Opencv camera fps python

Python opencv video with fps code example

Have a look into PyAV extended example for custom PTS: Solution: You can use with loop to read frame by frame from two videos, stitch frames in new frame (using — ie. ) and save it in new file (also frame by frame) Later I create example. It seems AVFoundation (or the OpenCV api) can’t handle well an fps value with many significant digits, like 29.7787878779, and something was being rounded incorrectly either in OpenCV’s api or AVFoundation.

How to play any video with a fixed frame rate (fps) using OpenCV?

Take a look at this article. It shows how to play back AVI files with OpenCV. Here, the frame rate is read using

int fps = ( int ) cvGetCaptureProperty( capture, CV_CAP_PROP_FPS ); 

Hence, by controlling the fps variable, you can get the play back rate you want.

int fps = (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FPS); int delay = 1000 / fps; while (true) < clock_t startTime = clock(); capture.read(frame); process(); imshow("video", frame); while (clock() - startTime < delay) < waitKey(1); >> 

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How to write variable frame rate videos in Python

OpenCV is not a media library. it does not give you this flexibility.

extended example for custom PTS:

#!/usr/bin/env python3 # extended from https://github.com/PyAV-Org/PyAV/blob/main/examples/numpy/generate_video.py # added: custom PTS import numpy as np import av from fractions import Fraction total_frames = 20 container = av.open('test.mp4', mode='w') stream = container.add_stream('mpeg4', rate=25) # alibi frame rate stream.width = 480 stream.height = 320 stream.pix_fmt = 'yuv420p' # we'll show frames for 0.5 or 1.0 seconds # my_pts will say when the next frame is due # time_base is somewhat arbitrary. this is milliseconds. nice round numbers. I could use 1/2 for my desired PTSes. stream.codec_context.time_base = Fraction(1, 1000) my_pts = 0 # ffmpeg time is "complicated". read more at https://github.com/PyAV-Org/PyAV/blob/main/docs/api/time.rst for frame_i in range(total_frames): img = np.empty((480, 320, 3)) img[:, :, 0] = 0.5 + 0.5 * np.sin(2 * np.pi * (0 / 3 + frame_i / total_frames)) img[:, :, 1] = 0.5 + 0.5 * np.sin(2 * np.pi * (1 / 3 + frame_i / total_frames)) img[:, :, 2] = 0.5 + 0.5 * np.sin(2 * np.pi * (2 / 3 + frame_i / total_frames)) img = np.round(255 * img).astype(np.uint8) img = np.clip(img, 0, 255) frame = av.VideoFrame.from_ndarray(img, format='rgb24') frame.pts = int(my_pts / stream.codec_context.time_base) # seconds -> counts of time_base # calculate time of *next* frame, i.e. how long *this* frame will show # show three in quick succession, three slowly, repeat my_pts += 0.5 if ((frame_i // 3) % 2 == 0) else 1.0 for packet in stream.encode(frame): container.mux(packet) # Flush stream for packet in stream.encode(): container.mux(packet) # Close the file container.close() 

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Video Stitching using Open CV

You can use OpenCV with for/while loop to read frame by frame from two videos, stitch frames in new frame (using numpy — ie. hstack() ) and save it in new file (also frame by frame)

But it may be simpler to use specialized modules like MoviePy, ffmpeg-python or Manim.
Probably all of them use program ffmpeg which has many functions and filters.

Example with MoviePy — it creates array with with two movies in one row but it can create array with many rows and columns.

from moviepy.editor import * clip1 = VideoFileClip('input1.mp4') clip2 = VideoFileClip('input2.mp4') final_clip = clips_array([[clip1,clip2]]) # two videos in one row final_clip.write_videofile('output.mp4') 

And two videos in one column

final_clip = clips_array([[clip1], [clip2]]) # two videos in one column 

final_clip = clips_array([[clip1, clip2], [clip3,clip4]]) 

It is longer and more complex but it displays video.

import cv2 import numpy as np clip1 = cv2.VideoCapture('input1.mp4') clip2 = cv2.VideoCapture('input2.mp4') width = clip1.get(cv2.CAP_PROP_FRAME_WIDTH) height = clip1.get(cv2.CAP_PROP_FRAME_HEIGHT) fps = clip1.get(cv2.CAP_PROP_FPS) print('fps:', fps) video_format = cv2.VideoWriter_fourcc(*'MP42') # .avi final_clip = cv2.VideoWriter('output.avi', video_format, fps, (int(width), int(height))) delay = int(1000/fps) print('delay:', delay) while True: ret1, frame1 = clip1.read() ret2, frame2 = clip1.read() if not ret1 or not ret2: break final_frame = np.vstack([frame1, frame2]) # two videos in one row final_clip.write(final_frame) cv2.imshow('Video', final_frame) key = cv2.waitKey(delay) & 0xFF if key == 27: break cv2.destroyWindow('Video') clip1.release() clip2.release() 

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Python opencv videoWriter fps rounding

OpenCV uses some toolkit to do the writing. In my case, on iOS, OpenCV uses the native AVFoundation library. It seems AVFoundation (or the OpenCV api) can’t handle well an fps value with many significant digits, like 29.7787878779, and something was being rounded incorrectly either in OpenCV’s api or AVFoundation.

To fix the issue, I rounded off some of the significant digits before calling VideoWriter::open

normalizedFPS = round(1000.0 * normalizedFPS) / 1000.0; 

Hope it works for you also!

I’ve seen 30,000 used as a timescale recommendation, so perhaps test out 1000.0 vs 30,000.0

Python — Video Stitching using Open CV, 1 Answer. You can use OpenCV with for/while loop to read frame by frame from two videos, stitch frames in new frame (using numpy — ie. hstack ()) …

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Find frame rate (frames per second-fps) in OpenCV (Python/C++)

In OpenCV the class VideoCapture handles reading videos and grabbing frames from connected cameras. There is a lot of information you can find about the video file you are playing by using the get(PROPERTY_NAME) method in VideoCapture. One of the common properties you may want to know is to find frame rate or frames per second. You can download all code and example images used in this post here.

How to find frame rate of a camera / webcam in OpenCV ?

In OpenCV finding the frame rate of a connected camera / webcam is not straight forward. The documentation says that get(CAP_PROP_FPS) or get(CV_CAP_PROP_FPS) gives the frames per second. Now that is true for video files, but not for webcams. For webcams and many other connected cameras, you have to calculate the frames per second manually. You can read a certain number of frames from the video and see how much time has elapsed to calculate frames per second.

Download Code To easily follow along this tutorial, please download code by clicking on the button below. It’s FREE!

Python

#!/usr/bin/env python import cv2 import time if __name__ == '__main__' : # Start default camera video = cv2.VideoCapture(0); # Find OpenCV version (major_ver, minor_ver, subminor_ver) = (cv2.__version__).split('.') # With webcam get(CV_CAP_PROP_FPS) does not work. # Let's see for ourselves. if int(major_ver) < 3 : fps = video.get(cv2.cv.CV_CAP_PROP_FPS) print("Frames per second using video.get(cv2.cv.CV_CAP_PROP_FPS): ".format(fps)) else : fps = video.get(cv2.CAP_PROP_FPS) print("Frames per second using video.get(cv2.CAP_PROP_FPS) : ".format(fps)) # Number of frames to capture num_frames = 120; print("Capturing frames".format(num_frames)) # Start time start = time.time() # Grab a few frames for i in range(0, num_frames) : ret, frame = video.read() # End time end = time.time() # Time elapsed seconds = end - start print ("Time taken : seconds".format(seconds)) # Calculate frames per second fps = num_frames / seconds print("Estimated frames per second : ".format(fps)) # Release video video.release()

C++

#include "opencv2/opencv.hpp" #include using namespace cv; using namespace std; int main(int argc, char** argv) < // Start default camera VideoCapture video(0); // With webcam get(CV_CAP_PROP_FPS) does not work. // Let's see for ourselves. // double fps = video.get(CV_CAP_PROP_FPS); // If you do not care about backward compatibility // You can use the following instead for OpenCV 3 double fps = video.get(CAP_PROP_FPS); cout > frame; > // End Time time(&end); // Time elapsed double seconds = difftime (end, start); cout 

How to find frame rate of a video in OpenCV ?

If you are reading a video file you can simply use the get method to obtain frames per second. The following examples show the usage.

import cv2 if __name__ == '__main__' : video = cv2.VideoCapture("video.mp4"); # Find OpenCV version (major_ver, minor_ver, subminor_ver) = (cv2.__version__).split('.') if int(major_ver) < 3 : fps = video.get(cv2.cv.CV_CAP_PROP_FPS) print ("Frames per second using video.get(cv2.cv.CV_CAP_PROP_FPS): ".format(fps)) else : fps = video.get(cv2.CAP_PROP_FPS) print ("Frames per second using video.get(cv2.CAP_PROP_FPS) : ".format(fps)) video.release()

#include "opencv2/opencv.hpp" using namespace cv; using namespace std; int main(int argc, char** argv) < // Open video file VideoCapture video("video.mp4"); // double fps = video.get(CV_CAP_PROP_FPS); // For OpenCV 3, you can also use the following double fps = video.get(CAP_PROP_FPS); cout

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Summary

In this we discussed finding the frames per second-fps in OpenCV. We also provided the Python/C++ code for practice and study.

Key Takeaways

1. OpenCV class VideoCapture handles reading videos and grabbing frames from connected cameras.
2. The method PROPERTY_NAME helps find lot of information about the video file being played.
3. Common property we may want to know, frame rate or frames per second, is discussed in detail.
4. When reading a video file simply use the get method to obtain frames per second.

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