ExtractBitrates.cpp

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#include "ExtractBitrates.h"
#include <string>
#include <sstream>
#include <cassert>
#include <limits>
#include <map>

namespace
{
  /// Maintains a sum and a sample-count for calculating averages
  class Tally
  {
    public:

      /// Contructs a new zeroed tally
      Tally( ): m_sum( 0.0 ), m_numSlices( 0 ) { }

      /// Adds to the sum and increments the sample-count
      void add( double in ) { ++m_numSlices; m_sum += in; }

      /// \return The calculated average
      double average( ) const { return m_sum / ( double )m_numSlices; }

    private:
      double m_sum;
      unsigned long m_numSlices;
  };

  /// Ignores all of the the characters up to and including a given character
  /// \param line The line being read from
  /// \param iLine The active input stream
  /// \param character The character to ignore up to
  /// \throw POCParseException if the stream goes bad before character is encountered or just after character is encountered
  void ignoreUpTo( const std::string& line, std::istream& iLine, char character )
  {
    while( iLine.good( ) && character != iLine.get( ) )
      ;
    if( !iLine.good( ) )
    {
      throw POCParseException( line );
    }
  }

  /// Extracts the average bitrates for each of the temporal layers from the given log
  /// \param i The input stream that represents the log
  /// \return A map that countains the average bitrates for each temporal layer.  Each pair contains the QP value in first and the average bitrate in second.
  /// \throw POCParseException if an error occured while parsing a POC line
  std::map< unsigned char, double > extractBitratesForQPs( std::istream& i )
  {
    std::map< unsigned char, Tally > tallyMap;

    while( i.good( ) )
    {
      // Initialize variables for this line
      std::string line;
      std::getline( i, line );
      std::istringstream iLine( line );
      if( !iLine.good( ) )
      {
        continue;
      }

      // Ignore the "POC"
      if( iLine.get( ) != 'P' )
      {
        continue;
      }
      if( !iLine.good( ) )
      {
        continue;
      }
      if( iLine.get( ) != 'O' )
      {
        continue;
      }
      if( !iLine.good( ) )
      {
        continue;
      }
      if( iLine.get( ) != 'C' )
      {
        continue;
      }
      if( !iLine.good( ) )
      {
        throw POCParseException( line );
      }

      ignoreUpTo( line, iLine, '(' );

      if( iLine.get( ) != ' ' )
      {
        throw POCParseException( line );
      }
      if( !iLine.good( ) )
      {
        throw POCParseException( line );
      }

      if( 'I' == iLine.get( ) )
      {
        continue;
      }
      if( !iLine.good( ) )
      {
        throw POCParseException( line );
      }

      ignoreUpTo( line, iLine, ' ' );
      ignoreUpTo( line, iLine, ' ' );

      // Parse the qpIndex
      long qpIndexLong;
      iLine >> qpIndexLong;
      if( ( long )std::numeric_limits< unsigned char >::max( ) < qpIndexLong )
      {
        throw POCParseException( line );
      }
      unsigned char qpIndex( ( unsigned char )qpIndexLong );
      if( !iLine.good( ) )
      {
        throw POCParseException( line );
      }

      ignoreUpTo( line, iLine, ')' );
      ignoreUpTo( line, iLine, ' ' );

      // Parse the number of bits
      unsigned long bitsULong;
      iLine >> bitsULong;
      if( !iLine.good( ) )
      {
        throw POCParseException( line );
      }

      // Find the tally that corresponds to our QP.  If there is no such tally yet, then add a new one to the map.
      std::map< unsigned char, Tally >::iterator iter( tallyMap.find( qpIndex ) );
      if( tallyMap.end( ) == iter )
      {
        tallyMap[ qpIndex ] = Tally( );
        iter = tallyMap.find( qpIndex );
      }
      assert( iter != tallyMap.end( ) );

      iter->second.add( ( double )bitsULong );
    }

    // Populate and return the result based on all of the tallies
    std::map< unsigned char, double > result;
    for( std::map< unsigned char, Tally >::const_iterator iter( tallyMap.begin( ) ); iter != tallyMap.end( ); ++iter )
    {
      result[ iter->first ] = iter->second.average( );
    }
    return result;
  }
}

std::vector< double > extractBitratesForTemporalLayers( std::istream& i )
{
  std::vector< double > result;

  std::map< unsigned char, double > bitratesForQPsMap( extractBitratesForQPs( i ) );
  if( !bitratesForQPsMap.empty( ) )
  {
    unsigned char expectedNextQPIndex( bitratesForQPsMap.begin( )->first );

    for( std::map< unsigned char, double >::const_iterator i( bitratesForQPsMap.begin( ) ); i != bitratesForQPsMap.end( ); ++i )
    {
      if( i->first != expectedNextQPIndex )
      {
        throw NonContiguousQPSetException( );
      }
      ++expectedNextQPIndex;
      result.push_back( i->second );
    }
  }

  return result;
}