Unity3D下Linux平台播放RTSP或RTMP流

背景

尽管Windows平台有诸多优势，Linux平台的发展还是势不可挡，特别实在传统行业，然而Linux生态构建，总是差点意思，特别是有些常用的组件，本文基于已有的Linux平台RTSP、RTMP播放模块，构建Unity下的RTSP和RTMP直播播放。

技术实现

实际上，Unity层面这块没什么好介绍的，和Windows、Android、iOS平台一样，调用原生的播放模块，回调解码后的数据，在Unity绘制，主要的技术难点，还在原生的处理，也就是拉流、解码、回调数据这块。

先上个直观感受图，本视频以Windows平台采集秒表计时器窗体，然后编码打包传输到RTMP服务，Unity3D的Linux平台RTMP播放器拉流播放，整体延迟毫秒级。

Linux平台，我们是回调的YUV的数据，也就是 NT_SP_E_VIDEO_FRAME_FROMAT_I420：

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/*定义视频帧图像格式*/
public enum NT_SP_E_VIDEO_FRAME_FORMAT : uint
{
    NT_SP_E_VIDEO_FRAME_FORMAT_RGB32 = 1, // 32位的rgb格式, r, g, b各占8, 另外一个字节保留, 内存字节格式为: bb gg rr xx, 主要是和windows位图匹配, 在小端模式下，按DWORD类型操作，最高位是xx, 依次是rr, gg, bb
    NT_SP_E_VIDEO_FRAME_FORMAT_ARGB = 2, // 32位的argb格式，内存字节格式是: bb gg rr aa 这种类型，和windows位图匹配
    NT_SP_E_VIDEO_FRAME_FROMAT_I420 = 3, // YUV420格式, 三个分量保存在三个面上
}

开始播放之前，把回调设置下去：

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//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_);

视频帧结构：

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/*定义视频帧结构.*/
[StructLayoutAttribute(LayoutKind.Sequential)]
public struct NT_SP_VideoFrame
{
    public Int32 format_;  // 图像格式, 请参考NT_SP_E_VIDEO_FRAME_FORMAT
    public Int32 width_;   // 图像宽
    public Int32 height_;  // 图像高

    public Int64 timestamp_; // 时间戳, 一般是0,不使用, 以ms为单位的

    //具体的图像数据, argb和rgb32只用第一个, I420用前三个
    public IntPtr plane0_;
    public IntPtr plane1_;
    public IntPtr plane2_;
    public IntPtr plane3_;

    // 每一个平面的每一行的字节数，对于argb和rgb32，为了保持和windows位图兼容，必须是width_*4
    // 对于I420, stride0_ 是y的步长, stride1_ 是u的步长, stride2_ 是v的步长,
    public Int32 stride0_;
    public Int32 stride1_;
    public Int32 stride2_;
    public Int32 stride3_;
}

具体回调处理：

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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;
    }
}

Unity层拿到video frame后，刷新即可：

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private void UpdateProc(int sel)
{
   VideoFrame video_frame = null;

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

        videoctrl[sel].cur_video_frame_ = null;
    }

    if ( video_frame == null )
        return;

    if (!videoctrl[sel].is_need_get_frame_)
        return;

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

    if ( !videoctrl[sel].is_need_init_texture_)
    {
        if (  video_frame.width_ != videoctrl[sel].video_width_
            || video_frame.height_ != videoctrl[sel].video_height_
            || video_frame.y_stride_ != videoctrl[sel].y_row_bytes_
            || video_frame.u_stride_ != videoctrl[sel].u_row_bytes_
            || video_frame.v_stride_ != videoctrl[sel].v_row_bytes_ )
        {
            videoctrl[sel].is_need_init_texture_ = true;
        }
    }

    if (videoctrl[sel].is_need_init_texture_)
    {
        if (InitYUVTexture(video_frame, sel))
        {
            videoctrl[sel].is_need_init_texture_ = false;
        }
    }

    UpdateYUVTexture(video_frame, sel);
}

UpdateYUVTexture相关实现：

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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();
    }
}

相关Player封装：

代码语言：javascript复制

/*
 * SmartPlayerLinuxMono.cs
 *
 * WebSite: https://daniusdk.com
 * Github: https://github.com/daniulive/SmarterStreaming
 */

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 = 1;
    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;
}

调用到的OpenPlayer实现：

OpenPlayer主要是调用底层NT_SP_Open()接口，获取播放实例句柄，然后设置Event回调等。

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private void OpenPlayer(int sel)
{
    window_handle_ = IntPtr.Zero;

    if (videoctrl[sel].player_handle_ == IntPtr.Zero)
    {
        videoctrl[sel].player_handle_ = new IntPtr();
        UInt32 ret_open = NTSmartPlayerSDK.NT_SP_Open(out videoctrl[sel].player_handle_, window_handle_, 0, IntPtr.Zero);
        if (ret_open != 0)
        {
            videoctrl[sel].player_handle_ = IntPtr.Zero;
            Debug.LogError("调用NT_SP_Open失败..");
            return;
        }
    }

    videoctrl[sel].event_call_back_ = new SP_SDKEventCallBack(NT_SP_SDKEventCallBack);
    NTSmartPlayerSDK.NT_SP_SetEventCallBack(videoctrl[sel].player_handle_, window_handle_, videoctrl[sel].event_call_back_);

    videoctrl[sel].sdk_video_frame_call_back_ = new VideoControl.SetVideoFrameCallBack(SDKVideoFrameCallBack);
    videoctrl[sel].sdk_event_call_back_ = new VideoControl.SetEventCallBack(SDKEventCallBack);
}

关闭播放：

代码语言：javascript复制

private void ClosePlayer(int sel)
{
    videoctrl[sel].is_need_get_frame_ = false;
    videoctrl[sel].is_need_init_texture_ = false;

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

    UInt32 flag = NTSmartPlayerSDK.NT_SP_StopPlay(videoctrl[sel].player_handle_);
    if (flag == DANIULIVE_RETURN_OK)
    {
        Debug.Log("停止成功");
    }
    else
    {
        Debug.LogError("停止失败");
    }

    videoctrl[sel].player_handle_ = IntPtr.Zero;

    videoctrl[sel].is_running = false;
}

总结

Unity环境下的直播播放，Windows平台或者Android的比较多，用在Linux平台的少之又少，一方面Linux平台本身需求不大，另一方面，Linux平台这块，可参考的例程不多，实际上，如果已经完成Windows或Android平台下的核心功能实现，再移植到Linux下，非常方便。

Unity下，简单来说就是拉流解码回调，上层绘制，其实也没有那么复杂，需要注意的是DllImport的写法、之前C 结构体或枚举的转换、Unity3D对Linux的版本兼容等一些细节，对熟悉C#的开发者来说，不具备多大的技术难度。

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