函数 avdevice_list_devices 

pub unsafe extern "C" fn avdevice_list_devices(
    s: *mut AVFormatContext,
    device_list: *mut *mut AVDeviceInfoList,
) -> c_int

List devices.

Returns available device names and their parameters.

@note: Some devices may accept system-dependent device names that cannot be autodetected. The list returned by this function cannot be assumed to be always completed.

@param s device context. @param[out] device_list list of autodetected devices. @return count of autodetected devices, negative on error.