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• Use ffmpeg to modify single frame without remux ?

  6 février 2017, par 1337GameDev

  I am curious of a fast way to modify a video, slightly, as to force the video to hash differently than the source. I want to avoid changes to meta tags, as these are parsed from the container file and not the video data itself.

  I will be using a process to compare videos for analytical work, but the process requires the 2 inputs to have differing hashes for the video content (otherwise the analytical process yields odd results). I am testing an improvement on this process, and need to have very similar videos.

  I have currently just used a ffmpeg bash script and filtered a VERY light 2x2 pixel for the first second of the video (90% transparent) and this seems to do the trick as they hash differently, but it requires demux / remux of the video, which takes forever if I want to analyze a lot of videos.

  Is there a way, using ffmpeg, to simple modify a single frame (specified by a time value) and change a single pixel and just copy the rest of the video contents ?

• ffmpeg : Considers AVPixelFormat as Int ?

  16 mars 2014, par jamie_y

  I would like to use a function ff_load_image.

  program.c

  #include "../ffmpeg/libavfilter/lavfutils.h"
  
  
  
  int main ()
  
  {
  
    uint8_t* data;
  
  
  
    int linesize, width, height, log_ctx;
  
  
  
    int i = ff_load_image(&data, &linesize, &width, &height, AV_PIX_FMT_RGB24, "blue.jpg", &log_ctx);
  
  }

  This compiles, but gives a warning.

  program.c: In function 'main':
  
  program.c:11: warning: passing argument 5 of 'ff_load_image' makes pointer from integer without a cast
  
  ../ffmpeg/libavfilter/lavfutils.h:39: note: expected 'enum AVPixelFormat *' but argument is of type 'int'

  When I run the program, it segment faults. I can't think of any other way to specify a pixel format. Why would ffmpeg think AV_PIX_FMT_RGB8 is an integer ? It's obviously an AVPixelFormat.

• ffmpeg doesn't always create wave picture

  17 février 2017, par Sean

  @LordNeckbeard and other ffmpeg experts,

  can you please help me with generating wave picture. the following command works perfectly on some videos and it doesn’t on other videos :

  ffmpeg  -i "input.mp4" -filter_complex "[0:a]aformat = channel_layouts = mono, compand = gain = -6, showwavespic = s = 1920x384: colors =red|blue[fg]; color = s = 1920x384: color =#444444, drawgrid = width = 38:height = 38:color =#555555@0.5[bg]; [bg][fg]overlay = format = rgb, drawbox = x = (iw - w) / 2:y = (ih - h) / 2:w = iw:h = 2:color =#000000@0.4" -vframes 1  "output.png" 

  when working, it generates the following wave pic :
  working example

  on other videos, it shows the grid but it seems that the wave signal is hidden behind the grid

  wave hidden behind the grid

  Your help is greatly appreciated !

  Thank you,
  Sean.