Waves Audio IDR360 Bit Re-Quantizer User Guide

IDR360° Bit Requantizer

Software Audio Processor

User’s Guide

Waves L360° software guide page 1 of 4

IDR – Increased Digital Resolution

IDR stands for Increased Digital Resolution. This technology, developed by
Waves and the late Michael Gerzon, incorporates Dithering and Noise Shaping
to make optimal bit depth re-quantization happen with minimal loss of audio
information. In fact, if you are taking a 24-bit source down to 16 bits, you will get
perceived audio resolution equal to a 19-bit word length.

IDR technology has been incorporated into the Waves L1 and L2
Ultramaximizers. In those cases where CD audio mastering (16-bit at 44.1kHz)
was a definite goal, the incorporation of IDR into the Peak Limiter was obvious
because, in most cases, the process would need to go down to 16-bit. In
Surround we believe that a 24-bit master is the common format but we provided
this multichannel version of IDR for special cases where bit depth reduction is
still required.

Dither

The Dither generates low-level random noise and forces quantization error to
become part of the dither noise rather than add program-correlated noise
distortion. The dither will appear in the last two bits of the audio sample, or the
least significant bits. Hence, the noise generated will be apparent only at the
lowest 12dB of the signal’s dynamic range. In a 16-bit file this is between 96 and
84dBfs.

Noise Shaping

Noise shaping makes the dither and quantization noise even less audible by
shaping the noise so that it is lower in the most audible frequency ranges and
higher in the less audible frequency ranges.

The following pictures illustrate the effect of noise shaping on pure dither.
Dither without noise shaping

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