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• Basic "pass-through" use of FFmpegReader/FFmpegWriter in scikit-video

  6 février 2021, par JonathanZ supports MonicaC

  I am starting to use scikit-video and am having trouble writing files. I have reduced the problem to the simplest possible example

  


  vid_file = "6710185719062326259_stamp_25pct.mp4"
output_file = "out_temp3.mp4"
reader = skvideo.io.FFmpegReader(vid_file)
writer = skvideo.io.FFmpegWriter(output_file)
for frame in reader.nextFrame():
        writer.writeFrame(frame)
writer.close()


  


  I'm playing the files in VLC, and the vid_file is valid but the output file, though playable, is mostly big green blocks (though I can discern some details from the original video in it).

  


  My goal, or course, is to do "interesting" manipulations of the frame before I write it out, but I need to get the "no modifications" version working correctly first. I'm also going to be using this on large files, so the vread/vwrite functions that process an entire file at once are not appropriate.

  


  I'm guessing I need to set the appropriate values in the outputdict parameter for the FFmpegWriter, but there are so many that I don't know where to start. I have tried

  


  writer = skvideo.io.FFmpegWriter(output_file, outputdict={'-crf': '0', '-pix_fmt': 'rgb24'})


  


  (-crf 0 to suppress any compression, -pixfmt rgb24 as that's what FFmpegReader says it delivers by default, but these don't work either.

  


  Any ideas on how to make this work ?

  


  Here's the skvideo.io.ffprobe video information for the input file.

  


  {
    "@index": "0",
    "@codec_name": "h264",
    "@codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
    "@profile": "High",
    "@codec_type": "video",
    "@codec_time_base": "1/30",
    "@codec_tag_string": "avc1",
    "@codec_tag": "0x31637661",
    "@width": "480",
    "@height": "270",
    "@coded_width": "480",
    "@coded_height": "272",
    "@has_b_frames": "2",
    "@pix_fmt": "yuv420p",
    "@level": "21",
    "@chroma_location": "left",
    "@refs": "1",
    "@is_avc": "true",
    "@nal_length_size": "4",
    "@r_frame_rate": "15/1",
    "@avg_frame_rate": "15/1",
    "@time_base": "1/15360",
    "@start_pts": "0",
    "@start_time": "0.000000",
    "@duration_ts": "122880",
    "@duration": "8.000000",
    "@bit_rate": "183806",
    "@bits_per_raw_sample": "8",
    "@nb_frames": "120",
    "disposition": {
        "@default": "1",
        "@dub": "0",
        "@original": "0",
        "@comment": "0",
        "@lyrics": "0",
        "@karaoke": "0",
        "@forced": "0",
        "@hearing_impaired": "0",
        "@visual_impaired": "0",
        "@clean_effects": "0",
        "@attached_pic": "0",
        "@timed_thumbnails": "0"
    },
    "tag": [
        {
            "@key": "language",
            "@value": "und"
        },
        {
            "@key": "handler_name",
            "@value": "VideoHandler"
        }
    ]
}


  


  I will mention that when I ffprobe the output file the only differences I see are 1) the timing data is different, which isn't surprising, and 2) the output file has

  


      "@has_b_frames": "0",
    "@pix_fmt": "yuv444p",


  


  I'm pretty confident the reader is working okay, because if I write out the data with

  


  skimage.io.imsave('x.png', frame,  check_contrast=False)


  


  it looks good.

  


• Why does ffmpeg could only record the first 100 frames of the animation ?

  9 février 2020, par jack fang

  I am using the following Python code to make an animation and want to save it as a video through FFmpeg (in PyCharm) :

  import numpy as np
  
  import matplotlib.pyplot as plt
  
  import matplotlib.animation as animation
  
  from matplotlib.animation import FFMpegWriter
  
  
  
  def func():
  
      for j in range(1, len(t)):
  
          time = j * 0.01
  
          print('time:{:2}'.format(time))
  
          yield time
  
  
  
  def animate(data):
  
      time = data
  
      ax2.plot(time, time, **{'marker':'o'})
  
      ax2.set_title('t = {:.2}'.format(time))
  
      return  ax2
  
  
  
  def init():
  
      ax2.plot(0, 0)
  
      return ax2
  
  
  
  dt = 0.01
  
  t = np.arange(0, 50, dt)
  
  
  
  fig2 = plt.figure()
  
  ax2 = fig2.add_subplot(111, autoscale_on=True)
  
  ax2.grid()
  
  
  
  ani = animation.FuncAnimation(fig2, animate, func, interval=dt*1000, blit=False, init_func=init, repeat=False)
  
  
  
  plt.rcParams['animation.ffmpeg_path'] = 'C:\Program Files\\ffmpeg\\bin\\ffmpeg.exe'
  
  writer = FFMpegWriter(fps=15, metadata=dict(artist='Me'), bitrate=1800)
  
  ani.save("movie.mp4", writer=writer)
  
  
  
  #plt.show()

  But when time reaches 1.0, the process stopped but it is supposed to stop when time reaches 50.0. The following picture shows when the process stopped. The PyCharm Run console
  I then check movie.mp4 and find that the video ends when time reaches 1.0.
  That is to say, only the first 100 frames of the animation were converted into the .mp4 file, so I was very confused where did the rest of the frames went ?

  I tried to run the code through windows cmd but got the same result.
  I then uncomment the line #plt.show() and found that the process stopped when time reaches 50.0 and the animation could be displayed properly but still only the first 100 frames was converted.

  I am now very confused about this problem and don’t know how to solve it. Appreciated for your help. :)

• Can't download Accord NuGet in VS 2015 nor VS 2017

  26 juin 2017, par John Leone

  Here is the package,,, NuGet Accord.Video.FFMPEG

  Here is the error,,,
  Package restore failed. Rolling back package changes for ’EssentialTimeLapseVideo’.

  I used this NuGet in a Windows Form app I am working on, and had no issues. Then something came up with Time Lapse, and I wanted to use it in a UWP, but, for some reason it won’t install.

  I tried the mirror suggested, and got the following.
  

  Any help would be appreciated. Thanks, John.