可见光通信技术(Visible Light Communication，VLC)是指利用可见光波段的光作为信息载体，不使用光纤等有线信道的传输介质，而在空气中直接传输光信号的通信方式。LED可见光通信是基于可见光发光二极管(Light Emitting Diode，LED)比荧光灯和白炽灯切换速度快的特点，利用配备LED的室内外大型显示屏、照明设备、信号器和汽车前尾灯等发出的用肉眼观察不到的高速调制光波信号来对信息调制和传输，然后利用光电二极管等光电转换器件接收光载波信号并获得信息。无论应用于室内还是室外的可见光LED通信系统，在其物理实现上均分为光信号发射和光信号接收两部分。光信号发射部分包括：将信号源信号转换成便于光信道传输的电信号的输入和处理电路、将电信号变化调制成光载波强度变化的LED可见光驱动调制电路。光信号接收部分包括：能对信号光源实现最佳接收的光学系统、将光信号还原成电信号的光电探测器和前置放大电路、将电信号转换成可被终端识别的信号处理和输出电路。
using System; using System.Reflection; using System.Runtime.InteropServices; using System.Security; using System.Collections.Generic; using System.Text; namespace DXApplication1 { class VlcPlayer { private IntPtr libvlc_instance_; private IntPtr libvlc_media_player_; private double duration_; public VlcPlayer(string pluginPath) { string plugin_arg = "--plugin-path=" + pluginPath; string[] arguments = { "-I", "dummy", "--ignore-config", "--no-video-title", plugin_arg }; libvlc_instance_ = LibVlcAPI.libvlc_new(arguments); libvlc_media_player_ = LibVlcAPI.libvlc_media_player_new(libvlc_instance_); } public void SetRenderWindow(int wndHandle) { if (libvlc_instance_ != IntPtr.Zero && wndHandle != 0) { LibVlcAPI.libvlc_media_player_set_hwnd(libvlc_media_player_, wndHandle); } } public void PlayFile(string filePath) { IntPtr libvlc_media = LibVlcAPI.libvlc_media_new_path(libvlc_instance_, filePath); if (libvlc_media != IntPtr.Zero) { LibVlcAPI.libvlc_media_parse(libvlc_media); duration_ = LibVlcAPI.libvlc_media_get_duration(libvlc_media) / 1000.0; LibVlcAPI.libvlc_media_player_set_media(libvlc_media_player_, libvlc_media); LibVlcAPI.libvlc_media_release(libvlc_media); LibVlcAPI.libvlc_media_player_play(libvlc_media_player_); } } public void Pause() { if (libvlc_media_player_ != IntPtr.Zero) { LibVlcAPI.libvlc_media_player_pause(libvlc_media_player_); } } public void Stop() { if (libvlc_media_player_ != IntPtr.Zero) { LibVlcAPI.libvlc_media_player_stop(libvlc_media_player_); } } public double GetPlayTime() { return LibVlcAPI.libvlc_media_player_get_time(libvlc_media_player_) / 1000.0; } public void SetPlayTime(double seekTime) { LibVlcAPI.libvlc_media_player_set_time(libvlc_media_player_, (Int64)(seekTime * 1000)); } public int GetVolume() { return LibVlcAPI.libvlc_audio_get_volume(libvlc_media_player_); } public void SetVolume(int volume) { LibVlcAPI.libvlc_audio_set_volume(libvlc_media_player_, volume); } public void SetFullScreen(bool istrue) { LibVlcAPI.libvlc_set_fullscreen(libvlc_media_player_, istrue ? 1 : 0); } public double Duration() { return duration_; } public string Version() { return LibVlcAPI.libvlc_get_version(); } } internal static class LibVlcAPI { internal struct PointerToArrayOfPointerHelper { [MarshalAs(UnmanagedType.ByValArray, SizeConst = 11)] public IntPtr[] pointers; } public static IntPtr libvlc_new(string[] arguments) { PointerToArrayOfPointerHelper argv = new PointerToArrayOfPointerHelper(); argv.pointers = new IntPtr[11]; for (int i = 0; i < arguments.Length; i++) { argv.pointers[i] = Marshal.StringToHGlobalAnsi(arguments[i]); } IntPtr argvPtr = IntPtr.Zero; try { int size = Marshal.SizeOf(typeof(PointerToArrayOfPointerHelper)); argvPtr = Marshal.AllocHGlobal(size); Marshal.StructureToPtr(argv, argvPtr, false); return libvlc_new(arguments.Length, argvPtr); } finally { for (int i = 0; i < arguments.Length + 1; i++) { if (argv.pointers[i] != IntPtr.Zero) { Marshal.FreeHGlobal(argv.pointers[i]); } } if (argvPtr != IntPtr.Zero) { Marshal.FreeHGlobal(argvPtr); } } } public static IntPtr libvlc_media_new_path(IntPtr libvlc_instance, string path) { IntPtr pMrl = IntPtr.Zero; try { byte[] bytes = Encoding.UTF8.GetBytes(path); pMrl = Marshal.AllocHGlobal(bytes.Length + 1); Marshal.Copy(bytes, 0, pMrl, bytes.Length); Marshal.WriteByte(pMrl, bytes.Length, 0); return libvlc_media_new_path(libvlc_instance, pMrl); } finally { if (pMrl != IntPtr.Zero) { Marshal.FreeHGlobal(pMrl); } } } public static IntPtr libvlc_media_new_location(IntPtr libvlc_instance, string path) { IntPtr pMrl = IntPtr.Zero; try { byte[] bytes = Encoding.UTF8.GetBytes(path); pMrl = Marshal.AllocHGlobal(bytes.Length + 1); Marshal.Copy(bytes, 0, pMrl, bytes.Length); Marshal.WriteByte(pMrl, bytes.Length, 0); return libvlc_media_new_path(libvlc_instance, pMrl); } finally { if (pMrl != IntPtr.Zero) { Marshal.FreeHGlobal(pMrl); } } } // ---------------------------------------------------------------------------------------- // 以下是libvlc.dll导出函数 // DllImport的CallingConvention的属性,默认值是CallingCovention.Stdcall, 此处更改成Cdecl // 创建一个libvlc实例，它是引用计数的 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] private static extern IntPtr libvlc_new(int argc, IntPtr argv); // 释放libvlc实例 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_release(IntPtr libvlc_instance); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern String libvlc_get_version(); // 从视频来源(例如Url)构建一个libvlc_meida [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] private static extern IntPtr libvlc_media_new_location(IntPtr libvlc_instance, IntPtr path); // 从本地文件路径构建一个libvlc_media [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] private static extern IntPtr libvlc_media_new_path(IntPtr libvlc_instance, IntPtr path); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_release(IntPtr libvlc_media_inst); // 创建libvlc_media_player(播放核心) [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern IntPtr libvlc_media_player_new(IntPtr libvlc_instance); // 将视频(libvlc_media)绑定到播放器上 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_set_media(IntPtr libvlc_media_player, IntPtr libvlc_media); // 设置图像输出的窗口 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_set_hwnd(IntPtr libvlc_mediaplayer, Int32 drawable); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_play(IntPtr libvlc_mediaplayer); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_pause(IntPtr libvlc_mediaplayer); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_stop(IntPtr libvlc_mediaplayer); // 解析视频资源的媒体信息(如时长等) [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_parse(IntPtr libvlc_media); // 返回视频的时长(必须先调用libvlc_media_parse之后，该函数才会生效) [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern Int64 libvlc_media_get_duration(IntPtr libvlc_media); // 当前播放的时间 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern Int64 libvlc_media_player_get_time(IntPtr libvlc_mediaplayer); // 设置播放位置(拖动) [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_set_time(IntPtr libvlc_mediaplayer, Int64 time); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_media_player_release(IntPtr libvlc_mediaplayer); // 获取和设置音量 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern int libvlc_audio_get_volume(IntPtr libvlc_media_player); [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_audio_set_volume(IntPtr libvlc_media_player, int volume); // 设置全屏 [DllImport("libvlc", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)] [SuppressUnmanagedCodeSecurity] public static extern void libvlc_set_fullscreen(IntPtr libvlc_media_player, int isFullScreen); } }
