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• How to publish selfmade stream with ffmpeg and c++ to rtmp server ?

  10 janvier 2024, par rLino

  Have a nice day to you, people !

  



  I am writing an application for Windows that will capture the screen and send the stream to Wowza server by rtmp (for broadcasting). My application use ffmpeg and Qt.
I capture the screen with WinApi, convert a buffer to YUV444(because it's simplest) and encode frame as described at the file decoding_encoding.c (from FFmpeg examples) :

  



  ///////////////////////////
//Encoder initialization
///////////////////////////
avcodec_register_all();
codec=avcodec_find_encoder(AV_CODEC_ID_H264);
c = avcodec_alloc_context3(codec);
c->width=scr_width;
c->height=scr_height;
c->bit_rate = 400000;
int base_num=1;
int base_den=1;//for one frame per second
c->time_base= (AVRational){base_num,base_den};
c->gop_size = 10;
c->max_b_frames=1;
c->pix_fmt = AV_PIX_FMT_YUV444P;
av_opt_set(c->priv_data, "preset", "slow", 0);

frame = avcodec_alloc_frame();
frame->format = c->pix_fmt;
frame->width  = c->width;
frame->height = c->height;

for(int counter=0;counter<10;counter++)
{
///////////////////////////
//Capturing Screen
///////////////////////////
    GetCapScr(shotbuf,scr_width,scr_height);//result: shotbuf is filled by screendata from HBITMAP
///////////////////////////
//Convert buffer to YUV444 (standard formula)
//It's handmade function because of problems with prepare buffer to swscale from HBITMAP
///////////////////////////
    RGBtoYUV(shotbuf,frame->linesize,frame->data,scr_width,scr_height);//result in frame->data
///////////////////////////
//Encode Screenshot
///////////////////////////
    av_init_packet(&pkt);
    pkt.data = NULL;    // packet data will be allocated by the encoder
    pkt.size = 0;
    frame->pts = counter;
    avcodec_encode_video2(c, &pkt, frame, &got_output);
    if (got_output) 
    {
        //I think that  sending packet by rtmp  must be here!
        av_free_packet(&pkt);             

    }

}
// Get the delayed frames
for (int got_output = 1,i=0; got_output; i++)
{
    ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
    if (ret < 0)
        {
            fprintf(stderr, "Error encoding frame\n");
            exit(1);
        }
        if (got_output)
        {
        //I think that  sending packet by rtmp  must be here!
        av_free_packet(&pkt);      
        }
}

///////////////////////////
//Deinitialize encoder
///////////////////////////
avcodec_close(c);
av_free(c);
av_freep(&frame->data[0]);
avcodec_free_frame(&frame);


  



  I need to send video stream generated by this code to RTMP server.
In other words, I need c++/c analog for this command :

  



  ffmpeg -re -i "sample.h264" -f flv rtmp://sample.url.com/screen/test_stream


  



  It's useful, but I don't want to save stream to file, I want to use ffmpeg libraries for realtime encoding screen capture and sending encoded frames to RTMP server inside my own application.
Please give me a little example how to initialize AVFormatContext properly and to send my encoded video AVPackets to server.

  



  Thanks.

  


• avcodec_open2 returns -22 "Invalid argument" trying to encode AV_CODEC_ID_H264

  26 mai 2023, par Fries of Doom

  I'm trying to use libavcodec to encode h264 video but avcodec_open2 returns -22 "Invalid argument" and I can't figure out why. Here is my code, which is mostly a copy from the encode example from libavcodec.

  


      /* find the mpeg1video encoder */
    const AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_H264);
    if (!codec) {
        fprintf(stderr, "Codec '%s' not found\n", "h.264");
        exit(1);
    }

    AVCodecContext* codecContext = avcodec_alloc_context3(codec);
    if (!codecContext) {
        fprintf(stderr, "Could not allocate video codec context\n");
        exit(1);
    }

    AVPacket* pkt = av_packet_alloc();
    if (!pkt)
        exit(1);

    /* put sample parameters */
    codecContext->bit_rate = 400000;
    /* resolution must be a multiple of two */
    codecContext->width = 1920;
    codecContext->height = 1080;
    /* frames per second */
    codecContext->time_base = { 1, 25 };
    codecContext->framerate = { 25, 1 };

    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    codecContext->gop_size = 10;
    codecContext->max_b_frames = 1;
    codecContext->codec_type = AVMEDIA_TYPE_VIDEO;
    codecContext->pix_fmt = AV_PIX_FMT_YUV420P;

    if (codec->id == AV_CODEC_ID_H264)
        av_opt_set(codecContext->priv_data, "profile", "baseline", 0);

    /* open it */
    int ret = avcodec_open2(codecContext, codec, nullptr);
    if (ret < 0) {
        char eb[AV_ERROR_MAX_STRING_SIZE];
        fprintf(stderr, "Could not open codec: %s\n", av_make_error_string(eb, AV_ERROR_MAX_STRING_SIZE, ret));
        exit(1);
    }


  


  Does anyone know what I'm doing wrong ?

  


• avcodec_open2 returns Invalid Argument (errnum -22)

  7 avril 2023, par nokla

  I am trying to encode a vector of AVFrames to an MP4 file using the h264 codec.

  


  Everything seems to work fine until the avcodec_open2 function, which returns an "Invalid Argument" (-22) error.

  


  *The stream parameter is a pointer to AVStream.

  


  Here is the code that sets the stream parameters :

  


      stream->codecpar->codec_id = AV_CODEC_ID_H264;
    stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
    stream->codecpar->width = settings.resolution[0]; // 270
    stream->codecpar->height = settings.resolution[1]; // 480
    stream->codecpar->format = AV_PIX_FMT_YUV420P;
    stream->codecpar->bit_rate = 400000;
    AVRational framerate = { 1, 30};
    stream->time_base = av_inv_q(framerate);


  


  And here is the code that opens the codec context :

  


      // Open the codec context
    AVCodecContext* codec_ctx = avcodec_alloc_context3(codec);
    if (!codec_ctx) {
        std::cout << "Error allocating codec context" << std::endl;
        avformat_free_context(format_ctx);
        return;
    }

    ret = avcodec_parameters_to_context(codec_ctx, stream->codecpar);
    if (ret < 0) {
        std::cout << "Error setting codec context parameters: " << av_err2str(ret) << std::endl;
        avcodec_free_context(&codec_ctx);
        avformat_free_context(format_ctx);
        return;
    }

    ret = avcodec_open2(codec_ctx, codec, nullptr);
    if (ret < 0) {
        wxMessageBox("Error opening codec: ");
        wxMessageBox(av_err2str(ret));
        avcodec_free_context(&codec_ctx);
        avformat_free_context(format_ctx);
        return;
    }


  


  I tried the solution that @philipp suggested in ffmpeg-avcodec-open2-returns-invalid-argument but it didn't resolve my error.

  


  I don't know what's causing this error in my code, can someone please help me ?