MPEG-4 AAC audio encoder is developed. AAC main and AAC low complexity object types, defined as part of main profile in general audio part of ISO/IEC 14496-3 (MPEG-4) standard, are implemented. Encoder targets high-quality, wideband, complex audio. Encoder was carefully designed to respect present accomplishments in audio coding (standardized in MPEG-4). At the same time, several implementation novelties were introduced. Encoder achieves 'perceptible but not annoying' 44.1 kHz audio quality at bit rate 64 kb/s/ch, while satisfying quality is accomplished at 48 kb/s/ch.