How parse and decode H264 file with libav/ffmpeg?

Question

According to official documentations I try decode my test.mp4 with AV_CODEC_ID_H264.

Of course I can do this with av_read_frame(), but how do it with av_parser_parse2()?

The problem occurs at avcodec_send_packet(...) at decode_nal_units(...) at ff_h2645_packet_split(...) [h264dec.c]

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

//#define INBUF_SIZE 4096
#define INBUF_SIZE 256000

void decode(AVCodecContext* dec_ctx, AVFrame* frame, AVPacket* pkt, const char* filename);

int main(int argc, char** argv)
{
    const char* filename;
    const AVCodec* codec;
    AVFormatContext* formatCtx = NULL;
    AVCodecParserContext* parser;
    AVCodecContext* c = NULL;
    AVStream* videoStream = NULL;
    FILE* f;
    AVFrame* frame;
    uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
    uint8_t* data;
    size_t   data_size;
    int ret;
    AVPacket* pkt;

    filename = "D:\\test.mp4";

    //if (avformat_open_input(&formatCtx, filename, nullptr, nullptr) < 0) {
    //    throw std::exception("Could not open source file");
    //}

    //if (avformat_find_stream_info(formatCtx, nullptr) < 0) {
    //    throw std::exception("Could not find stream information");
    //}

    //videoStream = formatCtx->streams[0];



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

    /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
    memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);

    /* find the MPEG-1 video decoder */
    //codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO);
    codec = avcodec_find_decoder(AV_CODEC_ID_H264);
    if (!codec) {
        fprintf(stderr, "Codec not found\n");
        exit(1);
    }

    parser = av_parser_init(codec->id);
    if (!parser) {
        fprintf(stderr, "parser not found\n");
        exit(1);
    }

    parser->flags = PARSER_FLAG_COMPLETE_FRAMES;

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

    /* For some codecs, such as msmpeg4 and mpeg4, width and height
       MUST be initialized there because this information is not
       available in the bitstream. */

    //avcodec_parameters_to_context(c, videoStream->codecpar);

       /* open it */
    if (avcodec_open2(c, codec, NULL) < 0) {
        fprintf(stderr, "Could not open codec\n");
        exit(1);
    }

    f = fopen(filename, "rb");
    if (!f) {
        fprintf(stderr, "Could not open %s\n", filename);
        exit(1);
    }

    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }

    // ---- Use parser to get packets ----
    while (!feof(f)) {
        /* read raw data from the input file */
        data_size = fread(inbuf, 1, INBUF_SIZE, f);
        if (!data_size)
            break;

        /* use the parser to split the data into frames */
        data = inbuf;
        while (data_size > 0) {
            ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size, data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
            if (ret < 0) {
                fprintf(stderr, "Error while parsing\n");
                exit(1);
            }
            data += ret;
            data_size -= ret;

            if (pkt->size)
                decode(c, frame, pkt, outfilename);
        }
    }

    // ---- Use FormatContext to get packets ----
    //  while (av_read_frame(fmt_ctx, pkt) == 0)
    //  {
    //      if (pkt->stream_index == AVMEDIA_TYPE_VIDEO) {
    //          if (pkt->size > 0)
    //              decode(cdc_ctx, frame, pkt, fp_out);
    //      }
    //  }

    /* flush the decoder */
    decode(c, frame, NULL, outfilename);

    fclose(f);

    av_parser_close(parser);
    avcodec_free_context(&c);
    av_frame_free(&frame);
    av_packet_free(&pkt);

    return 0;
}

void decode(AVCodecContext* dec_ctx, AVFrame* frame, AVPacket* pkt, const char* filename)
{
    char buf[1024];
    int ret;

    ret = avcodec_send_packet(dec_ctx, pkt);
    if (ret < 0) {
        char buff[255]{ 0 };
        std::string strError = av_make_error_string(buff, 255, ret);
        fprintf(stderr, "Error sending a packet for decoding\n");
        exit(1);
    }

    while (ret >= 0) {
        ret = avcodec_receive_frame(dec_ctx, frame);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
            return;
        else if (ret < 0) {
            fprintf(stderr, "Error during decoding\n");
            exit(1);
        }

        printf("saving frame %3d\n", dec_ctx->frame_number);
        fflush(stdout);
        /* the picture is allocated by the decoder. no need to
           free it */
        // handle frame ...
    }
}