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• Kill an unresolved promise (or ignore and move on)

  17 septembre 2017, par Trees4theForest

  Using node child process exec, I’m calling a ffmpeg conversion via a promise that takes a bit of time. Each time the use clicks "next" it starts the FFMpeg command on a new file :

  function doFFMpeg(path){
  
    return new Promise((resolve, reject) => {
  
      exec('ffmpeg (long running command)', (error, stdout, stderr) => {
  
        if (error) {
  
          reject();
  
        }
  
      }).on('exit', (code) => { // Exit returns code 0 for good 1 bad
  
        if (code) {
  
          reject();
  
        } else {
  
          resolve();
  
        }
  
      });
  
    });
  
  }

  The problem is, if the user moves on to the next video before the promise is returned, I need to scrap the process and move on to converting the next video.

  How do I either :

  A) (Ideally) Cancel the current promised exec process*
  B) Let the current promised exec process complete, but just ignore that promise while I start a new one.

  *I realize that promise.cancel is not yet in ECMA, but I’d like to know of a workaround — preferably without using a 3rd party module / library.

  Attempt :

  let myChildProcess;
  
  
  
  function doFFMpeg(path){
  
  
  
    myChildProcess.kill();
  
  
  
    return new Promise((resolve, reject) => {
  
      myChildProcess = exec('ffmpeg (long running command)', (error, stdout, stderr) => {
  
        if (error) {
  
          reject();
  
        }
  
      }).on('exit', (code) => { // Exit returns code 0 for good 1 bad
  
        if (code) {
  
          reject();
  
        } else {
  
          resolve();
  
        }
  
      });
  
    });
  
  }

• How to Play a Video file in javacv / javacpp

  28 mars 2017, par Floesmaan

  Does someone have some example code to play a simple video file with the current javaCPP/javaCV version and the FFmpegFrameGrabber ?

  I tried this solution, but its apparently too old and does not work with the current javacv version because of an incompatible FrameGrabber interface (returns a "Frame"-Object instead of an "IplImage"-Object). If I change the code manually (using Frame instead of IplImage), it returns the error message :

  java.lang.VerifyError: Bad type on operand stack
  
  Exception Details:
  
    Location:
  
      org/bytedeco/javacv/FFmpegFrameGrabber.startUnsafe()V @1291: invokespecial
  
    Reason:
  
      Type 'org/bytedeco/javacpp/avutil$AVFrame' (current frame, stack[2]) is not assignable to 'org/bytedeco/javacpp/Pointer'
  
    Current Frame:
  
      bci: @1291
  
      flags: { }
  
      locals: { 'org/bytedeco/javacv/FFmpegFrameGrabber', integer, 'org/bytedeco/javacpp/avformat$AVInputFormat', 'org/bytedeco/javacpp/avutil$AVDictionary', integer, 'org/bytedeco/javacpp/avcodec$AVCodec', integer, integer, integer, integer }
  
      stack: { uninitialized 1283, uninitialized 1283, 'org/bytedeco/javacpp/avutil$AVFrame' }
  
    Bytecode:
  
      0x0000000: 2a01 b500 332a bb00 8659 01b7 0087 b500............

  FYI : I’m comparing different java libraries for playing video files and extract their pixel data (xuggler, vlcj, ...) and search for the best one. I really like to include javacv in my tests but it’s not working :(

• ffmpeg-python - checking if file is video

  14 avril 2021, par Gwen J

  How do I go about identifying if the file is an actual video media file ?
While doing a probe, it returns a 'codec_type' : 'video' even for a text file.

  


  vid_info = ffmpeg.probe(f'{filepath}/test.txt')['streams'];