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• Encryption of OpenCV VideoWriter output

  19 June 2017, by 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.

• How to stitch(concat) two transport stream with two different resolution and I-frame slices format without loosing resolution and slices information

  2 October 2019, by ART

  I have been trying to test a use case with steam captured from multimedia device and that didn't work. And then I have been trying to create this specific transport stream for like two days now without success, so requesting some help.

  



  I need to create transport stream with two different resolution and two different slicing format.

  



  I divided the task in following steps and in last two steps I need help.

  



  Step 1 : Download sample video with resolution : 1920x1080.
  
 I downloaded big buck bunny mp4 .

  



  Step 2 : Create transport stream with following
  
resolution : 1920x720, H264 I frame slices per frame: 1
  
I used following ffmpeg commands to do that.

  



  #Rename file to input.mp4
$ mv bbb_sunflower_1080p_30fps_normal.mp4 input.mp4
#Extract transport stream
$ ffmpeg -i input.mp4 -c copy first.ts


  



  first.ts is having 1980x720 resolution and one H264 I slice per frame.

  



  Step 3 : Create another transport stream with smaller resolution using following commands

  



  #Get mp4 with lower resolution.
$ ffmpeg -i input.mp4 -s 640x480 temp.mp4
#Extract trans port stream from mp4
$ ffmpeg -i temp.mp4 -c copy low_r.ts


  



  Step 4 : Edit(and re-encode?) low_r.ts to have two H264 I frame slices.
I used following command to achieve it.

  



  $ x264 --slices 4 low_r.ts -o second.ts


  



  However when I play this second.ts on vlc using following command it doesn't play

  



  $ vlc ./second.ts 


  



  And using Elacard StreamEye software when I analyze the transport stream I see that it has 4 H264 I slices in only two times other than that lot of H264 p slices and H264 B slices. 
Need help here to figure out why second.ts doesn't play and why slicing is not correct.

  



  Step 5 : Combine both the transport stream without loosing resolution and slicing information.
Don't know command for this. Need help here.
I tried ffmpeg but that combines two stream with different resolution and makes one file with one resolution.

  



  Any suggestions/pointers would help me proceed. Let me also know if any of the above steps are not fine too.

  


• How to stitch(concat) two transport stream with two different resolution and I-frame slices format without loosing resolution and slices information

  2 October 2019, by AnkurTank

  I have been trying to test a use case with steam captured from multimedia device and that didn’t work. And then I have been trying to create this specific transport stream for like two days now without success, so requesting some help.

  I need to create transport stream with two different resolution and two different slicing format.

  I divided the task in following steps and in last two steps I need help.

  Step 1 : Download sample video with resolution : 1920x1080.
  I downloaded big buck bunny mp4 .

  Step 2 : Create transport stream with following
  resolution : 1920x720, H264 I frame slices per frame: 1
  I used following ffmpeg commands to do that.

  #Rename file to input.mp4
  
  $ mv bbb_sunflower_1080p_30fps_normal.mp4 input.mp4
  
  #Extract transport stream
  
  $ ffmpeg -i input.mp4 -c copy first.ts

  first.ts is having 1980x720 resolution and one H264 I slice per frame.

  Step 3 : Create another transport stream with smaller resolution using following commands

  #Get mp4 with lower resolution.
  
  $ ffmpeg -i input.mp4 -s 640x480 temp.mp4
  
  #Extract trans port stream from mp4
  
  $ ffmpeg -i temp.mp4 -c copy low_r.ts

  Step 4 : Edit(and re-encode?) low_r.ts to have two H264 I frame slices.
  I used following command to achieve it.

  $ x264 --slices 4 low_r.ts -o second.ts

  However when I play this second.ts on vlc using following command it doesn’t play

  $ vlc ./second.ts 

  And using Elacard StreamEye software when I analyze the transport stream I see that it has 4 H264 I slices in only two times other than that lot of H264 p slices and H264 B slices.
  Need help here to figure out why second.ts doesn’t play and why slicing is not correct.

  Step 5 : Combine both the transport stream without loosing resolution and slicing information.
  Don’t know command for this. Need help here.
  I tried ffmpeg but that combines two stream with different resolution and makes one file with one resolution.

  Any suggestions/pointers would help me proceed. Let me also know if any of the above steps are not fine too.