REQ: Anaxwaves DDi Codec

DDi Codec is a precise digital emulation of the classic Dolby-B/C noise reduction system for analog audio tape. It is the world's first dedicated software for decoding or encoding Dolby-C formatted audio in digital domain, along with full backward compatibility with Dolby-B. Powered by the proprietary DSP engine, the decoding/encoding can be performed in realtime, which allows for instant processing, monitoring and fine-tuning.

Deeper optimal result can be achieved by using the fine-tuning tools that come with the software, as specified below:

Reference Vernier: the primary tool for calibrating Dolby Reference Level in a progressive and interactive manner. It supports either objective calibration (with Dolby Tone) or subjective estimation (trial-and-error without Dolby Tone).
Play Trim: originally developed by NAD and Dolby, this tool compensates for signal degradation with aged pre-recorded tapes.
Azimuth Correction: a limited-effect tool for remedying slight phase displacement and high-frequency loss caused by the azimuth error of the playback head.
Gap-Loss Compensation: A limited-effect tool for counteracting slight playback head wear.
EQ Converter: a utility for converting between IEC 120μs and 70μs EQ schemes, offering flexibility when the tape player/recorder lacks this option.
Ref. Tone Generator: offers 400Hz 0dB signal at Dolby Reference Level for easy calibration.

Each of these tools can operate independently of the Dolby-B/C codec, which can be used for refining the audio digitized from analog audio tapes, regardless of whether Dolby NR is involved.