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• RGB Steganography on Video Files

  12 novembre 2018, par HowellJenkins

  Hi I have done image steganography in Python Image Library (PIL).

  ::edit: :
  Using LSB technique on pixel color data e.g. (255, 255, 255)

  I want to read frames before they are displayed, modify the pixels to implement LSB steganography and then display the modified frame(s) using FFMpeg or similar media library.

  How do I modify the RGB value of frames for video playback ?

  What I have accomplished to date is limited to images only. In PIL, one can open an image and access a 2-D pixel array and introduce a new tuple of RGB values.

  Also, I have tried using Python Image Library to create an animated gif as an alternative using images as frames, but there is a loss of quality ; hence, affecting the payload for the steganography. There is a grainy effect and it was used with PNG files to GIF, both utilizing lossless compression ; however, I read it had to do with a generalized color palette chosen to render the images.

  To modify the video stream in say an mp4 file, would require extensive knowledge of the moov and mdat atoms and the structure of the video container.

  FFMpeg is fairly complex as well. I noticed that the AVPacket structure may contain frame data.

• Huge latency in HTTP streaming desktop to browser

  29 janvier 2019, par fineman

  I’m trying to put together a reliable, reasonably low (<2s) latency desktop window share to browser solution. Currently I have :

  client sender using FFMPEG :

  ffmpeg -f gdigrab -i "title=notepad.exe" -r 10 -framerate 10  -c:v libx264 -g 50  -preset fast -tune zerolatency -f rtp rtp://192.168.1.85:1234

  server re-stream to HTTP using VLC :

  vlc -vv test.sdp  --sout=#transcode{vcodec=theo,vb=1600,scale=1,channels=1,acodec=none}:http{dst=:8080/webcam.ogg} :no-sout-rtp-sap :no-sout-standard-sap :sout-keep 

  where the sdp file is generated from the output of the ffmpeg command

  Client browser :

  <video autoplay="autoplay" loop="loop" muted="muted" preload="auto">
  
  <source src="http://192.168.1.85:8080/webcam.ogg" type="video/ogg"></source>
  
  </video>

  This works and gives good quality. But the latency is terrible (around 10s) and I’m at a loss to know how to tune it. I know that the latency is in the VLC transcoding/restreaming - displaying the RTP stream from the client on the server only has around 1s lag.

  I guess there are two questions - can this approach be sensibly tuned, or is the approach wrong to start with ?

• Understanding ffmpeg re parameter

  4 septembre 2024, par formatkaka

  I was reading about the -re option in ffmpeg .&#xA;What they have mentioned is

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  From the docs

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  -re (input)

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  Read input at the native frame rate. Mainly used to simulate a grab device, or live input stream (e.g. when reading from a file). Should not be used with actual grab devices or live input streams (where it can cause packet loss). By default ffmpeg attempts to read the input(s) as fast as possible. This option will slow down the reading of the input(s) to the native frame rate of the input(s). It is useful for real-time output (e.g. live streaming).

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  My doubt is basically the part of the above description that I highlighted. It is suggested to not use the option during live input streams but in the end, it is suggested to use it in real-time output.

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  Considering a situation where both the input and output are in rtmp format, should I use it or not ?

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