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• building c++ code into a shared library

  11 avril 2016, par gaurav

  I have some c++ code which i use as shared library in a java application.My c++ code uses some libraries like ffmpeg and boost. and ffmpeg libraries in turn depend on libx264. my first question is - can i build my c++ into a "fat" shared library which contains all the symbols from all libraries used so that on a new machine if i just copy the fat .so file everything works.
  If thats not possible then can you help me fix my current build process. This is what i am doing currently -

  1)on a local VM(ubuntu 64) i compile ffmpeg code using -fPIC flag and install h264 and boost using apt-get commands.
  2) on the same VM i compile my code using make file which looks like this-

  INCLUDES =   -I/opt/ffmpeg/include -I/usr/lib/jvm/java-7-openjdk-   amd64/include -I/usr/lib/jvm/java-7-openjdk-amd64/include/linux
  
  
  
  LDFLAGS =   -L/home/ubuntu/ffmpeg_shared
  
  
  
  LIBRARIES = -lavformat -lavcodec -lswscale -lavutil -lpthread  -lx264 -lboost_system -lboost_thread -lboost_chrono 
  
  
  
  CC = g++ -std=c++11 -fPIC
  
  
  
  all:clean final
  
  
  
  final:Api.o ImageSequence.o OverlayAnimation.o Utils.o ImageFrame.o 
  
  $(CC)  -o final.so Api.o ImageSequence.o OverlayAnimation.o Utils.o  ImageFrame.o $(LDFLAGS) $(LIBRARIES) -shared 

  3) on a new machine where java app will run. i install h264 and boost using apt-get commands and copy ffmpeg’s compiled library files to /usr/local/lib.

  4) copy the final.so file to this new machine. but when the java code tries to use the final.so file i see it tries to use wierdly named files. for example - it tries to find libavcodec.so.57 , libavformat.so.57 etc. to fix this i just created a copy of these files ie libavcodec.so copied to libavcodec.so.57.

  5)But these ffmpeg libraries in turn uses a differently named lib264.so file. on my new machine the apt-get command for x264 installed a file named libx264.so.148 but one of ffmpeg libraries is searching for file libx264.so.142 even if i rename this libx264.so file i get new errors where ffmpeg libraries tries to call libx264’s methods which has these numbers attached.

  6) at this time the only working option for me is to bring the c++ code on every new machine and build final.so file locally. this is something i want to avoid since i want to distribute the .so file along with jar file to my clients which they can easily use without having to build and install stuff.

• FFMPEG Flutter : attaching captions to a video issue

  24 juillet 2024, par Aqib Javed

  I am working on an app where i first extract audio from a video, then transcribe it and then i wanna attach that transcribed captions or subtitles to the original video.

  


  Everything is working smooth except the subtitles attaching part
if im running the FFMPEG command directly in terminal, it works fine but not in flutter

  


  here is my code of attaching the subtitles to the video :

  


   Future<void> attachCaptionsToVideo(DeepGramResponse deepGramResponse) async {&#xA;    var tempDir = await getTemporaryDirectory();&#xA;&#xA;    final outputPath = "${tempDir.path}/outputWithCaptions.mp4";&#xA;    final String subtitlePath = deepGramResponse.captionsPath&#xA;        .replaceAll(&#x27;\\&#x27;, &#x27;\\\\&#x27;)&#xA;        .replaceAll(&#x27; &#x27;, &#x27;\\ &#x27;);&#xA;    final String command =&#xA;        &#x27;-y -i ${deepGramResponse.videoPath} -vf subtitles=$subtitlePath $outputPath&#x27;;&#xA;    await FFmpegKit.executeAsync(command, (session) async {&#xA;      final returnCode = await session.getReturnCode();&#xA;      final output = await session.getOutput();&#xA;      final error = await session.getFailStackTrace();&#xA;&#xA;      log(&#x27;FFmpeg command executed with return code: $returnCode&#x27;);&#xA;      if (ReturnCode.isSuccess(returnCode)) {&#xA;        log(&#x27;Captions attached successfully&#x27;);&#xA;        deepGramResponse.copyWith(&#xA;          videoPath: outputPath,&#xA;        );&#xA;        Get.to(() => VideoPlayerScreen(videoPath: outputPath));&#xA;      } else {&#xA;        log(&#x27;FFmpeg command failed&#x27;);&#xA;        log(&#x27;Error output: $output&#x27;);&#xA;        log(&#x27;Error details: $error&#x27;);&#xA;        Fluttertoast.showToast(&#xA;            msg: &#x27;Something went wrong, please try again later&#x27;);&#xA;      }&#xA;    });&#xA;  }&#xA;</void>

  


  here is the error im getting :

  


  


  [AVFilterGraph @ 0x7b8a3f35f0] No option name near
'/data/user/0/com.example.blink/app_flutter/captions.srt'
[AVFilterGraph @ 0x7b8a3f35f0] Error parsing a filter description around :
[AVFilterGraph @ 0x7b8a3f35f0] Error parsing filterchain 'subtitles=/data/user/0/com.example.blink/app_flutter/captions.srt'
around :
Error reinitializing filters !
Failed to inject frame into filter network : Invalid argument
Error while processing the decoded data for stream #0:0
Conversion failed !

  


  


• Overlaying video with ffmpeg

  11 novembre 2012, par elee

  I'm attempting to write a script that will merge 2 separate video files into 1 wider one, in which both videos play back simultaneously. I have it mostly figured out, but when I view the final output, the video that I'm overlaying is extremely slow.

  Here's what I'm doing :

  1. Expand the left video to the final video dimensions

     ffmpeg -i left.avi -vf "pad=640:240:0:0:black" left_wide.avi

  2. Overlay the right video on top of the left one

     ffmpeg -i left_wide.avi -vf "movie=right.avi [mv] ; [in][mv] overlay=320:0" combined_video.avi

  In the resulting video, the playback on the right video is about half the speed of the left video. Any idea how I can get these files to sync up ?