Method and device for processing internal channels for low complexity format conversion

An apparatus for processing an audio signal, the apparatus comprising:

• a receiver configured to receive a channel pair element that is encoded by using an MPEG surround 212 (MPS212);
• an internal channel processor configured to calculate an internal channel gain with respect to the received channel pair element based on MPS212 parameters and rendering parameters including equalizer (EQ) gain values and gain values, and to generate an internal channel signal based on the received channel pair element and the calculated internal channel gain;
• and
• a stereo output signal generator configured to generate stereo output channel signals based on the generated internal channel signal,
• wherein the internal channel gain GICHl,m calculated by using
• G
• ICH
• l
• ,
• m
• =
• (
• c
• left
• l
• ,
• m
• ×
• G
• left
• ×
• G
• EQ
• ,
• left
• m
• )
• 2
• +
• (
• c
• right
• l
• ,
• m
• ×
• G
• right
• ×
• G
• EQ
• ,
• right
• m
• )
• 2
• where l denotes a time slot index and m denotes a frequency band index,
• cleftl,m and crightl,m are channel level difference (CLD) values for the CPE,
• Gleft and Gright are the gain values defined in a format converter according to the MPS212 output channels, and
• GEQ,leftm and GEQ,rightm are the equalizer (EQ) gain values defined in the format converter according to the MPS212 output channels.