opencv - videowriter control bitrate

问题

I have a working python script that uses the video writer from opencv.

source https://gist.github.com/stanchiang/b4e4890160a054a9c1d65f9152172600

If i take in a file, and regardless of whether I simply pass the video frame through to the writer (effectively duplicating the file) or if i try to edit the frame, the file is always larger. I would like for it to be no larger than the original (since if you read my script i'm blurring a lot of stuff).

After checking their metadata, with ffprobe -v quiet -print_format json -show_format -show_streams inputFile.mp4 I notice that the bitrate of the new file is over 5.5x higher than before.

source https://www.diffchecker.com/8r2syeln

since bitrate is a big determinant of file size, I'm wondering if

i can hardcode the desired bitrate of the new file through the video writer
whether for some reason the heavily increased bit rate is needed

回答1:

basically this answer https://stackoverflow.com/a/13298538/1079379

# import packages
from PIL import Image
from subprocess import Popen, PIPE
from imutils.video import VideoStream
from imutils.object_detection import non_max_suppression
from imutils import paths
import cv2
import numpy as np
import imutils

# ffmpeg setup
p = Popen(['ffmpeg', '-y', '-f', 'image2pipe', '-vcodec', 'mjpeg', '-r', '24', '-i', '-', '-vcodec', 'h264', '-qscale', '5', '-r', '24', 'video.mp4'], stdin=PIPE)

video = cv2.VideoCapture('videos.mp4')

while True:
    ret, frame = video.read()
    if ret:
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        im = Image.fromarray(frame)
        im.save(p.stdin, 'JPEG')
    else:
        break

p.stdin.close()
p.wait()
video.release()
cv2.destroyAllWindows()

来源：https://stackoverflow.com/questions/38686359/opencv-videowriter-control-bitrate

标签

python

OpenCV

video-processing