get the number of frame of a video using vision.VideoFileReader and VideoReader

Using VideoReader:

obj = VideoReader(vidfullfile);
obj.NumOfFrames

Using vision.VideoFileReader:

videoFileReader = vision.VideoFileReader(vidfullfile);
count= 0;
while ~isDone(videoFileReader)

      % Read a video frame and run the detector.
      videoFrame = step(videoFileReader);
      count= ind+1;
  end

But obj.NumOfFrames does not equal to count for my video file. Actually count = obj.NumOfFrames+1.

Can anyone explain this?

Thanks, Zhong

[ALEX]

correction here:

obj.NumberOfFrames

[Royi Avital]

Where is NumberOfFrames documented?

[Walter Roberson]

Royi, see https://www.mathworks.com/matlabcentral/answers/250033-number-of-frames-in-video-file-with-matlab-2015b#answer_196870

Answer 1

[Behzad Taheri]

If you try:

>>obj = VideoReader('atrium.avi');

>> obj

obj = VideoReader with properties:

   General Properties:
            Name: 'atrium.avi'
            Path: 'C:\Program Files\MATLAB\R2015a\toolbox\vision\visiondata'
        Duration: 47
     CurrentTime: 0
             Tag: ''
        UserData: []
   Video Properties:
           Width: 640
          Height: 360
       FrameRate: 30
    BitsPerPixel: 24
     VideoFormat: 'RGB24'

you will see that, only Duration and FrameRate are available. So the number of frames can be calculated as: Duration x FrameRate = 47 x 30 = 1410

[Walter Roberson]

Vision.VideoFileReader especially is designed to support files with variable framerates where framerate times duration might not give you the correct total number of frames.

[Yunxing Tian]

In my experiment, the actural frame number is 296, however, the durition is 9.9200 and the fps is 30. floor(9.92*30) = 297

Answer 2

[OJ27]

because you set count=0. Remember matlab indexing starts the count at 1.

Answer 3

[Walter Roberson]

See also https://www.mathworks.com/matlabcentral/answers/250033-number-of-frames-in-video-file-with-matlab-2015b#answer_196870

Basically, you need to scan the entire movie to find the number of frames correctly. The NumberOfFrames, when it existed, was an estimate.

Answer 4

[Gerard Wensink]

Best method: (Direct by calculating right parameters, confirmed by ffmpeg)

Cmd ->

ffprobe.exe -v error -select_streams v:0 -show_entries stream=r_frame_rate,duration -of default=nw=1 "d:\movies\The.Matrix.1999.1080p.BrRip.x264.YIFY.dut.mp4"

Result ->

r_frame_rate=24000/1001

duration=8177.794625

Calculation ->

Frames=24000/1001*8177.794625=196071 (exactly... ;P)

Proof ->

ffmpeg -i "d:\movies\The.Matrix.1999.1080p.BrRip.x264.YIFY.dut.mp4" -f null /dev/null

ffmpeg version N-92938-g0aaaca25e0-ffmpeg-windows-pacman Copyright (c) 2000-2019 the FFmpeg developers

built with gcc 8.2.0 (GCC)

configuration: --pkg-config=pkg-config --pkg-config-flags=--static --extra-version=ffmpeg-windows-pacman --enable-version3 --disable-debug --disable-w32threads --arch=x86_64 --target-os=mingw32 --cross-prefix=/opt/sandbox/cross_compilers/mingw-w64-x86_64/bin/x86_64-w64-mingw32- --enable-libcaca --enable-gray --enable-libtesseract --enable-fontconfig --enable-gmp --enable-gnutls --enable-libass --enable-libbluray --enable-libbs2b --enable-libflite --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libzimg --enable-libzvbi --enable-libmysofa --enable-libaom --enable-libopenjpeg --enable-libopenh264 --enable-liblensfun --enable-nvenc --enable-nvdec --extra-libs=-lm --extra-libs=-lpthread --extra-cflags=-DLIBTWOLAME_STATIC --extra-cflags=-DMODPLUG_STATIC --extra-cflags=-DCACA_STATIC --enable-amf --enable-libmfx --enable-gpl --enable-avisynth --enable-frei0r --enable-filter=frei0r --enable-librubberband --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxvid --enable-libxavs --enable-avresample --extra-cflags='-march=core2' --extra-cflags=-O2 --enable-static --disable-shared --prefix=/opt/sandbox/cross_compilers/mingw-w64-x86_64/x86_64-w64-mingw32 --enable-nonfree --enable-decklink --enable-libfdk-aac

libavutil 56. 25.100 / 56. 25.100

libavcodec 58. 43.100 / 58. 43.100

libavformat 58. 25.100 / 58. 25.100

libavdevice 58. 6.101 / 58. 6.101

libavfilter 7. 47.100 / 7. 47.100

libavresample 4. 0. 0 / 4. 0. 0

libswscale 5. 4.100 / 5. 4.100

libswresample 3. 4.100 / 3. 4.100

libpostproc 55. 4.100 / 55. 4.100

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'd:\movies\The.Matrix.1999.1080p.BrRip.x264.YIFY.dut.mp4':

Metadata:

major_brand : isom

minor_version : 512

compatible_brands: isomiso2avc1mp41

encoder : Lavf58.25.100

Duration: 02:16:17.91, start: 0.000000, bitrate: 2497 kb/s

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x800 [SAR 1:1 DAR 12:5], 2397 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)

Metadata:

handler_name : VideoHandler

Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 93 kb/s (default)

Metadata:

handler_name : GPAC ISO Audio Handler

Stream mapping:

Stream #0:0 -> #0:0 (h264 (native) -> wrapped_avframe (native))

Stream #0:1 -> #0:1 (aac (native) -> pcm_s16le (native))

Press [q] to stop, [?] for help

Output #0, null, to '/dev/null':

Metadata:

major_brand : isom

minor_version : 512

compatible_brands: isomiso2avc1mp41

encoder : Lavf58.25.100

Stream #0:0(und): Video: wrapped_avframe, yuv420p, 1920x800 [SAR 1:1 DAR 12:5], q=2-31, 200 kb/s, 23.98 fps, 23.98 tbn, 23.98 tbc (default)

Metadata:

handler_name : VideoHandler

encoder : Lavc58.43.100 wrapped_avframe

Stream #0:1(und): Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s (default)

Metadata:

handler_name : GPAC ISO Audio Handler

encoder : Lavc58.43.100 pcm_s16le

HERE!!! ->

frame=196071 fps=331 q=-0.0 Lsize=N/A time=02:16:17.90 bitrate=N/A speed=13.8x

YOU SEE???? GREAT IS'NT IT EH?

video:102631kB audio:1408772kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

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