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• My webcam works fine, while using cv2.Videocapture() but while trying to read from hard drive it shows error cap.isOpened() returns false, why ?

  27 septembre 2017, par Hu Yang

  import cv2
  video_capture = cv2.VideoCapture("rtsp ://admin:Trust1986_@10.58.94.47:554/h264/ch1/main/av_stream")
  video_capture.isOpened()

  False

  Other information below here, and ffmpeg I had installed.

    Video I/O:
  
      DC1394 1.x:                  NO
  
      DC1394 2.x:                  NO
  
      FFMPEG:                      NO
  
        avcodec:                   NO
  
        avformat:                  NO
  
        avutil:                    NO
  
        swscale:                   NO
  
        avresample:                NO
  
      GStreamer:                   NO
  
      OpenNI:                      NO
  
      OpenNI PrimeSensor Modules:  NO
  
      OpenNI2:                     NO
  
      PvAPI:                       NO
  
      GigEVisionSDK:               NO
  
      Aravis SDK:                  NO
  
      UniCap:                      NO
  
      UniCap ucil:                 NO
  
      V4L/V4L2:                    NO/NO
  
      XIMEA:                       NO
  
      Xine:                        NO
  
      Intel Media SDK:             NO
  
      gPhoto2:                     NO
  
  
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# ffmpeg -version
  
  ffmpeg version 3.3.4 Copyright (c) 2000-2017 the FFmpeg developers
  
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
  configuration: 
  
  libavutil      55. 58.100 / 55. 58.100
  
  libavcodec     57. 89.100 / 57. 89.100
  
  libavformat    57. 71.100 / 57. 71.100
  
  libavdevice    57.  6.100 / 57.  6.100
  
  libavfilter     6. 82.100 /  6. 82.100
  
  libswscale      4.  6.100 /  4.  6.100
  
  libswresample   2.  7.100 /  2.  7.100
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# 
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# python3.6m -V
  
  Python 3.6.2
  
  root@ubuntu:/home/face_recognition/opencv/ffmpeg/ffmpeg-3.3.4# pkg-config --modversion opencv  
  
  3.3.0

  what shall I do next step ? Thanks.

• VideoCapture() returns None in opencv & install opencv with ffmpeg

  16 décembre 2017, par Wentai Chen

  System : UBUNTU 16.04
  Python version : 3.5

  I would like to use cv2.VideoCapture() function to process my mp4 file. However, when I run the script below, I always get a result of None, so I am not able to continue my work after.

  import cv2
  
  video_cap = cv2.VideoCapture('demo.mp4')
  
  ret,frame = video_cap.read()
  
  print(ret,frame)
  
  
  
  result: False,None

  By searching a lot I realized the problem : opencv is not properly installed with ffmpeg, so that the video function in opencv does not work.

  However I didn’t find a efficient tutorial on how to properly install opencv. I wonder if anyone could help. Thank you !

• FFmpeg uses all memory and crashes when inputs used multiple times in filter_complex

  28 octobre 2020, par ed22

  If I define some dummy filter_complex say :

  


  [3:v]split=2[3_1][3_2]
[3_1]format=yuv420p,scale='640:360',setsar='1/1'[1]
[3_2]format=yuv420p,scale='640:360',setsar='1/1'[2]
[4:v]split=2[4_1][4_2]
[4_1]format=yuv420p,scale='640:360',setsar='1/1'[3]
[4_2]format=yuv420p,scale='640:360',setsar='1/1'[4]
[1][2][3][4]concat=n=4:v=1:a=0[video_out]


  


  FFmpeg uses all the memory and crashes. What might be the reason ?
The same happens for :

  


  [3:v]format=yuv420p,scale='640:360',setsar='1/1'[1]
[3:v]format=yuv420p,scale='640:360',setsar='1/1'[2]
[4:v]format=yuv420p,scale='640:360',setsar='1/1'[3]
[4:v]format=yuv420p,scale='640:360',setsar='1/1'[4]
[1][2][3][4]concat=n=4:v=1:a=0[video_out]


  


  I know the examples are silly but I am here asking about why this uses all my RAM ? (and how to work around this)

  


  This works great by the way (inputs used once) :

  


  [3:v]format=yuv420p,scale='640:360',setsar='1/1'[1]
[4:v]format=yuv420p,scale='640:360',setsar='1/1'[2]
[1][2]concat=n=2:v=1:a=0[video_out]


  


  UPDATE :
The full log. While it runs it reaches 2GB memory usage in about 5s and continues to grow.

  


  ffmpeg.exe -y -f lavfi -i nullsrc=s=640x360 -i 1000211803.mp4 -i 220710.mp4 -i 223157.mp4 -i 232365.mp4 -i 1000000046.mp4 -i 1000238585.mp4 -filter_complex_script "c:\Users\wojtek\Desktop\Development\video_grid_ffmpeg_nodejs\filter_complex_param.txt" -vsync 2 -map "[video_out]" out.mp4
ffmpeg version n4.3.1-20-g8a2acdc6da Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3-win32 (GCC) 20200320
  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-version3 --disable-debug --enable-iconv --enable-zlib --enable-libxml2 --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-opencl --enable-libvmaf --disable-vulkan --enable-libvorbis --enable-amf --enable-libaom --disable-avisynth --enable-libdav1d --disable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --disable-libglslang --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libtwolame --disable-libvidstab --disable-libx264 --disable-libx265 --disable-libxavs2 --disable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-libs=-lgomp
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
Input #0, lavfi, from 'nullsrc=s=640x360':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x360 [SAR 1:1 DAR 16:9], 25 tbr, 25 tbn, 25 tbc
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from '1000211803.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 00:55:35.33, start: 0.000000, bitrate: 136 kb/s
    Stream #1:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 134 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #2, mov,mp4,m4a,3gp,3g2,mj2, from '220710.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 00:57:21.43, start: 0.000000, bitrate: 102 kb/s
    Stream #2:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 99 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #3, mov,mp4,m4a,3gp,3g2,mj2, from '223157.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 01:01:11.27, start: 0.000000, bitrate: 156 kb/s
    Stream #3:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 153 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #4, mov,mp4,m4a,3gp,3g2,mj2, from '232365.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 01:01:07.20, start: 0.000000, bitrate: 127 kb/s
    Stream #4:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 124 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #5, mov,mp4,m4a,3gp,3g2,mj2, from '1000000046.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 00:52:17.23, start: 0.000000, bitrate: 190 kb/s
    Stream #5:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 188 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #6, mov,mp4,m4a,3gp,3g2,mj2, from '1000238585.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.33.100
  Duration: 00:50:58.77, start: 0.000000, bitrate: 106 kb/s
    Stream #6:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 376x210 [SAR 1:1 DAR 188:105], 103 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Stream mapping:
  Stream #3:0 (h264) -> format
  Stream #3:0 (h264) -> format
  Stream #4:0 (h264) -> format
  Stream #4:0 (h264) -> format
  concat -> Stream #0:0 (mpeg4)
Press [q] to stop, [?] for help
Output #0, mp4, to 'out.mp4':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: mpeg4 (mp4v / 0x7634706D), yuv420p, 640x360 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 30 fps, 15360 tbn, 30 tbc (default)
    Metadata:
      encoder         : Lavc58.91.100 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: N/A
frame= 6130 fps=610 q=20.6 Lsize=    5334kB time=00:03:24.30 bitrate= 213.9kbits/s speed=20.3x
video:5307kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.507003%


  


  The above has been produced using this filter_complex parameter value :

  


  [3:v]format=yuv420p,scale='-1:360',crop='640:in_h',setsar='1/1'[i2_640_360]
[3:v]format=yuv420p,scale='-1:360',crop='640:in_h',setsar='1/1'[i2_320_360]
[4:v]format=yuv420p,scale='-1:360',crop='640:in_h',setsar='1/1'[i3_320_360]
[4:v]format=yuv420p,scale='-1:360',crop='640:in_h',setsar='1/1'[i3_640_360]
[i2_640_360][i2_320_360][i3_320_360][i3_640_360]concat=n=4:v=1:a=0[video_out]


  


  I did not wait for it to give the out of memory error.