Recherche avancée

Sur d’autres sites (4596)

• Saving highest quality video from video-capture card

  23 décembre 2013, par DusteD

  I have a machine with 2x3 3ghz dual-core xeon and 4x10krpm scsi 320 disks in raid0.
  The capture card is an osprey 560 64 bit pci card.
  Operating system is currently Windows Server 2003.

  The video-stream that I can open with VLC using direct show is rather nice quality.
  However, trying to save this video-stream without loss of quality has proven quite difficult,
  using the h264 codec I am able to achieve a satisfying quality, however, all 4 cores jump to 100% load after a few second and then it start dropping frames, the machine is not powerful enough for realtime encoding. I've not been able to achieve satisfying mpeg1 or 4 quality, no matter which bitrate I set..

  Thing is, the disks in this machine are pretty fast even by todays standard, and they are bored.. I don't care about disk-usage, I want quality.
  I have searched in vain for a way to pump that beautiful videostream that I see in VLC onto the disk for later encoding, I reckon the disks would be fast enough, or maybe something which would apply a light compression, enough that the disks can keep up, but not so much as to loose visible quality.

  I have tried FFMPEG as it seems capable of streaming a yuv4 stream down to the disk, but ofcause FFMPEG is unable to open the dshow device ( same error as this guy Ffmpeg streaming from capturing device Osprey 450e fails )

  Please recommend a capable and (preferably) software which can do this.

• ffplay : simplify early frame drop code

  25 mai 2013, par Marton Balint

  ffplay : simplify early frame drop code
  Also never early frame drop the first frame after a flush.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] ffplay.c

• How to fetch both live video frame and its timestamp from ffmpeg on Windows

  22 février 2017, par vijiboy

  Searching for an alternative as OpenCV would not provide timestamps for live camera stream (on Windows), which are required in my computer vision algorithm, I found ffmpeg and this excellent article https://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/
  The solution uses ffmpeg, accessing its standard output (stdout) stream. I extended it to read the standard error (stderr) stream as well.

  Working up the python code on windows, while I received the video frames from ffmpeg stdout, but the stderr freezes after delivering the showinfo videofilter details (timestamp) for first frame.

  I recollected seeing on ffmpeg forum somewhere that the video filters like showinfo are bypassed when redirected. Is this why the following code does not work as expected ?

  Expected : It should write video frames to disk as well as print timestamp details.
  Actual : It writes video files but does not get the timestamp (showinfo) details.

  Here’s the code I tried :

  import subprocess as sp
  
  import numpy
  
  import cv2
  
  
  
  command = [ 'ffmpeg', 
  
              '-i', 'e:\sample.wmv',
  
              '-pix_fmt', 'rgb24',
  
              '-vcodec', 'rawvideo',
  
              '-vf', 'showinfo', # video filter - showinfo will provide frame timestamps
  
              '-an','-sn', #-an, -sn disables audio and sub-title processing respectively
  
              '-f', 'image2pipe', '-'] # we need to output to a pipe
  
  
  
  pipe = sp.Popen(command, stdout = sp.PIPE, stderr = sp.PIPE) # TODO someone on ffmpeg forum said video filters (e.g. showinfo) are bypassed when stdout is redirected to pipes??? 
  
  
  
  for i in range(10):
  
      raw_image = pipe.stdout.read(1280*720*3)
  
      img_info = pipe.stderr.read(244) # 244 characters is the current output of showinfo video filter
  
      print "showinfo output", img_info
  
      image1 =  numpy.fromstring(raw_image, dtype='uint8')
  
      image2 = image1.reshape((720,1280,3))  
  
  
  
      # write video frame to file just to verify
  
      videoFrameName = 'Video_Frame{0}.png'.format(i)
  
      cv2.imwrite(videoFrameName,image2)
  
  
  
      # throw away the data in the pipe's buffer.
  
      pipe.stdout.flush()
  
      pipe.stderr.flush()

  So how to still get the frame timestamps from ffmpeg into python code so that it can be used in my computer vision algorithm...