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• FFMpeg Command work in command line, but in python script the image is blueish ? (Semi Solved)

  17 juin 2015, par Fooldj

  Okay, kind of a weird problem. But I’m not sure whether it’s python, ffmpeg, or some stupid thing I’m doing wrong.

  I’m trying to take a video, and take 1 frame a second, and output that frame to an image. Right now, if i use the command line with ffmpeg :

  ffmpeg -i test.avi -r 1 -f image2 image-%3d.jpeg -pix_fmt rgb24 -vcodec rawrvideo

  It outputs about 10 images, the images look fine, awesome. Now I have this code (right now some code from some github, as I wanted stuff that i was relatively sure would work, and mine is allll convoluted)

  import subprocess as sp
  
  import numpy as np
  
  import re
  
  import cv2
  
  import time
  
  
  
  FFMPEG_BIN = r'ffmpeg.exe'
  
  INPUT_VID = 'test.avi'
  
  
  
  def getInfo():
  
      command = [FFMPEG_BIN,'-i', INPUT_VID, '-']
  
      pipe = sp.Popen(command, stdout=sp.PIPE, stderr=sp.PIPE)
  
      pipe.stdout.readline()
  
      pipe.terminate()
  
      infos = pipe.stderr.read()
  
      infos_list = infos.split('\r\n')
  
      res = re.search(' \d+x\d+ ',infos)
  
      res = [int(x) for x in res.group(0).split('x')]
  
      return res
  
  res = getInfo()
  
  command = [ FFMPEG_BIN,
  
          '-i', INPUT_VID,
  
          '-f', 'image2pipe',
  
          '-pix_fmt', 'rgb24',
  
          '-vcodec', 'rawvideo', '-']
  
  pipe = sp.Popen(command, stdout = sp.PIPE, bufsize=10**8)
  
  n = 0
  
  im2 = []
  
  try:
  
      mog = cv2.BackgroundSubtractorMOG2(120,2,True)
  
      while True:
  
          raw_image = pipe.stdout.read(res[0]*res[1]*3)
  
          # transform the byte read into a numpy array
  
          image =  np.fromstring(raw_image, dtype='uint8')
  
          image = image.reshape((res[1],res[0],3))
  
          rgbImg = image.copy()
  
  
  
          fname = ('_tmp%03d.png'%time.time())
  
          cv2.imwrite(fname, rgbImg)
  
          # throw away the data in the pipe's buffer.
  
          #pipe.stdout.flush()
  
          n += 1
  
          print n
  
  except:
  
      print 'done',n
  
      pipe.kill()
  
      cv2.destroyAllWindows()

  When I run this, I get 10 images, but they all have a Blue Tint ! I cannot for the life of me figure out why. I’ve done tons of searches, I’ve tried quite a few different codecs (usually just messes things up worse). The media info for the video file is here :

   General
  
   Complete name                            : test.avi
  
  Format                                   : AVI
  
  Format/Info                              : Audio Video Interleave
  
  File size                                : 85.0 KiB
  
  Duration                                 : 133ms
  
  Overall bit rate                         : 5 235 Kbps
  
  
  
  Video
  
  ID                                       : 0
  
  Format                                   : JPEG
  
  Codec ID                                 : MJPG
  
  Duration                                 : 133ms
  
  Bit rate                                 : 1 240 Kbps
  
  Width                                    : 640 pixels
  
  Height                                   : 480 pixels
  
  Display aspect ratio                     : 4:3
  
  Frame rate                               : 30.000 fps
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:2
  
  Bit depth                                : 8 bits
  
  Compression mode                         : Lossy
  
  Bits/(Pixel*Frame)                       : 0.135
  
  Stream size                              : 20.1 KiB (24%)

  Any suggestions ? It seems like it should be an RGB mixup...just not sure where at...

  EDIT : So I fixed the problem by switching the blue and red channels with this code :
  bChannel = rgbImg[ :, :,0]
  rChannel = rgbImg[ :, :,2]
  gChannel = rgbImg[ :, :,1]

              rgbArray = np.zeros((res[1],res[0],3), 'uint8')
  
              rgbArray[...,0] = rChannel
  
              rgbArray[...,1] = gChannel
  
              rgbArray[...,2] = bChannel

  So I guess this is now a question of, why is python mixing up these channels ? Is it a problem with python, or ffmpeg, the codec ?

  Thanks !

• FFMPEG - How to replace a specifed set of colors in a video with another specified set of colors ?

  18 juillet 2022, par pixerstoodios

  For example, I have a video of red, yellow, green, cyan, blue, and magenta objects. I have a list of hex codes consisting of those colors and i want to replace each of those specific hex colors with another, completely different arbitrary color (i.e. brown, royal purple, navy blue, burgundy, tan, and white, respectively.)

  


  An illustration.

  


  What would be a command that can efficiently accomplish this task ?

  


• How to extract a video snippet from a video file that is being written in by ffmpeg in realtime

  26 février 2015, par alex.b

  At the moment i am recording a LIVE stream video from youtube with youtube-dl (https://github.com/rg3/youtube-dl)

  The command i use for this :

  youtube-dl --id -f 92 https://www.youtube.com/watch?v=VYlQJbsVs48

  92 is a format code that i got after executing a command to get the formats, that gave me this list :

  format code  extension  resolution note
  
  140          m4a        audio only DASH audio  144k , m4a_dash container, aac  @128k (48000Hz)
  
  141          m4a        audio only DASH audio  272k , m4a_dash container, aac  @256k (48000Hz)
  
  160          mp4        256x144    DASH video  124k , 15fps, video only
  
  133          mp4        426x240    DASH video  258k , 30fps, video only
  
  134          mp4        640x360    DASH video  616k , 30fps, video only
  
  135          mp4        854x480    DASH video 1116k , 30fps, video only
  
  136          mp4        1280x720   DASH video 2216k , 30fps, video only
  
  137          mp4        1920x1080  DASH video 4141k , 30fps, video only
  
  151          mp4        72p        HLS
  
  132          mp4        240p       HLS
  
  92           mp4        240p       HLS
  
  93           mp4        360p       HLS
  
  94           mp4        480p       HLS
  
  95           mp4        720p       HLS
  
  96           mp4        1080p      HLS  (best)

  This is creating a file called VYlQJbsVs48.mp4.part that gets bigger and bigger of course.

  Is there a way to extract a video snippet from that live stream or form the part file ? Or maybe there is a better way of doing this ?

  What i have noticed is that if i force quit iTerm2 while youtube-dl is running the .part file it creates wont contain any index information (something to do with an moov atom not being present in the mp4 file - which is the information about the number of frames and other things - metadata i think), so it makes me think i cannot extract from the file.

  Maybe if there would be a way that youtube-dl can write the index information at all times or maybe another way that i can record the live stream and get video snippets while its recording.

  I forgot to mention i am doing this on OSX Yosemite. I have FFMPEG installed with homebrew and youtoube-dl

  I am more than happy to try stuff on UBUNTU if there is a solution.

  Any help would be greatly appreciated.

  Thank you.

  Alex