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• Why does OpenCV read video faster than FFMPEG ?

  17 septembre 2022, par tadejsv

  I noticed that OpenCV reads video frames almost 2x faster than FFMPEG.

  


  Why is that ? I thought all OpenCV does is call FFMPEG under the hood, possibly adding its own overhead.

  


  Here's the code I use to obtain these results

  


  import cv2
import time
import numpy as np

cap = cv2.VideoCapture("BigBuckBunny.mp4", apiPreference=cv2.CAP_FFMPEG)
frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

start = time.perf_counter()
while True:
    ret, frame = cap.read()
    if ret is False:
        break
    assert frame.shape == (720, 1280, 3)
    assert frame.dtype == np.uint8
end = time.perf_counter()

print(f"{frames/(end-start):.1f} frames per second")
# Output: 692.3 frames per second

cap.release()


  


  For FFMPEG (using the python-ffmpeg library :

  


  import ffmpeg
import numpy as np
import time

vid_info = ffmpeg.probe("BigBuckBunny.mp4")['streams'][1]
frames = int(vid_info['nb_frames'])

process1 = (
    ffmpeg
    .input("BigBuckBunny.mp4")
    .output('pipe:', format='rawvideo', pix_fmt='bgr24')
)
print(process1.compile())
# Output: ['ffmpeg', '-i', 'BigBuckBunny.mp4', '-f', 'rawvideo', '-pix_fmt', 'bgr24', 'pipe:']


process1 = process1.run_async(pipe_stdout=True)

start = time.perf_counter()
while True:
    in_bytes = process1.stdout.read(1280 * 720 * 3)
    if not in_bytes:
        break
    frame = np.frombuffer(in_bytes, np.uint8).reshape([720, 1280, 3])
end = time.perf_counter()
print(f"{frames/(end-start):.1f} frames per second")
# Output: 373.6 frames per second
process1.wait()


  


  Here's information about the video ( 10 minutes length)

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'BigBuckBunny.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isomavc1mp42
    creation_time   : 2010-01-10T08:29:06.000000Z
  Duration: 00:09:56.47, start: 0.000000, bitrate: 2119 kb/s
  Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)
    Metadata:
      creation_time   : 2010-01-10T08:29:06.000000Z
      handler_name    : (C) 2007 Google Inc. v08.13.2007.
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1991 kb/s, 24 fps, 24 tbr, 24k tbn, 48 tbc (default)
    Metadata:
      creation_time   : 2010-01-10T08:29:06.000000Z
      handler_name    : (C) 2007 Google Inc. v08.13.2007.
      vendor_id       : [0][0][0][0]


  


  And FFMPEG and OpenCV versions :

  


  ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers


  


  opencv-python-headless        4.6.0.66


  


• MP4 videos in Firefox and IE not respecting rotation

  3 novembre 2022, par jnevelson

  We have a webpage that plays back a faststart MP4 in a <video></video> tag - pretty simple, and it works great in Chrome and Safari. However, it seems as though Firefox 36 and IE10 are not respecting the rotation of the video, so they end up playing either upside down or rotated 90*.

  



  Here is what ffprobe says about one of the videos :

  



  
╰─$ ffprobe test
ffprobe version 2.6 Copyright (c) 2007-2015 the FFmpeg developers
  built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6_1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libvorbis --enable-libvpx --enable-libfaac --enable-nonfree --enable-vda
  libavutil      54. 20.100 / 54. 20.100
  libavcodec     56. 26.100 / 56. 26.100
  libavformat    56. 25.101 / 56. 25.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 11.102 /  5. 11.102
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test':
  Metadata:
    major_brand     : qt
    minor_version   : 512
    compatible_brands: qt
    date            : 2015-03-03T15:57:38-0800
    date-eng        : 2015-03-03T15:57:38-0800
    encoder         : Lavf56.25.101
  Duration: 00:00:06.29, start: 0.000000, bitrate: 25699 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 25862 kb/s, 59.98 fps, 60 tbr, 19200 tbn, 38400 tbc (default)
    Metadata:
      rotate          : 180
      handler_name    : DataHandler
      encoder         : H.264
    Side data:
      displaymatrix: rotation of 180.00 degrees
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 63 kb/s (default)
    Metadata:
      handler_name    : DataHandler


  



  I've Googled around and haven't found any information or bug reports on this, so I'm wondering if it's something we're missing or doing wrong. The video itself is only run through ffmpeg to make it faststart so we can stream it - no other encoding/transcoding is done.

  



  I'm hoping there's a better solution than to return the rotation alongside the video and transform it via CSS - especially because it's rotated properly in Chrome and Safari.

  



  Thanks !

  


• FFMPEG Outputs gets blurry when scaled

  17 octobre 2022, par Ps Sarvna

  I'm trying to scale my input video to standard 1280x720 resolution, but my output looks blurred when compared to the input.

  


  FFMPEG CMD

  


  ffmpeg -i input.webm -filter_complex "[0:v] scale=1280.0:720.0 [v0]" -map [v0] output.webm


  


  Input File FFProbe

  


  ffprobe version 4.4.2 Copyright (c) 2007-2021 the FFmpeg developers
  built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
  configuration: --prefix='/opt/homebrew/Cellar/ffmpeg@4/4.4.2_3' --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-avresample --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, matroska,webm, from 'input.webm':
  Metadata:
    ENCODER         : Lavf58.76.100
  Duration: 00:00:20.01, start: 0.000000, bitrate: 1929 kb/s
  Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv, bt470bg/bt709/bt709, progressive), 1512x982, SAR 1:1 DAR 756:491, 29.08 fps, 29.08 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      ENCODER         : Lavc58.134.100 libvpx-vp9
      DURATION        : 00:00:20.011000000


  


  Output File FFProbe

  


  ffprobe version 4.4.2 Copyright (c) 2007-2021 the FFmpeg developers
  built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
  configuration: --prefix='/opt/homebrew/Cellar/ffmpeg@4/4.4.2_3' --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-avresample --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, matroska,webm, from 'output.webm':
  Metadata:
    ENCODER         : Lavf58.76.100
  Duration: 00:00:20.01, start: 0.000000, bitrate: 1699 kb/s
  Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv, bt470bg/bt709/bt709, progressive), 1280x720, SAR 1109:1280 DAR 1109:720, 29.08 fps, 29.08 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      ENCODER         : Lavc58.134.100 libvpx-vp9
      DURATION        : 00:00:20.011000000


  


  Input Video :

  


  

  


  Output Video :