inconsistent loudness with OSBA and EXT output

Basic info

• Commit SHA: 7d2306a7
• Platform:

Bug description

When using EXT output from an OSBA bitstream, the output loudness depends on the bitrate. The low-BRs are scaled by 0.5 in the encoder, while this does not happen for the high bitrates. For other output modes, the scaling then happens in the decoder. This is missing for EXT output.

Ways to reproduce

./IVAS_cod -ism_sba 4 3 scripts/testv/stvISM1.csv scripts/testv/stvISM2.csv scripts/testv/stvISM3.csv scripts/testv/stvISM4.csv 256000 48 scripts/testv/stvOSBA_4ISM_3OA48c.wav bit_80

./IVAS_cod -ism_sba 4 3 scripts/testv/stvISM1.csv scripts/testv/stvISM2.csv scripts/testv/stvISM3.csv scripts/testv/stvISM4.csv 256000 48 scripts/testv/stvOSBA_4ISM_3OA48c.wav bit_256

./IVAS_dec EXT 48 bit_[80|256]_sba dec.wav