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• Use 0x88 as stream id when muxing DTS in program streams.

  10 septembre 2013, par Carl Eugen Hoyos

  Use 0x88 as stream id when muxing DTS in program streams.
  This is what other open source software uses and what
  
  some hardware players expect.
  
  Tested by trac user iuqbgq9h-1 at yahoo
  

  • [DH] libavformat/mpeg.h

• Is there a way to apply a curve bend in ffmpeg ?

  25 mars 2020, par stevendesu

  I have four cameras each feeding me a different portion of a basketball court. Due to the slight offset of the cameras physical locations and lens distortion around the edges of the camera, I cannot simply stitch the videos together without some kind of correction.

  I’ve looked into ffmpeg’s perspective filter, as well as the lenscorrection filter. In the former case it was only able to create a trapezoid, not the curved image I want. In the latter case using negative values to k1 and k2 seemed to be heading in the right direction, but it either disorted the top and bottom of the image to the point of being nonsensical noise, or it zoomed in to the image so much that I lost important details.

  For the sample picture below, ultimately I want the midcourt line (the blue vertical line on the right side) to be vertical, and I want the mess of wires on the white desk at the bottom to remain visible and identifiable.

  Given a video which looks like the following :

  

  I wish to produce something like the following :

  

  This image was made using the "Curve Bend" filter in GIMP, but I just eye-balled it - so it’s not perfect. Ideally once I get the exact parameters the midcourt line will be perfectly vertical

  When using the lenscorrection filter, no values for k1 and k2 seemed to get the effect I want :

  Negative k1, negative k2 :

  

  Negative k1, positive k2 :

  

  Positive k1, negative k2 :

  

  Positive k1, positive k2 :

  

  In general :

  • negative / negative distorted the image beyond recognition
  • negative / positive looked alright, but the midcourt line was off the screen and it wasn’t clear if any distortion had been applied
  • positive / negative looked the best, but while the top and bottom curved in the middle of the left and right actually bulged out, leaving the midcourt line distorted
  • positive / positive was the opposite of the desired effect

• Encryption of OpenCV VideoWriter output

  19 juin 2017, par Aryan

  In an embedded project I was using opencv cv::VideoWriter to store frames as video files, also utilising lossless compression codecs (e.g.Lagarith). Now I have the requirement to encrypt the video files before storing them.

  1. Is it possible to get the encoded output from cv::VideoWriter so that an encryption step can be applied before writing the frame to disk ?

  2. Alternatively, is it possible to make cv::VideoWriter output to a custom output stream ? That way encryption steps can be applied on the stream.

  3. If neither of above is possible then is there an alternative to cv::VideoWriter that I can use to get the video format encoding done ?

  The end requirement is to write encrypted files which, after only a decryption step, become video files compatible with standard video players.