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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


  


• error while compiling simple c++ file with libavformat library

  21 février 2023, par Abdo Daood

  i create simple c++ file called test.cpp

  


  #include <iostream>&#xA;#include &#xA;using namespace std;&#xA;&#xA;int main() &#xA;{&#xA;    cout &lt;&lt; "Hello, World!";&#xA;    return 0;&#xA;}&#xA;&#xA;</iostream>

  


  and using g++ in terminal to compile test.cpp file with the command :

  


  


  g++ test.cpp -o test

  


  


  i get this error =>

  


  test.cpp:2:10: fatal error: libavformat\avformat.h: No such file or directory
    2 | #include 
      |          ^~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.


  


  Notes :
libavformat\avformat.h path is : /usr/include/x86_64-linux-gnu/libavformat/avformat.h

  


  and using ffmpeg version is :

  


  $ ffmpeg -version

  


  ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
configuration : —prefix=/usr —extra-version=0ubuntu0.22.04.1 —toolchain=hardened —libdir=/usr/lib/x86_64-linux-gnu —incdir=/usr/include/x86_64-linux-gnu —arch=amd64 —enable-gpl —disable-stripping —enable-gnutls —enable-ladspa —enable-libaom —enable-libass —enable-libbluray —enable-libbs2b —enable-libcaca —enable-libcdio —enable-libcodec2 —enable-libdav1d —enable-libflite —enable-libfontconfig —enable-libfreetype —enable-libfribidi —enable-libgme —enable-libgsm —enable-libjack —enable-libmp3lame —enable-libmysofa —enable-libopenjpeg —enable-libopenmpt —enable-libopus —enable-libpulse —enable-librabbitmq —enable-librubberband —enable-libshine —enable-libsnappy —enable-libsoxr —enable-libspeex —enable-libsrt —enable-libssh —enable-libtheora —enable-libtwolame —enable-libvidstab —enable-libvorbis —enable-libvpx —enable-libwebp —enable-libx265 —enable-libxml2 —enable-libxvid —enable-libzimg —enable-libzmq —enable-libzvbi —enable-lv2 —enable-omx —enable-openal —enable-opencl —enable-opengl —enable-sdl2 —enable-pocketsphinx —enable-librsvg —enable-libmfx —enable-libdc1394 —enable-libdrm —enable-libiec61883 —enable-chromaprint —enable-frei0r —enable-libx264 —enable-shared
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
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100

  


  using this command :

  


  g++ `pkg-config --cflags libavformat` test.cpp  `pkg-config --libs libavformat` -o test



  


• ffmpeg -f sdl works, ffmpeg -c codec -f sdl doesn't

  3 octobre 2022, par lunadir

  running on windows
  
anyone knows why this works

  


  ffmpeg -re -i "sample_itunes.mp4" -an -f sdl2 -


  


  and this doesn't

  


  ffmpeg -re -i "sample_itunes.mp4" -an -c libx264 -f sdl2 -


  


  doesn't show any window, output is

  


  ffmpeg.exe -re -i "sample_itunes.mp4" -an -c libx264 -r 1 -f sdl2 -
ffmpeg version n4.4-79-gde1132a891-20210803 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20210803
  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
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'sample_itunes.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 2036-02-06T06:28:16.000000Z
    encoder         : HandBrake 0.10.2 2015060900
  Duration: 00:01:25.50, start: 0.000000, bitrate: 245 kb/s
  Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt709), 640x480 [SAR 1:1 DAR 4:3], 116 kb/s, 10 fps, 10 tbr, 90k tbn, 180k tbc (default)
    Metadata:
      creation_time   : 2036-02-06T06:28:16.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 125 kb/s (default)
    Metadata:
      creation_time   : 2036-02-06T06:28:16.000000Z
      handler_name    : Mono
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0000025cce1ab7c0] using SAR=1/1
[libx264 @ 0000025cce1ab7c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0000025cce1ab7c0] profile High, level 2.2, 4:2:0, 8-bit
[sdl,sdl2 @ 0000025cce769040] Only supports one rawvideo stream
Output #0, sdl,sdl2, to 'pipe:':
  Metadata:
    major_brand     : mp42
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.76.100
  Stream #0:0(und): Video: h264, yuv420p(tv, smpte170m/smpte170m/bt709, progressive), 640x480 [SAR 1:1 DAR 4:3], q=2-31, 1 fps, 1 tbn (default)
    Metadata:
      creation_time   : 2036-02-06T06:28:16.000000Z
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc58.134.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 3 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 3 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 4 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 3 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 4 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
    Last message repeated 3 times
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTSrate=N/A speed=   0x
debug=1
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
    Last message repeated 4 times
[h264 @ 0000025ccc8fd8c0] nal_unit_type: 1(Coded slice of a non-IDR picture), nal_ref_idc: 0
[libx264 @ 0000025cce1ab7c0] non-strictly-monotonic PTS
[h264 @ 0000025ccc8fd8c0] slice:1 F mb:0 B fix frame:15 poc:65622/65622 ref:1/1 qp:7 loop:1:0:0 weight:0 SPAT
cur_dts is invalid st:0 (0) [init:1 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
    Last message repeated 8 times
...
frame=   60 fps=8.4 q=25.0 Lsize=N/A time=-00:00:00.10 bitrate=N/A speed=N/A
video:1kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (sample_itunes.mp4):
  Input stream #0:0 (video): 74 packets read (22110 bytes); 61 frames decoded;
  Input stream #0:1 (audio): 1 packets read (18 bytes);
  Total: 75 packets (22128 bytes) demuxed
Output file #0 (pipe:):
  Output stream #0:0 (video): 60 frames encoded; 1 packets muxed (866 bytes);
  Total: 1 packets (866 bytes) muxed
61 frames successfully decoded, 0 decoding errors
[libx264 @ 000001d2952aa600] frame I:1     Avg QP: 7.93  size:   866
[libx264 @ 000001d2952aa600] frame P:23    Avg QP:13.48  size:   535
[libx264 @ 000001d2952aa600] frame B:36    Avg QP:10.98  size:    81
[libx264 @ 000001d2952aa600] consecutive B-frames: 16.7% 10.0%  0.0% 73.3%
[libx264 @ 000001d2952aa600] mb I  I16..4: 99.7%  0.1%  0.2%
[libx264 @ 000001d2952aa600] mb P  I16..4:  6.2%  3.1%  0.8%  P16..4:  1.4%  0.4%  0.2%  0.0%  0.0%    skip:88.1%
[libx264 @ 000001d2952aa600] mb B  I16..4:  0.2%  0.0%  0.0%  B16..8:  2.2%  0.2%  0.0%  direct: 0.1%  skip:97.2%  L0:35.9% L1:61.8% BI: 2.3%
[libx264 @ 000001d2952aa600] 8x8 transform intra:21.1% inter:48.3%
[libx264 @ 000001d2952aa600] coded y,uvDC,uvAC intra: 6.7% 1.9% 0.5% inter: 0.2% 0.1% 0.0%
[libx264 @ 000001d2952aa600] i16 v,h,dc,p: 57% 41%  2%  0%
[libx264 @ 000001d2952aa600] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 13% 34% 51%  0%  0%  0%  0%  1%  0%
[libx264 @ 000001d2952aa600] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 34% 21%  2%  2%  3%  3%  3%  2%
[libx264 @ 000001d2952aa600] i8c dc,h,v,p: 84% 15%  2%  0%
[libx264 @ 000001d2952aa600] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 000001d2952aa600] ref P L0: 84.5%  3.6%  6.3%  5.5%
[libx264 @ 000001d2952aa600] ref B L0: 78.0% 21.2%  0.9%
[libx264 @ 000001d2952aa600] ref B L1: 96.8%  3.2%
[libx264 @ 000001d2952aa600] kb/s:21.46
[AVIOContext @ 000001d29529e780] Statistics: 232272 bytes read, 2 seeks
Conversion failed!