I have written a python script to open my webcam in OpenCV and convert captured frames to video streams. I have followed some tutorials that basically do these things:
In my case, FFMpeg runs without errors, and using imshow() displays captured frames correctly, but the FFMpeg video output is corrupted.
code:
import cv2 as cv
import subprocess as sp
FPS = 24
WIDTH = 720
HEIGHT = 360
cap = cv.VideoCapture(0)
cap.set(cv.CAP_PROP_FPS, FPS)
cap.set(cv.CAP_PROP_FRAME_WIDTH, WIDTH)
cap.set(cv.CAP_PROP_FRAME_HEIGHT, HEIGHT)
# ffmpeg command
ffmpeg_cmd = [
"./libs/ffmpeg/bin/ffmpeg.exe",
'-hwaccel', 'auto', '-y',
'-f', 'rawvideo',
'-vcodec','rawvideo',
'-pix_fmt', 'bgr24',
'-s', f"{WIDTH}x{HEIGHT}",
'-r', str(FPS),
'-i', '-',
'-c:v', 'libx264',
'-pix_fmt', 'yuv420p',
'-preset', 'ultrafast',
'-f', 'flv',
'out.flv'
]
ffmpeg_sp = sp.Popen(ffmpeg_cmd, stdin=sp.PIPE)
while True:
ret,frame = cap.read()
# video capture test: OK
cv.imshow('video', frame)
if cv.waitKey(50)&0xFF == ord('q'):
break
#frame = cv.cvtColor(frame, cv.COLOR_BGR2YUV) # It doesn't work
# write to ffmpeg pipe
ffmpeg_sp.stdin.write(frame.tobytes())
ffmpeg_sp.stdin.close()
cap.release()
cv.destroyAllWindows()
I'm running Python 3.11.5, OpenCV 4.8.0.76 on Windows 11. The ffmpeg -version output is given below.
ffmpeg version N-112841-g2d9ed64859-20231125 Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 13.2.0 (crosstool-NG 1.25.0.232_c175b21)
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-libharfbuzz --enable-libvorbis --enable-opencl --disable-libpulse --enable-libvmaf --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libaribcaption --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libvpl --enable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --enable-vaapi --enable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20231125
libavutil 58. 32.100 / 58. 32.100
libavcodec 60. 34.100 / 60. 34.100
libavformat 60. 17.100 / 60. 17.100
libavdevice 60. 4.100 / 60. 4.100
libavfilter 9. 13.100 / 9. 13.100
libswscale 7. 6.100 / 7. 6.100
libswresample 4. 13.100 / 4. 13.100
libpostproc 57. 4.100 / 57. 4.100
I have been playing around with FFMpeg arguments for a while and none of them works. I have also transcoded video files using FFMpeg successfully. It somehow just doesn't work with raw video frames from OpenCV. Any help/advice is appreciated.
I figured out piping raw video frames causes the problem, so I followed guides from Pipe raw OpenCV images to FFmpeg to encode frames into images using imencode() before piping into FFMpeg, and it works!