腾讯云实时音视频客户端实现A+B->A和A+B->C混流方式

// 视频编码参数
TRTCVideoEncParam * videoEncParam = [[TRTCVideoEncParamalloc] init];
videoEncParam.resMode = TRTCVideoResolutionModePortrait;
videoEncParam.videoResolution = TRTCVideoResolution_960_720;
videoEncParam.videoBitrate = 1200;
videoEncParam.videoFps = 15;
videoEncParam.enableAdjustRes = NO;
[self.trtcCloudsetVideoEncoderParam:videoEncParam];

// 网络流控相关参数
TRTCNetworkQosParam * networkQosParam = [[TRTCNetworkQosParam alloc] init];
networkQosParam.preference = TRTCVideoQosPreferenceClear; // 保清晰
[self.trtcCloud setNetworkQosParam:networkQosParam];
画面渲染参数（经常出现的画面显示不完整、被裁减、有黑边等）：

//画面渲染参数
TRTCRenderParams *renderParams = [[TRTCRenderParams alloc] init];
/*
TRTCVideoFillMode_Fill = 0, ///< 图像铺满屏幕，超出显示视窗的视频部分将被裁剪
TRTCVideoFillMode_Fit = 1, ///< 图像长边填满屏幕，短边区域会被填充黑色
*/
renderParams.fillMode = TRTCVideoFillMode_Fit;
[self.trtcCloud setLocalRenderParams:renderParams];

[self.trtcCloud startLocalPreview:YES view:self.view];//开启摄像头，本地预览
TRTCParams * param = [[TRTCParams alloc] init];
param.sdkAppId = SDKAPPID;
param.userId = _roomInfo.userID;
param.strRoomId = _roomInfo.roomID;
param.role = TRTCRoleAnchor;//进房角色
param.userSig = [GenerateTestUserSig genTestUserSig:_roomInfo.userID];
param.streamId = @"streamIdChange";//修改流id
[self.trtcCloud enterRoom:param appScene:TRTCAppSceneLIVE];
[self.trtcCloud startLocalAudiTRTCAudioQualityDefault];//音频上行采集

TRTCTranscodingConfig *config = [[TRTCTranscodingConfig alloc] init];
// 设置分辨率为720 × 1280, 码率为1500kbps，帧率为20FPS
config.videoWidth      = 720;
config.videoHeight     = 1280;
config.videoBitrate    = 1500;
config.videoFramerate  = 20;
config.videoGOP        = 2;
config.audioSampleRate = 48000;
config.audioBitrate    = 64;
config.audioChannels   = 2;
config.streamId = @"ABCStream";//混流后的流id
// 采用预排版模式
config.mode = TRTCTranscodingConfigMode_Template_PresetLayout;
TRTCTranscodingConfig

NSMutableArray *users = [NSMutableArray new];
// 主播摄像头的画面位置
    TRTCMixUser* local = [TRTCMixUser new];
    local.userId = @"$PLACE_HOLDER_LOCAL_MAIN$";
    local.zOrder = 0;   // zOrder 为0代表主播画面位于最底层
    local.rect   = CGRectMake(0, 0, 720, 1280);
    local.roomID = nil; // 本地用户不用填写 roomID，远程需要
    [users addObject:local];
// 连麦者的画面位置
    TRTCMixUser* remote1 = [TRTCMixUser new];
    remote1.userId = @"$PLACE_HOLDER_REMOTE$";
    remote1.zOrder = 1;
    remote1.rect   = CGRectMake(720-180, 1280-500, 180, 240); //仅供参考
    remote1.roomID = self.roomInfo.roomID; // 本地用户不用填写 roomID，远程需要
    [users addObject:remote1];
// 连麦者的画面位置
    TRTCMixUser* remote2 = [TRTCMixUser new];
    remote2.userId = @"$PLACE_HOLDER_REMOTE$";
    remote2.zOrder = 1;
    remote2.rect   = CGRectMake(400, 500, 180, 240); //仅供参考
    remote2.roomID = self.roomInfo.roomID; // 本地用户不用填写 roomID，远程需要
    [users addObject:remote2];
    config.mixUsers = users;
// 发起云端混流
    [self.trtcCloud setMixTranscodingConfig:config];