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• Stream video and commands on same connection or split connections ?

  10 mai 2013, par bizzehdee

  Background

  I am in the middle of writing a client/server app that i will install on every machine within my office (roughly 30 - 35 machines). I currently have the client connecting to the server and it has an ability to send mouse movement, mouse clicks, key strokes and execute certain commands. The next step is to stream back a video output of the screen, i am using the GDI method from Fastest method of screen capturing to capture the entire screen and will be using the x264 encoder to compress the frames and transmit them back to the client which will then decode and display the stream.

  Question

  is it best (by means of reducing lag, ensuring all commands are delivered as fast as possible and that streaming is as live as possible) that i transmit back along the same connection that i established for the commands, or, should i establish a separate connection on the same port, or on a different port to stream back the video ?

  P.S.

  i am aware that VNC, RD and other things such as TeamViewer already exist and already do this sort of thing, but none of these support all the requirements needed for what we need within this system.

• Java ProcessBuilder : space within quotation marks

  29 mai 2014, par Zahlii

  I am using ProcessBuilder to run FFMPEG to convert and label some of my MP3-Files.

  Manually using the following in a .bat file works as expected :

  "E:\Dokumente\workspace\MusicBot\ffmpeg\bin\ffmpeg.exe" 
  
      -i "The Glitch Mob - We Can Make The World Stop.mp4" 
  
      -metadata author="The Glitch Mob" 
  
      -metadata title="We Can Make The World Stop" 
  
      -ab 320k "mob.mp3"

  Now what i am trying to achieve using java’s ProcessBuilder

  ProcessBuilder pr = new ProcessBuilder(FFMPEG_PATH, 
  
      "-i", target.getAbsolutePath(),
  
      "-metadata", "title=\"We Can Make The World Stop\"", 
  
      "-metadata", "author=\"The Glitch Mob\"", 
  
      "-ab", "320k", 
  
      tar.getAbsolutePath());

  results in a [NULL @ 000000000032f680] Unable to find a suitable output format for 'Can'.
  Using title and author without spaces in them works, however.

• Find/extract the frames which are different in two videos

  24 novembre 2022, par Greendrake

  I have two H.264 video files roughly 30GB each, with 256291 frames in each. Most, if not all, frames in the 1st video appear identical to their counterparts in the 2nd video. That said, the video content is seemingly almost (maybe completely) identical.

  


  The raw H.264 streams extracted from the video files are actually supposed to be identical but they are not : one is bigger than the other by about 2MB. So, it seems like there ought to be some differences in the picture somewhere.

  


  I have used the following command to extract a frame each 0.5s from the files and then compared the frames' md5 hashes. All 21356 frame files extracted from the first video exactly match their counterparts from the second video.

  


  for i in {0..21356} ; do ffmpeg -hide_banner -loglevel error -accurate_seek -ss `echo $i*0.5 | bc` -i video.mp4 -frames:v 1 frames/period_down_$i.bmp ; done


  


  So, the odds that the video is anyhow different are low. But not 0% chance as the one or a few different frames could just fall outside of the 0.5s picks that I tried.

  


  Is there any smart way to find/extract the diffing frames only ?

  


  I could extract all frames and compare them but that's not smart at all and would take lots of time / disk space.