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preprocess.py
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preprocess.py
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# Utilities for preprocessing video for scene detection.
# Frame skipping: will create a video that only one frame
# for each section of the original video.
# ROI extraction: which will create a video that only
# contains the specified region of interest.
# Updated to use OpenCV 3.1.0 and Python 3.5
import math
import cv2
import argparse
def getInfo(sourcePath):
cap = cv2.VideoCapture(sourcePath)
info = {
"framecount": cap.get(cv2.CAP_PROP_FRAME_COUNT),
"fps": cap.get(cv2.CAP_PROP_FPS),
"width": int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),
"height": int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)),
"codec": int(cap.get(cv2.CAP_PROP_FOURCC))
}
cap.release()
return info
#
# Extracts one frame for every second second of video.
# Effectively compresses a video down into much less data.
#
def extractFrames(sourcePath, destPath, verbose=False):
info = getInfo(sourcePath)
cap = cv2.VideoCapture(sourcePath)
fourcc = cv2.VideoWriter_fourcc('m', 'p', '4', 'v')
out = cv2.VideoWriter(destPath,
fourcc,
info["fps"],
(info["width"], info["height"]))
fps_int = math.ceil(info["fps"])
ret = True
while(cap.isOpened() and ret):
ret, frame = cap.read()
frame_number = math.ceil(cap.get(cv2.CAP_PROP_POS_FRAMES) - 1)
if frame_number % fps_int == 0:
out.write(frame)
if verbose:
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
out.release()
cv2.destroyAllWindows()
#
# Extracts a region of interest defined by a rect
# from a video
#
def extractROI(sourcePath, destPath, points, verbose=False):
info = getInfo(sourcePath)
# x, y, width, height = cv2.boundingRect(points)
# print(x,y,width,height)/
x = points[0][0]
y = points[0][1]
width = points[1][0] - points[0][0]
height = points[1][1] - points[0][1]
cap = cv2.VideoCapture(sourcePath)
fourcc = cv2.VideoWriter_fourcc('m', 'p', '4', 'v')
out = cv2.VideoWriter(destPath,
fourcc,
info["fps"],
(width, height))
ret = True
while(cap.isOpened() and ret):
ret, frame = cap.read()
if frame is None:
break
roi = frame[y:y+height, x:x+width]
out.write(roi)
if verbose:
cv2.imshow('frame', roi)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
out.release()
cv2.destroyAllWindows()
# Groups a list in n sized tuples
def group(lst, n):
return list(zip(*[lst[i::n] for i in range(n)]))
parser = argparse.ArgumentParser(description='Extract one frame from every second of video')
parser.add_argument('--source', help='source file', required=True)
parser.add_argument('--dest', help='source file', required=True)
parser.add_argument('--command', help='command to run', required=True)
parser.add_argument('--rect', help='x1,y2,x2,y2', required=False)
parser.add_argument('--verbose', action='store_true')
parser.set_defaults(verbose=False)
args = parser.parse_args()
if args.verbose:
info = getInfo(args.source)
print("Source Info: ", info)
if args.command == "shrink":
extractFrames(args.source, args.dest, args.verbose)
elif args.command == "roi":
points = [int(x) for x in args.rect.split(",")]
points = group(points, 2)
extractROI(args.source, args.dest, points, args.verbose)