实现流媒体推流RTSP之FFmpeg 代码

女爷i 2024-02-23 07:21 51阅读 0赞

实时录屏并把视频推流到RTSP服务器，具体流程是抓取屏幕内容(bitmap)，并把bitmap转化为YUV，接着把YUV编码成H264，再把H264码流推到RTSP服务器；把采集到的PCM编码为AAC，再把AAC推流至RTSP服务器。

![5598fae45baf41748d81bc5b391a111d.png][]

RTSP服务器使用的是HappyTime的免费试用版本。

1. bitmap转YUV

我抓到的bitmap是BGRA格式的，所以使用的图像格式是AV\_PIX\_FMT\_BGRA，cropImage是含有rgba图像的数组

bool init_RGB_to_YUV(){
        
        //BGRA 转 YUV
        swrCtxBGRA2YUV = sws_getContext(
            cap_w, cap_h, AV_PIX_FMT_BGRA,
            cap_w, cap_h, AV_PIX_FMT_YUV420P,
            SWS_BICUBIC,
            NULL, NULL, NULL
            );
     
        //创建BGRA帧
        frame_bgra = av_frame_alloc();
        frame_bgra->format = AV_PIX_FMT_BGRA;
        frame_bgra->width = cap_w;
        frame_bgra->height = cap_h;
        if (av_frame_get_buffer(frame_bgra, 32) < 0) {
            printf("Failed: av_frame_get_buffer\n");
            return false;
        }
        frame_bgra->data[0] = cropImage;
        
     
        //YUV帧
        frame_yuv = av_frame_alloc();
        frame_yuv->width = cap_w;
        frame_yuv->height = cap_h;
        frame_yuv->format = AV_PIX_FMT_YUV420P;
     
        //
        uint8_t *picture_buf = (uint8_t *)av_malloc(cap_w * cap_h * 1.5);
        if (av_image_fill_arrays(frame_yuv->data, frame_yuv->linesize, picture_buf, AV_PIX_FMT_YUV420P, cap_w, cap_h, 1) < 0){
            printf("Failed: av_image_fill_arrays\n");
            return false;
        }
        return true;
    }

调用：

//BGRA 转 YUV
        if (sws_scale(swrCtxBGRA2YUV,
            frame_bgra->data, frame_bgra->linesize,
            0, cap_h,
            frame_yuv->data, frame_yuv->linesize) < 0)
        {
            printf("失败：BGRA 转 YUV\n");
            return;
        }
     
        frame_yuv->pts = av_gettime();

由于我是实时抓取的屏幕，**frame\_yuv->pts**设为当前的时间戳，以保证能正常播放。

##### 2. H264编码 #####

bool init_YUV_to_H264(){
        //寻找编码器
        codec_h264 = avcodec_find_encoder(AV_CODEC_ID_H264);
        if (!codec_h264){
            printf("Fail: avcodec_find_encoder\n");
            return false;
        }
     
        //编码器上下文
        codec_ctx_h264 = avcodec_alloc_context3(codec_h264);
        if (!codec_ctx_h264){
            printf("Fail: avcodec_alloc_context3\n");
            return false;
        }
        codec_ctx_h264->pix_fmt = AV_PIX_FMT_YUV420P;
        codec_ctx_h264->codec_type = AVMEDIA_TYPE_VIDEO;
        codec_ctx_h264->width = cap_w;
        codec_ctx_h264->height = cap_h;
        codec_ctx_h264->channels = 3;
        codec_ctx_h264->time_base = { 1, 25 };
        codec_ctx_h264->gop_size = 5;   //图像组两个关键帧（I帧）的距离
        codec_ctx_h264->max_b_frames = 0;
        //codec_ctx_h264->qcompress = 0.6;
        //codec_ctx_h264->bit_rate = 90000;
        codec_ctx_h264->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;   //添加PPS、SPS
        
        av_opt_set(codec_ctx_h264->priv_data, "preset", "ultrafast", 0);    //快速编码，但会损失质量
        //av_opt_set(codec_ctx_h264->priv_data, "tune", "zerolatency", 0);  //适用于快速编码和低延迟流式传输,但是会出现绿屏
        //av_opt_set(codec_ctx_h264->priv_data, "x264opts", "crf=26:vbv-maxrate=728:vbv-bufsize=3640:keyint=25", 0);
     
     
        //打开编码器
        if (avcodec_open2(codec_ctx_h264, codec_h264, NULL) < 0){
            printf("Fail: avcodec_open2\n");
            return false;
        }
     
        //用于接收编码好的H264
        pkt_h264 = av_packet_alloc();
     
        return true;
    }

调用：

ret = avcodec_send_frame(codec_ctx_h264, frame_yuv);
        if (ret < 0){
            printf("send frame fail\n");
            return;
        }
     
        while (ret >= 0)        {
            ret = avcodec_receive_packet(codec_ctx_h264, pkt_h264);
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF){
                break;
            }
     
            if (ret < 0){
                printf("Error during encoding\n");
                break;
            }
     
            pkt_h264->stream_index = videoindex;
            //printf("pkt_h264 timestamp = %d\n", pkt_h264->pts);
     
            if (av_interleaved_write_frame(fmt_ctx, pkt_h264) < 0) {
                printf("Error muxing packet\n");
            }
     
            av_packet_unref(pkt_h264);
        }

### 3. AAC编码 ###

bool init_PCM_to_AAC(){
     
        codec_aac = avcodec_find_encoder(AV_CODEC_ID_AAC);
        if (!codec_aac) {
            printf("avcodec_find_encoder fail\n");
            return false;
        }
     
        codec_ctx_aac = avcodec_alloc_context3(codec_aac);
        if (!codec_ctx_aac) {
            printf("avcodec_find_encoder fail\n");
            return false;
        }
        codec_ctx_aac->sample_fmt = AV_SAMPLE_FMT_FLT;
        codec_ctx_aac->codec_type = AVMEDIA_TYPE_AUDIO;
        codec_ctx_aac->channels = channels;
        codec_ctx_aac->channel_layout = av_get_default_channel_layout(channels);
        codec_ctx_aac->sample_rate = sample_rete;
     
        if (avcodec_open2(codec_ctx_aac, codec_aac, NULL) < 0) {
            printf("open codec fail\n");
            return false;
        }
     
        swrCtxS162FLT = swr_alloc_set_opts(NULL,
            codec_ctx_aac->channel_layout, codec_ctx_aac->sample_fmt, codec_ctx_aac->sample_rate,
            codec_ctx_aac->channel_layout, AV_SAMPLE_FMT_S16, codec_ctx_aac->sample_rate,
            0, 0);
     
        if (!swrCtxS162FLT)
        {
            printf("swr_alloc_set_opts error\n");
            return false;
        }
        if (swr_init(swrCtxS162FLT) < 0) {
            printf("open resample fail\n");
            return false;
        }
     
        frame_pcm = av_frame_alloc();
        frame_pcm->nb_samples = nbSamples_; //一帧音频存放的样本数量
        frame_pcm->format = codec_ctx_aac->sample_fmt;
        frame_pcm->channels = codec_ctx_aac->channels;
        frame_pcm->channel_layout = codec_ctx_aac->channel_layout;
     
        if (av_frame_get_buffer(frame_pcm, 0) < 0) {
            printf("av_frame_get_buffer error\n");
            return false;
        }
     
        pkt_aac = av_packet_alloc();
     
        return true;
    }

调用：  
其中pcm\_buff是包含pcm数据的数组

const uint8_t *pcm[1];
            pcm[0] = pcm_buff;
            int len = swr_convert(swrCtxS162FLT,
                frame_pcm->data, frame_pcm->nb_samples,
                pcm, nbSamples_);
     
            if (len <= 0) {
                printf("---Encodec:PCM->AAC--- swr_convert fail \n");
                return;
            }
     
            frame_pcm->pts = av_gettime();
     
            //printf("channels = %d\n", frame_pcm->channels);
            //printf("framePCM->linesize = %6d %6d\n", frame_pcm->linesize[0], frame_pcm->linesize[1]);
     
            //AAC编码
            int ret = avcodec_send_frame(codec_ctx_aac, frame_pcm);
            if (ret < 0){
                printf("send frame fail\n");
                return;
            }
     
            ret = avcodec_receive_packet(codec_ctx_aac, pkt_aac);
            
            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF){
                return;
            }
     
            if (ret < 0){
                printf("Error during encoding\n");
                return;
            }
     
            pkt_aac->stream_index = audioindex;
            //printf("pkt_aac timestamp = %d\n", pkt_aac->pts);
     
            if (av_interleaved_write_frame(fmt_ctx, pkt_aac) < 0) {
                printf("Error muxing packet\n");
            }
            av_packet_unref(pkt_aac);

##### 4. 推流器 #####

使用udp传输时传到1400多帧就断开链接了，原因不明，所以改用使用tcp协议传输

bool init_rtsp_pusher(){
        
        //RTSP
        if (avformat_alloc_output_context2(&fmt_ctx, NULL, "RTSP", RTSP_URL.c_str()) < 0){
            printf("Fail: avformat_alloc_output_context2\n");
            return false;
        }
     
        //使用tcp协议传输
        av_opt_set(fmt_ctx->priv_data, "rtsp_transport", "tcp", 0);
     
        //检查所有流是否都有数据，如果没有数据会等待max_interleave_delta微秒
        fmt_ctx->max_interleave_delta = 1000000;
     
        //输出视频流
        AVStream *video_s = avformat_new_stream(fmt_ctx, codec_h264);
        if (!video_s){
            printf("Fail: avformat_new_stream\n");
            return false;
        }
        video_s->time_base = { 1, 25 };
        videoindex = video_s->id = fmt_ctx->nb_streams - 1;  //加入到fmt_ctx流
     
        //复制AVCodecContext的设置
        if (avcodec_copy_context(video_s->codec, codec_ctx_h264) < 0) {
            printf("Fail: avcodec_copy_context\n");
            return false;
        }
        video_s->codec->codec_tag = 0;
        if (fmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
            video_s->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
        
        avcodec_parameters_from_context(video_s->codecpar, codec_ctx_h264);
     
        
            //输出音频流
            AVStream *audio_s = avformat_new_stream(fmt_ctx, codec_ctx_aac->codec);
            if (!audio_s){
                printf("Fail: avformat_new_stream\n");
                return false;
            }
            audio_s->time_base = { 1, 25 };
            audioindex = audio_s->id = fmt_ctx->nb_streams - 1;
     
            //复制AVCodecContext的设置
            if (avcodec_copy_context(audio_s->codec, codec_ctx_aac) < 0) {
                printf("Fail: avcodec_copy_context\n");
                return false;
            }
            audio_s->codec->codec_tag = 0;
            if (fmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
                audio_s->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
            avcodec_parameters_from_context(audio_s->codecpar, codec_ctx_aac);
        
            //printf("fmt_ctx nb_streams = %d\n", fmt_ctx->nb_streams);
     
        av_dump_format(fmt_ctx, 0, fmt_ctx->filename, 1);
        if (!(fmt_ctx->oformat->flags & AVFMT_NOFILE)) {    //???
            //打开输出URL（Open output URL）
            if (avio_open(&fmt_ctx->pb, fmt_ctx->filename, AVIO_FLAG_WRITE) < 0) {
                printf("Fail: avio_open('%s')\n", fmt_ctx->filename);
                return false;
            }
        }
        return true;
    }

[5598fae45baf41748d81bc5b391a111d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/02/23/7b8b2ed73c1846c79ee1ba69a561326c.png