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• Revision 39882 : Si on n’a pas coloration code ... on affiche quand même quelque chose même ...

  17 août 2010, par kent1@… — Log

  Si on n’a pas coloration code ... on affiche quand même quelque chose même si c’est moche

• How to save video data in a vector using ffmpeg ? (C++)

  25 octobre 2022, par nokla

  I'm new to ffmpeg and I am trying to write a program for video editing.

  


  I want to import a video file and save it somehow in a vector so I could edit its frames later.
When I saved all the decoded AVFrames in a vector I saw it takes a lot of memory and that I need to find a better way to do so.

  


  The function I used for reading a video :

  


  ** the function is in a class that representing video, source type is std::vector<avframe></avframe>

  


  void VideoSource::ReadSource(std::string path)
{
    // Open the file using libavformat
    AVFormatContext* av_format_ctx = avformat_alloc_context();
    if (!av_format_ctx) {
        printf("Couldn't create AVFormatContext\n");
        return; 
    }
    if (avformat_open_input(&av_format_ctx, path.c_str(), NULL, NULL) != 0) {
        printf("Couldn't open video file\n");
        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 (int 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) {
        printf("Couldn't find valid video stream inside file\n");
        return;
    }

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

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

    AVFrame* av_frame = av_frame_alloc();
    if (!av_frame) {
        printf("Couldn't allocate AVFrame\n");
        return;
    }
    AVPacket* av_packet = av_packet_alloc();
    if (!av_packet) {
        printf("Couldn't allocate AVPacket\n");
        return;
    }
    int response;

    while (av_read_frame(av_format_ctx, av_packet) >= 0) {
        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) {
            printf("Failed to decode packet: %s\n", av_err2str(response));
            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) {
            printf("Failed to decode frame: %s\n", av_err2str(response));
            return;
        }
        av_packet_unref(av_packet);

        av_packet = av_packet_alloc();

        // response = avcodec_send_frame(av_codec_ctx, av_frame);

        source.push_back(*new AVFrame);
        source.back() = *av_frame_clone(av_frame);

        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);
}


  


  I thought maybe I should save it as a vector of encoded AVFrames or as a vector of encoded packet that contains some frames in it.

  


  When I tried to encode a single AVFrame, I added this line
response = avcodec_send_frame(av_codec_ctx, av_frame); before pushing the frame into the vector (You can see it marked as a comment in the code above).
  
It returned invalid argument (-22) and I am not sure why.

  


  Questions :

  


  

  1. Why did I get that error (-22) ?

  


  2. How to save an encoded packet with multiple AVFrame in it ?

  


  3. Is there a better way of working on a video that won't take as much memory ?

  


  


• When recording MP4 using ffmpeg suddenly power off

  2 décembre 2016, par wanglx

  Now I used C language and ffmpeg realize a multiplex real-time audio and video to MP4 files of the program and everything works fine, but when in the process of reuse of sudden power failure, the recording is MP4 file is damaged, VLC can not play this file.
  I think reason is no call to write the trailer function av_write_trailer , causing index and time stamp information lost, I use araxis merge tool compared the successful call av_write_trailer function of file and a no av_write_trailer to call the damaged files and found two different points :
  1. Damaged files in the file header box number value not right
  2. The damaged file no end of file.

  Now I want to repair after power on my program can automatically repair the damaged files, in Google did not find effective methods.
  my train of thought is in the normal recording process saves per second a damaged file is missing two information : box number and end of file, save it to a local file, when writing the MP4 file integrity delete this file after, if power off damaged, then in the next power, read the file and the corresponding information to write the damaged files corresponding position to. But now the problem is that I don’t know how to save the number of box and the end of the file, I this is feasible ? If possible, what should I do ? Looking forward to your reply !