Function set_format

rustcv-camera/src/backend/linux/sys.rs:188–204

Set the video format (VIDIOC_S_FMT). 设置视频格式（VIDIOC_S_FMT）。 The driver may adjust the requested values to the nearest supported ones. The returned struct contains the actual applied values. 驱动可能将请求值调整为最接近的支持值。返回的结构体包含实际应用的值。

(fd: RawFd, width: u32, height: u32, fourcc: u32)

/// The returned struct contains the actual applied values.
/// 驱动可能将请求值调整为最接近的支持值。返回的结构体包含实际应用的值。
pub fn set_format(fd: RawFd, width: u32, height: u32, fourcc: u32) -> io::Result<v4l2_format> {
    let mut fmt: v4l2_format = unsafe { std::mem::zeroed() };
    fmt.type_ = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    // Access the pix member of the anonymous union via raw pointer.
    // 通过裸指针访问匿名联合体的 pix 成员。
    let pix = unsafe { &mut fmt.fmt.pix };
    pix.width = width;
    pix.height = height;
    pix.pixelformat = fourcc;
    pix.field = V4L2_FIELD_NONE;

    unsafe {
        v4l2_ioctl(fd, VIDIOC_S_FMT, &mut fmt as *mut _ as *mut libc::c_void)?;
    }
    Ok(fmt)
}

// ─── Frame rate ─────────────────────────────────────────────────────────────