Method new

rustcv-backend-avf/src/stream.rs:80–182

初始化完整的采集管线（同步，不启动采集）。 # Arguments `device_id` — 由 `AvfDriver::list_devices` 返回的 `DeviceInfo.id` `config` — 采集配置（分辨率、FPS 等）

(device_id: &str, config: CameraConfig)

    /// * `device_id` — 由 `AvfDriver::list_devices` 返回的 `DeviceInfo.id`
    /// * `config` — 采集配置（分辨率、FPS 等）
    pub fn new(device_id: &str, config: CameraConfig) -> Result<Self> {
        unsafe {
            // 创建 Session
            let session = AVCaptureSession::new();

            // 开始修改配置
            session.beginConfiguration();

            // 查找设备
            let device = AVCaptureDevice::deviceWithUniqueID(&NSString::from_str(device_id))
                .ok_or_else(|| anyhow!("Device ID not found: {}", device_id))?;

            // 根据 config 选择最合适的分辨率 Preset
            let preset = select_best_preset(&session, &config);
            session.setSessionPreset(preset);

            // 配置 FPS (用 catch 包裹，因为如果申请了设备不支持的 FPS 会抛出 Objective-C 异常)
            if let Some((fps, _priority)) = config.fps_req {
                if device.lockForConfiguration().is_ok() {
                    let device_ref = std::panic::AssertUnwindSafe(&device);
                    let result = catch(|| {
                        let duration = CMTime {
                            value: 1,
                            timescale: fps as i32,
                            flags: CMTimeFlags::Valid,
                            epoch: 0,
                        };
                        device_ref.setActiveVideoMinFrameDuration(duration);
                        device_ref.setActiveVideoMaxFrameDuration(duration);
                    });
                    if let Err(e) = result {
                        println!("Warning: Failed to set FPS to {fps}. Device might not support it at this resolution. Exception: {:?}", e);
                    }
                    device.unlockForConfiguration();
                }
            }

            // ⑥ 包装为 Input 并添加到 Session
            let input = AVCaptureDeviceInput::deviceInputWithDevice_error(&device)
                .map_err(|e| anyhow!("Failed to create capture input: {:?}", e))?;

            if session.canAddInput(&input) {
                session.addInput(&input);
            } else {
                session.commitConfiguration();
                return Err(anyhow!("Cannot add input to session"));
            }

            // ⑥ 创建 Output，并配置像素格式和丢帧策略
            let output = AVCaptureVideoDataOutput::new();

            // 强制请求 32BGRA，避免后续 CPU YUV→RGB 转换的高昂开销
            // kCVPixelBufferPixelFormatTypeKey = "PixelFormatType"
            {
                use objc2::runtime::AnyObject;
                use objc2_foundation::{NSCopying, NSDictionary, NSObjectProtocol};

                let key = NSString::from_str("PixelFormatType");