c#万能视频播放器

　　本人之前很多的文章中均提到了使用libvlc为播放器内核制作的播放器，也许有些朋友对此感兴趣，于是我用c#写了一个调用libvlc api实现的万能视频播放器，与大家分享一下。说它“万能”，当然是因为我们站在了vlc的肩膀上。

　　vlc是一个强大而且开源的多媒体播放器，也可以说是一个多媒体平台。它支持非常广泛的媒体格式的本地播放，完全可以媲美mplayer，其对视频网络流的处理能力更是非常强悍。libvlc就是指的vlc的核心，它向外提供了一系列的接口，通过接口，来实现视频播放等复杂的功能。libvlc对外提供了c语言的接口，也有其他语言，包括.net的绑定，在其官网上就有，不过已经“年久失修”。我之前用Qt, MFC实现过基于libvlc的播放器，不过鉴于园子里c#开发人员较多，遂用c#封装了一下libvlc的API接口，并实现了一个视频播放器。

　　先上鉴赏图，外表很简单，不过，外表不是重点:)

　　首先是libvlc的一些导出函数，我在注释里对它们的功能都有说明

 1         // 创建一个libvlc实例，它是引用计数的
 2         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
 3         [SuppressUnmanagedCodeSecurity]
 4         private static extern IntPtr libvlc_new(int argc, IntPtr argv);
 5 
 6         // 释放libvlc实例
 7         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
 8         [SuppressUnmanagedCodeSecurity]
 9         public static extern void libvlc_release(IntPtr libvlc_instance);
10 
11         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
12         [SuppressUnmanagedCodeSecurity]
13         public static extern String libvlc_get_version();
14 
15         // 从视频来源(例如Url)构建一个libvlc_meida
16         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
17         [SuppressUnmanagedCodeSecurity]
18         private static extern IntPtr libvlc_media_new_location(IntPtr libvlc_instance, IntPtr path);
19 
20         // 从本地文件路径构建一个libvlc_media
21         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
22         [SuppressUnmanagedCodeSecurity]
23         private static extern IntPtr libvlc_media_new_path(IntPtr libvlc_instance, IntPtr path);
24 
25         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
26         [SuppressUnmanagedCodeSecurity]
27         public static extern void libvlc_media_release(IntPtr libvlc_media_inst);
28 
29         // 创建libvlc_media_player(播放核心)
30         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
31         [SuppressUnmanagedCodeSecurity]
32         public static extern IntPtr libvlc_media_player_new(IntPtr libvlc_instance);
33 
34         // 将视频(libvlc_media)绑定到播放器上
35         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
36         [SuppressUnmanagedCodeSecurity]
37         public static extern void libvlc_media_player_set_media(IntPtr libvlc_media_player, IntPtr libvlc_media);
38 
39         // 设置图像输出的窗口
40         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
41         [SuppressUnmanagedCodeSecurity]
42         public static extern void libvlc_media_player_set_hwnd(IntPtr libvlc_mediaplayer, Int32 drawable);
43 
44         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
45         [SuppressUnmanagedCodeSecurity]
46         public static extern void libvlc_media_player_play(IntPtr libvlc_mediaplayer);
47 
48         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
49         [SuppressUnmanagedCodeSecurity]
50         public static extern void libvlc_media_player_pause(IntPtr libvlc_mediaplayer);
51 
52         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
53         [SuppressUnmanagedCodeSecurity]
54         public static extern void libvlc_media_player_stop(IntPtr libvlc_mediaplayer);
55 
56         // 解析视频资源的媒体信息(如时长等)
57         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
58         [SuppressUnmanagedCodeSecurity]
59         public static extern void libvlc_media_parse(IntPtr libvlc_media);
60 
61         // 返回视频的时长(必须先调用libvlc_media_parse之后，该函数才会生效)
62         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
63         [SuppressUnmanagedCodeSecurity]
64         public static extern Int64 libvlc_media_get_duration(IntPtr libvlc_media);
65 
66         // 当前播放的时间
67         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
68         [SuppressUnmanagedCodeSecurity]
69         public static extern Int64 libvlc_media_player_get_time(IntPtr libvlc_mediaplayer);
70 
71         // 设置播放位置(拖动)
72         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
73         [SuppressUnmanagedCodeSecurity]
74         public static extern void libvlc_media_player_set_time(IntPtr libvlc_mediaplayer, Int64 time);
75 
76         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
77         [SuppressUnmanagedCodeSecurity]
78         public static extern void libvlc_media_player_release(IntPtr libvlc_mediaplayer);
79 
80         // 获取和设置音量
81         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
82         [SuppressUnmanagedCodeSecurity]
83         public static extern int libvlc_audio_get_volume(IntPtr libvlc_media_player);
84 
85         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
86         [SuppressUnmanagedCodeSecurity]
87         public static extern void libvlc_audio_set_volume(IntPtr libvlc_media_player, int volume);
88 
89         // 设置全屏
90         [DllImport("libvlc", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
91         [SuppressUnmanagedCodeSecurity]
92         public static extern void libvlc_set_fullscreen(IntPtr libvlc_media_player, int isFullScreen);

　　要使用libvlc api进行播放，首先需要创建一个libvlc的实例，就是lbvlc_instance，之后所有的操作都是基于这个实例来完成。

　　每一个播放窗口，对应一个libvlc_media_player，而每一个媒体文件，就是一个libvlc_media。所以，调用的步骤就是：

1. 创建libvlc_instance
2. 创建libvlc_media_player
3. 开始播放时，创建libvlc_media，通知libvlc_media_player要播放的媒体文件，之后就可以释放libvlc_media了
4. 操作libvlc_media_player，实现播放、暂停等功能

　　下面对这些操作进行封装，以供上层使用。

 1     class VlcPlayer
 2     {
 3         private IntPtr libvlc_instance_;
 4         private IntPtr libvlc_media_player_;
 5 
 6         private double duration_;
 7 
 8         public VlcPlayer(string pluginPath)
 9         {
10             string plugin_arg = "--plugin-path=" + pluginPath;
11             string[] arguments = { "-I", "dummy", "--ignore-config", "--no-video-title", plugin_arg };
12             libvlc_instance_ = LibVlcAPI.libvlc_new(arguments);
13 
14             libvlc_media_player_ = LibVlcAPI.libvlc_media_player_new(libvlc_instance_);
15         }
16 
17         public void SetRenderWindow(int wndHandle)
18         {
19             if (libvlc_instance_ != IntPtr.Zero && wndHandle != 0)
20             {
21                 LibVlcAPI.libvlc_media_player_set_hwnd(libvlc_media_player_, wndHandle);
22             }
23         }
24 
25         public void PlayFile(string filePath)
26         {
27             IntPtr libvlc_media = LibVlcAPI.libvlc_media_new_path(libvlc_instance_, filePath);
28             if (libvlc_media != IntPtr.Zero)
29             {
30                 LibVlcAPI.libvlc_media_parse(libvlc_media);
31                 duration_ = LibVlcAPI.libvlc_media_get_duration(libvlc_media) / 1000.0;
32 
33                 LibVlcAPI.libvlc_media_player_set_media(libvlc_media_player_, libvlc_media);
34                 LibVlcAPI.libvlc_media_release(libvlc_media);
35 
36                 LibVlcAPI.libvlc_media_player_play(libvlc_media_player_);
37             }
38         }
39 
40         public void Pause()
41         {
42             if (libvlc_media_player_ != IntPtr.Zero)
43             {
44                 LibVlcAPI.libvlc_media_player_pause(libvlc_media_player_);
45             }
46         }
47 
48         public void Stop()
49         {
50             if (libvlc_media_player_ != IntPtr.Zero)
51             {
52                 LibVlcAPI.libvlc_media_player_stop(libvlc_media_player_);
53             }
54         }
55 
56         public double GetPlayTime()
57         {
58             return LibVlcAPI.libvlc_media_player_get_time(libvlc_media_player_) / 1000.0;
59         }
60 
61         public void SetPlayTime(double seekTime)
62         {
63             LibVlcAPI.libvlc_media_player_set_time(libvlc_media_player_, (Int64)(seekTime * 1000));
64         }
65 
66         public int GetVolume()
67         {
68             return LibVlcAPI.libvlc_audio_get_volume(libvlc_media_player_);
69         }
70 
71         public void SetVolume(int volume)
72         {
73             LibVlcAPI.libvlc_audio_set_volume(libvlc_media_player_, volume);
74         }
75 
76         public void SetFullScreen(bool istrue)
77         {
78             LibVlcAPI.libvlc_set_fullscreen(libvlc_media_player_, istrue ? 1 : 0);
79         }
80 
81         public double Duration()
82         {
83             return duration_;
84         }
85 
86         public string Version()
87         {
88             return LibVlcAPI.libvlc_get_version();
89         }
90     }