Schreiben von Bildern in RTP mit ffmpeg

Question

Ich versuche tatsächlich, Echtzeitbilder über das Netzwerk effizient zu senden. Aus diesem Grund dachte ich, dass das RTP-Protokoll im Video-Streaming eine gute Möglichkeit ist, dies zu erreichen.

ich dies tatsächlich versucht:

extern "C" 
{ 
    #include <libavcodec/avcodec.h> 
    #include <libavformat/avformat.h> 
    #include <libswscale/swscale.h> 

    #include <libavutil/opt.h> 
    #include <libavutil/channel_layout.h> 
    #include <libavutil/common.h> 
    #include <libavutil/imgutils.h> 
    #include <libavutil/mathematics.h> 
    #include <libavutil/samplefmt.h> 
} 
#include <iostream> 
#include <unistd.h> 
#include <stdio.h> 

//Mainly based on https://stackoverflow.com/questions/40825300/ffmpeg-create-rtp-stream 
int main() 
{ 
    //Init ffmpeg 
    avcodec_register_all(); 
    av_register_all(); 
    avformat_network_init(); 

    //Init the codec used to encode our given image 
    AVCodecID codecID = AV_CODEC_ID_MPEG4; 
    AVCodec* codec; 
    AVCodecContext* codecCtx; 

    codec = avcodec_find_encoder(codecID); 
    codecCtx = avcodec_alloc_context3(codec); 

    //codecCtx->bit_rate  = 400000; 
    codecCtx->width   = 352; 
    codecCtx->height  = 288; 

    codecCtx->time_base.num = 1; 
    codecCtx->time_base.den = 25; 
    codecCtx->gop_size  = 25; 
    codecCtx->max_b_frames = 1; 
    codecCtx->pix_fmt  = AV_PIX_FMT_YUV420P; 
    codecCtx->codec_type = AVMEDIA_TYPE_VIDEO; 

    if (codecID == AV_CODEC_ID_H264) 
    { 
     av_opt_set(codecCtx->priv_data, "preset", "ultrafast", 0); 
     av_opt_set(codecCtx->priv_data, "tune", "zerolatency", 0); 
    } 

    avcodec_open2(codecCtx, codec, NULL); 

    //Init the Frame containing our raw data 
    AVFrame* frame; 

    frame   = av_frame_alloc(); 
    frame->format = codecCtx->pix_fmt; 
    frame->width = codecCtx->width; 
    frame->height = codecCtx->height; 
    av_image_alloc(frame->data, frame->linesize, frame->width, frame->height, codecCtx->pix_fmt, 32); 

    //Init the format context 
    AVFormatContext* fmtCtx = avformat_alloc_context(); 
    AVOutputFormat* format = av_guess_format("rtp", NULL, NULL); 
    avformat_alloc_output_context2(&fmtCtx, format, format->name, "rtp://127.0.0.1:49990"); 

    avio_open(&fmtCtx->pb, fmtCtx->filename, AVIO_FLAG_WRITE); 

    //Configure the AVStream for the output format context 
    struct AVStream* stream  = avformat_new_stream(fmtCtx, codec); 

    avcodec_parameters_from_context(stream->codecpar, codecCtx); 
    stream->time_base.num  = 1; 
    stream->time_base.den  = 25; 

    /* Rewrite the header */ 
    avformat_write_header(fmtCtx, NULL); 

    /* Write a file for VLC */ 
    char buf[200000]; 
    AVFormatContext *ac[] = { fmtCtx }; 
    av_sdp_create(ac, 1, buf, 20000); 
    printf("sdp:\n%s\n", buf); 
    FILE* fsdp = fopen("test.sdp", "w"); 
    fprintf(fsdp, "%s", buf); 
    fclose(fsdp); 

    AVPacket pkt; 
    int j = 0; 
    for(int i = 0; i < 10000; i++) 
    { 
     fflush(stdout); 
     av_init_packet(&pkt); 
     pkt.data = NULL; // packet data will be allocated by the encoder 
     pkt.size = 0; 

     int R, G, B; 
     R = G = B = i % 255; 

     int Y = 0.257 * R + 0.504 * G + 0.098 * B + 16; 
     int U = -0.148 * R - 0.291 * G + 0.439 * B + 128; 
     int V = 0.439 * R - 0.368 * G - 0.071 * B + 128; 

     /* prepare a dummy image */ 
     /* Y */ 
     for (int y = 0; y < codecCtx->height; y++) 
      for (int x = 0; x < codecCtx->width; x++) 
       frame->data[0][y * codecCtx->width + x] = Y; 

     for (int y = 0; y < codecCtx->height/2; y++) 
      for (int x=0; x < codecCtx->width/2; x++) 
      { 
       frame->data[1][y * frame->linesize[1] + x] = U; 
       frame->data[2][y * frame->linesize[2] + x] = V; 
      } 

     /* Which frame is it ? */ 
     frame->pts = i; 

     /* Send the frame to the codec */ 
     avcodec_send_frame(codecCtx, frame); 

     /* Use the data in the codec to the AVPacket */ 
     switch(avcodec_receive_packet(codecCtx, &pkt)) 
     { 
      case AVERROR_EOF: 
       printf("Stream EOF\n"); 
       break; 

      case AVERROR(EAGAIN): 
       printf("Stream EAGAIN\n"); 
       break; 

      default: 
       printf("Write frame %3d (size=%5d)\n", j++, pkt.size); 

       /* Write the data on the packet to the output format */ 
       av_interleaved_write_frame(fmtCtx, &pkt); 

       /* Reset the packet */ 
       av_packet_unref(&pkt); 
       break; 
     } 

     usleep(1e6/25); 
    } 

    // end 
    avcodec_send_frame(codecCtx, NULL); 

    //Free everything 
    av_free(codecCtx); 
    av_free(fmtCtx); 

    return 0; 
} 

Und ich kann mit VLC ein Bild zu sehen, aber nicht ein Video (ich habe es reaload ein anderes Bild in Graustufen zu sehen).

Weiß jemand, warum vlc mein Video nicht gut spielen? Vielen Dank !

Answer 1

Nach vieler Forschung, fand ich den Fehler: Ich brauchte

av_packet_rescale_ts(&pkt, codecCtx->time_base, stream->time_base); 

vor dem verschachtelten rief korrekt das Paket zu platzieren. Was für eine Schande ...