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• How can I open a video encrypted with FFMPEG using openCV ?

  19 juillet 2023, par Richard S.J. Hwang

  I am developing a program that encrypts and saves video files and allows them to play only in programs that have key values. (by C#)

  


  I was looking for a way to encrypt a video file and found a way to encrypt it using FFMPEG's CENC.

  


  ffmpeg -i SampleVideo.mp4 -vcodec copy -acodec copy -encryption_scheme cenc-aes-ctr -encryption_key 76a6c65c5ea762046bd749a2e632ccbb -encryption_kid a7e61c373e219033c21091fa607bf3b8 SampleVideo_encrypted.mp4

  


  ffplay SampleVideo_encrypted.mp4 -decryption_key 76a6c65c5ea762046bd749a2e632ccbb

  


  ffmpeg -decryption_key 76a6c65c5ea762046bd749a2e632ccbb -i SampleVideo_encrypted.mp4 -vcodec copy -acodec copy SampleVideo_decrypted.mp4

  


  FFmpeg : how to produce MP4 CENC (Common Encryption) videos

  


  It is easy to encrypt and makes use of the header information of the video file.

  


  But I couldn't find a way to apply decryption at the same time as the Capture Video of OpenCV.
I thought I could use FFMPEG of OpenCV Backend and set the options, so I found a way to set the Windows environment variable, but it didn't work.(Only the gray screen is output.)
As a result of the search, only options related to H/W acceleration appear in OS environ.

  


  How to add ffmpeg options to VideoCapture
(Post written in python)

  


  import os
os.environ["OPENCV_FFMPEG_CAPTURE_OPTIONS"] = "video_codec;h264_cuvid"
cap = cv2.VideoCapture(url)


  


  Code I tested (not worked, c#)

  


  System.Environment.SetEnvironmentVariable("OPENCV_FFMPEG_CAPTURE_OPTIONS",
                                          "decryption_key;76a6c65c5ea762046bd749a2e632ccbb");
VideoCapture video = new VideoCapture(filename, VideoCaptureAPIs.FFMPEG);
...


  


  How can I open a video encrypted with FFMPEG using openCV ?

  


  Regards.

  


• ffmpeg doesn't work when the script is launched by cron - No protocol specified, Cannot open display :0.0

  14 janvier 2024, par a k

  ffmpeg in my script doesn't work when the script is launched by cron of the root

  


  Error : No protocol specified, Cannot open display :0.0

  


  OS : Ubuntu 20.04

  


  #!/bin/bash
log=/var/log/log2/log2.txt

echo ______________ $(date) >> "$log"
echo "$""DISPLAY" "=      "  "$DISPLAY" >> "$log" ;
echo whoami '         ' $(whoami) >> "$log" 
echo pwd '            ' $(pwd) >> "$log" 
echo "$""USER" "=" '        ' "$USER" >> "$log"
echo PATH '           ' "$PATH" >> "$log"
echo which ffmpeg '   ' $(which ffmpeg)>> "$log" 
echo whereis ffmpeg ' ' $(whereis ffmpeg) >> "$log" 
echo "\nls -l /bin/* | grep ffmpeg" '        ' >> "$log"
ls -l /usr/bin/* | grep ffmpeg >> "$log"
echo "ls -l /var/log | grep log2" ' '>> "$log"
ls -l /var/log | grep log2 >> "$log"

ffmpeg -y -f x11grab -s 1366x768 -i :0.0 -r 25 /var/log/log2/test.mp4 -loglevel error 2>>"$log" &

echo "pid ffmpeg ""$""!"" = " "$!" >> "$log" 
sleep 5
kill "$!"
echo exit >> "$log"
exit


  


  When Cron (Cron of the root) launches the script, ffmpeg shows the error "No protocol specified, Cannot open display :0.0"

  


  /var/log/log2/log2.txt :

  


  ______________ ven. 05 mai 2023 04:10:01 CEST
$DISPLAY =       
whoami           root
pwd              /root
$USER =          
PATH             /usr/bin:/bin
which ffmpeg     /usr/bin/ffmpeg
whereis ffmpeg   ffmpeg: /usr/bin/ffmpeg /usr/share/ffmpeg /usr/share/man/man1/ffmpeg.1.gz
ls -l /usr/bin/* | grep ffmpeg  
-rwxr-xr-x 1 root   root      284976 mai   18  2022 /usr/bin/ffmpeg
ls -l /var/log | grep log2  
drwxrwxrwx  2 root              root               4096 mai    5 04:09 log2
pid ffmpeg $! =  74590
No protocol specified
[x11grab @ 0x56244aa06740] Cannot open display :0.0, error 1.
:0.0: Input/output error
exit


  


  When I launch the script manually as a not-root user (with sudo), everything work correctly :

  


  ______________ ven. 05 mai 2023 04:10:47 CEST
$DISPLAY =       :0
whoami           root
pwd              /home/an
$USER =          root
PATH             /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
which ffmpeg     /usr/bin/ffmpeg
whereis ffmpeg   ffmpeg: /usr/bin/ffmpeg /usr/share/ffmpeg /usr/share/man/man1/ffmpeg.1.gz
ls -l /usr/bin/* | grep ffmpeg  
-rwxr-xr-x 1 root   root      284976 mai   18  2022 /usr/bin/ffmpeg
ls -l /var/log | grep log2  
drwxrwxrwx  2 root              root               4096 mai    5 04:09 log2
pid ffmpeg $! =  74618
exit


  


  When I launch the script manually as the root, everything works correctly :

  


  ______________ ven. 05 mai 2023 04:11:27 CEST
$DISPLAY =       :0
whoami           root
pwd              /root
$USER =          root
PATH             /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
which ffmpeg     /usr/bin/ffmpeg
whereis ffmpeg   ffmpeg: /usr/bin/ffmpeg /usr/share/ffmpeg /usr/share/man/man1/ffmpeg.1.gz
ls -l /usr/bin/* | grep ffmpeg  
-rwxr-xr-x 1 root   root      284976 mai   18  2022 /usr/bin/ffmpeg
ls -l /var/log | grep log2  
drwxrwxrwx  2 root              root               4096 mai    5 04:11 log2
pid ffmpeg $! =  74683
exit


  


  When crontab of an ordinary user launches the script, it works correctly :

  


  $DISPLAY =       
whoami           an
pwd              /home/an
$USER =          
PATH             /usr/bin:/bin
which ffmpeg     /usr/bin/ffmpeg
whereis ffmpeg   ffmpeg: /usr/bin/ffmpeg /usr/share/ffmpeg /usr/share/man/man1/ffmpeg.1.gz
ls -l /usr/bin/* | grep ffmpeg  
-rwxr-xr-x 1 root   root      284976 mai   18  2022 /usr/bin/ffmpeg
ls -l /var/log | grep log2  
drwxrwxrwx  2 root              root               4096 mai    5 05:05 log2
pid ffmpeg $! =  77601
exit


  


  I have tried to put into the script :

  


  export DISPLAY=":0"

  


  export DISPLAY=":0.0"

  


  export DISPLAY=":1"

  


• fftools/ffmpeg : open decoders right after we know they are needed

  11 avril 2023, par Anton Khirnov

  fftools/ffmpeg : open decoders right after we know they are needed
  Will allow initializing subtitle encoding earlier.
  

  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg_demux.c