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• How to get real time video stream from iphone camera and send it to server ?

  7 novembre 2016, par Ron

  I am using AVCaptureSession to capture video and get real time frame from iPhone camera but how can I send it to server with multiplexing of frame and sound and how to use ffmpeg to complete this task, if any one have any tutorial about ffmpeg or any example please share here.

• How to check if OpenCV VideoCapture uses multithreading or multiprocessing internally when connecting to a camera [closed]

  20 décembre 2024, par Chen

  I'm using OpenCV's cv::VideoCapture in C++ (or Python) to connect to a camera stream. I would like to know if OpenCV internally uses multithreading or multiprocessing when opening and capturing frames from the camera.

  


  Specifically, I'm curious about :

  


  

  • Whether OpenCV spawns new threads or processes when using cv::VideoCapture.

  


  • If FFmpeg is enabled as the backend, does it use multithreading or multiprocessing under the hood ?

  


  • How can I verify the threading or process behavior during camera streaming ?

  


  


  What I Tried :
I checked the current process using psutil (in Python) and printed the number of threads :

  


  import cv2
import psutil

cap = cv2.VideoCapture("rtsp://camera_stream", cv2.CAP_FFMPEG)
process = psutil.Process()

print(f"Process ID: {process.pid}, Name: {process.name()}")
print(f"Thread count: {process.num_threads()}")

for thread in process.threads():
print(f"Thread ID: {thread.id}, CPU Time: {thread.user_time + thread.system_time}")

cap.release()


  


  

  • Does VideoCapture use multithreading or multiprocessing internally ?

  


  • Is there a reliable way to verify whether the underlying backend (e.g., FFmpeg) has enabled multithreading ?

  


  • Are there specific settings in OpenCV or FFmpeg that can control this behavior ?

  


  


• Record from camera, save to file, and acess last recorded frame

  18 février 2021, par 12.yakir

  I want to record video from a camera, save it to file, and at the same time have access to the last frame recorded.

  


  One idea would be to use ffmpeg's Multiple Outputs functionality where I split the stream into two, one gets saved to file, one spits out the last recorded frame (ideally, the frames won't need to be written to disk, but piped onwards for processing).

  


  What I don't know is how to get ffmpeg to spit "the last frame" from a stream.

  


  Any ideas ?