minimal-ffmpeg.cpp

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

#include <cassert>
#include <iostream>
void check(int ret)
{
  if (ret < 0 && ret != AVERROR_EOF)
  {
    char err[100]{0};
    av_make_error_string(err, 100, ret);
    std::cerr << ret << ": " << err << "\n";
  }
}

int main() {
  const char *filename = "04 - Rat King.flac";

  int ret{};

  av_register_all();
  avcodec_register_all();

  AVFormatContext *fmt_ctx{};
  ret = avformat_open_input(&fmt_ctx, filename, nullptr, nullptr);
  check(ret);
  assert(fmt_ctx);

  ret = avformat_find_stream_info(fmt_ctx, nullptr);
  check(ret);

  AVStream *stream{};
  for (std::size_t i = 0; i < fmt_ctx->nb_streams; i++) {
    if (fmt_ctx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
      stream = fmt_ctx->streams[i];
      break;
    }
  }
  assert(stream);

  auto codec = avcodec_find_decoder(stream->codecpar->codec_id);
  assert(codec);

  auto codec_ctx = avcodec_alloc_context3(codec);
  assert(codec_ctx);

  ret = avcodec_parameters_to_context(codec_ctx, stream->codecpar);
  check(ret);

  ret = avcodec_open2(codec_ctx, codec, nullptr);
  check(ret);

  AVPacket packet;
  AVFrame* frame = av_frame_alloc();
  assert(frame);

  ret = av_read_frame(fmt_ctx, &packet);
  check(ret);
  ret = avcodec_send_packet(codec_ctx, &packet);
  check(ret);
  ret = avcodec_receive_frame(codec_ctx, frame);
  check(ret);
}