阿里云RTC为您提供了输入外部音视频流的功能。通过阅读本文，您可以了解输入外部音视频流的方法。

输入外部视频流

说明 SDK允许先推流然后开启外部视频输入，但这种情况下，默认开始推流时，先推送出的是本地原始采集源（摄像头或屏幕捕获）的视频数据，直到启用外部输入。
  1. 调用setExternalVideoSource打开外部视频输入开关。 
    int ret = [self.engine setExternalVideoSource:YES useTexture:NO sourceType:AliRtcVideosourceCameraLargeType renderMode:AliRtcRenderModeAuto];
  2. 调用pushExternalVideoFrame输入视频数据。
    说明
    • 此处需要重新开启线程调用pushExternalVideoFrame。
    • 视频流类型仅支持AliRtcVideosourceCameraLargeType（大分辨率视频流）。
    float pcmHzFloat;
int yuvDataWidth;
int yuvDataHeight;
NSThread * yuvInputThread;
FILE * yuvInputFile;

- (void)inputYUVRun {

    int width = yuvDataWidth;
    int height = yuvDataHeight;
    int dataSize = width*height*3/2;

    char *yuv_read_data = (char *)malloc(dataSize);

    while (true) {

        if ([yuvInputThread isCancelled]) {
            break;
        }

        size_t read = fread(yuv_read_data,dataSize, 1, yuvInputFile);

        if (read > dataSize) {
            break;
        }
        if (read == 0) {

            fseek(yuvInputFile, 0,SEEK_SET);
            NSLog(@"input yuv reset head!");
            if (yuvInputThread) {
                continue;
            } else {
                break;
            }
        }

        bool push_error = false;

        while (true) {

            if (![yuvInputThread isExecuting]) {
                push_error = YES;
                break;
            }

            AliRtcVideoDataSample *dataSample = [[AliRtcVideoDataSample alloc] init];
            dataSample.dataPtr = (long)yuv_read_data;
            dataSample.format = AliRtcVideoFormat_I420;
            dataSample.width = width;
            dataSample.height = height;
            dataSample.strideY = width;
            dataSample.strideU = width/2;
            dataSample.strideV = width/2;
            dataSample.dataLength = dataSample.strideY * dataSample.height * 3/2;

            //加判断是否开启输入屏幕共享
            int ret = 0;
            if (yuvShareState != YES) {
            } else {
                ret = [self.engine pushExternalVideoFrame:dataSample sourceType:AliRtcVideosourceScreenShareType];
            }

            if (ret == AliRtcErrAudioBufferFull &&
                [yuvInputThread isCancelled] == NO) {

            } else {
                if (ret < 0) {
                    push_error = true ;
                }
            }

            //加判断频率, 默认为60hz(30毫秒)
            if (pcmHzFloat > 0) {
                float hz = 1.0/pcmHzFloat;
                [NSThread sleepForTimeInterval:hz];   // 指定频率
            } else {
                [NSThread sleepForTimeInterval:0.03];   // 默认30毫秒 (加延迟操作播放出流畅的画面)
            }

            break;
        }

        if (push_error) {
            break ;
        }
    }

    free(yuv_read_data);

    fclose(yuvInputFile);
    yuvInputFile = NULL ;
}

输入外部音频流

  1. 调用setExternalAudioSource启用外部音频输入，并调用setMixedWithMic设置外部音频输入是否与麦克风混合。 
    int ret = [self.engine setExternalAudioSource:YES withSampleRate:pcmSampleRate channelsPerFrame:pcmChannels];

// 完全替代麦克风采集
[self.engine setMixedWithMic:NO];
  2. 调用pushExternalAudioFrameRawData输入音频数据。
    说明 如果返回值为AliRtcErrAudioBufferFull，表示当前buffer队列饱和，建议您等待20ms，再继续输送数据。 
    int pcmSampleRate;
int pcmChannels;
NSThread * pcmInputThread;
FILE * pcmInputFile;

- (void)inputPCMRun {

    // 40ms
    int readbufSize = (pcmSampleRate/100)*4*sizeof(int16_t)*pcmChannels ;

    while (true) {

        if ([pcmInputThread isCancelled]) {
            break;
        }

        size_t read = fread(pcmData, 1, readbufSize, pcmInputFile) ;

        if (read > readbufSize) {
            break;
        }
        if (read == 0) {
            fseek(pcmInputFile, 0, SEEK_SET) ;
            NSLog(@"input pcm reset head!");
            if (pcmInputThread) {
                continue;
            } else {
                break;
            }
        }

        bool push_error = false;

        while (true) {
            if (![pcmInputThread isExecuting]) {
                push_error = YES;
                break;
            }

            int rc = [self.engine pushExternalAudioFrameRawData:pcmData samples:read timestamp:0];

            if ( rc == AliRtcErrAudioBufferFull && [pcmInputThread isCancelled ] == NO ) {
                [NSThread sleepForTimeInterval:0.08] ;
            } else {
                if (rc < 0) {
                    push_error = true ;
                }

                break;
            }

        }

        if (push_error) {
            break;
        }
    }

    fclose(pcmInputFile);
    pcmInputFile = NULL ;
}