使用 ffmpeg 实现视频流处理

本文将介绍如何使用 ffmpeg 实现视频流的推流与.edges （注：此处应为实际的输出 URL 或文件名）编码及传输。

软件预备条件

需预先安装 ffmpeg 及其相关依赖库，确保所有第三方组件可以正常运行。

推流前，需先启动流媒体服务器，并将流文件推送至服务器指定地址。

代码示例

#include 
   
    #include 
    
     #include 
     
      #include 
      
       #define __STDC_CONSTANT_MACROS extern "C"int main(int argc, char* argv[]) {    AVOutputFormat* ofmt = NULL;    AVFormatContext* ifmt_ctx = NULL;    AVFormatContext* ofmt_ctx = NULL;    AVPacket pkt;    const char* in_filename = "./video/input.mp4";    const char* out_filename = "rtmp://localhost/dash/test";    // 初始化 ffmpeg 库    av_register_all();    avformat_network_init();    // 打开输入文件    if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {        printf("Could not open input file.");        goto end;    }    // 获取流信息    if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {        printf("Failed to retrieve input stream information.");        goto end;    }    // 确定视频流索引    videoindex = -1;    for (i = 0; i < ifmt_ctx->nb_streams; i++) {        if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {            videoindex = i;            break;        }    }    // 输出子递交综述    av_dump_format(ifmt_ctx, 0, in_filename, 0);    // 创建输出流上下文    if ((ret = avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", out_filename)) < 0) {        printf("Could not create output context.");        ret = AVERROR_UNKNOWN;        goto end;    }    ofmt = ofmt_ctx->oformat;    // 创建输出流    for (i = 0; i < ifmt_ctx->nb_streams; i++) {        AVStream* in_stream = ifmt_ctx->streams[i];        AVStream* out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);        if (!out_stream) {            printf("Failed allocating output stream.");            ret = AVERROR_UNKNOWN;            goto end;        }        // 复制编码上下文        ret = avcodec_copy_context(out_stream->codec, in_stream->codec);        if (ret < 0) {            printf("Failed to copy context from input to output stream codec context.");            goto end;        }        out_stream->codec->codec_tag = 0;        if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) {            out_stream->codec->flags |= CODEC_FLAGS_GLOBAL_HEADER;        }    }    // 写出文件头信息    av_dump_format(ofmt_ctx, 0, out_filename, 1);    // 打开输出 URL    if (!(ofmt->flags & AVFMT_NOFILE)) {        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_WRITE);        if (ret < 0) {            printf("Could not open output URL '%s'", out_filename);            goto end;        }    }    // 写出文件头部    ret = avformat_write_header(ofmt_ctx, NULL);    if (ret < 0) {        printf("Error occurred when opening output URL.");        goto end;    }    // 视频流时间戳处理    AVRational time_base = ifmt_ctx->streams[videoindex]->time_base;    start_time = av_gettime();    while (1) {        // 读取流数据        ret = av_read_frame(ifmt_ctx, &pkt);        if (ret < 0) break;        // 处理时间戳        if (pkt.pts == AV_NOPTS_VALUE) {            AVRational time_base1 = ifmt_ctx->streams[videoindex]->time_base;            int64_t calc_duration = (double) AV_TIME_BASE / av_q2d(time_base1);            pkt.pts = (double)(frame_index * calc_duration) / av_q2d(time_base1) * AV_TIME_BASE;            pkt.dts = pkt.pts;            pkt.duration = calc_duration / av_q2d(time_base1) * AV_TIME_BASE;        }        // 视频流延迟处理        if (pkt.stream_index == videoindex) {            AVRational time_base = ifmt_ctx->streams[videoindex]->time_base;            int64_t pts_time = av_rescale_q(pkt.dts, time_base, {1, AV_TIME_BASE});            int64_t now_time = av_gettime() - start_time;            if (pts_time > now_time) {                av_usleep(pts_time - now_time);            }        }        // 处理流数据        in_stream = ifmt_ctx->streams[pkt.stream_index];        out_stream = ofmt_ctx->streams[pkt.stream_index];        pkt.pts = av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);        pkt.dts = av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX);        pkt.duration = av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);        if (ret = av_interleaved_write_frame(ofmt_ctx, &pkt)) {            frame_index++;        } else {            printf("Error muxing packet.");            break;        }        av_free_packet(&pkt);    }    av_write_trailer(ofmt_ctx);end:avformat_close_input(&ifmt_ctx);if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE)) {    avio_close(ofmt_ctx->pb);}avformat_free_context(ofmt_ctx);if (ret < 0 && ret != AVERROR_EOF) {    printf("Error occurred.");    return -1;}return 0;