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• Encoding 4K 60Hz lossless from a capture card

  13 décembre 2017, par Alex Pizzi

  Windows 10 64-bit
  Ryzen 7
  GTX 1080
  32GB RAM

  Hi all,

  I’m trying to encode 4K 30/60Hz video in a lossless format from a 4K capture card and everything I’ve tried gives me a similar error as in the linked image, [real-time buffer too full or near too full frame dropped]

  [Not mine]
  https://cloud.githubusercontent.com/assets/4932401/22171307/ef5c9864-df58-11e6-8821-4b74ce3f32d0.png

  This is the command I’ve tried most recently :

  ffmpeg.exe -f dshow -video_size 3840x2160 -framerate 30 -pixel_format bgr24 -rtbufsize INT_MAX -i video="MZ0380 PCI, Analog 01 Capture" -vf fps=30 out%d.BMP

  With the images dumped to a 10G RAM disk or 850 EVO. I’m doing this to skip the encoding step.

  I get the same error when encoding with h265 lossless and NVENC h265 lossless.

  I need the video to be lossless as it will be used to test hardware h265 encoders.

  Video source is a 4K Blu-ray.

  Any help would be greatly appreciated. Thank you.

  -Alex P

• No such file or directory when running an ffmpeg command from script

  23 novembre 2017, par A_Matar

  I have been trying to run this ffmpeg command from python script to generate video of certain length from a static image but I keep getting No such file or directory error !
  Here is my code :

  import subprocess
  
  
  
  def generate_white_vid (duration):
  
      ffmpeg_create_vid_from_static_img = 'ffmpeg -loop 1 -i /same_path/WhiteBackground.jpg -c:v libx264 -t %f -pix_fmt yuv420p -vf scale=1920:1080 /same_path/white_vid2.mp4' % duration
  
      print ffmpeg_create_vid_from_static_img
  
      pp = subprocess.Popen(ffmpeg_create_vid_from_static_img)
  
      pp.communicate()
  
  
  
  generate_white_vid(0.5)

  However when I run the same exact command :

  ffmpeg -loop 1 -i /same_path/WhiteBackground.jpg -t 0.500000 -pix_fmt yuv420p -vf scale=1920:1080 /same_path/white_vid2.mp4

  from the cli, it works just fine. Where am I missing up ?
  Here is the full trace :

  Traceback (most recent call last):
  
    File "gen.py", line 10, in <module>
  
      generate_white_vid(0.5)
  
    File "gen.py", line 7, in generate_white_vid
  
      pp = subprocess.Popen(ffmpeg_create_vid_from_static_img)
  
    File "/home/ubuntu/anaconda2/lib/python2.7/subprocess.py", line 390, in __init__
  
      errread, errwrite)
  
    File "/home/ubuntu/anaconda2/lib/python2.7/subprocess.py", line 1024, in _execute_child
  
      raise child_exception
  
  OSError: [Errno 2] No such file or directory
  
  </module>

  When I use a list to pass the ffmpeg commands parameters as following ffmpeg_create_vid_from_static_img = ['ffmpeg', '-loop', '1', '-i', '/same_path/WhiteBackground.jpg', '-c:v', 'libx264', '-t', duration, '-pix_fmt', 'yuv420p', '-vf', 'scale=1920:1080', '/same_path/white_vid.mp4'] , I get a type error :

  TypeError                                 Traceback (most recent call last)
  
   in <module>()
  
  ----> 1 generate_white_vid(0.5)
  
  
  
   in generate_white_vid(duration)
  
        3     ffmpeg_create_vid_from_static_img = ['ffmpeg', '-loop', '1', '-i', '/home/ubuntu/matar/multispectral/WhiteBackground.jpg', '-c:v', 'libx264', '-t', duration, '-pix_fmt yuv420p', '-vf', 'scale=1920:1080', '/home/ubuntu/matar/multispectral/white_vid.mp4']
  
        4     print ffmpeg_create_vid_from_static_img
  
  ----> 5     pp = subprocess.Popen(ffmpeg_create_vid_from_static_img)
  
        6     pp.communicate()
  
  
  
  /home/ubuntu/anaconda2/lib/python2.7/subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
  
      388                                 p2cread, p2cwrite,
  
      389                                 c2pread, c2pwrite,
  
  --> 390                                 errread, errwrite)
  
      391         except Exception:
  
      392             # Preserve original exception in case os.close raises.
  
  
  
  /home/ubuntu/anaconda2/lib/python2.7/subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, to_close, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
  
     1022                         raise
  
     1023                 child_exception = pickle.loads(data)
  
  -> 1024                 raise child_exception
  
     1025 
  
     1026 
  
  
  
  TypeError: execv() arg 2 must contain only strings
  
  </module>

• Getting video properties with Python without calling external software

  24 juillet 2019, par ullix

  [Update :] Yes, it is possible, now some 20 months later. See Update3 below ! [/update]

  Is that really impossible ? All I could find were variants of calling FFmpeg (or other software). My current solution is shown below, but what I really would like to get for portability is a Python-only solution that doesn’t require users to install additional software.

  After all, I can easily play videos using PyQt’s Phonon, yet I can’t get simply things like dimension or duration of the video ?

  My solution uses ffmpy (http://ffmpy.readthedocs.io/en/latest/ffmpy.html ) which is a wrapper for FFmpeg and FFprobe (http://trac.ffmpeg.org/wiki/FFprobeTips). Smoother than other offerings, yet it still requires an additional FFmpeg installation.

      import ffmpy, subprocess, json
  
      ffprobe = ffmpy.FFprobe(global_options="-loglevel quiet -sexagesimal -of json -show_entries stream=width,height,duration -show_entries format=duration -select_streams v:0", inputs={"myvideo.mp4": None})
  
      print("ffprobe.cmd:", ffprobe.cmd)  # printout the resulting ffprobe shell command
  
      stdout, stderr = ffprobe.run(stderr=subprocess.PIPE, stdout=subprocess.PIPE)
  
      # std* is byte sequence, but json in Python 3.5.2 requires str
  
      ff0string = str(stdout,'utf-8')
  
  
  
      ffinfo = json.loads(ff0string)
  
      print(json.dumps(ffinfo, indent=4)) # pretty print
  
  
  
      print("Video Dimensions: {}x{}".format(ffinfo["streams"][0]["width"], ffinfo["streams"][0]["height"]))
  
      print("Streams Duration:", ffinfo["streams"][0]["duration"])
  
      print("Format Duration: ", ffinfo["format"]["duration"])

  Results in output :

      ffprobe.cmd: ffprobe -loglevel quiet -sexagesimal -of json -show_entries stream=width,height,duration -show_entries format=duration -select_streams v:0 -i myvideo.mp4
  
      {
  
          "streams": [
  
              {
  
                  "duration": "0:00:32.033333",
  
                  "width": 1920,
  
                  "height": 1080
  
              }
  
          ],
  
          "programs": [],
  
          "format": {
  
              "duration": "0:00:32.064000"
  
          }
  
      }
  
      Video Dimensions: 1920x1080
  
      Streams Duration: 0:00:32.033333
  
      Format Duration:  0:00:32.064000

  UPDATE after several days of experimentation : The hachoire solution as proposed by Nick below does work, but will give you a lot of headaches, as the hachoire responses are too unpredictable. Not my choice.

  With opencv coding couldn’t be any easier :

  import cv2
  
  vid = cv2.VideoCapture( picfilename)
  
  height = vid.get(cv2.CAP_PROP_FRAME_HEIGHT) # always 0 in Linux python3
  
  width  = vid.get(cv2.CAP_PROP_FRAME_WIDTH)  # always 0 in Linux python3
  
  print ("opencv: height:{} width:{}".format( height, width))

  The problem is that it works well on Python2 but not on Py3. Quote : "IMPORTANT NOTE : MacOS and Linux packages do not support video related functionality (not compiled with FFmpeg)" (https://pypi.python.org/pypi/opencv-python).

  On top of this it seems that opencv needs the presence of the binary packages of FFmeg at runtime (https://docs.opencv.org/3.3.1/d0/da7/videoio_overview.html).

  Well, if I need an installation of FFmpeg anyway, I can stick to my original ffmpy example shown above :-/

  Thanks for the help.

  UPDATE2 : master_q (see below) proposed MediaInfo. While this failed to work on my Linux system (see my comments), the alternative of using pymediainfo, a py wrapper to MediaInfo, did work. It is simple to use, but it takes 4 times longer than my initial ffprobe approach to obtain duration, width and height, and still needs external software, i.e. MediaInfo :

  from pymediainfo import MediaInfo
  
  media_info = MediaInfo.parse("myvideofile")
  
  for track in media_info.tracks:
  
      if track.track_type == 'Video':
  
          print("duration (millisec):", track.duration)
  
          print("width, height:", track.width, track.height)

  UPDATE3 : OpenCV is finally available for Python3, and is claimed to run on Linux, Win, and Mac ! It makes it really easy, and I verfied that external software - in particular ffmpeg - is NOT needed !

  First install OpenCV via Pip :

  pip install opencv-python

  Run in Python :

  import cv2
  
  cv2video = cv2.VideoCapture( videofilename)
  
  height = cv2video.get(cv2.CAP_PROP_FRAME_HEIGHT)
  
  width  = cv2video.get(cv2.CAP_PROP_FRAME_WIDTH) 
  
  print ("Video Dimension: height:{} width:{}".format( height, width))
  
  
  
  framecount = cv2video.get(cv2.CAP_PROP_FRAME_COUNT ) 
  
  frames_per_sec = cv2video.get(cv2.CAP_PROP_FPS)
  
  print("Video duration (sec):", framecount / frames_per_sec)
  
  
  
  # equally easy to get this info from images
  
  cv2image = cv2.imread(imagefilename, flags=cv2.IMREAD_COLOR  )
  
  height, width, channel  = cv2image.shape
  
  print ("Image Dimension: height:{} width:{}".format( height, width))

  I also needed the first frame of a video as an image, and used ffmpeg for this to save the image in the file system. This also is easier with OpenCV :

  hasFrames, cv2image = cv2video.read()   # reads 1st frame
  
  cv2.imwrite("myfilename.png", cv2image) # extension defines image type

  But even better, as I need the image only in memory for use in the PyQt5 toolkit, I can directly read the cv2-image into an Qt-image :

  bytesPerLine = 3 * width
  
  # my_qt_image = QImage(cv2image, width, height, bytesPerLine, QImage.Format_RGB888) # may give false colors!
  
  my_qt_image = QImage(cv2image.data, width, height, bytesPerLine, QImage.Format_RGB888).rgbSwapped() # correct colors on my systems

  As OpenCV is a huge program, I was concerned about timing. Turned out, OpenCV was never behind the alternatives. I takes some 100ms to read a slide, all the rest combined takes never more than 10ms.

  I tested this successfully on Ubuntu Mate 16.04, 18.04, and 19.04, and on two different installations of Windows 10 Pro. (Did not have Mac avalable). I am really delighted about OpenCV !

  You can see it in action in my SlideSorter program, which allows to sort images and videos, preserve sort order, and present as slideshow. Available here : https://sourceforge.net/projects/slidesorter/