Unity下如何实现低延迟的全景RTMP|RTSP流渲染

技术背景

Unity3D可以用于创建各种类型的的应用程序，包括虚拟现实、培训模拟器等。以下是一些可以使用Unity3D全景播放的场景：

虚拟现实体验：全景视频可以用来创建逼真的虚拟环境，使用户能够感受到身临其境的感觉；
培训模拟器：全景视频可以用来创建真实的训练环境，例如飞行模拟器、驾驶模拟器等，以提供更加真实的训练体验；
建筑设计：全景视频可以用来展示建筑设计的或室内装潢，使客户能够感受到真实的的效果；
文旅导览：全景视频可以用来展示旅游景点或城市，使游客能够感受到身临其境的感觉。

在Unity3D平台上实现全景实时RTMP或RTSP流渲染，可以通过以下方式：

获取全景视频数据源：首先，需要拉取RTMP或RTSP流数据，解码后，把RGB或YUV数据，回调到unity，从而获取到全景视频流数据；
Unity创建个Sphere，创建个材质球(Material)，并把材质球挂在到Sphere；
实现实时渲染：使用Unity3D的渲染管道，您可以将纹理映射到球体或立方体的表面上，并使用着色器来处理纹理的坐标，以实现全景视频的实时渲染。

技术实现

本文以大牛直播SDK的RTMP推送端作为数据采集，获取全景窗体数据后，编码打包推送到RTMP服务，或启动个轻量级RTSP服务，对外提供个RTSP的拉流URL。

然后，播放端，拉取RTSP或RTMP的URL，把YUV或RGB数据回调上来，然后，再在Unity窗体绘制出来。

获取数据源：

    public void Play(int sel)
    {
        if (videoctrl[sel].is_running)
        {
            Debug.Log("已经在播放..");
            return;
        }

        lock (videoctrl[sel].frame_lock_)
        {
            videoctrl[sel].cur_video_frame_ = null;
        }

        OpenPlayer(sel);

        if (videoctrl[sel].player_handle_ == IntPtr.Zero)
            return;

        //设置播放URL
        NTSmartPlayerSDK.NT_SP_SetURL(videoctrl[sel].player_handle_, videoctrl[sel].videoUrl);

        /* ++ 播放前参数配置可加在此处 ++ */

        int play_buffer_time_ = 0;
        NTSmartPlayerSDK.NT_SP_SetBuffer(videoctrl[sel].player_handle_, play_buffer_time_);                 //设置buffer time

        int is_using_tcp = 0;        //TCP模式

        NTSmartPlayerSDK.NT_SP_SetRTSPTcpMode(videoctrl[sel].player_handle_, is_using_tcp);

        int timeout = 10;
        NTSmartPlayerSDK.NT_SP_SetRtspTimeout(videoctrl[sel].player_handle_, timeout);

        int is_auto_switch_tcp_udp = 1;
        NTSmartPlayerSDK.NT_SP_SetRtspAutoSwitchTcpUdp(videoctrl[sel].player_handle_, is_auto_switch_tcp_udp);

        Boolean is_mute_ = false;
        NTSmartPlayerSDK.NT_SP_SetMute(videoctrl[sel].player_handle_, is_mute_ ? 1 : 0);                    //是否启动播放的时候静音

        int is_fast_startup = 1;
        NTSmartPlayerSDK.NT_SP_SetFastStartup(videoctrl[sel].player_handle_, is_fast_startup);              //设置快速启动模式

        Boolean is_low_latency_ = false;
        NTSmartPlayerSDK.NT_SP_SetLowLatencyMode(videoctrl[sel].player_handle_, is_low_latency_ ? 1 : 0);    //设置是否启用低延迟模式

        //设置旋转角度(设置0， 90， 180， 270度有效，其他值无效)
        int rotate_degrees = 0;
        NTSmartPlayerSDK.NT_SP_SetRotation(videoctrl[sel].player_handle_, rotate_degrees);
		
		int volume = 100;
		NTSmartPlayerSDK.NT_SP_SetAudioVolume(videoctrl[sel].player_handle_, volume);	//设置播放音量, 范围是[0, 100], 0是静音，100是最大音量, 默认是100
		

        // 设置上传下载报速度
        int is_report = 0;
        int report_interval = 2;
        NTSmartPlayerSDK.NT_SP_SetReportDownloadSpeed(videoctrl[sel].player_handle_, is_report, report_interval);
        /* -- 播放前参数配置可加在此处 -- */

        //video frame callback (YUV/RGB)
        videoctrl[sel].video_frame_call_back_ = new SP_SDKVideoFrameCallBack(NT_SP_SetVideoFrameCallBack);
        NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(videoctrl[sel].player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FROMAT_I420, window_handle_, videoctrl[sel].video_frame_call_back_);

        UInt32 flag = NTSmartPlayerSDK.NT_SP_StartPlay(videoctrl[sel].player_handle_);

        if (flag == DANIULIVE_RETURN_OK)
        {
            videoctrl[sel].is_need_get_frame_ = true;
            Debug.Log("播放成功");
        }
        else
        {
            videoctrl[sel].is_need_get_frame_ = false;
            Debug.LogError("播放失败");
        }

        videoctrl[sel].is_running = true;
    }

针对数据处理：

    private void SDKVideoFrameCallBack(UInt32 status, IntPtr frame, int sel)
    {
        //这里拿到回调frame，进行相关操作
        NT_SP_VideoFrame video_frame = (NT_SP_VideoFrame)Marshal.PtrToStructure(frame, typeof(NT_SP_VideoFrame));

        VideoFrame  u3d_frame = new VideoFrame();

        u3d_frame.width_  = video_frame.width_;
        u3d_frame.height_ = video_frame.height_;

        u3d_frame.timestamp_ = (UInt64)video_frame.timestamp_;

        int d_y_stride = video_frame.width_;
        int d_u_stride = (video_frame.width_ + 1) / 2;
        int d_v_stride = d_u_stride;

        int d_y_size = d_y_stride * video_frame.height_;
        int d_u_size = d_u_stride * ((video_frame.height_ + 1) / 2);
        int d_v_size = d_u_size;

        int u_v_height = ((u3d_frame.height_ + 1) / 2);

        u3d_frame.y_stride_ = d_y_stride;
        u3d_frame.u_stride_ = d_u_stride;
        u3d_frame.v_stride_ = d_v_stride;

        u3d_frame.y_data_ = new byte[d_y_size];
        u3d_frame.u_data_ = new byte[d_u_size];
        u3d_frame.v_data_ = new byte[d_v_size];


        CopyFramePlane(u3d_frame.y_data_, d_y_stride,
            video_frame.plane0_, video_frame.stride0_, u3d_frame.height_);

        CopyFramePlane(u3d_frame.u_data_, d_u_stride,
           video_frame.plane1_, video_frame.stride1_, u_v_height);

        CopyFramePlane(u3d_frame.v_data_, d_v_stride,
           video_frame.plane2_, video_frame.stride2_, u_v_height);

        lock (videoctrl[sel].frame_lock_ )
        {
            videoctrl[sel].cur_video_frame_ = u3d_frame;
        }
    }

刷新Texture：

private void UpdateYUVTexture(VideoFrame video_frame, int sel)
{
    if (video_frame.y_data_ == null || video_frame.u_data_ == null || video_frame.v_data_ == null)
    {
        Debug.Log("video frame with null..");
        return;
    }
 
    if (videoctrl[sel].yTexture_ != null)
    {
        videoctrl[sel].yTexture_.LoadRawTextureData(video_frame.y_data_);
        videoctrl[sel].yTexture_.Apply();
    }
 
    if (videoctrl[sel].uTexture_ != null)
    {
        videoctrl[sel].uTexture_.LoadRawTextureData(video_frame.u_data_);
        videoctrl[sel].uTexture_.Apply();
    }
 
    if (videoctrl[sel].vTexture_ != null)
    {
        videoctrl[sel].vTexture_.LoadRawTextureData(video_frame.v_data_);
        videoctrl[sel].vTexture_.Apply();
    }
}

全景播放的时候，如果需要移动显示区域，可以用以下代码：

public class MouseMove : MonoBehaviour {
    Vector2 p1, p2;
    private Vector3 PreMouseMPos;
    private Vector3 PreMouseLPos;
    public float minimumY = -60F;
    public float maximumY = 60F;
    float rotationY = 0F;
    private float wheelSpeed = 5.0f;
	
    // Use this for initialization
    void Start () {
	}
	
	// Update is called once per frame
	void Update () {
        if (Input.GetMouseButton(0))
        {
            if (PreMouseLPos.x <= 0)
            {
                PreMouseLPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0.0f);
            }
            else
            {
                Vector3 CurMouseLPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0.0f);
                Vector3 offset = CurMouseLPos - PreMouseLPos;

                Quaternion tt = Quaternion.Euler(offset);
                float rotationX = transform.localEulerAngles.y - tt.x * 20;
                rotationY += tt.y * 20;
                rotationY = Mathf.Clamp(rotationY, minimumY, maximumY);
                transform.localEulerAngles = new Vector3(rotationY, rotationX, 0);

                PreMouseLPos = CurMouseLPos;
            }
        }
        else
        {
            PreMouseLPos = new Vector3(0.0f, 0.0f, 0.0f);
        }
	}
}