried to use XUGGLE too.
  Read somewhere that Xuggle is not really developed for mobile devices so left it. Now what i want is that it should apply this effect on voice on the run time i.e while recording the pitch of the sound should be alterd and saved immediately. And what i am getting with these libraries is that i can apply sound effect after video is recorded. So it means i need to rip the audio from the video and then apply the change in pitch and frequency and again concatenate this audio file with the old video file. And i have no idea how to do it.
  Please show me the right approach and tools if possible.

  Regards

• concat subsections of a video using ffmpeg [migrated]

  30 mars 2013, par jefftimesten

  I would like to take several subsections of a video and concatenate them using the concat ffmpeg filter. It's just like the the example in the FFmpeg documentation, except that all of the clips are from the same source video.

  Here is what I am trying :

  ffmpeg \
  
    -ss 1.0 -frames:v 20 -i myInput.mp4 \
  
    -ss 2.0 -frames:v 20 -i myInput.mp4 \
  
    -ss 3.0 -frames:v 20 -i myInput.mp4 \
  
    -filter_complex '[0:0][0:1][1:0][1:1][2:0][2:1]concat=n=3:v=1:a=2[v][a1][a2]' \
  
    -map '[v]' -map '[a1]' -map '[a2]' myOutput.mp4

  When I try this, I get the following error (full output here) :

  Stream specifier ':0' in filtergraph description [0:0][0:1][1:0][1:1][2:0][2:1]concat=n=3:v=1:a=2[v][a1][a2] matches no streams.

  A few things :

  • What's with the error ? According to the stderr output, those streams do exist. What am I missing ?
  • Shouldn't the -ss (and -frames:v) be reflected in the "Duration : ... start : ... " line of the stderr output when the inputs are listed ?
  • Will the "-frames:v" option even work to specify the duration of an input ? (apparently -t is only for output ??) Is there a way to specify the duration of an input with seconds instead of frames ?

  Help me LordNeckbeard — you're my only hope !

• Running ffmpeg as library in android

  4 février 2014, par szakal

  I've got a simple task to do. I need to merge set of pictures into a video using ffmpeg working in android environment.

  After over a week fighting with different tutorials and examples explaining how to run compile ffmpeg I have, let's say, middle success. I've finally compiled ffmpeg for android.

  I followed this example :
  https://github.com/appunite/AndroidFFmpeg
  which worked best for me.

  As a result of building ffmpeg a have following directory structure :

  [Project]/jni/ffmpeg-build/armeabi-v7a/libffmpeg.so
  
  [Project]/jni/ffmpeg-build/armeabi/libffmpeg.so
  
  [Project]/jni/ffmpeg-build/mips/libffmpeg.so
  
  [Project]/jni/ffmpeg-build/x86/libffmpeg.so

  I also followed the ndk examples so I have running c code from java :

  #include 
  
  #include 
  
  #include 
  
  #include 
  
  #include     
  
  #include <android></android>log.h>    
  
  #include 
  
  #include 
  
  
  
  bool initted = false;    
  
  static JavaVM *sVm;
  
  
  
  jstring Java_com_example_hellojni_HelloJni_stringFromJNI(JNIEnv* env, jobject thiz) {
  
  
  
      char **argv;
  
      char *cmd;
  
      int argc;
  
  
  
  //  cmd = "ffmpeg -version";
  
  //  argv = parsedargs(cmd, &amp;argc);
  
  //  ffmpeg(argc, argv);
  
  
  
      return (*env)->NewStringUTF(env, "Hello from JNI !");
  
  
  
  }

  My question is how to run function from ffmpeg from my "hello-jni" c-file. I've read I need to write a wrapper over ffmpeg which my hello-jni is intended to be.

  Here is my Android.mk which probably is importat part to achieve my goal, but honestly I don't understand some lines set in this file. Or simply I don't know how to make things work.

  LOCAL_PATH := $(call my-dir)
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_MODULE := ffmpeg-prebuilt
  
  LOCAL_SRC_FILES := ffmpeg-build/$(TARGET_ARCH_ABI)/libffmpeg.so
  
  LOCAL_EXPORT_C_INCLUDES := ffmpeg-build/$(TARGET_ARCH_ABI)/include
  
  LOCAL_EXPORT_LDLIBS := ffmpeg-build/$(TARGET_ARCH_ABI)/libffmpeg.so
  
  LOCAL_PRELINK_MODULE := true
  
  include $(PREBUILT_SHARED_LIBRARY)
  
  
  
  
  
  include $(CLEAR_VARS)
  
  LOCAL_ALLOW_UNDEFINED_SYMBOLS=true
  
  LOCAL_MODULE    := hello-jni
  
  LOCAL_SRC_FILES := hello-jni.c
  
  LOCAL_C_INCLUDES := $(LOCAL_PATH)/ffmpeg-build/$(TARGET_ARCH_ABI)/include
  
  LOCAL_SHARED_LIBRARY := ffmpeg-prebuilt
  
  #LOCAL_CFLAGS += -g -Iffmpeg-prebuilt -Ihello-jni -Wno-deprecated-declarations 
  
  #LOCAL_LDLIBS += -llog -lz -landroid ffmpeg-build/$(TARGET_ARCH_ABI)/libffmpeg.so 
  
  
  
  include $(BUILD_SHARED_LIBRARY)

  One more thing. I've found an example how to wrap ffmpeg's main function. It'd be the easiest way to use ffmpeg for me sinse I don't know ffmpeg's api and I hope it's possible to run ffmpeg this way :
  Can FFmpeg be used as a library, instead of a standalone program ?

  To sum up, I think my problems are due to completely lack of c/c++ knowledge at all, especially how to use run any function from .so library.

  I hope someone can help me :).