libav decoding frames

#include <iostream>
#include <stdexcept>

extern "C" {
#include <libavcodec/avcodec.h>    // required headers
#include <libavformat/avformat.h>
}
#ifndef AV_ERROR_MAX_STRING_SIZE
#define AV_ERROR_MAX_STRING_SIZE 256
#endif

#define checkResult(condition, message) if(! (condition) ) { \
    char errorString[AV_ERROR_MAX_STRING_SIZE]; \
    av_strerror(result, errorString, AV_ERROR_MAX_STRING_SIZE ); \
    cerr << message << ": " << errorString << endl; \
    throw std::runtime_error(string(message) + ": " + errorString) ;\
  }

#include <map>
#include <vector>
#include <sstream>
#include <chrono>
#include <iomanip>

using namespace std;
int main( int argc, char **argv )
{
  av_register_all();
  AVFormatContext *pFormatCtx = 0;

  if( argc < 2 )
  {
    cerr << "Usage: " << argv[0] << " filename" << endl;
    return 1;
  }

  int result = avformat_open_input( &pFormatCtx, argv[1], NULL, NULL );
  checkResult( result == 0, "Error opening file" );
  result = avformat_find_stream_info( pFormatCtx, NULL );
  checkResult( result >= 0, "Error finding infos" );

  AVPacket pkt;
  auto start = chrono::steady_clock::now();
  auto startPkt = start;
  cerr << "Media duration: " << pFormatCtx->duration << endl;
  int64_t mediaDurationSeconds = pFormatCtx->duration / AV_TIME_BASE;
  int64_t lastPts;
  while( av_read_frame( pFormatCtx, &pkt ) >= 0) {
    auto now = chrono::steady_clock::now();
    if(now - startPkt > chrono::milliseconds(700)) {
      auto time_base = pFormatCtx->streams[pkt.stream_index]->time_base;
      int64_t packetTime = pkt.pts * time_base.num / time_base.den;
      double percent = packetTime * 100.0 / mediaDurationSeconds;
      cerr << "Current percent: " << percent << "%" << endl;
      startPkt = now;
    }
   av_free_packet(&pkt);
  }
  auto elapsed = chrono::steady_clock::now() - start;
  cerr << "Finished\n" << "elapsed: " << chrono::duration_cast<chrono::seconds>(elapsed).count() << " seconds; last pts: " << lastPts << endl;
  return 0;
}