火山RTC 5 转推CDN 布局合成规则

实时音视频房间，转推CDN，文档：

转推直播--实时音视频-火山引擎

一、转推CDN

0、前提

* + 在调用该接口前，你需要在[控制台](https://console.volcengine.com/rtc/workplaceRTC)开启转推直播功能。<br>
* + 调用该方法后，关于启动结果和推流过程中的错误，会收到 onMixingEvent{@link #IMixedStreamObserver#onMixingEvent} 回调。<br>

（我测试的时候，使用的别的平台的CDN 地址，好像不开启，也能转推上去）

最多合并17路流

https://www.volcengine.com/docs/6348/69850

1、startPushMixedStreamToCDN

1）、接口

/**
     * @locale zh
     * @valid since 3.52
     * @hidden(Linux) not available
     * @type api
     * @region 多房间
     * @brief 新增合流转推直播任务，并设置合流的图片、视频视图布局和音频属性。  <br>
     *        同一个任务中转推多路直播流时，SDK 会先将多路流合成一路流，然后再进行转推。
     * @param task_id 转推直播任务 ID，长度不超过 126 字节。<br>
     *        你可以在同一房间内发起多个转推直播任务，并用不同的任务 ID 加以区分。当你需要发起多个转推直播任务时，应使用多个 ID；当你仅需发起一个转推直播任务时，建议使用空字符串。
     * @param config 转推直播配置参数。参看 IMixedStreamConfig{@link #IMixedStreamConfig}。
     * @param observer 端云一体转推直播观察者。参看 IMixedStreamObserver{@link #IMixedStreamObserver}。  <br>
     *        通过注册 observer 接收转推直播相关的回调。
     * @return 
     *        + 0: 成功<br>
     *        + !0: 失败
     * @note  
     *       + 在调用该接口前，你需要在[控制台](https://console.volcengine.com/rtc/workplaceRTC)开启转推直播功能。<br>
     *       + 调用该方法后，关于启动结果和推流过程中的错误，会收到 onMixingEvent{@link #IMixedStreamObserver#onMixingEvent} 回调。<br>
     *       + 如果已在[控制台](https://console.volcengine.com/rtc/cloudRTC?tab=callback)配置了转推直播的服务端回调，调用本接口会收到 [TranscodeStarted](https://www.volcengine.com/docs/6348/75125#transcodestarted)。重复调用该接口时，第二次调用会同时触发 [TranscodeStarted](https://www.volcengine.com/docs/6348/75125#transcodestarted) 和 [TranscodeUpdated](https://www.volcengine.com/docs/6348/75125#transcodeupdated)。<br>
     *       + 调用 stopPushStreamToCDN{@link #IRTCVideo#stopPushStreamToCDN} 停止转推直播。
     */
    /**
     * @locale en
     * @valid since 3.52
     * @hidden(Linux) not available
     * @type api
     * @region Multi-room
     * @brief Create a new task of pushing mixed media streams to CDN and sets the relevant configurations.  <br>
     *        When pushing more than one live streams in the same task, SDK will first mix those streams into one single stream and then push it to CDN.
     * @param task_id Task ID. The length should not exceed 126 bytes.<br>
     *        You may want to push more than one mixed stream to CDN from the same room. When you do that, use different ID for corresponding tasks; if you will start only one task, use an empty string.
     * @param config Configurations to be set when pushing streams to CDN. See IMixedStreamConfig{@link #IMixedStreamConfig}.
     * @param observer Register this observer to receive callbacks from the SDK. See IMixedStreamObserver{@link #IMixedStreamObserver}.
     * @return 
     *        + 0: Success<br>
     *        + !0: Failure
     * @note   
     *       + Before calling this API，you need to enable Push to CDN on the [console](https://console.byteplus.com/rtc/workplaceRTC).     <br>
     *       + After calling this API, you will be informed of the result and errors during the pushing process via the onMixingEvent{@link #IMixedStreamObserver#onMixingEvent} callback.<br>
     *       + If you have subscribed to the push-to-CDN server callback in the [console](https://console.byteplus.com/rtc/cloudRTC?tab=callback), calling this API will receive a [TranscodeStarted](https://docs.byteplus.com/en/byteplus-rtc/docs/75125#transcodestarted) server callback notification. When calling this API repeatedly, subsequent calls to this API will trigger both [TranscodeStarted](https://docs.byteplus.com/en/byteplus-rtc/docs/75125#transcodestarted) and [TranscodeUpdated](https://docs.byteplus.com/en/byteplus-rtc/docs/75125#transcodeupdated) callbacks.<br>
     *       + Call stopPushStreamToCDN{@link #IRTCVideo#stopPushStreamToCDN} to stop pushing streams to CDN.
     */
    virtual int startPushMixedStreamToCDN(const char* task_id, IMixedStreamConfig* config, IMixedStreamObserver* observer) = 0;

2）、IMixedStreamConfig 合流布局参数

config 转推直播配置参数。

/**
 * @locale zh
 * @type keytype
 * @brief 转推直播配置参数。(新)
 */
/**
 * @locale en
 * @type keytype
 * @brief Configurations to be set while pushing media streams to CDN.(New)
 */
class IMixedStreamConfig : public ITranscoderParamBase {
public:

    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取合流类型。
     * @return 合流类型，参看 MixedStreamType{@link #MixedStreamType}
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Gets the stream mixing type.
     * @return Stream mixing type. See MixedStreamType{@link #MixedStreamType}
     */
    virtual MixedStreamType getExpectedMixingType() = 0;
    /**
     * @locale zh
     * @type api
     * @brief 获取推流用户 ID。
     * @return 推流用户 ID。
     */
    /**
     * @locale en
     * @type api
     * @brief Gets the user ID for mixed stream.
     * @return The user ID for live mixed stream.
     */
    virtual const char* getUserID() = 0;
    /**
     * @locale zh
     * @type api
     * @brief 获取推流 CDN 地址。
     * @return 推流地址。
     */
    /**
     * @locale en
     * @type api
     * @brief Gets the URL for live mixed stream.
     * @return The CDN url.
     */
    virtual const char* getPushURL() = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取用户配置的额外信息。
     * @return UserConfigExtraInfo 信息。
     */
    /**
     * @locale en
     * @type api
     * @region Forward to live broadcast
     * @brief Get user config extra information.
     * @return extraI Information.
     */
    virtual const char* getUserConfigExtraInfo() = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取合流音频参数。
     * @return 合流音频参数内容，参看 MixedStreamAudioConfig{@link #MixedStreamAudioConfig}。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Gets the audio configurations.
     * @return Audio configurations. See MixedStreamAudioConfig{@link #MixedStreamAudioConfig}.
     */
    virtual MixedStreamAudioConfig getAudioConfig() = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取合流视频转码参数。
     * @return 合流视频转码参数内容，参看 MixedStreamVideoConfig{@link #MixedStreamVideoConfig}。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Gets the video configurations.
     * @return Video configurations. See MixedStreamVideoConfig{@link #MixedStreamVideoConfig}.
     */
    virtual MixedStreamVideoConfig getVideoConfig() = 0;
    /**
     * @locale zh
     * @hidden(Windows,macOS,Linux)
     * @type api
     * @brief 获取转推 CDN 时的空间音频参数。
     * @return 参看 MixedStreamSpatialAudioConfig{@link #MixedStreamSpatialAudioConfig}。
     */
    /**
     * @locale en
     * @hidden(Windows,macOS,Linux)
     * @type api
     * @brief Get the spatial audio configurations of pushing to CDN.
     * @return See MixedStreamSpatialAudioConfig{@link #MixedStreamSpatialAudioConfig}.
     */
    virtual MixedStreamSpatialAudioConfig getSpatialAudioConfig() = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取合流视窗布局信息。
     * @param index 视窗对应下标。
     * @return 合流视窗布局信息，参看 MixedStreamLayoutRegionConfig{@link #MixedStreamLayoutRegionConfig}。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Gets the video layout information of the mixed stream.
     * @param index The number of the view of which you want to get information.
     * @return Layout information. See MixedStreamLayoutRegionConfig{@link #MixedStreamLayoutRegionConfig}.
     */
    virtual MixedStreamLayoutRegionConfig getLayoutByIndex(int32_t index) = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @region 转推直播
     * @brief 获取动态扩展自定义参数
     * @return 动态扩展自定义参数
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @region Forward to live broadcast
     * @brief Get dynamically extend customizable parameters
     * @return dynamically extend customizable parameters
     */
    virtual const char* getAdvancedConfig() = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @region 转推直播
     * @brief 获取业务透传鉴权信息
     * @return 业务透传鉴权信息
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @region Forward to live broadcast
     * @brief Get Business Transparent Authentication Information
     * @return Business Transparent Authentication Information
     */
    virtual const char* getAuthInfo() = 0;
    /**
     * @locale zh
     * @type api
     * @brief 获取客户端合流信息。
     * @return 客户端合流信息，参看 MixedStreamClientMixConfig{@link #MixedStreamClientMixConfig}。
     */
    /**
     * @locale en
     * @type api
     * @brief Get client mixing parameters.
     * @return Client mixing parameters. See MixedStreamClientMixConfig{@link #MixedStreamClientMixConfig}.
     */
    virtual MixedStreamClientMixConfig getClientMixConfig()  = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @brief 获取转推直播同步参数。
     * @return 转推直播同步参数，参看 MixedStreamSyncControlConfig{@link #MixedStreamSyncControlConfig}。
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @brief Get transcoding sync control parameters.
     * @return Transcoding sync control parameters. See MixedStreamSyncControlConfig{@link #MixedStreamSyncControlConfig}.
     */
    virtual MixedStreamSyncControlConfig getSyncControlConfig() = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 设置合流类型。建议设置。
     * @param expected_mix_type 合流类型，参看 MixedStreamType{@link #MixedStreamType}
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Sets the expected stream mixing type. It's recommended to be set.
     * @param expected_mix_type Stream mixing type. See MixedStreamType{@link #MixedStreamType}
     */
    virtual void setExpectedMixingType(MixedStreamType expected_mix_type) = 0;
    /**
     * @locale zh
     * @type api
     * @brief 设置推流用户 ID。`room_id` 和 `user_id` 长度相加不得超过 126 字节。建议设置。<br>
     *        本参数不支持过程中更新。
     * @param user_id 推流用户 ID。
     */
    /**
     * @locale en
     * @type api
     * @brief Sets the user ID for live transcoding. The sum length of `room_id` and `user_id` should not exceed 126 bytes. It's recommended to be set.<br>
     *        This parameter cannot be updated while pushing stream to the CDN.
     * @param user_id The user ID for live transcoding.
     */
    virtual void setUserID(const char* user_id) = 0;
    /**
     * @locale zh
     * @type api
     * @brief 设置推流 CDN 地址。仅支持 RTMP 协议，Url 必须满足正则 `/^rtmps?:\/\//`。建议设置。<br>
     *        本参数不支持过程中更新。
     * @param url 推流地址。
     */
    /**
     * @locale en
     * @type api
     * @brief Sets the URL for live transcoding. Only supports live transcoding via RTMP. The URL should match the regular expression `/^rtmps?:\/\//`. It's recommended to be set.<br>
     *        This parameter cannot be updated while pushing stream to the CDN.
     * @param url The URL to be set.
     */
    virtual void setPushURL(const char* push_url) = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 设置音频参数。参看 MixedStreamAudioConfig{@link #MixedStreamAudioConfig}。建议设置。<br>
     *        本参数不支持过程中更新。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Sets audio configurations. See MixedStreamAudioConfig{@link #MixedStreamAudioConfig}. It's recommended to be set.<br>
     *        This parameters cannot be updated while pushing stream to the CDN.
     */
    virtual void setAudioConfig(const MixedStreamAudioConfig&) = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 设置视频参数。参看 MixedStreamVideoConfig{@link #MixedStreamVideoConfig}。建议设置。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Sets video configurations. See MixedStreamVideoConfig{@link #MixedStreamVideoConfig}. It's recommended to be set.
     */
    virtual void setVideoConfig(const MixedStreamVideoConfig&) = 0;
    /**
     * @locale zh
     * @hidden(Windows,macOS,Linux)
     * @type api
     * @brief 设定转推 CDN 时的空间音频效果。参看 MixedStreamSpatialAudioConfig{@link #MixedStreamSpatialAudioConfig}。
     */
    /**
     * @locale en
     * @hidden(Windows,macOS,Linux)
     * @type api
     * @brief Sets spatial audio configurations. See MixedStreamSpatialAudioConfig{@link #MixedStreamSpatialAudioConfig}.
     */
    virtual void setSpatialAudioConfig(const MixedStreamSpatialAudioConfig&) = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 设置视频流合流整体布局信息。
     * @param regions[] 用户布局信息列表。为 MixedStreamLayoutRegionConfig{@link #MixedStreamLayoutRegionConfig} 数据类型的数组。每一个该类型对象为一路单独的视频流的布局信息。<br>
     *                       值不合法或未设置时，自动使用默认值。建议设置。
     * @param regions_size 合流视窗数量。建议设置。
     * @param background_color 合流背景颜色，用十六进制颜色码（HEX）表示。例如，#FFFFFF 表示纯白，#000000 表示纯黑。默认值为 #000000。建议设置。<br>
     *                      值不合法或未设置时，自动使用默认值。
     * @param user_extra_info 透传的 App 数据。
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Sets the layout configurations.
     * @param regions[] User layout information list. It's a list of MixedStreamLayoutRegionConfig{@link #MixedStreamLayoutRegionConfig} that you construct for each stream.<br>
     *                       With invalid or empty input, the configurations will be set as the default values. It's recommended to be set.
     * @param regions_size Amount of views. It's recommended to be set.
     * @param background_color Background-color of the mixed stream in hexadecimal values such as #FFFFFF and #000000. The default value is #000000. It's recommended to be set.<br>
     *                      With invalid or empty input, the configurations will be set as the default values.
     * @param user_extra_info Additional data that you want to import.
     */
    virtual void setLayoutConfig(MixedStreamLayoutRegionConfig regions[],
                                int32_t regions_size,
                                const char* background_color,
                                const char* user_extra_info) = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @region 转推直播
     * @brief 设置动态扩展自定义参数
     * @param advanced_config 动态扩展自定义参数
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @region Forward to live broadcast
     * @brief Sets dynamically extend customizable parameters
     * @param advanced_config  dynamically extend customizable parameters
     */
    virtual void setAdvancedConfig(const char* advanced_config) = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @region 转推直播
     * @brief 设置业务透传鉴权信息
     * @param auth_info 业务透传鉴权信息
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @region Forward to live broadcast
     * @brief Sets Business Transparent Authentication Information
     * @param auth_info  Business Transparent Authentication Information
     */
    virtual void setAuthInfo(const char* auth_info) = 0;
    /**
     * @locale zh
     * @type api
     * @brief 设置客户端合流信息，参看 MixedStreamClientMixConfig{@link #MixedStreamClientMixConfig}。
     */
    /**
     * @locale en
     * @type api
     * @brief Sets client mixing parameters. See MixedStreamClientMixConfig{@link #MixedStreamClientMixConfig}.
     */
    virtual void setClientMixConfig(MixedStreamClientMixConfig&) = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @brief 设置转推直播同步参数。参看 MixedStreamSyncControlConfig{@link #MixedStreamSyncControlConfig}。
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @brief Sets transcoding sync control parameters. See MixedStreamSyncControlConfig{@link #MixedStreamSyncControlConfig}.
     */
    virtual void setSyncControlConfig(MixedStreamSyncControlConfig&) = 0;
    /**
     * @locale zh
     * @type api
     * @brief 获取服务端合流控制参数。参看 MixedStreamServerControlConfig{@link #MixedStreamServerControlConfig}。
     */
    /**
     * @locale en
     * @type api
     * @brief Gets the configurations while mixing streams on the server side. See MixedStreamServerControlConfig{@link #MixedStreamServerControlConfig}.
     */
    virtual MixedStreamServerControlConfig getServerControlConfig() = 0;
    /**
     * @locale zh
     * @type api
     * @brief 设置服务端合流控制参数。参看 MixedStreamServerControlConfig{@link #MixedStreamServerControlConfig}。
     */
    /**
     * @locale en
     * @type api
     * @brief Sets the configurations while mixing streams on the server side. See MixedStreamServerControlConfig{@link #MixedStreamServerControlConfig}.
     */
    virtual void setServerControlConfig(MixedStreamServerControlConfig& config) = 0;
    /**
     * @locale zh
     * @valid since 3.57
     * @type api
     * @brief 设置合流后整体画布的背景图片 URL，长度最大为 1024 bytes。<br>
     *        支持的图片格式包括：JPG, JPEG, PNG。如果背景图片的宽高和整体屏幕的宽高不一致，背景图片会缩放到铺满屏幕。
     */
    /**
     * @locale en
     * @valid since 3.57
     * @type api
     * @brief Sets the URL of the background image for the canvas that renders the mixed stream, with a maximum length of 1024 bytes.<br>
     *        You can input images in the following supported formats: JPG, JPEG, PNG.<br>
     *        If the width and height of the background image are different from the screen dimensions, the background image will be scaled to fill the screen.
     */
    virtual void setBackgroundImageURL(const char* background_image_url) = 0;
    /**
     * @locale zh
     * @valid since 3.57
     * @type api
     * @brief 获取背景图片的地址。
     */
    /**
     * @locale en
     * @type api
     * @brief Gets the background image URL.
     */
    virtual const char* getBackgroundImageURL() = 0;
    /**
     * @locale zh
     * @hidden for internal use only
     * @type api
     * @region 转推直播
     * @brief 将输入的 json 格式的字符串转成 ITranscoderParam 结构体
     * @param json_str json 格式字符串
     * @return 转换后的 ITranscoderParam 结构体
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type api
     * @region Push to CDN
     * @brief Convert the json format string into the ITranscoderParam structure
     * @param json_str Json format string
     * @return Converted ITranscoderParam structure
     */
    virtual IMixedStreamConfig* inflatten(const char* json_str) = 0;
    /**
     * @locale zh
     * @type api
     * @region 转推直播
     * @brief 获取默认的合流转推参数
     * @return 生成的 IMixedStreamConfig 结构体
     */
    /**
     * @locale en
     * @type api
     * @region Push to CDN
     * @brief Get default transcoding config
     * @return Default IMixedStreamConfig structure
     */
    virtual IMixedStreamConfig* defaultMixedStreamConfig() = 0;
    /**
     * @hidden constructor/destructor
     */
    virtual ~IMixedStreamConfig() = default;
    /**
     * @hidden for internal use only
     * @type api
     */
    virtual void setConvertFromOldTranscodeParam(bool is_from_old_param) = 0;
    /**
     * @hidden for internal use only
     * @type api
     */
    virtual bool getIsConvertFromOldTranscodeParam() = 0;
};

3）、IMixedStreamObserver

* @param observer 端云一体转推直播观察者。参看 IMixedStreamObserver{@link #IMixedStreamObserver}。 <br>
* 通过注册 observer 接收转推直播相关的回调。

3.1)、事件监听观察者

/**
 * @locale zh
 * @type callback
 * @region 转推直播
 * @brief 合流推流 Observer<br>
 * 注意：回调函数是在 SDK 内部线程（非 UI 线程）同步抛出来的，请不要做耗时操作或直接操作 UI，否则可能导致 app 崩溃。
 */
/**
 * @locale en
 * @type callback
 * @region Push to CDN
 * @brief Register this observer to receive stream mixing related callbacks from the SDK.<br>
 * Note: Callback functions are thrown synchronously in a non-UI thread within the SDK. Therefore, you must not perform any time-consuming operations or direct UI operations within the callback function, as this may cause the app to crash.
 */
class IMixedStreamObserver {
public:
    /**
     * @locale zh
     * @type callback
     * @region 转推直播
     * @brief 是否具有推流能力。  <br>
     *       + false：不具备推流能力（默认值）  <br>
     *       + true：具备推流能力
     * @note  
     *         + 如果需要开启端云一体转推直播功能，你必须确保你的 App 包含 librtmp，具有推流能力。此时，设置该回调为<br>
     * true。
     */
    /**
     * @locale en
     * @type callback
     * @region Push to CDN
     * @brief Whether your App has the ability to push streams to CDN.   <br>
     *        + True: Yes <br>
     *        + False: No (default value)
     * @note   
     *       + If you need to use the function of intelligently pushing streams to CDN, you should ensure that your App<br>
     * contains librtmp and has the ability to push streams out. If so, set the callback to True.
     */
    virtual bool isSupportClientPushStream() = 0;
    /**
     * @locale zh
     * @hidden(Linux) not available
     * @type callback
     * @region 转推直播
     * @brief 转推直播状态回调
     * @param event 转推直播任务状态，参看 StreamMixingEvent{@link #StreamMixingEvent}
     * @param task_id 转推直播任务 ID
     * @param error 转推直播错误码，参看 StreamMixingErrorCode{@link #StreamMixingErrorCode}。
     * @param mix_type 转推直播类型，参看 MixedStreamType{@link #MixedStreamType}
     */
    /**
     * @locale en
     * @hidden(Linux) not available
     * @type callback
     * @region Push to CDN
     * @brief Used for reporting events during pushing streams to CDN
     * @param event Type Stream mixing status, see StreamMixingEvent{@link #StreamMixingEvent}
     * @param task_id Task ID
     * @param error Errors occuring during the pushing process. See StreamMixingErrorCode{@link #StreamMixingErrorCode}
     * @param mix_type Stream mixing and pushing type. See MixedStreamType{@link #MixedStreamType}
     */
    virtual void onMixingEvent(
            StreamMixingEvent event, const char* task_id, StreamMixingErrorCode error, MixedStreamType mix_type) = 0;

    /**
     * @locale zh
     * @type callback
     * @region 转推直播
     * @brief 合流视频回调，运行在视频回调线程
     * @param task_id 合流任务 ID
     * @param video_frame 视频帧，参看 IVideoFrame{@link #IVideoFrame}。
     * @note 收到该回调的周期与视频的帧间隔一致。
     */
    /**
     * @locale en
     * @type callback
     * @region Push to CDN
     * @brief Callback with the video data after stream mixing, running on the video callback thread
     * @param task_id Task ID
     * @param video_frame Video Frame, see IVideoFrame{@link #IVideoFrame}.
     * @note The interval between callbacks is the same with that between video frames.
     */
    virtual void onMixingVideoFrame(const char* task_id, IVideoFrame* video_frame) = 0;

    /**
     * @locale zh
     * @type callback
     * @region 转推直播
     * @brief 合流音频回调，运行在音频回调线程
     * @param task_id 转推直播任务 ID
     * @param audio_frame 音频帧，参看 IAudioFrame{@link #IAudioFrame}。
     * @note 收到该回调的周期为每 10 毫秒一次，并且每次的音频数据量为 10 毫秒数据量。
     */
    /**
     * @locale en
     * @type callback
     * @region Push to CDN
     * @brief Callback with the audio data after stream mixing, running on the audio callback thread
     * @param task_id Task ID.
     * @param audio_frame Audio Frame, see IAudioFrame{@link #IAudioFrame}.
     * @note You will receive the callback every 10 milliseconds. Each callback carries data collected in the last 10<br>
     * milliseconds.
     */
    virtual void onMixingAudioFrame(const char* task_id, IAudioFrame* audio_frame) = 0;

    /**
     * @locale zh
     * @type callback
     * @region 转推直播
     * @brief 视频 SEI 帧回调，运行在视频回调线程
     * @param task_id 转推直播任务 ID
     * @param data_frame SEI 数据
     */
    /**
     * @locale en
     * @type callback
     * @region Push to CDN
     * @brief This callback carries SEI data, running on the video callback thread
     * @param task_id Task ID
     * @param data_frame SEI data
     */
    virtual void onMixingDataFrame(const char* task_id, IDataFrame* data_frame) = 0;

    /**
     * @locale zh
     * @hidden for internal use only
     * @type callback
     * @region 转推直播
     * @brief 同步视频帧回调。
     * @param task_id 转推直播任务 ID。
     * @param uids 同步视频帧对应的 uid 数组。
     * @param video_frames 同步视频帧数组，与 uids 对应。
     * @param data_frame SEI 数据。
     * @param count 数组的长度。
     */
    /**
     * @locale en
     * @hidden for internal use only
     * @type callback
     * @region Push to CDN
     * @brief Synchronized video frame callback.
     * @param task_id Task ID.
     * @param uids Array of synchronized video frames corresponding to uids.
     * @param video_frames Array of synchronized video frames corresponding to uids.
     * @param data_frame SEI data.
     * @param count The length of the array.
     */
    virtual void onCacheSyncVideoFrames(const char* task_id, const char* uids[], IVideoFrame* video_frames[],
            IDataFrame* data_frame[], int count) = 0;

    /**
     * @locale zh
     * @hidden constructor/destructor
     * @brief 析构函数
     */
    /**
     * @locale en
     * @hidden constructor/destructor
     * @brief Destructor
     */
    virtual ~IMixedStreamObserver() = default;
};

3.2）、示例：

class ByteRTCEventHandler : public QObject,
        public bytertc::IRTCVideoEventHandler,
        public bytertc::IAudioEffectPlayerEventHandler,
        public bytertc::IMixedStreamObserver,
                            public bytertc::IMediaPlayerEventHandler

{

    std::unique_ptr<ByteRTCEventHandler> m_handler;



..............................................................................
..............................................................................


    //isSupportClientPushStream
    //return false: 告诉SDK，使用服务端合流方式，即由RTCSDK推到CDN
    //return true:  告诉SDK，使用业务层转推RTMP能力，需要业务层具备转推到CDN的能力
    // 本功能展示的是 如何使用RTCSDK 服务器合流，业务层不支持转推CDN，因此需要return false;


    m_handler.reset(new ByteRTCEventHandler());
    m_handler->setIsSupportClientPushStream(false); //本Demo使用RTC服务器推流，因此isSupportClientPushStream返回false

 connect(m_handler.get(), &ByteRTCEventHandler::sigMixingEvent, this, &CDNStreamByServer::onSigMixingEvent);

  m_video = bytertc::createRTCVideo(g_appid.c_str(), m_handler.get(), nullptr);

    bytertc::IMixedStreamConfig* mixed_stream_param = getMixedStreamConfig();

    int ret = m_video->startPushMixedStreamToCDN(m_task.c_str(), mixed_stream_param, m_handler.get());

4）、调用示例：

    m_task = "task1";
    if (ui->lineEdit_url->text().isEmpty()) {
        QMessageBox box(QMessageBox::Warning, QStringLiteral("提示"), QString("url is empty"), QMessageBox::Ok);
        box.exec();
        return;
    }

    std::lock_guard<std::recursive_mutex> locker(m_mutex);
    if (m_video == nullptr) return;

    bytertc::IMixedStreamConfig* mixed_stream_param = getMixedStreamConfig();

    int ret = m_video->startPushMixedStreamToCDN(m_task.c_str(), mixed_stream_param, m_handler.get());
    if (ret != 0) {
        QMessageBox box(QMessageBox::Warning, QStringLiteral("提示"), QString("startPushMixedStreamToCDN error，请检查是否已经在控制台开通该功能"), QMessageBox::Ok);
        box.exec();
        return;
    }

2、updatePushMixedStreamToCDN

有人员变化时，实时更新合流配置

    /**
     * @locale zh
     * @valid since 3.52
     * @hidden(Linux) not available
     * @type api
     * @region 多房间
     * @brief 更新合流转推直播参数，会收到 onMixingEvent{@link #IMixedStreamObserver#onMixingEvent} 回调。  <br>
     *        使用 startPushMixedStreamToCDN{@link #IRTCVideo#startPushMixedStreamToCDN} 启用转推直播功能后，使用此方法更新功能配置参数。
     * @param task_id 转推直播任务 ID。指定想要更新参数设置的转推直播任务。
     * @param config 转推直播配置参数，参看 IMixedStreamConfig{@link #IMixedStreamConfig}。除特殊说明外，均支持过程中更新。<br>
     *        调用时，结构体中没有传入值的属性，会被更新为默认值。
     * @return 
     *        + 0: 成功<br>
     *        + !0: 失败
     */
    /**
     * @locale en
     * @valid since 3.52
     * @hidden(Linux) not available
     * @type api
     * @region Multi-room
     * @brief Update parameters needed when pushing mixed media streams to CDN.  You will be informed of the change via the onMixingEvent{@link #IMixedStreamObserver#onMixingEvent} callback. <br>
     *        After calling startPushMixedStreamToCDN{@link #IRTCVideo#startPushMixedStreamToCDN} to enable the function of pushing streams to CDN, you can call this API to update the relevant configurations.
     * @param task_id Task ID. Specifys of which pushing task you want to update the parameters.
     * @param config Configurations that you want to update. See IMixedStreamConfig{@link #IMixedStreamConfig} for specific indications. You can update any property for the task unless it is specified as unavailable for updates.<br>
     *        If you left some properties blank, you can expect these properties to be set to their default values.
     * @return 
     *        + 0: Success<br>
     *        + !0: Failure
     */
    virtual int updatePushMixedStreamToCDN(const char* task_id, IMixedStreamConfig* config) = 0;

    bytertc::IMixedStreamConfig* config = getMixedStreamConfig();
    int ret = m_video->updatePushMixedStreamToCDN(m_task.c_str(), config);
    if (ret != 0) {
        QMessageBox box(QMessageBox::Warning, QStringLiteral("提示"), QString("updatePushMixedStreamToCDN error，请检查参数"), QMessageBox::Ok);
        box.exec();
        return;
    }

3、getMixedStreamConfig 具体合流配置

音频总体、视频画布总体、每个人的位置/视频适配方式/混流音频视频方式

bytertc::IMixedStreamConfig* CDNStreamByServer::getMixedStreamConfig()
{
    // audio
    bytertc::MixedStreamAudioConfig audioParam;
    audioParam.audio_codec = bytertc::MixedStreamAudioCodecType::kMixedStreamAudioCodecTypeAAC;
    audioParam.channels = ui->comboBox_channel->currentText().toInt();
    audioParam.bitrate = ui->spinBox_a_bitrate->value();
    audioParam.sample_rate = ui->comboBox_samplerate->currentText().toInt();

    audioParam.audio_profile = bytertc::MixedStreamAudioProfile::kMixedStreamAudioProfileLC;

    // video
    bytertc::MixedStreamVideoConfig videoParam;
    videoParam.bitrate = ui->spinBox_v_bitrate->value();
    videoParam.fps = ui->spinBox_v_fps->value();
    videoParam.gop = 2;
    videoParam.width = 640;
    videoParam.height = 360;
    videoParam.enable_bframe = false;
    if (ui->comboBox_v_code->currentText().contains("264")) {
        videoParam.video_codec = bytertc::kMixedStreamVideoCodecTypeH264; //本参数不支持过程中更新
    }
    else {
        videoParam.video_codec = bytertc::kMixedStreamVideoCodecTypeByteVC1;
    }


    // layout
    bytertc::MixedStreamLayoutRegionConfig* layouts = new bytertc::MixedStreamLayoutRegionConfig[m_rendered_users.size()];
    int i = 0;
    std::map<std::string, UserWidget*>::iterator ite;

    for (ite = m_rendered_users.begin(); ite != m_rendered_users.end(); ite++) {
        bytertc::MixedStreamLayoutRegionConfig lay;
        lay.region_id = ite->first.c_str();
        lay.room_id = m_roomid.c_str();

        lay.location_x = (i % 2) * 0.5 * videoParam.width; 
        lay.location_y = (i / 2) * 0.5 *  videoParam.height;


        if (m_rendered_users.size() == 1) {
            lay.width = 0.8 * videoParam.width; 
            lay.height = 0.8 * videoParam.height;
        }
        else if (m_rendered_users.size() == 2) {
            lay.width = 0.4 * videoParam.width; 
            lay.height = 0.8 * videoParam.height;
        }
        else {
            lay.width = 0.4 * videoParam.width;
            lay.height = 0.4 * videoParam.height;
        }

        if (ite->first == m_localid) {
            lay.is_local_user = true;
        }
        else {
            lay.is_local_user = false;
        }

        lay.alpha = 1.0f;
        lay.z_order = 0;

       //  视频适配方式/混流 音频 视频方式 


        lay.render_mode = bytertc::MixedStreamRenderMode::kMixedStreamRenderModeHidden;
        lay.stream_type = bytertc::MixedStreamVideoType::kMixedStreamVideoTypeMain;
        lay.media_type = bytertc::MixedStreamMediaType::kMixedStreamMediaTypeAudioAndVideo;
        lay.apply_spatial_audio = false;
        layouts[i++] = lay;
    }

    bytertc::MixedStreamClientMixConfig client_conf;
    client_conf.use_audio_mixer = true;
    client_conf.video_format = bytertc::kMixedStreamClientMixVideoFormatI420;

    std::string url = ui->lineEdit_url->text().toStdString();

    bytertc::IMixedStreamConfig* mixed_stream_param = bytertc::createMixedStreamConfig();
    mixed_stream_param->setAudioConfig(audioParam);
    mixed_stream_param->setVideoConfig(videoParam);
    mixed_stream_param->setLayoutConfig(layouts, m_rendered_users.size(), m_str_color.c_str(), nullptr);
    mixed_stream_param->setExpectedMixingType(bytertc::kMixedStreamTypeByServer); 
    mixed_stream_param->setPushURL(url.c_str());
    mixed_stream_param->setRoomID(m_roomid.c_str());
    mixed_stream_param->setUserID(m_localid.c_str());
    mixed_stream_param->setClientMixConfig(client_conf);

    delete[]layouts;
    return mixed_stream_param;

    QStringList list = {"setAudioConfig", "setVideoConfig", "setLayoutConfig", "setExpectedMixingType", "setPushURL", "setRoomID", "setUserID", "setClientMixConfig"};
    appendAPI(list);
}