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• Audio and video out of sync. Stream mp4 files Concatenation using fluent-ffmpeg

  13 mars 2021, par JosepB

  First of all sorry if the question is duplicated. But I couldn't find out the right answer in other questions.

  


  I'm trying to concatenate AWS S3 mp4 files using streams and fluent-ffmpeg. I managed to download and upload the concatenated files without storing it to the disk.

  


  The concatenation seems correct but when I'm selecting a point in time of the video player (VLC media player or QuickTime) time bar seems the audio and video are out of sync.

  


  This is the nodejs fluent-ffmpeg implementation :

  


  concatenation = (listFileName, passthroughStream) => {

    return new Promise((resolve) => {  
        let command = ffmpeg().input(listFileName)
            .inputOptions(['-f concat', '-safe 0', '-protocol_whitelist', 'file,http,tcp,https,tls'])
            //.videoCodec('libx264')
            .outputFormat('mp4')
            .outputOptions('-movflags frag_keyframe+empty_moov')
            
            var ffstream = command.on('end', function() {
                const result = 'files have been merged succesfully';
                resolve(result);
            })
            .on('error', function(err) {
                console.log('an error happened: ' + err.message);
                reject(err);
            }).pipe(passthroughStream);
            ffstream.on('data', ((chunk) => {
                console.log('ffmpeg just wrote ' + chunk.length + ' bytes');
            }));
    });        
}


  


  I'm using S3 file signed URLs in the file. Somthing like this :

  


  file 'https://bucket.s3.region.amazonaws.com/file_0.mp4'
file 'https://bucket.s3.region.amazonaws.com/file_1.mp4'


  


  I think that this out of sync is because of the fragmentated output and maybe is not possible to do that without downloading the files, but maybe there's a possible solution.

  


  Is there some way to do the mp4 concatenation without storing the files to the disk ? Or am I doing something wrong ?

  


• how to crop the video with ffmpeg . needed c api to do same

  9 avril 2016, par OpenSource

  I want to crop the video at particular portion.Given height,width,x and y ,I want crop the particular region on the video with help of ffmpeg in iOS.
  any help

• Detect frames that have a given image/logo with FFmpeg

  7 juillet 2022, par scc

  I'm trying to split a video by detecting the presence of a marker (an image) in the frames. I've gone over the documentation and I see removelogo but not detectlogo.

  



  Does anyone know how this could be achieved ? I know what the logo is and the region it will be on.

  



  I'm thinking I can extract all frames to png's and then analyse them one by one (or n by n) but it might be a lengthy process...

  



  Any pointers ?