unable to write video (codec issues)

[adamteale]

Expected behaviour

Export a video file.

Actual behaviour

Incomplete/damaged file with error messages

Steps to reproduce

Hi everyone,

I am trying a simple test to read and write a file with OpenCV (opencv-python==4.2.0.34) on macOS 10.15.4. Python 3.7.6. Brew installed ffmpeg:

built with Apple clang version 11.0.0 (clang-1100.0.33.17)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack

The script is:

import cv2

cap = cv2.VideoCapture('sample.mov')

fourcc = cv2.VideoWriter_fourcc(*'MJPG')
out = cv2.VideoWriter('output.mov',fourcc, 23.98, (640,480))

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        out.write(frame)
    else:
        break

cap.release()
out.release()
cv2.destroyAllWindows()

I have tried several codecs which always end up with either nothing or a incomplete/damaged file and errors like this:

OpenCV: FFMPEG: tag 0x47504a4d/'MJPG' is not supported with codec id 7 and format 'mov / QuickTime / MOV'
OpenCV: FFMPEG: fallback to use tag 0x6765706a/'jpeg'

Any ideas? Am I missing anything?

Cheers!

Adam

[adamteale]

By changing the output frame size to match the source I was able to export the video.

[skvark]

For future reference, you don't need to install FFmpeg if you use the wheels provided by this repository. They already include FFmpeg binaries (vendored inside the wheel) -> installing FFmpeg separately won't have any effect on opencv-python.