#------------------------------------------------------------------------------
#Ref: karobben.github.io/2021/04/10/Python/opencv-v-paste
#Code adapted to add videos up/down: second video scaled to width of first video
#The code was tested on a video of resolution 1280x720 and the resultant video 
#having size 1280x1440 could be opened without any error on Ubuntu LTS 22.0 on
#15.4" screen with 100 DPI.
#------------------------------------------------------------------------------
import cv2
#Read the input videos and specify name of the output video
Vid1 = "v1.mp4"
Vid2 = "v2.mp4"
Out = "out.mp4"

cap1 = cv2.VideoCapture(Vid1) 
cap2 = cv2.VideoCapture(Vid2) 
Window = None  #or '1920x1080' or '1280x720' - check Aspect Ratio of input

#Get the fps and the size of the Video one
fps_c1 = cap1.get(cv2.CAP_PROP_FPS)
h1 = cap1.get(cv2.CAP_PROP_FRAME_HEIGHT)
w1 = cap1.get(cv2.CAP_PROP_FRAME_WIDTH)

nfrm = cap1.get(cv2.CAP_PROP_FRAME_COUNT)

fps_c2 = cap2.get(cv2.CAP_PROP_FPS)
h2 = cap2.get(cv2.CAP_PROP_FRAME_HEIGHT)
w2 = cap2.get(cv2.CAP_PROP_FRAME_WIDTH)
     
def frameConnect(f1, f2, h1, w1, h2, w2):
	f2 = cv2.resize(f2, (int(w1),int(h2)), interpolation = cv2.INTER_AREA)
	BG = cv2.resize(f1, (int(w1),int(h1+h2)), interpolation=cv2.INTER_AREA)
	BG[0:int(h1),0:int(w1)] = f1
	BG[int(h1):int(h1+h2),0:int(w1)] = f2
	return (BG)

# Set argument for Video Output
fps = fps_c1

if Window == None:
	size = (int(w1), int(h1+h2))
else:
	size = (int(Window.split("x")[0]), int(Window.split("x")[1]))

fourcc = cv2.VideoWriter_fourcc('m','p','4','v')
videowriter = cv2.VideoWriter(Out,fourcc,fps,size)
i = 1
while (i < nfrm): #Prevent reading Null image, the LAST frame of the video
	ret,f1=cap1.read()
	ret,f2=cap2.read()
	img = frameConnect(f1, f2, h1, w1,  h2, w2)
	img = cv2.resize(img, size, interpolation = cv2.INTER_AREA)
	videowriter.write(img)
	i = i + 1