随着VR类、游戏类场景的快速发展，开发者对Unity3d低延迟的直播需求量越来越大，前两年，大牛直播SDK发布了Windows平台、Android平台和iOS平台的Unity3d RTMP和RTSP的播放，好多公司用起来体验都非常好，以下介绍大概实现流程。

本文以Android平台为例，我们的实现：基于大牛直播SDK现有非常成熟的native RTMP和RTSP播放模块，回调解码后的原始数据，传递给Unity3d，实现相应的绘制即可，对应demo，可以参考 Github。

具体步骤如下：

1. Native RTSP或RTSP直播播放SDK回调RGB/YUV420/NV12等其中的一种未压缩的图像格式；
2. Unity3D创建相应的RGB/YUV420等Shader；

3.Unity3D从各个平台获取图像数据来填充纹理即可。

以Android平台为例，我们在原有接口基础上，做了桥接接口，供Unity平台使用：

/// <summary>
/// Init
/// </summary>
public int NT_U3D_Init()
{
    return DANIULIVE_RETURN_OK;
}

/// <summary>
/// 开始
/// 返回播放句柄
/// </summary>
public long NT_U3D_Open()
{
    if ( 0 != player_obj_.Call<int>("Init", java_obj_cur_activity_) )
    {
        return 0;
    }

    return player_obj_.Call<long>("Open");
}

/// <summary>
/// Register Game Object,用于消息传递
/// </summary>
public int NT_U3D_Set_Game_Object(long handle, string gameObjectName)
{
    return player_obj_.Call<int>("SetGameObject", handle, gameObjectName);
}

/// <summary>
/// 设置H.264解码方式 false 软件解码 true 硬件解码 默认为false
/// </summary>
/// <param name="isHwDecoder"></param>
public int NT_U3D_SetVideoDecoderMode(long handle, int isHwDecoder)
{
    return player_obj_.Call<int>("SetPlayerVideoHWDecoder", handle, isHwDecoder);
}

/// <summary>
/// 设置H.265 解码方式 false 软件解码 true 硬件解码 默认为false
/// </summary>
/// <param name="isHevcHwDecoder"></param>
public int NT_U3D_SetVideoHevcDecoderMode(long handle, int isHevcHwDecoder)
{
    return player_obj_.Call<int>("SetPlayerVideoHevcHWDecoder", handle, isHevcHwDecoder);
}

/// <summary>
/// 设置音频输出模式: if 0: 自动选择; if with 1: audiotrack模式
/// </summary>
/// <param name="use_audiotrack"></param>
public int NT_U3D_SetAudioOutputType(long handle, int use_audiotrack)
{
    return player_obj_.Call<int>("SetAudioOutputType", handle, use_audiotrack);
}

/// <summary>
/// 设置播放端缓存大小, 默认200毫秒
/// </summary>
/// <param name="buffer"></param>
public int NT_U3D_SetBuffer(long handle, int buffer)
{
    return player_obj_.Call<int>("SetBuffer", handle, buffer);
}

/// <summary>
/// 接口可实时调用：设置是否实时静音，1：静音; 0: 取消静音
/// </summary>
/// <param name="is_mute"></param>
public int NT_U3D_SetMute(long handle, int is_mute)
{
    return player_obj_.Call<int>("SetMute", handle, is_mute);
}

/// <summary>
/// 设置RTSP TCP模式, 1: TCP; 0: UDP
/// </summary>
/// <param name="is_using_tcp"></param>
public int NT_U3D_SetRTSPTcpMode(long handle, int is_using_tcp)
{
    return player_obj_.Call<int>("SetRTSPTcpMode", handle, is_using_tcp);
}

/// <summary>
/// 设置RTSP超时时间, timeout单位为秒，必须大于0
/// </summary>
/// <param name="timeout"></param>
public int NT_U3D_SetRTSPTimeout(long handle, int timeout)
{
    return player_obj_.Call<int>("SetRTSPTimeout", handle, timeout);
}

/// <summary>
/// 设置RTSP TCP/UDP自动切换
/// NOTE: 对于RTSP来说，有些可能支持rtp over udp方式，有些可能支持使用rtp over tcp方式.
/// 为了方便使用，有些场景下可以开启自动尝试切换开关, 打开后如果udp无法播放，sdk会自动尝试tcp, 如果tcp方式播放不了,sdk会自动尝试udp.
/// </summary>
/// <param name="timeout"></param>
/// timeout：如果设置1的话, sdk将在tcp和udp之间尝试切换播放，如果设置为0，则不尝试切换.
public int NT_U3D_SetRTSPAutoSwitchTcpUdp(long handle, int is_auto_switch_tcp_udp)
{
    return player_obj_.Call<int>("SetRTSPAutoSwitchTcpUdp", handle, is_auto_switch_tcp_udp);
}

/// <summary>
/// 设置快速启动该模式，
/// </summary>
/// <param name="is_fast_startup"></param>
public int NT_U3D_SetFastStartup(long handle, int is_fast_startup)
{
    return player_obj_.Call<int>("SetFastStartup", handle, is_fast_startup);
}

/// <summary>
/// 设置超低延迟模式 false不开启 true开启 默认false
/// </summary>
/// <param name="mode"></param>
public int NT_U3D_SetPlayerLowLatencyMode(long handle, int mode)
{
    return player_obj_.Call<int>("SetPlayerLowLatencyMode", handle, mode);
}

/// <summary>
/// 设置视频垂直反转
/// is_flip： 0: 不反转, 1: 反转
/// </summary>
/// <param name="is_flip"></param>
public int NT_U3D_SetFlipVertical(long handle, int is_flip)
{
    return player_obj_.Call<int>("SetFlipVertical", handle, is_flip);
}

/// <summary>
/// 设置视频水平反转
/// is_flip： 0: 不反转, 1: 反转
/// </summary>
/// <param name="is_flip"></param>
public int NT_U3D_SetFlipHorizontal(long handle, int is_flip)
{
    return player_obj_.Call<int>("SetFlipHorizontal", handle, is_flip);
}

/// <summary>
/// 设置顺时针旋转, 注意除了0度之外， 其他角度都会额外消耗性能
/// degress： 当前支持 0度，90度, 180度, 270度 旋转
/// </summary>
/// <param name="degress"></param>
public int NT_U3D_SetRotation(long handle, int degress)
{
    return player_obj_.Call<int>("SetRotation", handle, degress);
}

/// <summary>
/// 设置是否回调下载速度
/// is_report: if 1: 上报下载速度, 0: 不上报.
/// report_interval: 上报间隔，以秒为单位，>0.
/// </summary>
/// <param name="is_report"></param>
/// <param name="report_interval"></param>
public int NT_U3D_SetReportDownloadSpeed(long handle, int is_report, int report_interval)
{
    return player_obj_.Call<int>("SetReportDownloadSpeed", handle, is_report, report_interval);
}

/// <summary>
/// 设置是否需要在播放或录像过程中快照
/// </summary>
/// <param name="is_save_image"></param>
public int NT_U3D_SetSaveImageFlag(long handle, int is_save_image)
{
    return player_obj_.Call<int>("SetSaveImageFlag", handle, is_save_image);
}

/// <summary>
/// 播放或录像过程中快照
/// </summary>
/// <param name="imageName"></param>
public int NT_U3D_SaveCurImage(long handle, string imageName)
{
    return player_obj_.Call<int>("SaveCurImage", handle, imageName);
}

/// <summary>
/// 播放或录像过程中，快速切换url
/// </summary>
/// <param name="uri"></param>
public int NT_U3D_SwitchPlaybackUrl(long handle, string uri)
{
    return player_obj_.Call<int>("SwitchPlaybackUrl", handle, uri);
}

/// <summary>
/// 创建录像存储路径
/// </summary>
/// <param name="path"></param>
public int NT_U3D_CreateFileDirectory(string path)
{
    return player_obj_.Call<int>("CreateFileDirectory", path);
}

/// <summary>
/// 设置录像存储路径
/// </summary>
/// <param name="path"></param>
public int NT_U3D_SetRecorderDirectory(long handle, string path)
{
    return player_obj_.Call<int>("SetRecorderDirectory", handle, path);
}

/// <summary>
/// 设置单个录像文件大小
/// </summary>
/// <param name="size"></param>
public int NT_U3D_SetRecorderFileMaxSize(long handle, int size)
{
    return player_obj_.Call<int>("SetRecorderFileMaxSize", handle, size);
}

/// <summary>
/// 设置录像时音频转AAC编码的开关
/// aac比较通用，sdk增加其他音频编码(比如speex, pcmu, pcma等)转aac的功能.
/// 注意: 转码会增加性能消耗
/// </summary>
/// <param name="is_transcode"></param>
/// is_transcode：设置为1的话，如果音频编码不是aac，则转成aac，如果是aac，则不做转换. 设置为0的话，则不做任何转换. 默认是0.
public int NT_U3D_SetRecorderAudioTranscodeAAC(long handle, int is_transcode)
{
    return player_obj_.Call<int>("SetRecorderAudioTranscodeAAC", handle, is_transcode);
}

/// <summary>
/// 设置播放路径
/// </summary>
public int NT_U3D_SetUrl(long handle, string url)
{
    return player_obj_.Call<int>("SetUrl", handle, url);
}

/// <summary>
/// 开始播放
/// </summary>
public int NT_U3D_StartPlay(long handle)
{
    return player_obj_.Call<int>("StartPlay", handle);
}

/// <summary>
/// 获取YUV数据
/// </summary>
public AndroidJavaObject NT_U3D_GetVideoFrame(long handle)
{
    return player_obj_.Call<AndroidJavaObject>("GetVideoFrame", handle);
}

/// <summary>
/// 停止播放
/// </summary>
public int NT_U3D_StopPlay(long handle)
{
    return player_obj_.Call<int>("StopPlay", handle);
}

/// <summary>
/// 开始录像
/// </summary>
public int NT_U3D_StartRecorder(long handle)
{
    return player_obj_.Call<int>("StartRecorder", handle);
}

/// <summary>
/// 停止录像
/// </summary>
public int NT_U3D_StopRecorder(long handle)
{
    return player_obj_.Call<int>("StopRecorder", handle);
}

/// <summary>
/// 关闭播放
/// </summary>
public int NT_U3D_Close(long handle)
{
    return player_obj_.Call<int>("Close", handle);
}

/// <summary>
/// UnInit Player
/// </summary>
public int NT_U3D_UnInit()
{
    return DANIULIVE_RETURN_OK;
}

Event传递，我们在unity3d里面解析相应的字串即可：

///

/// android 传递过来 code
/// </summary>
/// <param name="code"></param>
public void onNTSmartEvent(string param)
{
    if (!param.Contains(","))
    {
        Debug.Log("[onNTSmartEvent] android传递参数错误");
        return;
    }

   string[] strs = param.Split(',');

   string player_handle =strs[0];
   string code = strs[1];
   string param1 = strs[2];
   string param2 = strs[3];
   string param3 = strs[4];
   string param4 = strs[5];
    
   Debug.Log("[onNTSmartEvent] code: 0x" + Convert.ToString(Convert.ToInt32(code), 16));

    switch (Convert.ToInt32(code))
    {
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_STARTED:
            Debug.Log("开始。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_CONNECTING:
            Debug.Log("连接中。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_CONNECTION_FAILED:
            Debug.Log("连接失败。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_CONNECTED:
            Debug.Log("连接成功。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_DISCONNECTED:
            Debug.Log("连接断开。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_STOP:
            Debug.Log("停止播放。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_RESOLUTION_INFO:
            Debug.Log("分辨率信息: width: " + Convert.ToInt32(param1) + ", height: " + Convert.ToInt32(param2));
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_NO_MEDIADATA_RECEIVED:
            Debug.Log("收不到媒体数据，可能是url错误。。");
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_SWITCH_URL:
            Debug.Log("切换播放URL。。");
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_CAPTURE_IMAGE:
            Debug.Log("快照: " + param1 + " 路径：" + param3);

            if (Convert.ToInt32(param1) == 0)
            {
                Debug.Log("截取快照成功。.");
            }
            else
            {
                Debug.Log("截取快照失败。.");
            }
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_RECORDER_START_NEW_FILE:
            Debug.Log("[record]开始一个新的录像文件 : " + param3);
            break;
        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_ONE_RECORDER_FILE_FINISHED:
            Debug.Log("[record]已生成一个录像文件 : " + param3);
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_START_BUFFERING:
            Debug.Log("Start_Buffering");
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_BUFFERING:
            Debug.Log("Buffering: " + Convert.ToInt32(param1));
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_STOP_BUFFERING:
            Debug.Log("Stop_Buffering");
            break;

        case EVENTID.EVENT_DANIULIVE_ERC_PLAYER_DOWNLOAD_SPEED:
            Debug.Log("download_speed:" + param1 + "Byte/s" + ", "
                    + (Convert.ToInt32(param1) * 8 / 1000) + "kbps" + ", " + (Convert.ToInt32(param1) / 1024)
                    + "KB/s");
            break;
    }

}

开始播放：

public void Play()
{
    if (is_running)
    {
        Debug.Log("已经在播放。。");   
        return;
    }

    //获取输入框的url
    string url = input_url_.text.Trim();

    if (!url.StartsWith("rtmp://") && !url.StartsWith("rtsp://"))
    {
        videoUrl = "rtmp://202.69.69.180:443/webcast/bshdlive-pc";
    }
    else
    {
        videoUrl = url;
    }

    OpenPlayer();

    if ( player_handle_ == 0 )
        return;

    NT_U3D_Set_Game_Object(player_handle_, game_object_);

    NT_U3D_SetUrl(player_handle_, videoUrl);

    /* ++ 播放前参数配置可加在此处 ++ */
    int is_using_tcp = 0;        //TCP/UDP模式设置
    NT_U3D_SetRTSPTcpMode(player_handle_, is_using_tcp);

    int is_report = 0;
    int report_interval = 1;
    NT_U3D_SetReportDownloadSpeed(player_handle_, is_report, report_interval);  //下载速度回调

    NT_U3D_SetBuffer(player_handle_, play_buffer_time_);                        //设置buffer time

    NT_U3D_SetPlayerLowLatencyMode(player_handle_, is_low_latency_ ? 1 : 0);    //设置是否启用低延迟模式

    NT_U3D_SetMute(player_handle_, is_mute_ ? 1 : 0);                           //是否启动播放的时候静音

    NT_U3D_SetVideoDecoderMode(player_handle_, is_hw_decode_ ? 1 : 0);          //设置H.264软硬解模式

    NT_U3D_SetVideoHevcDecoderMode(player_handle_, is_hw_decode_ ? 1 : 0);          //设置H.265软硬解模式

    int is_fast_startup = 1;
    NT_U3D_SetFastStartup(player_handle_, is_fast_startup);                     //设置快速启动模式

    int rtsp_timeout = 10;
    NT_U3D_SetRTSPTimeout(player_handle_, rtsp_timeout);                        //设置RTSP超时时间

    int is_auto_switch_tcp_udp = 1;
    NT_U3D_SetRTSPAutoSwitchTcpUdp(player_handle_, is_auto_switch_tcp_udp);    //设置TCP/UDP模式自动切换
    /* -- 播放前参数配置可加在此处 -- */

    int flag = NT_U3D_StartPlay(player_handle_);

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

    is_running = true;  
}

开始播放后，native模块，回调yuv/rgb数据，unity3d模块，做相应的绘制处理即可。

private void Update()
{
    if (!is_need_get_frame_)
        return;

    if (player_handle_ == 0)
        return;

    AndroidJavaObject u3d_video_frame_obj = NT_U3D_GetVideoFrame(player_handle_);

    if (u3d_video_frame_obj == null)
        return;

    VideoFrame converted_video_frame = ConvertToVideoFrame(u3d_video_frame_obj);

    if (converted_video_frame == null)
        return;

    if ( !is_need_init_texture_)
    {
        if (converted_video_frame.width_ != video_width_
            || converted_video_frame.height_ != video_height_
            || converted_video_frame.y_stride_ != y_row_bytes_
            || converted_video_frame.u_stride_ != u_row_bytes_
            || converted_video_frame.v_stride_ != v_row_bytes_)
        {
            is_need_init_texture_ = true;
        }
    }

    if (is_need_init_texture_)
    {
        if (InitYUVTexture(converted_video_frame))
        {
            is_need_init_texture_ = false;
        }
    }

    UpdateYUVTexture(converted_video_frame);

    converted_video_frame = null;
}

关闭播放：

private void ClosePlayer()
{
    is_need_get_frame_ = false;
    is_need_init_texture_ = false;

    int flag = NT_U3D_StopPlay(player_handle_);
    if (flag == DANIULIVE_RETURN_OK)
    {
        Debug.Log("停止成功");
    }
    else
    {
        Debug.LogError("停止失败");
    }

    flag = NT_U3D_Close(player_handle_);
    if (flag == DANIULIVE_RETURN_OK)
    {
        Debug.Log("关闭成功");
    }
    else
    {
        Debug.LogError("关闭失败");
    }

    player_handle_ = 0;

    NT_U3D_UnInit();

    is_running = false;
}

以上是大概的实现流程，Unity环境下，实际测试时延，和 native直播模块相差无几，都是毫秒级延迟。Windows平台和iOS平台也是如此。