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• Extracting number of duplicate (or dropped) frames in ffmpeg via C/C++ API

  20 septembre 2023, par userDtrm

  Is there a way to extract number of duplicated or dropped video frames during the decoding of a .mp4 or .ts file through ffmpeg's C/C++ API ?

  


  This information is reported by ffmpeg when using the command line tool. However, I have a requirement that I need this information to be extracted in C/C++.

  


• Estimating number of frames and fps in opencv

  11 mai 2021, par mrgloom

  I have some .mp4 video, ffmpeg shows me this info :

  


    Duration: 00:00:07.02, start: 0.000000, bitrate: 18001 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709/bt709/iec61966-2-1, progressive), 886x1920, 14299 kb/s, 22.54 fps, 60 tbr, 600 tbn, 1200 tbc (default)
    Metadata:
      rotate          : 270
      creation_time   : 2021-04-30T13:56:51.000000Z
      handler_name    : Core Media Video
      encoder         : 'avc1'
    Side data:
      displaymatrix: rotation of 90.00 degrees


  


  So as I understand it should be 7.02 sec * 22.54 fps 158 frames

  


  When I try to read it in opencv :

  


  def print_info_cap_reading(video_filepath):
    cap = cv2.VideoCapture(video_filepath)

    fps = cap.get(cv2.CAP_PROP_FPS)
    n_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

    print('fps:', round(fps, 2))
    print('n_frames', n_frames)

    counter = 0
    while True:
        ret, frame = cap.read()
        if ret == False:
            break
        counter += 1

    print('counter:', counter)


  


  It shows me

  


  # fps: 22.54
# n_frames 199
# counter: 175


  


  When I tried to convert it to separate frames via ffmpeg it produce 422 frames :

  


  ffmpeg -i source1.mp4 tmp/img%03d.jpg


  


  So I wonder :

  


  

  1. Why fps is float value and not int value ?

  


  2. What is the right way to estimate fps and number of frames ?

  


  3. Why cv2.CAP_PROP_FRAME_COUNT in opencv and actually reading frames produce different number of frames ?

  


  


  Update :

  


  -ignore_editlist 1 not helped, ffmpeg still produce 422 frames :

  


   ffmpeg -i source1.mp4 tmp1/img%03d.jpg
 ffmpeg -i source1.mp4 -ignore_editlist 1 tmp2/img%03d.jpg


  


  Here is some ffmpeg output :

  


  Output #0, image2, to 'tmp1/img%03d.jpg':
  Metadata:
    major_brand     : qt
    minor_version   : 0
    compatible_brands: qt
    com.apple.quicktime.author: ReplayKitRecording
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 1920x886, q=2-31, 200 kb/s, 60 fps, 60 tbn, 60 tbc (default)
    Metadata:
      encoder         : Lavc58.91.100 mjpeg
      creation_time   : 2021-04-30T13:56:51.000000Z
      handler_name    : Core Media Video
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
      displaymatrix: rotation of -0.00 degrees
frame=  422 fps=224 q=24.8 Lsize=N/A time=00:00:07.03 bitrate=N/A dup=247 drop=0 speed=3.74x
video:13709kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  


  Update :

  


  mkdir tmp3 && ffmpeg -ignore_editlist 1 -i source1.mp4 tmp3/img%03d.jpg produce even more frames - 529.

  


  Output #0, image2, to 'tmp3/img%03d.jpg':
  Metadata:
    major_brand     : qt
    minor_version   : 0
    compatible_brands: qt
    com.apple.quicktime.author: ReplayKitRecording
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: mjpeg, yuvj420p(pc), 1920x886, q=2-31, 200 kb/s, 60 fps, 60 tbn, 60 tbc (default)
    Metadata:
      encoder         : Lavc58.91.100 mjpeg
      creation_time   : 2021-04-30T13:56:51.000000Z
      handler_name    : Core Media Video
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
      displaymatrix: rotation of -0.00 degrees
frame=  529 fps=221 q=24.8 Lsize=N/A time=00:00:08.81 bitrate=N/A dup=330 drop=0 speed=3.68x
video:16178kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  


• Core : Update elementValue method to deal with type="number" fields

  29 avril 2014, par jamierytlewski

  Core : Update elementValue method to deal with type="number" fields
  The HTML5 draft defines, for type="number" inputs : "The value
  
  sanitization algorithm is as follows : If the value of the element is not
  
  a valid floating-point number, then set it to the empty string instead."
  
  If the constraint validation considers the input invalid, return false
  
  as the value, instead of the empty string, for the number and digit
  
  methods to output their messages.
  This would break in browsers that support type="number", but not the
  
  constraint validation API. I don’t know of any existing browser where
  
  that applies.
  Fixes #858
  
  Fixes #922
  
  Closes #1093