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• Access violation reading location when opening avfromat_open_input

  28 mai 2023, par nokla

  I am trying to build a function for reading a video from .mp4 file using ffmpeg and c++.

  


  This function was already working on one computer but when I copied the code to another one, with the same environment it returned the following error :

  


  Exception thrown at 0x00007FFC81B7667C (avutil-57.dll)
in VideoEditor.exe: 0xC0000005: Access violation 
reading location 0x0000000000000000.


  


  If anyone has ever encountered such an issue or have any idea how to solve it please share.

  


  ---

  


  This is the function :

  


  void VideoSource::ReadSource()
{
    auto lock = this->LockSource();
    std::vector> newSource;

    // Open the file using libavformat
    AVFormatContext* av_format_ctx = avformat_alloc_context();
    if (!av_format_ctx) {
        //wxMessageBox("Couldn't create AVFormatContext\n");
        read = false;
        return;
    }
    if (avformat_open_input(&av_format_ctx, path.c_str(), NULL, NULL) != 0) { // error here
        //wxMessageBox("Couldn't open video file\n");
        read = false;
        return;
    }

    // Find the first valid video stream inside the file
    int video_stream_index = -1;
    AVCodecParameters* av_codec_params = NULL;
    const AVCodec* av_codec = NULL;
    for (uint i = 0; i < av_format_ctx->nb_streams; i)
    {
        av_codec_params = av_format_ctx->streams[i]->codecpar;
        av_codec = avcodec_find_decoder(av_codec_params->codec_id);

        if (!av_codec) {
            continue;
        }
        if (av_codec_params->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_index = i;
            break;
        }
    }

    if (video_stream_index == -1) {
        //wxMessageBox("Couldn't find valid video stream inside file\n");
        read = false;
        return;
    }

    // Set up a codec context for the decoder
    AVCodecContext* av_codec_ctx = avcodec_alloc_context3(av_codec);
    if (!av_codec_ctx) {
        //wxMessageBox("Couldn't create AVCpdecContext\n");
        read = false;
        return;
    }

    if (avcodec_parameters_to_context(av_codec_ctx, av_codec_params) < 0)
    {
        //wxMessageBox("Couldn't initialize AVCodecContext\n");
        read = false;
        return;
    }
    if (avcodec_open2(av_codec_ctx, av_codec, NULL) < 0) {
        //wxMessageBox("Couldn't open codec\n");

        read = false;
        return;
    }

    AVFrame* av_frame = av_frame_alloc();
    if (!av_frame) {
        //wxMessageBox("Couldn't allocate AVFrame\n");

        read = false;
        return;
    }
    AVPacket* av_packet = av_packet_alloc();
    if (!av_packet) {
        //wxMessageBox("Couldn't allocate AVPacket\n");

        read = false;
        return;
    }
    int response;
    int counter = 0;
    while (av_read_frame(av_format_ctx, av_packet) >= 0 && counter < 100000) {
        if (av_packet->stream_index != video_stream_index) {
            av_packet_unref(av_packet);
            continue;
        }
        response = avcodec_send_packet(av_codec_ctx, av_packet);
        if (response < 0) {
            //wxMessageBox("Failed to decode packet: %s\n", av_err2str(response));

            read = false;
            return;
        }
        response = avcodec_receive_frame(av_codec_ctx, av_frame);
        if (response == AVERROR(EAGAIN) || response == AVERROR_EOF) {
            av_packet_unref(av_packet);
            continue;
        }
        else if (response < 0) {
            //wxMessageBox("Failed to decode frame: %s\n", av_err2str(response));

            read = false;
            return;
        }
        counter++;
        av_packet_unref(av_packet);

        av_packet = av_packet_alloc();

        response = avcodec_send_frame(av_codec_ctx, av_frame);
        std::string tmp = av_err2str(response);
        //source.push_back(*av_frame);
        //auto mat_frame = Avframe2Cvmat(av_frame);

        //source.push_back(im);
        //bool isEqual = (cv::sum(Avframe2Cvmat(av_frame) != Avframe2Cvmat(&source[0])) == cv::Scalar(0, 0, 0, 0));
        //bool isEqual = (cv::sum(im != source[0]) == cv::Scalar(0, 0, 0, 0));
        //im.release();
        newSource.push_back(SyncObject(av_frame_clone(av_frame)));

        /*
        if (int iRet = av_frame_copy(&source.back(), av_frame) == 0) {
            av_log(NULL, AV_LOG_INFO, "Ok");
        }
        else {
            av_log(NULL, AV_LOG_INFO, "Error: %s\n", av_err2str(iRet));
        }*/
        av_frame_unref(av_frame);
    }


    avformat_close_input(&av_format_ctx);
    avformat_free_context(av_format_ctx);
    av_frame_free(&av_frame);
    av_packet_free(&av_packet);
    avcodec_free_context(&av_codec_ctx);
    //this->LockSource();
    source_.swap(newSource);
}


  


  This function is inside A class and those are its memebers :

  


      bool created;
    bool read;
    std::string path; // THE PATH TO THE FILE
    std::vector> source_; // vector containing all of the video frames


  


  

  


  This is what I get in the debugger when the error accures :

  


  [![Debugger values][1]][1]


  


• fftools/ffmpeg : move opening decoders to a new file

  11 avril 2023, par Anton Khirnov

  fftools/ffmpeg : move opening decoders to a new file
  All decoding code will be moved to this file in the future.
  

  • [DH] fftools/Makefile
  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg.h
  • [DH] fftools/ffmpeg_dec.c

• Why opening multiple ffmpeg.exe causes IIS stuck ?

  24 mars 2023, par Wen

  I've been working on this project for several months, trying to convert RTSP streams to JPEG images and send them back to the client. I'm using C# ProcessStartInfo and multipart/x-mixed-replace to achieve this goal. It worked well for only one camera. Unfortunately, I found that the IIS would deadlock after opening too many RTSP streams or maybe ffmepg.exe. After that, I must restart IIS, or the program cannot execute. I've been searching for the answer for more than three weeks. Here is part of my code :

  


  public HttpResponseMessage GetVideo(int id){
      HttpResponseMessage response = Request.CreateResponse();
      var pushStreamContent = new PushStreamContent((stream, content, context) =>{
          this.stream = stream;
          FrameReader();
       });

       pushStreamContent.Headers.ContentType =      
       **System.Net.Http.Headers.MediaTypeHeaderValue.Parse("multipart/x-mixed-replace");**
       response.Content = pushStreamContent;
       return response;
   }



public async Task FrameReader(){
     ProcessStartInfo startInfo = new ProcessStartInfo{
                      StandardErrorEncoding = Encoding.UTF8,
                      FileName = ffmpegPath,
                      **Arguments = $"-rtsp_transport tcp -timeout 1000000 -i {rtsp_url} -f image2pipe -"**,
                      UseShellExecute = false,
                      CreateNoWindow = true
     };

using (var ffmpegProcess = new Process { StartInfo = startInfo }){
                    ffmpegProcess.Start();
                    ffmpegProcess.BeginErrorReadLine();

  //Here is a portion related to image processing
 }

}


  


  Really need some advices, thank you in advance !!!