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• How to save h264 frames as jpeg images using ffmpeg ?

  17 août 2020, par Matthew Czarnek

  I would like to save thumbnails from a h264 stream that I'm turning into ffmpeg avpackets as jpegs.

  


  I'm started with a h264 AVPacket (iframe) and decode it into an AVFrame using avcodec_send_packet/avcodec_receive_frame. Now trying to go from AVFrame and convert into AVPacket using avcodec_send_frame/avcodec_receive_packet

  


  I can convert to png instead jpg, though I do get a the video looking like it's outputting three separate frames squeezed side by side into one. Wondering if it's one frame is R, next G, and finally B. I'm not sure, clearly I'm doing something wrong there. I figured it's possible it's the png encoder and I don't need it, so let's get jpg working first. But jpg is outputting unopenable files.

  


  Any advice ?

  


  Here is my code :

  


  int output_thumbnails(AVPacket* video_packet)
{
    char png_file_name[max_chars_per_filename];
    char thumbnail_id_char[10];
    _itoa_s(thumbnail_id, thumbnail_id_char, 10);
    strcpy_s(png_file_name, max_chars_per_filename, time_stamped_filepath);
    strcat_s(png_file_name, max_chars_per_filename, time_stamped_filename);
    strcat_s(png_file_name, max_chars_per_filename, thumbnail_id_char);
    strcat_s(png_file_name, max_chars_per_filename, ".jpg");
    thumbnail_id++;

    int error_code = send_AVPacket_to_videocard(video_packet, av_codec_context_RTSP);

    //if (error_code == AVERROR_EOF)
    //{
    //  //  error_code = videocard_to_PNG(png_file_name, av_codec_context_RTSP, av_codec_RTSP);
    //}
    if (error_code == AVERROR(EAGAIN)) //send packets to videocard until function returns EAGAIN
    {
        error_code = videocard_to_PNG(png_file_name, av_codec_context_RTSP);

        //EAGAIN means that the video card buffer is ready to have the png pulled off of it
        if (error_code == AVERROR_EOF)
        {
            //  error_code = videocard_to_PNG(png_file_name, av_codec_context_RTSP, av_codec_RTSP);
        }
        else if (error_code == AVERROR(EAGAIN))
        {

        }
        else
        {
            deal_with_av_errors(error_code, __LINE__, __FILE__);
        }
    }
    else
    {
        deal_with_av_errors(error_code, __LINE__, __FILE__);
    }
    
    return 0;
}


  


  VideoThumbnailGenerator.h :
#include "VideoThumbnailGenerator.h"

  


  bool decoder_context_created = false;
bool encoder_context_created = false;

AVCodecContext* h264_decoder_codec_ctx;
AVCodecContext* thumbnail_encoder_codec_ctx;

int send_AVPacket_to_videocard(AVPacket* packet, AVCodecContext* codec_ctx)
{
    if(!decoder_context_created)
    {
        AVCodec* h264_codec = avcodec_find_decoder(codec_ctx->codec_id);
        h264_decoder_codec_ctx = avcodec_alloc_context3(h264_codec);

        h264_decoder_codec_ctx->width = codec_ctx->width;
        h264_decoder_codec_ctx->height = codec_ctx->height;
        h264_decoder_codec_ctx->pix_fmt = AV_PIX_FMT_RGB24;
        h264_decoder_codec_ctx->codec_type = AVMEDIA_TYPE_VIDEO;
        h264_decoder_codec_ctx->skip_frame = AVDISCARD_NONINTRA;//AVDISCARD_NONREF;//AVDISCARD_NONINTRA;
        
        h264_decoder_codec_ctx->time_base.num = 1;
        h264_decoder_codec_ctx->time_base.den = 30;

        h264_decoder_codec_ctx->extradata = codec_ctx->extradata;
        h264_decoder_codec_ctx->extradata_size = codec_ctx->extradata_size;
        
        int error_code = avcodec_open2(h264_decoder_codec_ctx, h264_codec, NULL);
        if (!h264_codec) {
            return -1;
        }

        if (error_code < 0)
        {
            return error_code;
        }
        decoder_context_created = true;
    }

    
    //use hardware decoding to decode video frame
    int error_code = avcodec_send_packet(h264_decoder_codec_ctx, packet);
    if(error_code == AVERROR(EAGAIN))
    {
        return AVERROR(EAGAIN);
    }
    if(error_code<0)
    {
        printf("Error: Could not send packet to video card");
        return error_code;
    }

    return 0;
}

int videocard_to_PNG(char *png_file_path, AVCodecContext* codec_ctx)
{
    if (!encoder_context_created)
    {
        //AVCodec* thumbnail_codec = avcodec_find_encoder(AV_CODEC_ID_PNG);
        AVCodec* thumbnail_codec = avcodec_find_encoder(AV_CODEC_ID_JPEG2000);
        thumbnail_encoder_codec_ctx = avcodec_alloc_context3(thumbnail_codec);

        thumbnail_encoder_codec_ctx->width = 128;
        thumbnail_encoder_codec_ctx->height = (int)(((float)codec_ctx->height/(float)codec_ctx->width) * 128);
        thumbnail_encoder_codec_ctx->pix_fmt = AV_PIX_FMT_RGB24; //AV_PIX_FMT_YUVJ420P
        thumbnail_encoder_codec_ctx->codec_type = AVMEDIA_TYPE_VIDEO;

        thumbnail_encoder_codec_ctx->time_base.num = 1;
        thumbnail_encoder_codec_ctx->time_base.den = 30;

        bool thread_check = thumbnail_encoder_codec_ctx->thread_type & FF_THREAD_FRAME;
        bool frame_threads_check = thumbnail_encoder_codec_ctx->codec->capabilities & AV_CODEC_CAP_FRAME_THREADS;
        
        int error_code = avcodec_open2(thumbnail_encoder_codec_ctx, thumbnail_codec, NULL);
        if (!thumbnail_codec) {
            return -1;
        }

        if (error_code < 0)
        {
            return error_code;
        }
        encoder_context_created = true;
    }
    
    AVFrame* thumbnail_frame = av_frame_alloc();
    AVPacket* thumbnail_packet = av_packet_alloc();
    //av_init_packet(png_packet);
    int error_code = avcodec_receive_frame(h264_decoder_codec_ctx, thumbnail_frame);

    //check for errors everytime
    //note EAGAIN errors won't get here since they won't get past while
    if (error_code < 0 && error_code != AVERROR(EAGAIN))
    {
        printf("Error: Could not get frame from video card");
        return error_code;
    }
    //empty buffer if there are any more frames to pull (there shouldn't be)
    //while(error_code != AVERROR(EAGAIN))
    //{
    //  //check for errors everytime
    //  //note EAGAIN errors won't get here since they won't get past while
    //  if (error_code < 0)
    //  {
    //      printf("Error: Could not get frame from video card");
    //      return error_code;
    //  }
    //  
    //  error_code = avcodec_receive_frame(h264_decoder_codec_ctx, png_frame);
    //}

    //now we convert back to AVPacket, this time one holding PNG info, so we can store to file
    error_code = avcodec_send_frame(thumbnail_encoder_codec_ctx, thumbnail_frame);

    if (error_code >= 0) {
        error_code = avcodec_receive_packet(thumbnail_encoder_codec_ctx, thumbnail_packet);

        FILE* out_PNG;

        errno_t err = fopen_s(&out_PNG, png_file_path, "wb");
        if (err == 0) {
            fwrite(thumbnail_packet->data, thumbnail_packet->size, 1, out_PNG);
        }
        fclose(out_PNG);

    }
    return error_code;
}


  


• Get Stream and save as jpeg file from IP Camera using ffmpeg

  10 novembre 2011, par mekici

  How i can get stream from Ip Camera, Its using RTP, stream is MPEG4, i have multicast address and port,and i have ip camera's IP address and Port Number. And I cant reach via http forexample (http://ip/jpeg) And I cant reach stream with VLC Player too. forexample (rtp ://ipadressofcam:port) and (rtp ://multicastaddress:port)
  So What is ffmpeg command of that ?
  I have windows OS, I only write code with C#, I dont know, c or c++.
  But producer created their own ocx which used for viewing cam,that plugin can work on .net but i dont want to use it becouse it doesnt have much funcionality, I mean you cant get current picture or snapshot of cams, thats why i have to do it myself i already asked before in that link
  Thanks

• Get Stream and save as jpeg (image) file from IP Camera using ffmpeg

  17 février 2014, par Mustafa Ekici

  How i can get stream from Ip Camera, Its using RTP, stream is MPEG4, i have multicast address and port,and i have ip camera's IP address and Port Number.
  And I cant reach via http forexample (http://ip/jpeg) And I cant reach stream with VLC Player too. forexample (rtp ://ipadressofcam:port) and (rtp ://multicastaddress:port)
  So What is ffmpeg command of that ?
  I have windows OS, I only write code with C# right now.
  But producer created their own ocx which used for viewing cam,that plugin can work on .net but i dont want to use it becouse it doesnt have much funcionality, I mean you cant get current picture or snapshot of cams, thats why i have to do it myself.