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PD NAD

Decoder Source: no longer available (try http://www.glop.org/nad)
Version: 0.93 and 0.94pb3 © 1998 The House of Axe
Price: free
Settings: Mapping Mode 2; Output system: .wav file
Similar products: NAD's author apparently went to work for Sonique.
Verdict: Fair
VBR: None
Full file: Rarely
Major Flaws: Can't handle VBR files
Minor Flaws: Errors above 15kHz; clips end off most files
Output level: correct
1-bit relative accuracy: Excellent
1-bit absolute accuracy: Excellent

I receive more email about NAD than any other subject! NAD is an mp3 player, which can also decode mp3 files to wav files by setting the output to .wav file (see screenshots for more details). NAD is no longer being developed: Version 0.94pb3, released in May 1998, is the latest and last. However, it claims to give superior decoding performance, using 110bit accurate arithmetic. I have been asked to test it numerous times, so here are the results.

NAD cannot cope with VBR files. At best, it adds strange sounds to them; at worst, it gives up decoding or crashes. If it is closed (or crashes) whilst in .wav output mode, it cannot be restarted. (Edit the nad.ini file and set AudioOutputSystem=0 to remedy this before re-starting).

NAD offers several Mapping modes to "deal with the slightly different ways various encoders store high frequency information." All gave the same (incorrect) result with a CEP FhG 128kbps encoded file. Mode 2 gave a different result from the other modes with an mp3 producer pro 256kbps encoded file, but the decode still contained high-frequency errors. This was verified using NAD versions 0.94pb3 and 0.93. The high frequency errors cannot be corrected by changing the mapping mode.

The high frequency errors in NAD decoded mp3s take the form of extra high frequency components (i.e. it adds sound, rather than taking it away!). These errors are occasional (1 or 2 every couple of seconds). Sometimes, the high frequency part of a sound is repeated (echoed), as shown in the following plots.

l3dec correctly decodes the click at the end of this tone sweep
correct decode by l3dec

NAD adds an echo after the click at the end of this tone sweep
extra high-frequency click added by NAD

Sometimes, selected high frequency components are amplified for one instant. The following plot contrasts the spectrum of a burst of noise as decoded by l3dec compared with the same noise decoded by NAD.

spectrum of noise burst as decoded by l3dec and NAD (animated gif)
Animation contrasting frequency spectrum of noise burst, as decoded by l3dec (correct) and NAD (high frequencies amplified)

In Conclusion, NAD does not live up to it's reputation. Though low level accuracy is excellent (as good as the best, but not measurably better), the player cannot handle VBR files, and adds high frequency errors to many files. Not recommended.

EXTRA NOTES:

  1. The splash screen to version 0.93 (not shown here) says 0.92. However, the about box correctly identifies the software as version 0.93.
  2. Since this review was written, version 1.0 has appeared on the web. It still has the same decoding problems as version 0.94pb3 (tested here).

    Screenshots

    NAD 0.94 splash screen
    NAD 0.94 splash screen

    NAD 0.94pb3 in use
    NAD 0.94pb3 in use

    Selecting the .wav output
    Selecting the .wav output

    About NAD 0.94pb3
    About NAD 0.94pb3

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    Essential Tests: [ Full Decode ] . [ VBR compatibility ] . [ 8191+ / 100Hz bug ] . [ Objective sound quality ] . [ 16-bit accuracy ]

    Optional Features: [ 24-bit accuracy ] . [ ID3v2 compatibility ] . [ Corrupt file recovery ] . [ Free Format compatibility ]

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    Copyright 2000 David J M Robinson. All Rights reserved. You may not re-publish any information or content from this site without the authors' express permission.