opencv and python 3 -- cannot write video frames to disk - opencv

Python 3.5.2, anaconda 4.2.0 on Windows 10.
OpenCV installed from conda, version 3.1.0.
I'm trying to process a video file by opening it, transforming each frame, and putting the result into a new video file. The output file is created, but the size is about 800 bytes and its empty. The input file has ~4,000 frames and it's about 150 MB.
Here's my code, which follows the guide on the OpenCV documentation pretty closely.
import cv2
import progressbar
# preprocess video
# args.input is a valid file name
outname = 'foo.mp4'
cap = cv2.VideoCapture(args.input)
codec = int(cap.get(cv2.CAP_PROP_FOURCC))
framerate = app_config.camera.framerate #240
size = (app_config.camera.width, app_config.camera.height) #1080 x 720
vw = cv2.VideoWriter(filename=outname, fourcc=codec, fps=framerate, frameSize=size, isColor=False)
curframe = 0
with progressbar.ProgressBar(min_value=0, max_value=int(cap.get(cv2.CAP_PROP_FRAME_COUNT))) as pb:
while cap.isOpened():
ret, frame = cap.read()
if ret:
#update the progress bar
curframe += 1
pb.update(curframe)
# convert to greyscale
grey = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# invert colors
inverted = cv2.bitwise_not(grey)
vw.write(inverted)
#cv2.imshow('right', right)
#if cv2.waitKey(1) & 0xFF == ord('q'):
# break
else:
break
cap.release()
vw.release()
cv2.destroyAllWindows()
I receive the following error:
OpenCV: FFMPEG: tag 0x7634706d/'mp4v' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???'
I receive similar errors (as well as a warning that I have an incorrect environment variable for h.264 library path) if i try to set codec = cv2.VideoWriter_fourcc(*'H264').

Ensure that the dimensions of inverted match the dimensions of the size parameter in the videoWriter definition.
Also use 'M','P','4','V' codec with the .mp4 container.

Related

How to write video then download using cv2 in Google colab?

I am trying to do some image processing on a video, then save the resulting video using opencv on colab. However, I am not able to access the resulting video file that I am writing to.
import cv2
from google.colab.patches import cv2_imshow
import numpy as np
fourcc = cv2.VideoWriter_fourcc(*'H264')
cap = cv2.VideoCapture(vid_file)
out = cv2.VideoWriter('output.mp4',fourcc,30.0,(1124,1080))
cnt = 0
ret = True
while(ret):
ret,frame = cap.read()
print(cnt,end=' ')
# check if prey was tracked on this frame
match = np.where(prey_frames==cnt)[0]
if match:
prey_frame = match[0]
# print(prey_frame)
image = cv2.circle(frame,(int(prey_px[prey_frame].x),95+int(prey_px[prey_frame].y)),
radius=5,color=(255,0,255),thickness=2)
else:
image = frame
out.write(image)
cnt += 1
out.release()
cap.release()
cv2.destroyAllWindows()
From what I understand, this should write to a file called 'output.mp4'. This code runs without error, but there is no file in the current directory, and no file of that name available to download (using files.download('output.mp4') returns 'cannot find file' error).
Any help would be appreciated!
I've hit this problem a few times and I believe that it has to do with the fact that Colab's operating environment only supports a few video encodings.
I was able to get the video writer working with the following:
fourcc = cv2.VideoWriter_fourcc('F','M','P','4')

cv2.VideoCapture(0, cv2.DSHOW) returns none

I'm trying to capture video from an in-build webcam on a laptop (or external USB camera) using opencv, specifically VideoCapture with the DSHOW argument.
I know there is a way to set the resolution and even FPS, however the DirectShow argument for the API returns none when I included it in the code.
For example;
# returns my webcam's stream, but all optional arguments are ignored
camera = cv2.VideoCapture(0)
camera = cv2.VideoCapture(0, cv2.CAP_V4L2)
# returns none and loops infinitely or errors out when *if im.any()*
camera = cv2.VideoCapture(0, cv2.CAP_DSHOW)
This is the code that follows after the above;
# should set resolution, settings are always ignored
camera.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)
camera.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)
while(True):
retval, im = camera.read()
if im.any(): # errors out when image is none
cv2.imshow("image", im)
k = cv2.waitKey(33)
if k==27: # Esc key press
print('Resolution: {0}x and {1}y'.format(im.shape[1],im.shape[0]))
print('FPS: {0}'.format(camera.get(cv2.CAP_PROP_FPS)))
break
camera.release()
cv2.destroyAllWindows()
Is the DSHOW the correct API to use and is it the only API to use that can change resolution and FPS of a camera stream using opencv? Or is there something else I'm doing incorrectly?
More details about the system.
Ubuntu 18.04.6
python 3.9.5
opencv-python 4.5.2.52
Thank you in advance for the help!
Regards, Tiz
DSHOW (and MSMF) are windows only.
on linux, use V4L, FFMPEG or GSTREAMER
also, please check the return val of capture.set(),
not all properties/values will be supported on any given machine

I am getting an error while trying to vonvert a bgr image to gray scale [duplicate]

This question already has answers here:
How to load a video in opencv(python)
(5 answers)
Closed 1 year ago.
I am reading a video here:
VideoCap = cv2.VideoCapture("E:\Omar's Stuff\College related\Forth Year\Project\Kalman Filter
code\video_randomball.avi")
ret, frame = VideoCap.read()
and sending the frames to a detect function here:
# Detect object
centers = detect(frame,debugMode)
trying to convert here:
def detect(frame,debugMode):
# Convert frame from BGR to GRAY
#frame = frame.astype('uint8')
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
and getting this error:
OpenCV(3.4.2) c:\projects\opencv-python\opencv\modules\imgproc\src\color.hpp:253: error:
(-215:Assertion failed) VScn::contains(scn) && VDcn::contains(dcn) && VDepth::contains(depth) in
function 'cv::CvtHelper<struct cv::Set<3,4,-1>,struct cv::Set<1,-1,-1>,struct
cv::Set<0,2,5>,2>::CvtHelper'
how to fix it?
Something wrong with the video file path that you have passed in cv2.VideoCapture() method so try to correct the path and if not able to correct then simply drag and drop the video file along with the python script folder then it will work.
Here is sample code to read the video in the same directory where the python script is located
import cv2
import numpy as np
# Create a VideoCapture object and read from input file
cap = cv2.VideoCapture('tree.mp4')
# Check if camera opened successfully
if (cap.isOpened()== False):
print("Error opening video file")
# Read until video is completed
while(cap.isOpened()):
# Capture frame-by-frame
ret, frame = cap.read()
if ret == True:
# Display the resulting frame
cv2.imshow('Frame', frame)
# Press Q on keyboard to exit
if cv2.waitKey(25) & 0xFF == ord('q'):
break
# Break the loop
else:
break
# When everything done, release
# the video capture object
cap.release()
# Closes all the frames
cv2.destroyAllWindows()

OpenCV 4.1.1.26 reports 90000.0 fps for a 25fps RTSP stream

I have an RTP/RTSP stream that's running at 25fps, as verified by ffprobe -i <URI>. Also, VLC plays back the RTSP stream at a real-time rate, but doesn't show me the FPS in the Media Information window.
However, when I use OpenCV 4.1.1.26 to retrieve the input stream's frame rate, it is giving me a response of 90000.0.
Question: How can I use OpenCV to probe for the correct frame rate of the RTSP stream? What would cause it to report 90000.0 instead of 25?
Here's my Python function to retrieve the frame rate:
import cv2
vid : cv2.VideoCapture = cv2.VideoCapture('rtsp://192.168.1.10/cam1/mpeg4')
def get_framerate(video: cv2.VideoCapture):
fps = video.get(cv2.CAP_PROP_FPS)
print('FPS is {0}'.format(fps))
get_framerate(vid)
MacOS Catalina
Python 3.7.4
I hope this helps you somehow. It is a simple calculator that takes cont captures and measure the beginning and the ending time. Then with the rule of three, i converted it to fps.
Related to you second question i read here that it could be due to bad installation. Also, you can check that your camera is working properly by printing ret variable. If it is true then you should be able to see the fps, if it is false then you can have an unpredictable result.
cv2.imshow() and key = cv2.waitKey(1) should be commented as it adds ping/delay resulting in bad measurement.
I post this as a comment because i do not have enough reputation points.
img = cv2.VideoCapture('rtsp://192.168.1.10/cam1/mpeg4')
while True:
if cont == 50:
a = datetime.now() - start
b = (a.seconds * 10e6 + a.microseconds)
print((a.seconds * 10e6 + a.microseconds), "fps = ", (50 * 10e6)/ b)
break
ret, frame = img.read()
# Comment for best test
cv2.imshow('fer', frame)
key = cv2.waitKey(1)
if key == ord('q'):
break
cont+=1
img.release()
cv2.destroyAllWindows()`

CAP_PROP_FPS doesn't change in opencv 3

So I set
cap = cv2.VideoCapture(0)
cap.set(cv2.CAP_PROP_FPS, 60)
I also tried integer 5 instead of cv2.CAP_PROP_FPS. Neverteless, frame rate doesn't change. I get 30 when I
print(cap.get(cv2.CAP_PROP_FPS))
Why?
The problem maybe is with the codec of the camera stream and not with the FPS itself, for example, if your camera only supports YUYV it is probably that you could only work with some specific FPS, try with the app guvcview to check this in a GUI.
Try to change the codec to MJPG and then change the FPS using CAP_PROP_FPS. I'm using a Logitech C922 pro and this works for me to configure 1080p and 30fps, if you have other camera probably yu need to use a lower resolution to achieve 30fps:
import cv2 as cv
def decode_fourcc(v):
v = int(v)
return "".join([chr((v >> 8 * i) & 0xFF) for i in range(4)])
def setfourccmjpg(cap):
oldfourcc = decode_fourcc(cap.get(cv.CAP_PROP_FOURCC))
codec = cv.VideoWriter_fourcc(*'MJPG')
res=cap.set(cv.CAP_PROP_FOURCC,codec)
if res:
print("codec in ",decode_fourcc(cap.get(cv.CAP_PROP_FOURCC)))
else:
print("error, codec in ",decode_fourcc(cap.get(cv.CAP_PROP_FOURCC)))
cap = cv.VideoCapture(CAMERANUM)
cu.setfourccmjpg(cap)
w=1920
h=1080
fps=30
res1=cap.set(cv.CAP_PROP_FRAME_WIDTH,w)
res2=cap.set(cv.CAP_PROP_FRAME_HEIGHT,h)
res3=cap.set(cv.CAP_PROP_FPS,fps)
then resume your normal video capture polling loop.
Not all openCV parameters are supported by all cameras from an opencv standpoint. Each camera has a different set of parameters that need to be set. You need to find out what parameters are supported by your camera...

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