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。
先上个只管感受图，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：
/*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：
//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：
/*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：
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：
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：
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：
/* * 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。
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：
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。
