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• Convert frames to video on demand

  29 janvier 2020, par user3900456

  I’m working on a c++ project that generates frames to be converted to a video later.
  The project currently dumps all frames as jpg or png files in a folder and then I run ffmpeg manually to generate a mp4 video file.

  This project runs on a web server and an ios/android app (under development) will call this web server to have the video generated and downloaded.

  The web service is pretty much done and working fine.

  I don’t like this approach for obvious reasons like a server dependency, cost etc...
  I successfully created a POC that exposes the frame generator lib to android and I got it to save the frames in a folder, my next step now is to convert it to video. I considered using any ffmpeg for android/ios lib and just call it when the frames are done.

  Although it seems like I fixed half of the problem, I found a new one which is... each frame depending on the configuration could end up having 200kb+ in size, so depending on the amount of frames, it will take a lot of space from the user’s device.
  I’m sure this will become a huge problem very easily.

  So I believe that the ideal solution would be to generate the mp4 file on demand as each frame is created, so in the end there would be no storage space being taken as I woudn’t need to save a file for the frame.

  The problem is that I don’t know how to do that, I don’t know much about ffmpeg, I know it’s open source but I have no idea how to include a reference to it from the frames generator and generate the video "on demand".
  I heard about libav as well but again, same problem...

  I would really appreciate any sugestion on how to do it. What I need is basically a way to generate a mp4 video file given a list of frames.

  thanks for any help !

• ffmpeg4.4 missing in OpenCV3.4.13 + Android Studio4.2.1 ? No tutorial gives answer how to fix

  8 juin 2021, par Fab

  Finally opencv is working in my Android Studio project (solved with help of https://www.youtube.com/watch?v=-0Yx1UzozzQ). But theres is no Video I/O information visible so I guess i didnt connected ffmpeg correctly in my project and it isnt used at all !?

  


  My steps so far :

  


  


  • ffmpeg download : https://www.videohelp.com/software/ffmpeg

    


  


  • added ffmpeg to path like explained here :
https://soundartifacts.com/how-to/186-how-to-install-ffmpeg-on-windows-10-amp-add-ffmpeg-to-windows-path.html#video
powershell shows installation.

    


  


  • when printing Core.getBuildInformation() in the project I see that the Video I/O section is empty and I assume there has to be some information about FFMPEG etc...see picture :
enter image description here

    


  


  


  

  • I dont get any error messages. I try to VideoCapture.open("somestring") and returned is just false.

  


  


  I know there are a lot of similar questions but I cant identify which one really addresses my issue.
Really appreciate your help. Thanks, Fabian

  


• Android.mk : how to 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 (with inside libffmpeg.so file) 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 my jni_part.cpp code I try to include some ffmpeg files/libraries "#include <libavutil></libavutil>avstring.h>" 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