|Decoder Source:||no longer available (try http://www.glop.org/nad)|
|Version:||0.93 and 0.94pb3 © 1998 The House of Axe|
|Settings:||Mapping Mode 2; Output system: .wav file|
|Similar products:||NAD's author apparently went to work for Sonique.|
|Major Flaws:||Can't handle VBR files|
|Minor Flaws:||Errors above 15kHz; clips end off most files|
|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.
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.
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.
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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.