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• Alter YUV values of AVFrames in FFMpeg

  1er février 2012, par Kage

  I'm trying to apply an effect to a video by altering the YUV values using FFMpeg programmatically in C.

  Let's say I want to increase the luminescence of each pixel of each frame by 100.

  I tried just altering the first frame of a video stream. I decoded the frame, added 100 to each Y value in the AVFrame->data[0], encoded the frame again and saved it into the video.

  However when I play the video back, it is not only the first frame that has been altered, but the first 30 frames.

  Why are the other frames effected when I only change the AVFrame->data of the first frame ?

  I tried again by changing all the Y, U and V values in AVFrame->data to 0 for only the first frame.

  When I play back the video, it starts off completely green like expected, after the first frame the video stays green for 30 frames. I can see the other frames start to come slowly through the green for 30 frames and then suddenly the green disappears and the video plays as normal. Why is it not just the first frame that is green ?

  My method is as follows :

  Video Stream

   |
  
   |     *(Get a frame)*
  
   |
  
   v

  AVPacket (encoded data)

   |
  
   |     *(Decode the frame)*
  
   |
  
   v

  AVFrame (raw data) --------------------------------------------------> AVFrame (raw data)

                    *(Edit AVFrame->data values)*
  
  
  
                                                         |
  
                                                         |     *(encode frame)*
  
                                                         |
  
                                                         V
  
                                                AVPacket (encoded data)
  
  
  
                                                         |
  
                                                         |     *(save frame)*
  
                                                         |
  
                                                         V
  
                                                    Video Stream

  Am I doing something obviously wrong ?

  How can I change just one frame without effecting the others ?

• Saving stream video on event FFMPEG CCTV RTSP ://

  25 avril 2017, par Josh

  I have a problem that I’m hoping some of the great minds here could help me with.

  I have a CCTV system that provides 4 RTSP streams (one from each camera) that will be covering a short 60 second event (roughly, so I can’t predefine a duration). The issue I have is I need FFMPEG to take clips from the stream triggered from a JSON feed. There are two commands or states, Door Open - Stop Recording and Door Closed - Begin Recording.

  Now getting FFMPEG to start recording on the door close is pretty simple in batch as I’m currently experimenting HOWEVER I can’t seem to find a way to get FFMPEG to start recording and then stop recording on demand. In batch it’s pretty straight forward using Ctrl+C to have FFMPEG commit the recording to file. The question is, how do I get FFMPEG PHP to send a command to an already closed handle to stop the recording and commit to file ?

  Many Thanks,
  Josh

• Installing gifify on Windows

  23 février 2016, par Robert Wojciechowski

  So gifify is a pretty awesome script that converts videos to gifs via command line : https://github.com/vvo/gifify

  I’m keen to get this working on my Windows 10 machine. I’m pretty new to windows and relatively new to coding, but I was able to get a few things working, but ran into a problem.

  Here is what I did :

  1. Installed node.js + npm
  2. Installed FFmpeg using npm
  3. Installed ImageMagick using npm (i think i did this wrong, might have only installed the wrapper).
  4. Downloaded giflossy. It needed to be built (?)
  5. Installed Visual Studio 2015, tried to build it using nmake and got this error :

  NMAKE : fatal error U1073: don't know how to make 'win32cfg.h'

  The command I used was :

  PS C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin> .\nmake -f "C:\Users\Robert's Workstation\.npm-global\node_modules\giflossy-lossy-1.82.1\src\Makefile.w32"

  Would really appreciate some help with this :D