I ran into a considerable amount of difficulty writing a video-file using OpenCV (under Python). Almost every video-writing example on the Internet is only concerned with capturing from a webcam, and, even for the relevant examples, I kept getting an empty/insubstantial file.
In order to write a video-file, you need to declare the FOURCC code that you require. I prefer H.264, so I [unsuccessfully] gave it “H264”. I also heard somewhere that since H.264 is actually the standard, I needed to use “X264” to refer to the codec. This didn’t work either. I also tried “XVID” and “DIVX”. I eventually resorted to trying to pass (-1), as this will allegedly prompt you to make a choice (thereby showing you what options are available). Naturally, no prompt was given and yet it still seemed to execute to the end. There doesn’t appear to be a way to show the available codecs. I was out of options.
It turns out that you still have one or more raw-format codecs available. For example, “8BPS” and “IYUV” are available. MJPEG (“MJPG”) also ended-up working, too. This is the best option (so that we can get compression).
It’s important to note that the nicer codecs might’ve not been available simply due to dependencies. At one point, I reinstalled OpenCV (using Brew) with the “–with-ffmpeg” option. This seemed to pull-down XVID and other codecs. However, I still had the same problems. Note that, since this was installed at the time that I tested “MJPG”, the latter may actually require the former.
Code, using MJPEG:
import numpy as np
_CANVAS_WIDTH = 500
_CANVAS_HEIGHT = 500
_COLOR_DEPTH = 3
_CIRCLE_RADIUS = 40
_STROKE_THICKNESS = -1
_VIDEO_FPS = 1
def _make_image(x, y, b, g, r):
img = np.zeros((_CANVAS_WIDTH, _CANVAS_HEIGHT, _COLOR_DEPTH), np.uint8)
position = (x, y)
color = (b, g, r)
cv2.circle(img, position, _CIRCLE_RADIUS, color, _STROKE_THICKNESS)
# Works without FFMPEG.
#fourcc = cv.FOURCC('8', 'B', 'P', 'S')
# Works, but we don't have a viewer for it.
#fourcc = cv.CV_FOURCC('i','Y','U', 'V')
# Works (but might require FFMPEG).
fourcc = cv.CV_FOURCC('M', 'J', 'P', 'G')
# Prompt. This never works, though (the prompt never shows).
#fourcc = -1
w = cv2.VideoWriter(
img = _make_image(100, 100, 0, 0, 255)
img = _make_image(200, 200, 0, 255, 0)
img = _make_image(300, 300, 255, 0, 0)
if __name__ == '__main__':