Windows平台基于RTMP实现一对一互动直播

目前市面上大多一对一互动都是基于WebRTC，缺点如下：

1. 服务器部署非常复杂，不利于私有部署，在一些私密性高的场景下，无法使用，如公安、市政等体系；
2. 传输基于UDP，很难保证传输质量，由于UDP是不可靠的传输协议，在复杂的公网网络环境下，各种突发流量、偶尔的传输错误、网络抖动、超时等等都会引起丢包异常，都会在一定程度上影响音视频通信的质量；
3. 难以应对复杂的互联网环境，如跨区跨运营商、低带宽、高丢包等场景；
4. 整个框架体系不够灵活，代码复杂度高，行话说的好：从demo到实用,中间还差1万个WebRTC。

RTMP一对一互动技术特点：

•  基于现有RTMP推拉流体系，产品稳定度高，整体延迟低；
•  加入噪音抑制、回音消除、自动增益控制等特性，确保通话效果；
•  采用通用的RTMP和RTSP服务器，如nginx、SRS，更有利于私有部署；
•  支持H.264的扩展SEI消息发送机制；
•  支持H.265编码和H.264可变码率设定；
•  支持H.265解码，直播播放器支持的功能，一对一互动模块都可以有选择的支持；
•  适用于应急指挥、教育培训等领域；
•  支持RTMP扩展AES/SM4加解密，确保音视频数据安全性。

废话不多说，上封装代码：

基于 https://github.com/daniulive/SmarterStreaming/ 拉流端封装的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Drawing2D;
using NT;

namespace SmartEchoCancellationDemo
{
    public delegate void DelGetPlayerEventMsg(String msg);
    public delegate void DelGetVideoSize(String size);

    class nt_player_wrapper : IDisposable
    {
        [DllImport("kernel32", EntryPoint = "CopyMemory")]
        static extern void CopyMemory(IntPtr Destination, IntPtr Source, uint Length);

        private bool disposed_ = false;

        private IntPtr player_handle_ = IntPtr.Zero;
        private System.Windows.Forms.Control render_wnd_ = null;
        private System.Windows.Forms.PaintEventHandler render_wnd_paint_event_ = null;

        private bool is_playing_ = false;
        private bool is_mute_ = false;
        private int  play_buffer_ = 100;

        private NT_SP_VideoFrame cur_video_frame_ = new NT_SP_VideoFrame();

        private WeakReference sync_invoke_ = null;

        //分辨率信息回调
        delegate void ResolutionNotifyCallback(Int32 width, Int32 height);
        ResolutionNotifyCallback resolution_notify_callback_;
        SP_SDKVideoSizeCallBack video_size_call_back_;

        //视频数据回调
        SP_SDKVideoFrameCallBack video_frame_call_back_;
        delegate void VideoFrameCallBack(UInt32 status, NT_SP_VideoFrame frame);
        VideoFrameCallBack set_video_frame_call_back_;

        //event事件回调
        //拉流端事件
        SP_SDKEventCallBack pull_event_call_back_;
        delegate void SetPullEventCallBack(UInt32 event_id,
                Int64 param1,
                Int64 param2,
                UInt64 param3,
                [MarshalAs(UnmanagedType.LPStr)] String param4,
                [MarshalAs(UnmanagedType.LPStr)] String param5,
                IntPtr param6);
        SetPullEventCallBack set_pull_event_call_back_;

        private UInt32 connection_status_ = 0;
        private UInt32 buffer_status_ = 0;
        private Int32 buffer_percent_ = 0;
        private Int32 download_speed_ = -1;

        public event DelGetPlayerEventMsg EventGetPlayerEventMsg;
        public event DelGetVideoSize EventGetVideoSize;

        public nt_player_wrapper(System.Windows.Forms.Control render_wnd, System.ComponentModel.ISynchronizeInvoke sync_invoke)
        {
            render_wnd_ = render_wnd;
            sync_invoke_ =  new WeakReference(sync_invoke);
            set_pull_event_call_back_ = new SetPullEventCallBack(PullEventCallBack);

            if (render_wnd_ != null)
            {
                render_wnd_paint_event_ = new System.Windows.Forms.PaintEventHandler(this.OnRenderWindowPaint);
                render_wnd_.Paint += render_wnd_paint_event_;
            }
        }

        public void Dispose()
        {
            Dispose(true);

            // This object will be cleaned up by the Dispose method.
            // Therefore, you should call GC.SupressFinalize to
            // take this object off the finalization queue
            // and prevent finalization code for this object
            // from executing a second time.
            // GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            // Check to see if Dispose has already been called.
            if (!this.disposed_)
            {
                if (disposing)
                {
                }

                if (IsPlaying())
                {
                   StopPlay(false);
                }

                if (render_wnd_ != null && render_wnd_paint_event_ != null)
                {
                    render_wnd_.Paint -= render_wnd_paint_event_;
                }

                render_wnd_paint_event_ = null;

                if (cur_video_frame_.plane0_ != IntPtr.Zero)
                {
                    Marshal.FreeHGlobal(cur_video_frame_.plane0_);
                    cur_video_frame_.plane0_ = IntPtr.Zero;
                }
             
                // Note disposing has been done.
                disposed_ = true;
            }
        }

 
        ~nt_player_wrapper()
        {
            Dispose(false);
        }

        public void SetVideoFrameCallBack(IntPtr handle, IntPtr userData, UInt32 status, IntPtr frame)
        {
            if (frame == IntPtr.Zero)
            {
                return;
            }

            //如需直接处理RGB数据，请参考以下流程
            NT_SP_VideoFrame video_frame = (NT_SP_VideoFrame)Marshal.PtrToStructure(frame, typeof(NT_SP_VideoFrame));

            if (video_frame.format_ != (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32)
                return;

            NT_SP_VideoFrame pVideoFrame = new NT_SP_VideoFrame();

            pVideoFrame.format_ = video_frame.format_;
            pVideoFrame.width_ = video_frame.width_;
            pVideoFrame.height_ = video_frame.height_;

            pVideoFrame.timestamp_ = video_frame.timestamp_;
            pVideoFrame.stride0_ = video_frame.stride0_;
            pVideoFrame.stride1_ = video_frame.stride1_;
            pVideoFrame.stride2_ = video_frame.stride2_;
            pVideoFrame.stride3_ = video_frame.stride3_;

            if (sync_invoke_ != null)
            {
                System.ComponentModel.ISynchronizeInvoke sync_invoke_target = sync_invoke_.Target as System.ComponentModel.ISynchronizeInvoke;

                if (sync_invoke_target != null)
                {
                    Int32 argb_size = video_frame.stride0_ * video_frame.height_;

                    pVideoFrame.plane0_ = Marshal.AllocHGlobal(argb_size);
                    CopyMemory(pVideoFrame.plane0_, video_frame.plane0_, (UInt32)argb_size);

                    if (sync_invoke_target.InvokeRequired)
                    {
                        sync_invoke_target.BeginInvoke(set_video_frame_call_back_, new object[] { status, pVideoFrame });
                    }
                    else
                    {
                        set_video_frame_call_back_(status, pVideoFrame);
                    }
                }
            }
        }

        public void SDKVideoFrameCallBack(UInt32 status, NT_SP_VideoFrame frame)
        {
            if (cur_video_frame_.plane0_ != IntPtr.Zero)
            {
                Marshal.FreeHGlobal(cur_video_frame_.plane0_);
                cur_video_frame_.plane0_ = IntPtr.Zero;
            }

            cur_video_frame_ = frame;

            if (render_wnd_ != null)
            {
                render_wnd_.Invalidate();
            }
        }

        public void SDKPullEventCallBack(IntPtr handle, IntPtr user_data,
            UInt32 event_id,
            Int64 param1,
            Int64 param2,
            UInt64 param3,
            [MarshalAs(UnmanagedType.LPStr)] String param4,
            [MarshalAs(UnmanagedType.LPStr)] String param5,
            IntPtr param6)
        {
            if (sync_invoke_ != null)
            {
                System.ComponentModel.ISynchronizeInvoke sync_invoke_target = sync_invoke_.Target as System.ComponentModel.ISynchronizeInvoke;

                if (sync_invoke_target  != null )
                {
                    if (sync_invoke_target.InvokeRequired)
                    {
                        sync_invoke_target.BeginInvoke(set_pull_event_call_back_, new object[] { event_id, param1, param2, param3, param4, param5, param6 });
                    }
                    else
                    {
                        set_pull_event_call_back_(event_id, param1, param2, param3, param4, param5, param6);
                    }
                }
            }
        }

        private void PullEventCallBack(UInt32 event_id,
            Int64 param1,
            Int64 param2,
            UInt64 param3,
            [MarshalAs(UnmanagedType.LPStr)] String param4,
            [MarshalAs(UnmanagedType.LPStr)] String param5,
            IntPtr param6)
        {
            if (!is_playing_)
            {
                return;
            }

            String show_str = "";

            if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_PLAYBACK_REACH_EOS == event_id)
            {
                StopPlay();
                return;
            }
            else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_RTSP_STATUS_CODE == event_id)
            {
                int status_code = (int)param1;
                show_str = "RTSP incorrect status code received: " + status_code.ToString() + ", 请确保用户名/密码正确";
            }

            if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTING == event_id
                || (UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTION_FAILED == event_id
                || (UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTED == event_id
                || (UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_DISCONNECTED == event_id)
            {
                connection_status_ = event_id;
            }

            if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_START_BUFFERING == event_id
                || (UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_BUFFERING == event_id
                || (UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_STOP_BUFFERING == event_id)
            {
                buffer_status_ = event_id;

                if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_BUFFERING == event_id)
                {
                    buffer_percent_ = (Int32)param1;
                }
            }

            if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_DOWNLOAD_SPEED == event_id)
            {
                download_speed_ = (Int32)param1;
            }

            if (connection_status_ != 0)
            {
                show_str += "连接状态: ";

                if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTING == connection_status_)
                {
                    show_str += "连接中";
                }
                else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTION_FAILED == connection_status_)
                {
                    show_str += "连接失败";
                }
                else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_CONNECTED == connection_status_)
                {
                    show_str += "连接成功";
                }
                else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_DISCONNECTED == connection_status_)
                {
                    show_str += "断开连接";
                }
            }

            if (download_speed_ != -1)
            {
                String ss = "  下载速度: " + (download_speed_ * 8 / 1000).ToString() + "kbps " + (download_speed_ / 1024).ToString() + "KB/s";

                show_str += ss;
            }

            if (buffer_status_ != 0)
            {
                show_str += "  缓冲状态: ";

                if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_START_BUFFERING == buffer_status_)
                {
                    show_str += "开始缓冲";
                }
                else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_BUFFERING == buffer_status_)
                {
                    String ss = "缓冲中 " + buffer_percent_.ToString() + "%";
                    show_str += ss;
                }
                else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_STOP_BUFFERING == buffer_status_)
                {
                    show_str += "结束缓冲";
                }
            }

            if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_NEED_KEY == event_id)
            {
                show_str = "RTMP加密流，请设置播放需要的Key..";
            }
            else if ((UInt32)NTSmartPlayerDefine.NT_SP_E_EVENT_ID.NT_SP_E_EVENT_ID_KEY_ERROR == event_id)
            {
                show_str = "RTMP加密流，Key错误，请重新设置..";
            }

            EventGetPlayerEventMsg(show_str);
        }

        public void SetMute(bool is_mute)
        {
            is_mute_ = is_mute;

	        if ( !is_playing_ )
		        return;

            NTSmartPlayerSDK.NT_SP_SetMute(player_handle_, is_mute ? 1 : 0); 
        }

        public void SetBuffer(int buffer_time)
        {
            if (buffer_time >= 0)
            {
                play_buffer_ = buffer_time;
            }
        }

        public bool IsPlaying()
        { 
            return is_playing_; 
        }

        public bool OpenPullHandle(String url, bool is_rtsp_tcp_mode, bool is_mute)
        {
	        if ( player_handle_ != IntPtr.Zero )
		        return true;

	        if ( String.IsNullOrEmpty(url) )
		        return false;

	        IntPtr pull_handle = IntPtr.Zero;

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPlayerSDK.NT_SP_Open(out pull_handle, IntPtr.Zero, 0, IntPtr.Zero))
            {
		        return false;
	        }

            if (pull_handle == IntPtr.Zero)
            {
                return false;
            }

            pull_event_call_back_ = new SP_SDKEventCallBack(SDKPullEventCallBack);
            NTSmartPlayerSDK.NT_SP_SetEventCallBack(pull_handle, IntPtr.Zero, pull_event_call_back_);

            resolution_notify_callback_ = new ResolutionNotifyCallback(PlaybackWindowResized);

            set_video_frame_call_back_ = new VideoFrameCallBack(SDKVideoFrameCallBack);

            NTSmartPlayerSDK.NT_SP_SetBuffer(pull_handle, play_buffer_);
            NTSmartPlayerSDK.NT_SP_SetFastStartup(pull_handle, 1);
            NTSmartPlayerSDK.NT_SP_SetRtspAutoSwitchTcpUdp(pull_handle, 1);
            NTSmartPlayerSDK.NT_SP_SetRTSPTcpMode(pull_handle, is_rtsp_tcp_mode ? 1 : 0);

            NTSmartPlayerSDK.NT_SP_SetMute(pull_handle, is_mute_ ? 1 : 0);

            //RTSP timeout设置
            Int32 rtsp_timeout = 10;
            NTSmartPlayerSDK.NT_SP_SetRtspTimeout(pull_handle, rtsp_timeout);

            //RTSP TCP/UDP自动切换设置
            Int32 is_auto_switch_tcp_udp = 1;
            NTSmartPlayerSDK.NT_SP_SetRtspAutoSwitchTcpUdp(pull_handle, is_auto_switch_tcp_udp);

            NTSmartPlayerSDK.NT_SP_SetMute(pull_handle, is_mute ? 1 : 0);

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPlayerSDK.NT_SP_SetURL(pull_handle, url))
            {
                NTSmartPlayerSDK.NT_SP_Close(pull_handle);
                pull_handle = IntPtr.Zero;
                return false;
            }

            player_handle_ = pull_handle;

            return true;
        }

        private void PlaybackWindowResized(Int32 width, Int32 height)
        {
            String resolution = width + "*" + height;
            EventGetVideoSize(resolution);
        }

        public void SP_SDKVideoSizeHandle(IntPtr handle, IntPtr userData, Int32 width, Int32 height)
        {
            if (null == sync_invoke_)
                return;

            System.ComponentModel.ISynchronizeInvoke sync_invoke_target = sync_invoke_.Target as System.ComponentModel.ISynchronizeInvoke;

            if (sync_invoke_target != null)
            {
                if (sync_invoke_target.InvokeRequired)
                {
                    sync_invoke_target.BeginInvoke(resolution_notify_callback_, new object[] { width, height });
                }
                else
                {
                    resolution_notify_callback_(width, height);
                }
            }
         
        }

        public bool StartPlay(String url, bool is_rtsp_tcp_mode, bool is_mute)
        {
	        if ( is_playing_ )
		        return false;

	        if ( !OpenPullHandle(url, is_rtsp_tcp_mode, is_mute) )
		        return false;

	        NTSmartPlayerSDK.NT_SP_SetMute(player_handle_, is_mute ? 1 : 0);

            //video resolution callback
            video_size_call_back_ = new SP_SDKVideoSizeCallBack(SP_SDKVideoSizeHandle);
            NTSmartPlayerSDK.NT_SP_SetVideoSizeCallBack(player_handle_, IntPtr.Zero, video_size_call_back_);

            bool is_support_d3d_render = false;
            Int32 in_support_d3d_render = 0;

            if (NT.NTBaseCodeDefine.NT_ERC_OK == NTSmartPlayerSDK.NT_SP_IsSupportD3DRender(player_handle_, render_wnd_.Handle, ref in_support_d3d_render))
            {
                if (1 == in_support_d3d_render)
                {
                    is_support_d3d_render = true;
                }
            }

            // is_support_d3d_render = false;

            if (is_support_d3d_render)
            {
                // 支持d3d绘制的话，就用D3D绘制
                NTSmartPlayerSDK.NT_SP_SetRenderWindow(player_handle_, render_wnd_.Handle);
                NTSmartPlayerSDK.NT_SP_SetRenderScaleMode(player_handle_, 1);
            }
            else
            {
                // 不支持D3D就让播放器吐出数据来，用GDI绘制，本demo仅用来展示一对一互动使用，具体可参考播放端的demo

                //video frame callback (YUV/RGB)
                //format请参见 NT_SP_E_VIDEO_FRAME_FORMAT，如需回调YUV，请设置为 NT_SP_E_VIDEO_FRAME_FROMAT_I420
                video_frame_call_back_ = new SP_SDKVideoFrameCallBack(SetVideoFrameCallBack);
                NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32, IntPtr.Zero, video_frame_call_back_);
            }

	        uint ret = NTSmartPlayerSDK.NT_SP_StartPlay(player_handle_);
	        if ( NTBaseCodeDefine.NT_ERC_OK != ret )
	        {
                NTSmartPlayerSDK.NT_SP_Close(player_handle_);
			    player_handle_ = IntPtr.Zero;

		        return false;
	        }

	        is_playing_ = true;

	        return true;
        }

        public void StopPlay(bool is_update_ui =true)
        {
	        if ( !is_playing_ )
		        return;

            NTSmartPlayerSDK.NT_SP_StopPlay(player_handle_);
            
            NTSmartPlayerSDK.NT_SP_Close(player_handle_);
		    player_handle_ = IntPtr.Zero;

	        is_playing_ = false;

            if (is_update_ui && render_wnd_ != null)
            {
                render_wnd_.Invalidate();
            }
        }

        private void GetRenderRect(int limtWidth, int limtHeight, int image_w, int image_h, ref int left_offset, ref int top_offset, ref int dw, ref int dh)
        {
            if (limtWidth < 1 || limtHeight < 1)
            {
                left_offset = 0;
                top_offset = 0;

                dw = limtWidth;
                dh = limtHeight;
                return;
            }

            if (image_w < 1 || image_h < 1)
            {
                left_offset = 0;
                top_offset = 0;

                dw = limtWidth;
                dh = limtHeight;
                return;
            }

            // 按比例
            double limit_ratio = limtWidth * 1.0 / limtHeight;
            double video_ratio = image_w * 1.0 / image_h;

            if (video_ratio > limit_ratio)
            {
                dw = limtWidth;
                dh = (int)(dw * image_h * 1.0 / image_w);

                if (dh > limtHeight)
                    dh = limtHeight;
            }
            else
            {
                dh = limtHeight;
                dw = (int)(dh * image_w * 1.0 / image_h);

                if (dw > limtWidth)
                    dw = limtWidth;
            }

            left_offset = limtWidth / 2 - dw / 2;
            if (left_offset < 0)
                left_offset = 0;

            top_offset = limtHeight / 2 - dh / 2;
            if (top_offset < 0)
                top_offset = 0;
        }

        private void OnRenderWindowPaint(object sender, PaintEventArgs e)
        {
            if (render_wnd_.Width < 1 || render_wnd_.Height < 1)
                return;

            Graphics g = e.Graphics;

            Brush brush = new SolidBrush(Color.Black);
            g.FillRectangle(brush, 0, 0, render_wnd_.Width, render_wnd_.Height);

            if ( IsPlaying() && cur_video_frame_.plane0_ != IntPtr.Zero)
            {
                g.SmoothingMode = SmoothingMode.HighSpeed;
     
                int image_width = cur_video_frame_.width_;
                int image_height = cur_video_frame_.height_;

                Bitmap bitmap = new Bitmap(image_width, image_height, cur_video_frame_.stride0_,
                System.Drawing.Imaging.PixelFormat.Format32bppRgb, cur_video_frame_.plane0_);

                int d_w = 0, d_h = 0;
                int left_offset = 0;
                int top_offset = 0;

                GetRenderRect(render_wnd_.Width, render_wnd_.Height, image_width, image_height, ref left_offset, ref top_offset, ref d_w, ref d_h);
                g.DrawImage(bitmap,  left_offset, top_offset, d_w, d_h);   //在窗体的画布中绘画出内存中的图像
            }         
        }
    }
}

基于 https://github.com/daniulive/SmarterStreaming/ 推流端封装的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Drawing2D;
using NT;

namespace SmartEchoCancellationDemo
{
    public delegate void DelGetPublisherEventMsg(String msg);   //推送端Event消息

    public struct NT_VideoFrame
    {
        public Int32 width_;   // 图像宽
        public Int32 height_;  // 图像高
        public IntPtr plane_;
        public Int32 stride_;
    }

    public struct CameraInfo
    {
        public String name_;
        public String id_;
        public List<NT_PB_VideoCaptureCapability> capabilities_;
    };

    class nt_publisher_wrapper : IDisposable
    {
        [DllImport("kernel32", EntryPoint = "CopyMemory")]
        static extern void CopyMemory(IntPtr Destination, IntPtr Source, uint Length);

        private bool disposed_ = false;

        private IntPtr publisher_handle_ = IntPtr.Zero;
        private System.Windows.Forms.Control render_wnd_ = null;
        private System.Windows.Forms.PaintEventHandler render_wnd_paint_event_ = null;
        private int publisher_handle_count_;

        private bool is_publishing_ = false;
        private bool is_previewing_ = false;

        private WeakReference sync_invoke_ = null;

        //event事件回调
        NT_PB_SDKEventCallBack pb_event_call_back_;
        delegate void PbSetEventCallBack(UInt32 event_id,
                Int64 param1,
                Int64 param2,
                UInt64 param3,
                UInt64 param4,
                [MarshalAs(UnmanagedType.LPStr)] String param5,
                [MarshalAs(UnmanagedType.LPStr)] String param6,
                IntPtr param7);
        PbSetEventCallBack pb_set_event_call_back_;

        //预览数据回调
        NT_PB_SDKVideoPreviewImageCallBack video_preview_image_callback_;
        delegate void SetVideoPreviewImageCallBack(NT_VideoFrame frame);
        SetVideoPreviewImageCallBack set_video_preview_image_callback_;

        private NT_VideoFrame cur_image_ = new NT_VideoFrame();

        public event DelGetPublisherEventMsg EventGetPublisherEventMsg;

        public nt_publisher_wrapper(System.Windows.Forms.Control render_wnd, System.ComponentModel.ISynchronizeInvoke sync_invoke)
        {
            render_wnd_ = render_wnd;
            sync_invoke_ = new WeakReference(sync_invoke); ;
            pb_set_event_call_back_ = new PbSetEventCallBack(PbEventCallBack);

            if (render_wnd_ != null)
            {
                render_wnd_paint_event_ = new System.Windows.Forms.PaintEventHandler(this.OnRenderWindowPaint);
                render_wnd_.Paint += render_wnd_paint_event_;
            }
        }

        public void Dispose()
        {
            Dispose(true);

            // This object will be cleaned up by the Dispose method.
            // Therefore, you should call GC.SupressFinalize to
            // take this object off the finalization queue
            // and prevent finalization code for this object
            // from executing a second time.
            // GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            // Check to see if Dispose has already been called.
            if (!this.disposed_)
            {
                if (disposing)
                {
                }

                if (render_wnd_ != null && render_wnd_paint_event_ != null)
                {
                    render_wnd_.Paint -= render_wnd_paint_event_;
                }

                render_wnd_paint_event_ = null;

                if (cur_image_.plane_ != IntPtr.Zero)
                {
                    Marshal.FreeHGlobal(cur_image_.plane_);
                    cur_image_.plane_ = IntPtr.Zero;
                }

                // Note disposing has been done.
                disposed_ = true;
            }
        }

        ~nt_publisher_wrapper()
        {
            Dispose(false);
        }

        private void PbEventCallBack(UInt32 event_id,
            Int64 param1,
            Int64 param2,
            UInt64 param3,
            UInt64 param4,
            [MarshalAs(UnmanagedType.LPStr)] String param5,
            [MarshalAs(UnmanagedType.LPStr)] String param6,
            IntPtr param7)
        {
            String event_log = "";

            switch (event_id)
            {
                case (uint)NTSmartPublisherDefine.NT_PB_E_EVENT_ID.NT_PB_E_EVENT_ID_CONNECTING:
                    event_log = "连接中";
                    if (!String.IsNullOrEmpty(param5))
                    {
                        event_log = event_log + " url:" + param5;
                    }
                    break;

                case (uint)NTSmartPublisherDefine.NT_PB_E_EVENT_ID.NT_PB_E_EVENT_ID_CONNECTION_FAILED:
                    event_log = "连接失败";
                    if (!String.IsNullOrEmpty(param5))
                    {
                        event_log = event_log + " url:" + param5;
                    }
                    break;

                case (uint)NTSmartPublisherDefine.NT_PB_E_EVENT_ID.NT_PB_E_EVENT_ID_CONNECTED:
                    event_log = "已连接";
                    if (!String.IsNullOrEmpty(param5))
                    {
                        event_log = event_log + " url:" + param5;
                    }
                    break;

                case (uint)NTSmartPublisherDefine.NT_PB_E_EVENT_ID.NT_PB_E_EVENT_ID_DISCONNECTED:
                    event_log = "断开连接";
                    if (!String.IsNullOrEmpty(param5))
                    {
                        event_log = event_log + " url:" + param5;
                    }
                    break;

                default:
                    break;
            }

            EventGetPublisherEventMsg(event_log);
        }

        public int CalBitRate(int frame_rate, int w, int h)
        {
            int kbit_rate = 2000;

            int area = w * h;

            if (area <= (320 * 300))
            {
                kbit_rate = 280;
            }
            else if (area <= (360 * 320))
            {
                kbit_rate = 360;
            }
            else if (area <= (640 * 480))
            {
                kbit_rate = 580;
            }
            else if (area <= (800 * 600))
            {
                kbit_rate = 620;
            }
            else if (area <= (900 * 700))
            {
                kbit_rate = 820;
            }
            else if (area <= (1280 * 720))
            {
                kbit_rate = 1600;
            }
            else if (area <= (1366 * 768))
            {
                kbit_rate = 2000;
            }
            else if (area <= (1600 * 900))
            {
                kbit_rate = 2300;
            }
            else if (area <= (1600 * 1050))
            {
                kbit_rate = 2500;
            }
            else
            {
                kbit_rate = 2800;
            }

            kbit_rate = kbit_rate * frame_rate / 25;

            if (kbit_rate < 80)
                kbit_rate = 80;

            return kbit_rate;
        }

        public int CalMaxKBitRate(int frame_rate, int w, int h, bool is_var_bitrate)
        {
            int max_kbit_rate = 2000;

            int area = w * h;

            if (area <= (320 * 300))
            {
                max_kbit_rate = is_var_bitrate ? 320 : 600;
            }
            else if (area <= (360 * 320))
            {
                max_kbit_rate = is_var_bitrate ? 400 : 800;
            }
            else if (area <= (640 * 360))
            {
                max_kbit_rate = is_var_bitrate ? 600 : 1000;
            }
            else if (area <= (640 * 480))
            {
                max_kbit_rate = is_var_bitrate ? 680 : 1300;
            }
            else if (area <= (800 * 600))
            {
                max_kbit_rate = is_var_bitrate ? 700 : 1500;
            }
            else if (area <= (900 * 700))
            {
                max_kbit_rate = is_var_bitrate ? 920 : 2200;
            }
            else if (area <= (1280 * 720))
            {
                max_kbit_rate = is_var_bitrate ? 1600 : 3000;
            }
            else if (area <= (1366 * 768))
            {
                max_kbit_rate = is_var_bitrate ? 1700 : 3300;
            }
            else if (area <= (1600 * 900))
            {
                max_kbit_rate = is_var_bitrate ? 2400 : 3400;
            }
            else if (area <= (1600 * 1050))
            {
                max_kbit_rate = is_var_bitrate ? 2600 : 3600;
            }
            else if (area <= (1920 * 1080))
            {
                max_kbit_rate = is_var_bitrate ? 2900 : 3800;
            }
            else
            {
                max_kbit_rate = is_var_bitrate ? 3500 : 5500;
            }

            max_kbit_rate = max_kbit_rate * frame_rate / 25;

            if (area <= (320 * 240))
            {
                if (max_kbit_rate < 150)
                    max_kbit_rate = 150;
            }
            else if (area <= (640 * 480))
            {
                if (max_kbit_rate < 300)
                    max_kbit_rate = 300;
            }
            else if (area <= (1280 * 720))
            {
                if (max_kbit_rate < 600)
                    max_kbit_rate = 600;
            }
            else if (area <= (1920 * 1080))
            {
                if (max_kbit_rate < 960)
                    max_kbit_rate = 960;
            }
            else
            {
                if (max_kbit_rate < 1500)
                    max_kbit_rate = 1500;
            }

            return max_kbit_rate;
        }

        public int CalVideoQuality(int w, int h, bool is_h264)
        {
            int area = w * h;

            int quality = is_h264 ? 23 : 28;

            if (area <= (320 * 240))
            {
                quality = is_h264 ? 23 : 27;
            }
            else if (area <= (640 * 360))
            {
                quality = is_h264 ? 25 : 28;
            }
            else if (area <= (640 * 480))
            {
                quality = is_h264 ? 25 : 28;
            }
            else if (area <= (960 * 600))
            {
                quality = is_h264 ? 26 : 28;
            }
            else if (area <= (1280 * 720))
            {
                quality = is_h264 ? 27 : 29;
            }
            else if (area <= (1600 * 900))
            {
                quality = is_h264 ? 28 : 30;
            }
            else if (area <= (1920 * 1080))
            {
                quality = is_h264 ? 29 : 31;
            }
            else
            {
                quality = is_h264 ? 30 : 32;
            }

            return quality;
        }

        public int CalVideoEncoderSpeed(int w, int h, bool is_h264)
        {
            if (is_h264)
                return 3;

            int area = w * h;

            if (area <= (960 * 600))
            {
                return 3;
            }
            else if (area <= (1280 * 720))
            {
                return 2;
            }
            else
            {
                return 1;
            }
        }

        public int GetAudioInputDeviceNumber()
        {
            int auido_devices = 0;

            NTSmartPublisherSDK.NT_PB_GetAuidoInputDeviceNumber(ref auido_devices);

            return auido_devices;
        }

        public List<String> GetAudioInputDeviceName(int auido_devices)
        {
            List<String> audio_device_name = new List<string>();

            if (auido_devices > 0)
            {
                for (int i = 0; i < auido_devices; ++i)
                {
                    byte[] deviceNameBuffer = new byte[512];

                    string name = "";

                    if (NTBaseCodeDefine.NT_ERC_OK == NTSmartPublisherSDK.NT_PB_GetAuidoInputDeviceName((uint)i, deviceNameBuffer, 512))
                    {
                        int count = 0;
                        for (int j = 0; j < deviceNameBuffer.Length; ++j)
                        {
                            if (deviceNameBuffer[j] != 0)
                            {
                                count++;
                            }
                            else
                            {
                                break;
                            }
                        }

                        if (count > 0)
                        {
                            name = Encoding.UTF8.GetString(deviceNameBuffer, 0, count);
                        }
                    }

                    var audio_name = "";

                    if (name.Length == 0)
                    {
                        audio_name = "音频采集设备-";
                    }
                    else
                    {
                        audio_name = name + "-";
                    }

                    audio_name = audio_name + (i + 1);

                    audio_device_name.Add(name);
                }
            }

            return audio_device_name;
        }

        public bool IsCanCaptureSpeaker()
        {
            int is_capture_speader = 0;
            if (NTBaseCodeDefine.NT_ERC_OK == NTSmartPublisherSDK.NT_PB_IsCanCaptureSpeaker(ref is_capture_speader))
            {
                if (1 == is_capture_speader)
                {
                    return true;
                }
            }

            return false;
        }

        public bool OpenPublisherHandle(uint video_option, uint audio_option)
        {
            if (publisher_handle_ != IntPtr.Zero)
            {
                return true;
            }
          
            publisher_handle_count_ = 0;

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_Open(out publisher_handle_,
                video_option, audio_option, 0, IntPtr.Zero))
            {
                return false;
            }

            if (publisher_handle_ != IntPtr.Zero)
            {
                pb_event_call_back_ = new NT_PB_SDKEventCallBack(PbSDKEventCallBack);

                NTSmartPublisherSDK.NT_PB_SetEventCallBack(publisher_handle_, IntPtr.Zero, pb_event_call_back_);

                set_video_preview_image_callback_ = new SetVideoPreviewImageCallBack(VideoPreviewImageCallBack);

                return true;
            }
            else
            {
                return false;
            }
        }

        public void PbSDKEventCallBack(IntPtr handle, IntPtr user_data,
            UInt32 event_id,
            Int64 param1,
            Int64 param2,
            UInt64 param3,
            UInt64 param4,
            [MarshalAs(UnmanagedType.LPStr)] String param5,
            [MarshalAs(UnmanagedType.LPStr)] String param6,
            IntPtr param7)
        {
            if (sync_invoke_ != null)
            {
                System.ComponentModel.ISynchronizeInvoke sync_invoke_target = sync_invoke_.Target as System.ComponentModel.ISynchronizeInvoke;

                if (sync_invoke_target != null)
                {
                    if (sync_invoke_target.InvokeRequired)
                    {
                        sync_invoke_target.BeginInvoke(pb_set_event_call_back_, new object[] { event_id, param1, param2, param3, param4, param5, param6, param7 });
                    }
                    else
                    {
                        pb_set_event_call_back_(event_id, param1, param2, param3, param4, param5, param6, param7);
                    }
                }
            }
        }

        //预览数据回调
        public void SDKVideoPreviewImageCallBack(IntPtr handle, IntPtr user_data, IntPtr image)
        {
            NT_PB_Image pb_image = (NT_PB_Image)Marshal.PtrToStructure(image, typeof(NT_PB_Image));

            NT_VideoFrame pVideoFrame = new NT_VideoFrame();

            pVideoFrame.width_  = pb_image.width_;
            pVideoFrame.height_ = pb_image.height_;

            pVideoFrame.stride_ = pb_image.stride_[0];

            Int32 argb_size = pb_image.stride_[0] * pb_image.height_;

            pVideoFrame.plane_ = Marshal.AllocHGlobal(argb_size);

            CopyMemory(pVideoFrame.plane_, pb_image.plane_[0], (UInt32)argb_size);

            if (sync_invoke_ != null)
            {
                System.ComponentModel.ISynchronizeInvoke sync_invoke_target = sync_invoke_.Target as System.ComponentModel.ISynchronizeInvoke;

                if (sync_invoke_target != null)
                {

                    if (sync_invoke_target.InvokeRequired)
                    {
                        sync_invoke_target.BeginInvoke(set_video_preview_image_callback_, new object[] { pVideoFrame });
                    }
                    else
                    {
                        set_video_preview_image_callback_(pVideoFrame);
                    }
                }
            }
        }

        public void VideoPreviewImageCallBack(NT_VideoFrame frame)
        {
            if (cur_image_.plane_ != IntPtr.Zero)
            {
                Marshal.FreeHGlobal(cur_image_.plane_);
                cur_image_.plane_ = IntPtr.Zero;
            }

            cur_image_ = frame;

            if ( render_wnd_ != null)
            {
                render_wnd_.Invalidate();
            }
        }

        public List<CameraInfo> GetCameraInfos()
        {
            List<CameraInfo> cameras = new List<CameraInfo>();

            int device_number = 0;

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_GetVideoCaptureDeviceNumber(ref device_number))
            {
                return cameras;
            }

            if (device_number < 1)
            {
                return cameras;
            }

            for (int i = 0; i < device_number; ++i)
            {
                CameraInfo info = new CameraInfo();

                info.capabilities_ = new List<NT_PB_VideoCaptureCapability>();

                StringBuilder name = new StringBuilder(256);
                StringBuilder id = new StringBuilder(1024);

                if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_GetVideoCaptureDeviceInfo(i,
                    name, 256,
                    id, 1024))
                {
                    continue;
                }

                info.name_ = name.ToString();
                info.id_ = id.ToString();

                int capability_number = 0;
                if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_GetVideoCaptureDeviceCapabilityNumber(
                    id.ToString(), ref capability_number))
                {
                    continue;
                }

                bool is_failed = false;

                for (int j = 0; j < capability_number; ++j)
                {
                    NT_PB_VideoCaptureCapability capability = new NT_PB_VideoCaptureCapability();

                    if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_GetVideoCaptureDeviceCapability(
                        id.ToString(), j, ref capability))
                    {
                        is_failed = true;
                        break;
                    }

                    info.capabilities_.Add(capability);
                }

                if (!is_failed)
                {
                    cameras.Add(info);
                }
            }

            return cameras;
        }

        public bool StartPreview()
        {
            video_preview_image_callback_ = new NT_PB_SDKVideoPreviewImageCallBack(SDKVideoPreviewImageCallBack);

            NTSmartPublisherSDK.NT_PB_SetVideoPreviewImageCallBack(publisher_handle_, (int)NTSmartPublisherDefine.NT_PB_E_IMAGE_FORMAT.NT_PB_E_IMAGE_FORMAT_RGB32, IntPtr.Zero, video_preview_image_callback_);

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_StartPreview(publisher_handle_, 0, IntPtr.Zero))
            {
                if (0 == publisher_handle_count_)
                {
                    NTSmartPublisherSDK.NT_PB_Close(publisher_handle_);
                    publisher_handle_ = IntPtr.Zero;
                }

                return false;
            }

            publisher_handle_count_++;

            is_previewing_ = true;

            return true;
        }

        public void StopPreview()
        {
            is_previewing_ = false;

            publisher_handle_count_--;
            NTSmartPublisherSDK.NT_PB_StopPreview(publisher_handle_);

            if (0 == publisher_handle_count_)
            {
                NTSmartPublisherSDK.NT_PB_Close(publisher_handle_);
                publisher_handle_ = IntPtr.Zero;
            }

            if (render_wnd_ != null)
            {
                render_wnd_.Invalidate();
            }
        }

        public bool StartPublisher(String url)
        {
            if (publisher_handle_ == IntPtr.Zero)
            {
                return false;
            }
            if (!String.IsNullOrEmpty(url))
            {
                NTSmartPublisherSDK.NT_PB_SetURL(publisher_handle_, url, IntPtr.Zero);
            }

            if (NTBaseCodeDefine.NT_ERC_OK != NTSmartPublisherSDK.NT_PB_StartPublisher(publisher_handle_, IntPtr.Zero))
            {
                if (0 == publisher_handle_count_)
                {
                    NTSmartPublisherSDK.NT_PB_Close(publisher_handle_);
                    publisher_handle_ = IntPtr.Zero;
                }

                is_publishing_ = false;

                return false;
            }

            publisher_handle_count_++;

            is_publishing_ = true;

            return true;
        }

        public void StopPublisher()
        {
            publisher_handle_count_--;
            NTSmartPublisherSDK.NT_PB_StopPublisher(publisher_handle_);

            if (0 == publisher_handle_count_)
            {
                NTSmartPublisherSDK.NT_PB_Close(publisher_handle_);
                publisher_handle_ = IntPtr.Zero;
            }

            is_publishing_ = false;
        }

        public void Close()
        {
            if (0 == publisher_handle_count_)
            {
                NTSmartPublisherSDK.NT_PB_Close(publisher_handle_);
                publisher_handle_ = IntPtr.Zero;
            }
        }

        public bool IsPreviewing()
        {
            return is_previewing_;
        }

        public bool IsPublishing()
        {
            return is_publishing_;
        }

        public bool IsPublisherHandleAvailable()
        {
            return publisher_handle_ != IntPtr.Zero ? true : false;
        }

        public int GetPublisherHandleCount()
        {
            return publisher_handle_count_;
        }

        public void SetVideoCaptureDeviceBaseParameter(String camera_id, UInt32 width, UInt32 height)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoCaptureDeviceBaseParameter(publisher_handle_, camera_id, width, height);
        }

        public void SetFrameRate(UInt32 frame_rate)
        {
            NTSmartPublisherSDK.NT_PB_SetFrameRate(publisher_handle_, frame_rate);
        }

        public void SetVideoEncoderType(Int32 encode_type)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoEncoderType(publisher_handle_, encode_type);
        }

        public void SetVideoQualityV2(Int32 quality)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoQualityV2(publisher_handle_, quality);
        }
        
        public void SetVideoMaxBitRate(Int32 kbit_rate)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoMaxBitRate(publisher_handle_, kbit_rate);
        }

        public void SetVideoKeyFrameInterval(Int32 interval)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoKeyFrameInterval(publisher_handle_, interval);
        }

        public void SetVideoEncoderProfile(Int32 profile)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoEncoderProfile(publisher_handle_, profile);
        }

        public void SetVideoEncoderSpeed(Int32 speed)
        {
            NTSmartPublisherSDK.NT_PB_SetVideoEncoderSpeed(publisher_handle_, speed);
        }

        public void SetAuidoInputDeviceId(UInt32 device_id)
        {
            NTSmartPublisherSDK.NT_PB_SetAuidoInputDeviceId(publisher_handle_, device_id);
        }

        public void SetPublisherAudioCodecType(Int32 type)
        {
            NTSmartPublisherSDK.NT_PB_SetPublisherAudioCodecType(publisher_handle_, type);
        }

        public void SetPublisherMute(bool is_mute)
        {
            NTSmartPublisherSDK.NT_PB_SetMute(publisher_handle_, is_mute ? 1 : 0); 
        }

        public void SetEchoCancellation(Int32 isCancel, Int32 delay)
        {
            NTSmartPublisherSDK.NT_PB_SetEchoCancellation(publisher_handle_, isCancel, delay);
        }

        public void SetNoiseSuppression(Int32 isNS)
        {
            NTSmartPublisherSDK.NT_PB_SetNoiseSuppression(publisher_handle_, isNS);
        }
        
        public void SetAGC(Int32 isAGC)
        {
            NTSmartPublisherSDK.NT_PB_SetAGC(publisher_handle_, isAGC);
        }

        public void SetVAD(Int32 isVAD)
        {
            NTSmartPublisherSDK.NT_PB_SetVAD(publisher_handle_, isVAD);
        }

        private void GetRenderRect(int limtWidth, int limtHeight, int image_w, int image_h, ref int left_offset, ref int top_offset, ref int dw, ref int dh)
        {
            if (limtWidth < 1 || limtHeight < 1)
            {
                left_offset = 0;
                top_offset = 0;

                dw = limtWidth;
                dh = limtHeight;
                return;
            }

            if (image_w < 1 || image_h < 1)
            {
                left_offset = 0;
                top_offset = 0;

                dw = limtWidth;
                dh = limtHeight;
                return;
            }

            // 按比例
            double limit_ratio = limtWidth * 1.0 / limtHeight;
            double video_ratio = image_w * 1.0 / image_h;

            if (video_ratio > limit_ratio)
            {
                dw = limtWidth;
                dh = (int)(dw * image_h * 1.0 / image_w);

                if (dh > limtHeight)
                    dh = limtHeight;
            }
            else
            {
                dh = limtHeight;
                dw = (int)(dh * image_w * 1.0 / image_h);

                if (dw > limtWidth)
                    dw = limtWidth;
            }

            left_offset = limtWidth / 2 - dw / 2;
            if (left_offset < 0)
                left_offset = 0;

            top_offset = limtHeight / 2 - dh / 2;
            if (top_offset < 0)
                top_offset = 0;
        }

        private void OnRenderWindowPaint(object sender, PaintEventArgs e)
        {
            if (render_wnd_.Width < 1 || render_wnd_.Height < 1)
                return;

            Graphics g = e.Graphics;

            Brush brush = new SolidBrush(Color.Black);
            g.FillRectangle(brush, 0, 0, render_wnd_.Width, render_wnd_.Height);

            if (is_previewing_ && cur_image_.plane_ != IntPtr.Zero)
            {
                g.SmoothingMode = SmoothingMode.HighSpeed;

                int image_width = cur_image_.width_;
                int image_height = cur_image_.height_;

                Bitmap bitmap = new Bitmap(image_width, image_height, cur_image_.stride_,
                System.Drawing.Imaging.PixelFormat.Format32bppRgb, cur_image_.plane_);

                int d_w = 0, d_h = 0;
                int left_offset = 0;
                int top_offset = 0;

                GetRenderRect(render_wnd_.Width, render_wnd_.Height, image_width, image_height, ref left_offset, ref top_offset, ref d_w, ref d_h);
                g.DrawImage(bitmap, left_offset, top_offset, d_w, d_h);   //在窗体的画布中绘画出内存中的图像
            }
        }
    }
}

由于RTMP在0缓冲下，延迟在200-400毫秒区间，常规的对延迟不是非常苛刻的场景下，足够用了。