Rust opencv crate摄像头严重卡顿问题排查与解决方案

环境信息 #

• Ubuntu 22.04 系统
• Rust 版本 1.76.0
• opencv crate 版本 0.88.8
• 已执行 apt install libopencv-dev clang libclang-dev 完成依赖部署

问题现象 #

运行OpenCV官方示例代码调用摄像头时，功能正常但画面严重卡顿。摄像头原生支持22-24FPS，通过帧率测试代码测得实际帧率仅约8FPS；相同场景下的Python版OpenCV代码无任何卡顿。

初始卡顿的Rust代码 #

use opencv::{highgui, prelude::*, videoio, Result};

fn main() -> Result<()> {
    let window = "video capture";
    highgui::named_window(window, highgui::WINDOW_AUTOSIZE)?;
    let mut cam = videoio::VideoCapture::new(0, videoio::CAP_ANY)?; // 0为默认摄像头
    let opened = videoio::VideoCapture::is_opened(&cam)?;
    if !opened {
        panic!("无法打开默认摄像头！");
    }
    loop {
        let mut frame = Mat::default();
        cam.read(&mut frame)?;
        if frame.size()?.width > 0 {
            highgui::imshow(window, &frame)?;
        }
        let key = highgui::wait_key(10)?;
        if key > 0 && key != 255 {
            break;
        }
    }
    Ok(())
}

帧率测试代码片段 #

let fps_start = Instant::now();             
    let num_frames_to_measure = 60;             
    for _ in 0..num_frames_to_measure {         
        let mut temp_frame = Mat::default();    
        cam.read(&mut temp_frame)?;             
    }                                           
    let fps_duration = fps_start.elapsed();     
    let fps = num_frames_to_measure as f64 / fps_duration.as_secs_f64();
    println!("实际帧率: {:?}", fps);        

无卡顿的Python对比代码 #

import cv2


vid = cv2.VideoCapture(0)
while True:
    ret, frame = vid.read()
    cv2.imshow('window', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

vid.release()
cv2.destroyAllWindows()

解决方法 #

通过显式设置摄像头的宽高参数，可让摄像头工作在其支持的高帧率模式下，解决卡顿问题。修正后的完整代码如下：

修正后的Rust代码 #

use opencv::core::Vector;
use opencv::{
    highgui,
    prelude::*,
    videoio,
    imgcodecs
};
use std::time::Instant;


fn main() -> Result<(), Box<dyn std::error::Error>> {
    // 1. 初始化
    let setup_start = Instant::now();
    let mut cam = videoio::VideoCapture::new(0, videoio::CAP_ANY)?;  // 0为默认摄像头
    let opened = videoio::VideoCapture::is_opened(&cam)?;
    if !opened {
        println!("无法打开默认摄像头！");
        return Ok(());
    }
    cam.set(videoio::CAP_PROP_FRAME_WIDTH, 640.0)?; // 设置帧宽度
    cam.set(videoio::CAP_PROP_FRAME_HEIGHT, 480.0)?; // 设置帧高度
    let setup_duration = setup_start.elapsed().as_secs_f64(); // 计算初始化耗时
    println!("初始化耗时: {:?}", setup_duration); // 打印初始化耗时

    // 2. 测试帧率
    let fps_start = Instant::now();
    let num_frames_to_measure = 60;
    for _ in 0..num_frames_to_measure {
        let mut temp_frame = Mat::default();
        cam.read(&mut temp_frame)?;
    }
    let fps_duration = fps_start.elapsed();
    let fps = num_frames_to_measure as f64 / fps_duration.as_secs_f64();
    println!("实际帧率: {:?}", fps);

    // 3. 显示摄像头画面
    loop {
        let mut frame = Mat::default();
        cam.read(&mut frame)?;
        if frame.size()?.width > 0 {
            highgui::imshow("camera", &frame)?;
            let key = highgui::wait_key(1)?;
            if key == 13 {  // 按下回车键退出程序
                break;
            }
        }
    }
    
    Ok(())
}

内容的提问来源于stack exchange，提问作者RedRum69