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• FFMPEG Crop with side by side merge

  14 février 2016, par Alan

  I am trying to create a shell/ffmpeg script that can show multiple files after they have been processed using different filters in a side by side / tiled way. An example of desired output would be : https://www.youtube.com/watch?v=DoPuhMRYem4.

  In order to create the desired output I need to crop off the right half of video1 and the left half of video2 and then join them back with [video1+video2] side by side. I have played around with a bunch of different ways of joining them, this does OK :

  ffmpeg -i input1.mp4 -i input2.mp4 -filter_complex "
  
  nullsrc=size=800x400 [background];
  
  [0:v] setpts=PTS-STARTPTS, scale=400x400 [left];
  
  [1:v] setpts=PTS-STARTPTS, scale=400x400 [right];
  
  [background][left]       overlay=shortest=1       [background+left];
  
  [background+left][right] overlay=shortest=1:x=400 [left+right]
  
  " -map '[left+right]' joined.mp4

  How can I modify this to detect the video width (they won’t always be the same width), divide the width in half and crop either the left or right sides off ?

• images->video->web canvas : RGB/YUV issues

  5 février 2016, par nrob

  We’ve written an web app which :

  1. takes 3D, time dependent weather data
  2. tiles each 3D time point to make a 2D frame (written out as a png image)
  3. stitches these frames together into a video (using ffmpeg/avconv)
  4. streams this video into a web app
  5. polls the canvas for frames
  6. sends the frames to the GPU where they are converted back to 3D and ray traced

  You can see the app here, code here and you can see the data video here

  Currently the pngs are written as RGB images, the video codec is in YUV and getting frames from the canvas returns RGB. As such there is a significant loss of information due to the conversion between image spaces.

  Does anyone have suggestions what is the best way round this ?

  I’ve tried a bunch of RGB video codecs, but I can’t get any to work, and I don’t know if the web browser will support it anyway. Can anyone suggest a good RGB codec (both lossy and lossless would be great)

  Also, is it possible to write to YUV images/read them from a video canvas in HTML5 ?

  Ultimately, I don’t even want anything to do with images/videos, I’m just hacking the codecs to stream/compress large animated 3D data volumes

• What is the point of encrypting HLS files ?

  29 janvier 2016, par APITC

  I am currently working on a project of videos on demand where I convert videos to HLS using FFMPEG.

  Videos are publicly hosted on AWS S3 and there is an API giving the URL of the HLS playlist.

  Now, I was looking at encrypting HLS files with AES-128 so that people can’t download and watch the video offline.
  I found the procedure which consists in hosting the key online and using that key while converting the video to encrypt the segments.

  The URL of the key is written in the HLS playlist, and the file is publicly available online.

  So anyone has access to the encryption key.

  I don’t understand what is the point of encrypting the segments if anyone has access to the key.

  Can someone enlighten me ? I know I must be missing something. Thanks !