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• How to transcode flash movie to mp4, then upload to s3

  13 octobre 2017, par user1790300

  I am using the fluent-ffmpeg library with node.js to transcode videos originally in a flash movie format to the mp3 format with multiple resolutions, 1080p, etc.. Once the transcoding is complete, I would like to move the transcoded video to an s3 bucket.

  I pull the original .flv file from a source s3 bucket and pass the stream to the ffmpeg constructor function. The issue is after the transcoding completes, how do I then get the stream of the mp4 data to send to s3.

  Here is the code I have so far :

          var params = {
  
              Bucket: process.env.SOURCE_BUCKET,
  
              Key: fileName
  
          };
  
          s3.getObject(params, function(err, data) {
  
              if (err) console.log(err, err.stack); // an error occurred
  
  
  
              var format = ffmpeg(data)
  
              .size('854x480')
  
              .videoCodec('libx264')
  
              .format('flv')
  
              .toFormat('mp4');
  
              .on('end', function () {
  
                  //Ideally, I would like to do the uploading here
  
  
  
                  var params = {
  
                     Body: //{This is my confusion, how do I get the stream to add here?},
  
                     Bucket: process.env.TRANSCODED_BUCKET,
  
                     Key: fileName
  
                  };
  
                  s3.putObject(params, function (err, data) {
  
  
  
                 });
  
              })
  
              .on('error', function (err) {
  
                  console.log('an error happened: ' + err.message);
  
              });
  
  
  
          });

  For the code above, where can I get the transcoded stream to add to the "Body" property of the params object ?

• Fast movie creation using MATLAB and ffmpeg

  24 février 2018, par hyiltiz

  I have some time series data that I would like to create into movies. The data could be 2D (about 500x10000) or 3D (500x500x10000). For 2D data, the movie frames are simply line plot using plot, and for 3D data, we can use surf, imagesc, contour etc. Then we create a video file using these frames in MATLAB, then compress the video file using ffmpeg.

  To do it fast, one would try not to render all the images to display, nor save the data to disk then read it back again during the process. Usually, one would use getframe or VideoWriter to create movie in MATLAB, but they seem to easily get tricky if one tries not to display the figures to screen. Some even suggest plotting in hidden figures, then saving them as images to disk as .png files, then compress them using ffmpeg (e.g. with x265 encoder into .mp4). However, saving the output of imagesc in my iMac took 3.5s the first time, then 0.5s after. I also find it not fast enough to save so many files to disk only to ask ffmpeg to read them again. One could hardcopy the data as this suggests, but I am not sure whether it works regardless of the plotting method (e.g. plot, surf etc.), and how one would transfer data over to ffmpeg with minimal disk access.

  This is similiar to this, but immovie is too slow. This post 3 is similar, but advocates writing images to disk then reading them (slow IO).

• Regarding rotation information when rotating a movie in Avfoundation

  15 août 2017, par howmanylife

  I was able to rotate the movie with the following code

  videoCompositionTrack.preferredTransform = CGAffineTransform(rotationAngle: CGFloat(M_PI_2))

  I confirmed the information of the rotated video by ffmpeg. Rotate in the tag does not fluctuate as shown below, but a tag called side_data_list was generated and the value of rotation in side_data_list fluctuated, while keeping the information of rotate in tag unchanged.I want to change "tag" information.

  "tags": {
  
                  "rotate": "90"
  
          },
  
  "side_data_list": [
  
                  {
  
  "rotation": -90
  
                  }

  Are there any good advice on AVFoundation and ffmpeg ?