Based on frequency domain techniques, coding of high quality digital audio with bit rates of down to 64 kbit/sec. is possible. The NMR (Noise-to-Mask Ratio) has been introduced for quality evaluation and optimization for low bit rate coding schemes. Real time implementations of low bit rate codecs and a measurement system have been developed. Several coding schemes (Optimum Coding in the Frequency domain (OCF), Low-Complexity Adaptive Transform Coding (LCATC), Sub-Band Coding (SBC)) are compared using NMR. Comparison results for different types of music and test signals are presented.
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.