I want to read a video after I write it with cv2.VideoWriter without saving the video.
For example:
video = cv2.VideoWriter('using.mp4', cv2.VideoWriter_fourcc(*'MJPG'), 10, size)
Now, after writing this cv2.VideoWriter object, is it possible to read it likevideo.read(), but since read() is a function of cv2.VideoCapture and it will throw an error
Exception has occurred: AttributeError
'cv2.VideoWriter' object has no attribute 'read'
So, is there possible way of reading the cv2.VideoWriter?
An alternative to reading frames from the video writer, is to save the frames in a list instead of saving each frame in the the loop. when you finished, you can write them outside the loop and have the save affect as video.read()
video = cv2.VideoWriter('using.mp4', cv2.VideoWriter_fourcc(*'MJPG'), 10, size)
for frame in frames:
writer.write(frame)
for frame in frames:
# do other stuff here
detailed example (Notice i changed the fourcc - your example didnt work for me)
import cv2
def cam_test(port: int = 0) -> None:
frames = []
cap = cv2.VideoCapture(port)
if not cap.isOpened(): # Check if the web cam is opened correctly
print("failed to open cam")
else:
print('cam opened on port {}'.format(port))
for i in range(10 ** 10):
success, cv_frame = cap.read()
if not success:
print('failed to capture frame on iter {}'.format(i))
break
frames.append(cv_frame)
cv2.imshow('Input', cv_frame)
k = cv2.waitKey(1)
if k == ord('q'):
break
cap.release()
cv2.destroyAllWindows()
# Now you have the frames at hand
if len(frames) > 0:
# if you want to write them
size = (frames[0].shape[1], frames[0].shape[0])
video = cv2.VideoWriter(
filename='using.mp4',
fourcc=cv2.VideoWriter_fourcc(c1='m', c2='p', c3='4', c4='v'),
fps=10,
frameSize=size
)
for frame in frames:
video.write(frame)
# and to answer your question, you wanted to do video.read() which would have gave you frame by frame
for frame in frames:
pass # each iteration is like video.read() if video.read() was possible
return
if __name__ == '__main__':
cam_test()
I'm trying to convert the following video to images
https://www.signingsavvy.com/media/mp4-ld/24/24851.mp4
however, I have done it by using OpenCV
# Importing all necessary libraries
import cv2
import os
# Read the video from specified path
cam = cv2.VideoCapture("C:\Users\ahmad\Hi_ASL.mp4")
print(cam.get(cv2.CAP_PROP_FPS))
try:
# creating a folder named data
if not os.path.exists('data'):
os.makedirs('data')
# if not created then raise error
except OSError:
print ('Error: Creating directory of data')
# frame
currentframe = 0
while(True):
# reading from frame
ret,frame = cam.read()
if ret:
# if video is still left continue creating images
name = './data/frame' + str(currentframe) + '.jpg'
# print ('Creating...' + name)
# writing the extracted images
cv2.imwrite(name, frame)
# increasing counter so that it will
# show how many frames are created
currentframe += 1
else:
break
# ret,frame = cam.read()
# Release all space and windows once done
cam.release()
cv2.destroyAllWindows()
After I have done it. I want to convert those images to video to be like the one above and I wrote this code
img = [img for img in os.listdir('data')]
frame = cv2.imread('data\' + img[0])
h , w , l = frame.shape
vid = cv2.VideoWriter('hiV.mp4' , 0 ,1 ,(w,h))
for imgg in img:
vid.write(cv2.imread('data\' + imgg))
cv2.destroyAllWindows()
vid.release()
The problem is the result of combining the images to a video using OpenCV is not the same as the original video. So, what is the problem? I want it to be the same as the original one.
The result of the code above is this video https://drive.google.com/file/d/16vwT35wzc95tBleK5VCpZJQkaLxSiKVd/view?usp=sharing
And thanks.
You should change cv2.VideoWriter('hiV.mp4' , 0 ,1 ,(w,h)) to cv2.VideoWriter('hiV.mp4' , 0 ,30 ,(w,h)) As the 1 sets the fps and that means that you write 1 frame every second and not 30 or 29.97(NTSC) as the original video.
I am running a Camera Calibration program from Python using openCV. I am using my computer camera from an XPS 15 9575 in order to capture different frames of a classic black and white checkerboard that I printed. For some reason, it never registers in the program that there is a checkerboard.
I've run this program by itself and with already produced images and it works. It only doesn't work as I try to capture new ones and process them instantly.
This is the beginning of the code. It runs to check to see if it finds the corners and then moves onto the next step. When running, it never makes it past this.
cam = cv2.VideoCapture(0)
cv2.namedWindow("test")
img_counter = 0
imgNames = []
size = (5,5)
while True:
ret, frame = cam.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow("test", gray)
if not ret:
break
k = cv2.waitKey(1)
if k%256 == 27:
break
elif k%256 == 32:
img_name = "{}.png".format(img_counter)
imgtemp = cv2.imread(img_name)
graytemp = cv2.cvtColor(imgtemp,cv2.COLOR_BGR2GRAY)
ret, corners = cv2.findChessboardCorners(graytemp, size,None)
print (ret)
if ret == True:
print ("good!")
imgNames.append(img_name)
cv2.imwrite(img_name, frame)
img_counter += 1
else:
print ("again")
In your code above, you are trying to read an image which actually doesn't exist. See these lines:
img_name = "{}.png".format(img_counter)
imgtemp = cv2.imread(img_name)
Here, img_name is just a string, which doesn't point to an image file yet. You can do one thing, capture a frame and save it here and give it a name img_name and then try to read it via cv2.imread function, like below:
img_name = "{}.png".format(img_counter)
cv2.imwrite(img_name, frame)
imgtemp = cv2.imread(img_name)
Alternatively, you can replace imgtemp = cv2.imread(img_name) with imgtemp = frame. In this case, you don't have to save and then process a frame. Here, once a spacebar is pressed, processing is done on the current captured video frame without saving it.
And don't forget to add below lines at the end of your code:
cam.release()
cv2.destroyAllWindows()
Aim : Detect the motion and save only the motion periods in files with names of the starting time.
Now I met the issue about how to save the video to the files with video starting time.
What I tested :
I tested my program part by part. It seems that each part works well except the saving part.
Running status: No error. But in the saving folder, there is no video. If I use a static saving path instead, the video will be saved successfully, but the video will be override by the next video. My codes are below:
import cv2
import numpy as np
import time
cap = cv2.VideoCapture( 0 )
bgst = cv2.createBackgroundSubtractorMOG2()
fourcc=cv2.VideoWriter_fourcc(*'DIVX')
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)), int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
n = "start_time"
while True:
ret, frame = cap.read()
dst = bgst.apply(frame)
dst = np.array(dst, np.int8)
if np.count_nonzero(dst)>3000: # use this value to adjust the "Sensitivity“
print('something is moving %s' %(time.ctime()))
path = r'E:\OpenCV\Motion_Detection\%s.avi' %n
out = cv2.VideoWriter( path, fourcc, 50, size )
out.write(frame)
key = cv2.waitKey(3)
if key == 32:
break
else:
out.release()
n = time.ctime()
print("No motion Detected %s" %n)
What I meant is:
import cv2
import numpy as np
import time
cap = cv2.VideoCapture( 0 )
bgst = cv2.createBackgroundSubtractorMOG2()
fourcc=cv2.VideoWriter_fourcc(*'DIVX')
size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
path = r'E:\OpenCV\Motion_Detection\%s.avi' %(time.ctime())
out = cv2.VideoWriter( path, fourcc, 16, size )
while True:
ret, frame = cap.read()
dst = bgst.apply(frame)
dst = np.array(dst, np.int8)
for i in range(number of frames in the video):
if np.count_nonzero(dst)<3000: # use this value to adjust the "Sensitivity“
print("No Motion Detected")
out.release()
else:
print('something is moving %s' %(time.ctime()))
#label each frame you want to output here
out.write(frame(i))
key = cv2.waitKey(1)
if key == 32:
break
cap.release()
cv2.destroyAllWindows()
If you see the code there will be a for loop, within which the process of saving is done.
I do not know the exact syntax involving for loop with frames, but I hope you have the gist of it. You have to find the number of frames present in the video and set that as the range in the for loop.
Each frame gets saved uniquely (see the else condition.) As I said I do not know the syntax. Please refer and follow this procedure.
Cheers!
I want to capture video from a webcam and save it to an mp4 file using opencv. I found example code on stackoverflow (below) that works great. The only hitch is that I'm trying to save it as mp4, not avi. Part of what I don't get is that the 'XVID' argument passed to the FOURCC writer is supposed to be, I think, an mp4 codec (from this link). If I change the filename to 'output.mp4' it tells me that the tag is invalid, so I have to believe that the XVID codec is actually making an avi file. Is this a stupid question? How do I write to an mp4?
I have found links showing how to convert an avi to an mp4 after the fact but that seems inefficient. Seems like I should be able to do it during the initial write.
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.cv.CV_FOURCC(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
This worked for me.
self._name = name + '.mp4'
self._cap = VideoCapture(0)
self._fourcc = VideoWriter_fourcc(*'MP4V')
self._out = VideoWriter(self._name, self._fourcc, 20.0, (640,480))
What worked for me was to make sure the input 'frame' size is equal to output video's size (in this case, (680, 480) ).
http://answers.opencv.org/question/27902/how-to-record-video-using-opencv-and-python/
Here is my working code (Mac OSX Sierra 10.12.6):
cap = cv2.VideoCapture(0)
cap.set(3,640)
cap.set(4,480)
fourcc = cv2.VideoWriter_fourcc(*'MP4V')
out = cv2.VideoWriter('output.mp4', fourcc, 20.0, (640,480))
while(True):
ret, frame = cap.read()
out.write(frame)
cv2.imshow('frame', frame)
c = cv2.waitKey(1)
if c & 0xFF == ord('q'):
break
cap.release()
out.release()
cv2.destroyAllWindows()
Note: I installed openh264 as suggested by #10SecTom but I'm not sure if that was relevant to the problem.
Just in case:
brew install openh264
There are some things to change in your code:
Change the name of your output to 'output.mp4' (change to .mp4)
I had the the same issues that people have in the comments, so I changed the fourcc to 0x7634706d: out = cv2.VideoWriter('output.mp4',0x7634706d , 20.0, (640,480))
This is the default code given to save a video captured by camera
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
For about two minutes of a clip captured that FULL HD
Using
cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
cap.set(3,1920)
cap.set(4,1080)
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (1920,1080))
The file saved was more than 150MB
Then had to use ffmpeg to reduce the size of the file saved, between 30MB to 60MB based on the quality of the video that is required changed using crf lower the crf better the quality of the video and larger the file size generated. You can also change the format avi,mp4,mkv,etc
Then i found ffmpeg-python
Here a code to save numpy array of each frame as video using ffmpeg-python
import numpy as np
import cv2
import ffmpeg
def save_video(cap,saving_file_name,fps=33.0):
while cap.isOpened():
ret, frame = cap.read()
if ret:
i_width,i_height = frame.shape[1],frame.shape[0]
break
process = (
ffmpeg
.input('pipe:',format='rawvideo', pix_fmt='rgb24',s='{}x{}'.format(i_width,i_height))
.output(saved_video_file_name,pix_fmt='yuv420p',vcodec='libx264',r=fps,crf=37)
.overwrite_output()
.run_async(pipe_stdin=True)
)
return process
if __name__=='__main__':
cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)
cap.set(3,1920)
cap.set(4,1080)
saved_video_file_name = 'output.avi'
process = save_video(cap,saved_video_file_name)
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
process.stdin.write(
cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
.astype(np.uint8)
.tobytes()
)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
process.stdin.close()
process.wait()
cap.release()
cv2.destroyAllWindows()
break
else:
process.stdin.close()
process.wait()
cap.release()
cv2.destroyAllWindows()
break
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
'mp4v' returns no errors unlike 'MP4V' which is defined inside fourcc
for the error:
"OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id
13 and format 'mp4 / MP4 (MPEG-4 Part 14)' OpenCV: FFMPEG: fallback to
use tag 0x00000020/' ???'"
This worked for me, I added images.sort() to keep the sequence order:
import cv2
import numpy as np
import os
image_folder = 'data-set-race-01'
video_file = 'race-01.mp4'
image_size = (160, 120)
fps = 24
images = [img for img in os.listdir(image_folder) if img.endswith(".jpg")]
images.sort()
out = cv2.VideoWriter(video_file, cv2.VideoWriter_fourcc(*'MP4V'), fps, image_size)
img_array = []
for filename in images:
img = cv2.imread(os.path.join(image_folder, filename))
img_array.append(img)
out.write(img)
out.release()
For someone whoe still struggle with the problem. According this article I used this sample and it works for me:
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'X264')
out = cv2.VideoWriter('output.mp4',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
So I had to use cv2.VideoWriter_fourcc(*'X264') codec. Tested with OpenCV 3.4.3 compiled from sources.
Anyone who's looking for most convenient and robust way of writing MP4 files with OpenCV or FFmpeg, can see my state-of-the-art VidGear Video-Processing Python library's WriteGear API that works with both OpenCV backend and FFmpeg backend and even supports GPU encoders. Here's an example to encode with H264 encoder in WriteGear with FFmpeg backend:
# import required libraries
from vidgear.gears import WriteGear
import cv2
# define suitable (Codec,CRF,preset) FFmpeg parameters for writer
output_params = {"-vcodec":"libx264", "-crf": 0, "-preset": "fast"}
# Open suitable video stream, such as webcam on first index(i.e. 0)
stream = cv2.VideoCapture(0)
# Define writer with defined parameters and suitable output filename for e.g. `Output.mp4`
writer = WriteGear(output_filename = 'Output.mp4', logging = True, **output_params)
# loop over
while True:
# read frames from stream
(grabbed, frame) = stream.read()
# check for frame if not grabbed
if not grabbed:
break
# {do something with the frame here}
# lets convert frame to gray for this example
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# write gray frame to writer
writer.write(gray)
# Show output window
cv2.imshow("Output Gray Frame", gray)
# check for 'q' key if pressed
key = cv2.waitKey(1) & 0xFF
if key == ord("q"):
break
# close output window
cv2.destroyAllWindows()
# safely close video stream
stream.release()
# safely close writer
writer.close()
Source: https://github.com/abhiTronix/vidgear
Docs:
https://abhitronix.github.io/vidgear/
More FFmpeg backend examples:https://abhitronix.github.io/vidgear/latest/gears/writegear/compression/usage/
OpenCV backend examples:
https://abhitronix.github.io/vidgear/gears/writegear/non_compression/usage/
The problem such as OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id 13 and format 'mp4 / MP4 (MPEG-4 Part 14)' OpenCV: FFMPEG: fallback to use tag 0x00000020/' ???' maybe that your output video size is not the same as original video. You can look over the frame size of video first.
You need to set the codec to 'mp4v' (lowercase). If set in uppercase, an error would be thrown saying that is not supported, suggesting to use lowercase instead: OpenCV:FFMPEG:fallback to use tag 0x7634706d/'mp4v'. You may also want to have a look at the documentation of VideoWriter, as well as the examples given here. Also, please make sure your output video's size is equal to your input frame size (the below takes care of this, using the dimensions of the VideoCapture object).
cap = cv2.VideoCapture(0)
w = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
h = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
fps = cap.get(cv2.CAP_PROP_FPS)
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
out = cv2.VideoWriter('output.mp4', fourcc, fps, (int(w),int(h)))
You can get the entire list of codecs available for mp4, etc., by setting fourcc=-1. For instance:
out = cv2.VideoWriter('output.mp4', -1, fps, (int(w),int(h)))
The OpenCV documentation is not very rich with regard to the VideoWriter, however I managed to get it working in the following way (by looking at the stacktrace):
import cv2
HEIGHT = 480
WIDTH = 640
FPS = 30.0
cap = cv2.VideoCapture(0, cv2.CAP_ANY)
cap.set(cv2.CAP_PROP_FPS, FPS)
cap.set(cv2.CAP_PROP_CONVERT_RGB , 1)
cap.set(cv2.CAP_PROP_BUFFERSIZE, 100)
cap.set(cv2.CAP_PROP_FRAME_WIDTH, WIDTH)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, HEIGHT)
fourcc = cv2.VideoWriter_fourcc(*'mp4v')
# output parameters such as fps and size can be changed
output = cv2.VideoWriter("output.mp4", fourcc, FPS, (WIDTH, HEIGHT))
while True:
if cap.isOpened():
(ret, frame) = cap.read()
if ret:
output.write(frame)
cv2.imshow("frame", frame)
if cv2.waitKey(10) == ord('q'):
break
output.release()
cap.release()
cv2.destroyAllWindows()
The stacktrace error was:
OpenCV: FFMPEG: tag 0x5634504d/'MP4V' is not supported with codec id 12 and
format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x7634706d/'mp4v'
Unfortunately, it is difficult to find a list of the official codecs used by OpenCV, or at least I could not find them. In any case, it appears that you have to enter the codec 'mp4v' written in lower case.
https://docs.opencv.org/3.4/dd/d01/group__videoio__c.html#gac005718f121379beffdbdbfb44f2646a
One important thing I noticed is that the aspect ratio of the frame and the output video must be the same, which is why I use two variables for height and width. If these two are different, the file is created, but the frames are not saved (you always end up with a 1KB mp4 file). To avoid any problems you could do the same for FPS.
just change the codec to "DIVX". This codec works with all formats.
fourcc = cv2.VideoWriter_fourcc(*'DIVX')
i hope this works for you!