Develop Reference

Changing codec of webcam is not possible using OpenCV/Python

I am using windows 10 and python 3.7 / OpenCV4 and a Logitech C922 webcam. While the cam seems to provide 30 fps using the windows camera app, i can not get more than 5-6 fps using OpenCV. Resolution is set to FHD.
cam = cv2.VideoCapture(cv2.CAP_DSHOW+0)
while(1):
ret,frame = cam.read()
if cv2.waitKey(1) & 0xFF == ord('q'):
break
In another post I found the solution to change the codec to MJPG. However, the camera does not accept changing the codec. I tried:
cam.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('m','j','p','g'))
cam.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M','J','P','G'))
cam.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc(*'MJPG'))
cam.set(cv2.CAP_PROP_FOURCC, float(cv2.VideoWriter_fourcc('m','j','p','g'))
cam.set(cv2.CAP_PROP_FOURCC, float(cv2.VideoWriter_fourcc('M','J','P','G'))
cam.set(cv2.CAP_PROP_FOURCC, 1196444237.0)
The camera always returns "844715353.0"
How can I achieve higher fps?

It seems that order matters. As I understand, OpenCv uses ffmpeg in the background. In ffmpeg the command should be something like this:
ffmpeg -f dshow -framerate 60 -video_size 1280x720 -input_format mjpeg -i video="my webcam" out.mkv
So that your OpenCV code should be something like this
my_cam_index = 0
cap = cv2.VideoCapture(my_cam_index, cv2.CAP_DSHOW)
cap.set(cv2.CAP_PROP_FPS, 60.0)
cap.set(cv2.CAP_PROP_FRAME_WIDTH,1280)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT,720)
cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter.fourcc('M','J','P','G'))

i work with Logitech c920 webcam and i test WebcamVideoStream class in imutils module and this module use threading and the queue data structure for improve the FPS when processing video streams with OpenCV is to move the I/O (i.e., the reading of frames from the camera sensor) to a separate thread, and you can set your custom resolution on this file webcamvideostream.py.
you can use threading to obtain higher FPS. maybe this solution help you.
plz see these links:
https://www.pyimagesearch.com/2015/12/21/increasing-webcam-fps-with-python-and-opencv/
https://www.pyimagesearch.com/2017/02/06/faster-video-file-fps-with-cv2-videocapture-and-opencv/
https://github.com/jrosebr1/imutils/blob/master/imutils/video/webcamvideostream.py

Using OpenCV to connect to USB camera

For some reason, my script fails to recognize the USB camera connected (MU500), it does, however, recognize and display my other camera which is an analog converted to USB camera. The below script is a portion of the GUI that runs and displays the video capture.
import cv
camera = int(self.camera.GetValue())-1
img_name = self.img_name.GetValue()+'.jpg'
cap = cv2.VideoCapture(camera)
while(cap.isOpened()):
ret, frame = cap.read()
cv2.imshow('Camera',frame)
if cv2.waitKey(1) & 0xFF==ord('q'):
cap.release()
cv2.destroyAllWindows()
break
elif cv2.waitKey(1)== ord('s'):
cv2.imwrite(filename=img_name, img=frame)
cap.release()
print("Image saved!")
break
The user inputs '1' to access camera 1, or '2' for camera 2 and so on. I have tried having just MU500 connected and both connected. Neither recognize MU500. MU500 uses an AmScope driver and is listed as an imaging device in device manager.
Is there anyone who can help me?

You may try to install:
sudo apt-get install v4l-utils
and use:
v4l2-ctl --list-devices
to list all your devices and their properties.

OpenCv error can't open camera through video capture

I was using my cam through opencv and suddenly after restarting I ran my code it shows below error:
[ WARN:0] global /io/opencv/modules/videoio/src/cap_v4l.cpp (802) open VIDEOIO ERROR: V4L: can't open camera by index 0
Traceback (most recent call last):
File "test.py", line 20, in <module>
retval, buffer_img = cv2.imencode('.jpg', frame)
cv2.error: OpenCV(4.1.2) /io/opencv/modules/imgcodecs/src/loadsave.cpp:877: error: (-215:Assertion failed) !image.empty() in function 'imencode'
cap = cv2.VideoCapture(0) # here it throws an error
import json
while(True):
# Capture frame-by-frame
ret, frame = cap.read()
retval, buffer_img = cv2.imencode('.jpg', frame)
resdata = base64.b64encode(buffer_img)
resdata = "data:image/png;base64,"+ str(resdata.decode("utf-8"))
PARAMS = {'image': resdata}
# Our operations on the frame come here
#gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# Display the resulting frame
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
I also tried with cap = cv2.VideoCapture(1) but then it shows can't find camera
How can I fix this issue?

I got the same error. Try changing 0 to -1
cap = cv2.VideoCapture(-1)
This solved the issue.

I got the same problem when I created more than one instance of the cv2.VideoCapture(0). So check if your code contains multiple initializations or sections which call cv2.VideoCapture(0) more than once. I was facing this problem while running the flask server in debug mode because it called cv2.VideoCapture(0) twice.
import cv2
cap = cv2.VideoCapture(0)
cap2 = cv2.VideoCapture(0)
while True:
ret, frame = cap.read()
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()
Error:
python3 debugCamera.py
[ WARN:0] global /io/opencv/modules/videoio/src/cap_v4l.cpp (887) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

Most likely a permission issue on /dev/video0.
Check if you are part of "video" group.
id -a
if you don't see video in your group list add
sudo usermod -a -G video
for Ubuntu users:(20.04)
sudo usermod -a -G video $LOGNAME
Logout and log back in and try it.

I've encountered the same issue and attempted several methods like cv2.VideoCapture(-1) or cv2.VideoCapture(1) but without much success.
I succeeded after reading this article and disabling debug-mode

I had the same problem,
Just change 0 to 1,then to -1 and back again to 0.
Don't know why this worked for me.

I found a solution in https://github.com/opencv/opencv/issues/19527 where the video capture is inside the function instead of outside. That worked for me (ubuntu)
def frame_generation():
camera = cv2.VideoCapture(0) #resolved, correct position
while(True):

I will not go to that part What you are trying to do, here is just a block of code that can open your camera every time you run it,
python: 3.7.3
OpenCV: 4.1.0
import cv2
cap = cv2.VideoCapture(0)
while True:
ret, frame = cap.read()
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

In my case, I just reconnected cam to the usb port, and then it was solved! I think this error is caused by closing the window in the wrong way. Please check if there is any exception on the terminal right after closing the window.

I also had the same problem. Just changed it to 1 and it was perfectly working. I guess it's related to the number of camera devices you have used.
For example, I guess I have Iruin external camera as my first option which I didn't connect this time.
Here is the error and corrected code.
global /tmp/pip-req-build-f51eratu/opencv/modules/videoio/src/cap_v4l.cpp (890) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
Code to change:
vid = cv2.VideoCapture(1)

The OP appears to be operating on a Raspberry PI. Raspberry is moving to a new system to manage cameras, so when the user upgrades the OS via sudo apt-get upgrade the camera system gets the new library and the legacy camera system is disabled. To enable the legacy camera system again, try
sudo raspi-config
Then select
3 Interface Options Configure connections to peripherals
then select
I1 Legacy Camera Enable/disable legacy camera support
and follow the directions to enable and then reboot.
Of course, this patch will only work for so long, as the legacy system has been deprecated.

I've also had this problem on Ubuntu
I've solved this by these comands
sudo adduser username video
sudo usermod -a -G video username
username - it is the name of your device
than write
id -a
and copy index from ()
for me it is 1000
so than just write:
camera = cv2.VideoCapture(1000)

Tried every anwser but only changing camera id from -1 to 1 and then back to 0 worked.

For Linux, make sure OpenCV is built using the WITH_V4L (with video for linux).

I have do everytime after restart or unplug usb camera and replug
chmod 777 /dev/video0

Don't know if this is still an issue.
In my case, I was getting the same error until I unplugged and plugged the usb camera. Even if I reboot, the error happened.
It's similar to someone said: my camera was already been captured.
The problem is that it was not used by my script, so it was hard to identify.
A few days before the issue, I installed the motion library, but just to test something and I didn't use it anymore. The motion starts at boot, so the camera was being captured by the service. That's why only the unplug-plug worked.
I uninstalled the library, and the error was gone.

video = cv2.VideoCapture(0,cv2.CAP_DSHOW)
This worked for me.

This issue is due to the interruption. Try to end the execution with the key 'q' for example, don't close the window suddenly.
I solved the same issue by opening terminal again and execute the same script again.

I want to receive RTSP stream in OpenCV from web URL [duplicate]

I have recently set up a Raspberry Pi camera and am streaming the frames over RTSP. While it may not be completely necessary, here is the command I am using the broadcast the video:
raspivid -o - -t 0 -w 1280 -h 800 |cvlc -vvv stream:///dev/stdin --sout '#rtp{sdp=rtsp://:8554/output.h264}' :demux=h264
This streams the video perfectly.
What I would now like to do is parse this stream with Python and read each frame individually. I would like to do some motion detection for surveillance purposes.
I am completely lost on where to start on this task. Can anyone point me to a good tutorial? If this is not achievable via Python, what tools/languages can I use to accomplish this?

Using the same method listed by "depu" worked perfectly for me.
I just replaced "video file" with "RTSP URL" of actual camera.
Example below worked on AXIS IP Camera.
(This was not working for a while in previous versions of OpenCV)
Works on OpenCV 3.4.1 Windows 10)
import cv2
cap = cv2.VideoCapture("rtsp://root:pass#192.168.0.91:554/axis-media/media.amp")
while(cap.isOpened()):
ret, frame = cap.read()
cv2.imshow('frame', frame)
if cv2.waitKey(20) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

Bit of a hacky solution, but you can use the VLC python bindings (you can install it with pip install python-vlc) and play the stream:
import vlc
player=vlc.MediaPlayer('rtsp://:8554/output.h264')
player.play()
Then take a snapshot every second or so:
while 1:
time.sleep(1)
player.video_take_snapshot(0, '.snapshot.tmp.png', 0, 0)
And then you can use SimpleCV or something for processing (just load the image file '.snapshot.tmp.png' into your processing library).

use opencv
video=cv2.VideoCapture("rtsp url")
and then you can capture framse. read openCV documentation visit: https://docs.opencv.org/3.0-beta/doc/py_tutorials/py_gui/py_video_display/py_video_display.html

Depending on the stream type, you can probably take a look at this project for some ideas.
https://code.google.com/p/python-mjpeg-over-rtsp-client/
If you want to be mega-pro, you could use something like http://opencv.org/ (Python modules available I believe) for handling the motion detection.

Here is yet one more option.
It's much more complicated than the other answers.
But this way, with just one connection to the camera, you could "fork" the same stream simultaneously to several multiprocesses, to the screen, recast it into multicast, write it to disk, etc.
Of course, just in the case you would need something like that (otherwise you'd prefer the earlier answers)
Let's create two independent python programs:
Server program (rtsp connection, decoding) server.py
Client program (reads frames from shared memory) client.py
Server must be started before the client, i.e.
python3 server.py
And then in another terminal:
python3 client.py
Here is the code:
(1) server.py
import time
from valkka.core import *
# YUV => RGB interpolation to the small size is done each 1000 milliseconds and passed on to the shmem ringbuffer
image_interval=1000
# define rgb image dimensions
width =1920//4
height =1080//4
# posix shared memory: identification tag and size of the ring buffer
shmem_name ="cam_example"
shmem_buffers =10
shmem_filter =RGBShmemFrameFilter(shmem_name, shmem_buffers, width, height)
sws_filter =SwScaleFrameFilter("sws_filter", width, height, shmem_filter)
interval_filter =TimeIntervalFrameFilter("interval_filter", image_interval, sws_filter)
avthread =AVThread("avthread",interval_filter)
av_in_filter =avthread.getFrameFilter()
livethread =LiveThread("livethread")
ctx =LiveConnectionContext(LiveConnectionType_rtsp, "rtsp://user:password#192.168.x.x", 1, av_in_filter)
avthread.startCall()
livethread.startCall()
avthread.decodingOnCall()
livethread.registerStreamCall(ctx)
livethread.playStreamCall(ctx)
# all those threads are written in cpp and they are running in the
# background. Sleep for 20 seconds - or do something else while
# the cpp threads are running and streaming video
time.sleep(20)
# stop threads
livethread.stopCall()
avthread.stopCall()
print("bye")
(2) client.py
import cv2
from valkka.api2 import ShmemRGBClient
width =1920//4
height =1080//4
# This identifies posix shared memory - must be same as in the server side
shmem_name ="cam_example"
# Size of the shmem ringbuffer - must be same as in the server side
shmem_buffers =10
client=ShmemRGBClient(
name =shmem_name,
n_ringbuffer =shmem_buffers,
width =width,
height =height,
mstimeout =1000, # client timeouts if nothing has been received in 1000 milliseconds
verbose =False
)
while True:
index, isize = client.pull()
if (index==None):
print("timeout")
else:
data =client.shmem_list[index][0:isize]
img =data.reshape((height,width,3))
img =cv2.GaussianBlur(img, (21, 21), 0)
cv2.imshow("valkka_opencv_demo",img)
cv2.waitKey(1)
If you got interested, check out some more in https://elsampsa.github.io/valkka-examples/

Hi reading frames from video can be achieved using python and OpenCV . Below is the sample code. Works fine with python and opencv2 version.
import cv2
import os
#Below code will capture the video frames and will sve it a folder (in current working directory)
dirname = 'myfolder'
#video path
cap = cv2.VideoCapture("your rtsp url")
count = 0
while(cap.isOpened()):
ret, frame = cap.read()
if not ret:
break
else:
cv2.imshow('frame', frame)
#The received "frame" will be saved. Or you can manipulate "frame" as per your needs.
name = "rec_frame"+str(count)+".jpg"
cv2.imwrite(os.path.join(dirname,name), frame)
count += 1
if cv2.waitKey(20) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()

Use in this
cv2.VideoCapture("rtsp://username:password#IPAddress:PortNO(rest of the link after the IPAdress)").

cv2.videocapture doesn't works on Raspberry-pi

How can i make the cv2.VideoCapture(0) recognize the USB camera of raspberry-pi.
def OnRecord(self, evt):
capture = cv2.VideoCapture(0)
if (not capture.isOpened()):
print "Error"
# video recorder
fourcc = cv2.cv.CV_FOURCC(*'XVID') # cv2.VideoWriter_fourcc() does not exist
video_writer = cv2.VideoWriter.open("output.mp4", fourcc, 20, (640, 480), True)
# record video
while (capture.isOpened()):
ret, frame = capture.read()
if ret==True:
video_writer.write(frame)
cv2.imshow('Video', frame)
else:
break
def OnCancel(self, evt):
capture.release()
video_writer.release()
cv2.destroyAllWindows()
but it only prints Error.
So i guess capture is not opening. What might be the reason?
I tried this code from opencv documentation but doesn't worked out for me.
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()
Any help would be greatly appreciated.

Load the correct video for linux drivers.
sudo modprobe bcm2835-v4l2

In my experience with CV2 replacing a webcam source on linux isn't always easy. How OpenCV works is it automatically draws from the systems default video source, which is known (usually) as video0. Unplug your usb webcam and go into a terminal and typing ls /dev/video*
Remember the number it says. Now plug in your USB webcam and type in ls /dev/video* again and look for any new /video, this is your USB webcam. Now type mv /dev/videoX videoY while X is the number of your USB webcam and Y the original number. This will replace your pi's default camera.
This isn't permanent as you will need to do this every time your pi starts up, an alternative to this is creating a bash file that runs on start up. Create a text file and copy the following into it.
#!/bin/bash
mv /dev/videoX videoY
(replace the X and Y of course)
and place that in /etc/init.d directory of your pi. Don't forget you may need to use
chmod 755 /etc/init.d/FILENAME.sh
to give it permission to run

Go to terminal and type lsusb and check whether the USB camera is recognized or not. If it is recognized then try to give different device ID such as 1 or 2 or 3 rather than 0.

looks Like you might have issue with codec, try using 'MJPG' codec instead of XVID.
For more details have a look here

Make sure that the camera that you are using is UVC compatible, as openCV running on linux based systems (like a raspi) starts to do some silly things when it is working with non UVC cameras.