ffmpeg将mp4文件推送到rtmp服务器

将mp4文件根据播放速度推送到rtmp服务器，只需要解复用得到包packet，无需解码packet得到frame。

ffmpeg命令实现

ffmpeg -re -i input.mp4 -c copy -f flv rtmp://localhost/live/app1

c语言实现

#include <libavformat/avformat.h>
#include <libavutil/time.h>
#include <libavutil/timestamp.h>



static double r2d(AVRational r)
{
    return r.num == 0 || r.den == 0 ? 0. : (double)r.num / (double)r.den;
}


static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
{
    AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;

    printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
            tag,
            av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
            av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
            av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
            pkt->stream_index);
}
 
int main(int argc, char **argv)
{
    const AVOutputFormat *ofmt = NULL;
    AVDictionary *opts = NULL;
    AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
    AVPacket *pkt = NULL;
    const char *in_filename, *out_filename;
    int ret, i;
    int stream_index = 0;
    int *stream_mapping = NULL;
    int stream_mapping_size = 0;


    in_filename  = "../input.mp4";
    out_filename = "rtmp://localhost/live/app1";

 
    pkt = av_packet_alloc();
    if (!pkt) {
        fprintf(stderr, "Could not allocate AVPacket\n");
        return 1;
    }
 
    if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
        fprintf(stderr, "Could not open input file '%s'", in_filename);
        goto end;
    }
 
    if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
        fprintf(stderr, "Failed to retrieve input stream information");
        goto end;
    }
 
    av_dump_format(ifmt_ctx, 0, in_filename, 0);
 

 	// avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, out_filename);
    avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", out_filename);
    if (!ofmt_ctx) {
        fprintf(stderr, "Could not create output context\n");
        ret = AVERROR_UNKNOWN;
        goto end;
    }
 
    stream_mapping_size = ifmt_ctx->nb_streams;
    stream_mapping = av_calloc(stream_mapping_size, sizeof(*stream_mapping));
    if (!stream_mapping) {
        ret = AVERROR(ENOMEM);
        goto end;
    }
 
    ofmt = ofmt_ctx->oformat;
 
    for (i = 0; i < ifmt_ctx->nb_streams; i++) {
        AVStream *out_stream;
        AVStream *in_stream = ifmt_ctx->streams[i];
        AVCodecParameters *in_codecpar = in_stream->codecpar;
 
        if (in_codecpar->codec_type != AVMEDIA_TYPE_AUDIO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
            in_codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            stream_mapping[i] = -1;
            continue;
        }
 
        stream_mapping[i] = stream_index++;
 
        out_stream = avformat_new_stream(ofmt_ctx, NULL);
        if (!out_stream) {
            fprintf(stderr, "Failed allocating output stream\n");
            ret = AVERROR_UNKNOWN;
            goto end;
        }
 
        ret = avcodec_parameters_copy(out_stream->codecpar, in_codecpar);
        if (ret < 0) {
            fprintf(stderr, "Failed to copy codec parameters\n");
            goto end;
        }
        out_stream->codecpar->codec_tag = 0;
    }
    av_dump_format(ofmt_ctx, 0, out_filename, 1);
 
    if (!(ofmt->flags & AVFMT_NOFILE)) {
        ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
        if (ret < 0) {
            fprintf(stderr, "Could not open output file '%s'", out_filename);
            goto end;
        }
    }

  	// 创建一个 AVDictionary 用于存放选项
    av_dict_set(&opts, "flvflags", "no_duration_filesize", 0);

    ret = avformat_write_header(ofmt_ctx, &opts);
    if (ret < 0) {
        fprintf(stderr, "Error occurred when opening output file\n");
        goto end;
    }
 
    long long startTime = av_gettime();
    while (1) {
        AVStream *in_stream, *out_stream;
 
        ret = av_read_frame(ifmt_ctx, pkt);
        if (ret < 0)
            break;
 
        in_stream  = ifmt_ctx->streams[pkt->stream_index];
        if (pkt->stream_index >= stream_mapping_size ||
            stream_mapping[pkt->stream_index] < 0) {
            av_packet_unref(pkt);
            continue;
        }
 
        pkt->stream_index = stream_mapping[pkt->stream_index];
        out_stream = ofmt_ctx->streams[pkt->stream_index];
        log_packet(ifmt_ctx, pkt, "in");
 
        /* copy packet */
        av_packet_rescale_ts(pkt, in_stream->time_base, out_stream->time_base);
        pkt->pos = -1;
        log_packet(ofmt_ctx, pkt, "out");


        //控制视频帧推送速度
        if (ifmt_ctx->streams[pkt->stream_index]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            AVRational tb = ofmt_ctx->streams[pkt->stream_index]->time_base;
            //已经过去的时间，单位微妙us
            long long now = av_gettime() - startTime;
            long long dts = pkt->dts * (1000 * 1000 * r2d(tb));

            if (dts > now)
            {
                av_usleep(dts - now);
            }
        }


        ret = av_interleaved_write_frame(ofmt_ctx, pkt);

        /* pkt is now blank (av_interleaved_write_frame() takes ownership of
         * its contents and resets pkt), so that no unreferencing is necessary.
         * This would be different if one used av_write_frame(). */
        if (ret < 0) {
            fprintf(stderr, "Error muxing packet\n");
            break;
        }
    }
 
    av_write_trailer(ofmt_ctx);
end:
    av_packet_free(&pkt);
 
    avformat_close_input(&ifmt_ctx);
 
    /* close output */
    if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
        avio_closep(&ofmt_ctx->pb);
    avformat_free_context(ofmt_ctx);
 
    av_freep(&stream_mapping);
 
    if (ret < 0 && ret != AVERROR_EOF) {
        fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
        return 1;
    }

    return 0;
}