test_camera_fps.py

import cv2
import time
import sys

def test_camera(device_id, width=640, height=480, fps=30):
    print(f"\n=== Testing Camera Index {device_id} ===")
    
    # 优先使用 V4L2 后端
    backend = cv2.CAP_V4L2 if hasattr(cv2, 'CAP_V4L2') else cv2.CAP_ANY
    backend_name = "V4L2" if backend == cv2.CAP_V4L2 else "ANY"
    print(f"Opening with backend: {backend_name}")

    cap = cv2.VideoCapture(device_id, backend)
    
    if not cap.isOpened():
        print(f"Error: Could not open camera {device_id}")
        return

    # 1. 强制 MJPG
    print("Attempting to set MJPG format...")
    cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'))
    
    # 2. 设置 FPS 和 分辨率
    cap.set(cv2.CAP_PROP_FPS, fps)
    cap.set(cv2.CAP_PROP_FRAME_WIDTH, width)
    cap.set(cv2.CAP_PROP_FRAME_HEIGHT, height)
    
    # 3. 关闭自动曝光 (Linux V4L2 特有，尝试通过 OpenCV 属性设置)
    # 0.25 通常对应 'Manual'，但在不同驱动下可能不同，这里仅作为尝试
    # cap.set(cv2.CAP_PROP_AUTO_EXPOSURE, 0.25) 

    # 4. 读取实际生效的设置
    actual_w = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
    actual_h = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
    actual_fps = cap.get(cv2.CAP_PROP_FPS)
    fourcc = int(cap.get(cv2.CAP_PROP_FOURCC))
    codec = "".join([chr((fourcc >> 8 * i) & 0xFF) for i in range(4)])
    
    print(f"----------------------------------------")
    print(f"Requested: {width}x{height} @ {fps} FPS, MJPG")
    print(f"Actual   : {actual_w}x{actual_h} @ {actual_fps} FPS, Codec: {codec}")
    print(f"----------------------------------------")
    
    if codec.upper() != "MJPG":
        print("WARNING: Codec is NOT MJPG! This is likely the cause of low FPS.")

    print("Warming up camera (skip 10 frames)...")
    for _ in range(10):
        cap.read()

    print(f"Starting capture loop for 100 frames...")
    count = 0
    start_time = time.time()
    
    while count < 100:
        ret, frame = cap.read()
        if not ret:
            print("Error: Failed to read frame during loop")
            break
        count += 1
        # 显示简略进度
        if count % 10 == 0:
            sys.stdout.write(f"{count}..")
            sys.stdout.flush()
            
    end_time = time.time()
    duration = end_time - start_time
    avg_fps = count / duration
    
    print(f"\n\nRESULT: Captured {count} frames in {duration:.2f} seconds.")
    print(f"AVERAGE FPS: {avg_fps:.2f}")
    
    cap.release()

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python test_camera_fps.py <device_id> [width] [height] [fps]")
        print("Example: python backend/scripts/test_camera_fps.py 0 640 480 30")
    else:
        dev_id = int(sys.argv[1])
        w = int(sys.argv[2]) if len(sys.argv) > 2 else 640
        h = int(sys.argv[3]) if len(sys.argv) > 3 else 480
        f = int(sys.argv[4]) if len(sys.argv) > 4 else 30
        test_camera(dev_id, w, h, f)