NorQualizer V1.20 - 2013 - V.Portet
NorQualizer is a smart self-adaptative equalizer / normalizer which operates on multimedia files
for audio processing, in a way that they all sound as similar in terms of audio spectrum and volume level.
It is easily launched by a simple command line.
Especially useful for preparing audio CDs and audio MP3 libraries, NorQualizer prevent the listener
from having to do annoying equalization and volume ajustements each time that he plays a new audio track.
NorQualizer is not intended to be an audio FX generator but a true physiological normalizer which not
only adjusts the volume level. Its use is much faster than manual edition means that can be used for
equalizing and normalizing series of audio files.
Compilation can easily be made by launching:
gcc norqualizer.c -o norqualizer
The executable file "norqualizer" can then be moved, as well as the "norqualizall" shell script (made
executable) in /usr/local/bin/ or ~/bin/
* USE of norqualizer:
Common syntax is: norqualizer [input file] <options>
[input file] can be a multimedia or WAV file. However, if FFMPEG is not installed only WAV files will be
The supported options for versions higher or equal to 1.00 are:
-R : When present, this flag makes norqualizer encode / re-encode the final result to MP3.
Anyway at least a WAV file will be generated (to be prefered for audio CD burning).
-B : Reduces bass profile. To be used only for tracks having no bass line nor beats at all.
-F : Forces the loading of files waves where the format and data header were not identified correctly.
(In this case, assumes that the stream is at 44100 spl/s, stereo, big endian)
-V : Activates the click and pop discriminator in case where soundtracks have been extracted from vinyl records.
(In this case clicks and pops are not taken into account for normalization because they can be clamped.
Note that clips and pops are not removed. This is not the purpose of NorQualizer.)
NB: For MP3 re-encoding LAME must be installed.
* USE of the SHELL SCRIPT:
The simple shell script 'norqualizall' enable the user to "norqualize" all MP3 files located in the
Modifying simply this script could be a way to process other kind of multimedia files (see: TIPS).
Generally, when extracting audio from various other multimedia files (avi, mpg, flv, ogg...) before
processing and/or audio CD burning, prefer the use of temporary WAV files at 44100Hz, stereo.
Example with FFMPEG: ffmpeg -i my_multimedia_file -f wav -ar 44100 -ac 2 my_extracted_file.wav
Then launch: norqualizer my_extracted_file.wav -R
The less conversions are done, the better final quality will be. Therefore if the audio track has to
be extracted for example from an FLV file, directly convert FLV to WAV and then call norqualizer.
(This way of proceeding is what norqualizer does automatically if it is called with the source
multimedia file as input).
For the same reasons, when burning an audio CD use the "norqualized" WAV file instead of using the
MP3 one. (Else it will be discretely converted back to WAV-like format by the burning software).
* FAQ (Or: Possibly asked questions)
- Why do you suggest to use temporary WAV files at 44100Hz stereo, whatever is the source quality ?
This format will be anyway the final one used by the CD burner when writing audio tracks. Therefore
it is better to proceed to this conversion at the begining of the processing chain, even if the
source quality is quite poor. Furthermore norqualizer works at this sample rate anyway.
- My source file has volume level variations resulting from an annoying dynamic compression caused
by improper recording conditions. What can I do ?
Norqualizer cannot solve that kind of problem, and this will even disturb it when trying to
analyze the acoustic perception of the audio track.
You must first use "WAV audio compressor" ( http://sourceforge.net/projects/compressor/ ) called
with this parameters (re-compression with fast attack and decay time):
"compress my_extracted_file.wav 15 8 4" will return "Cmy_extracted_file.wav"
Then launch: norqualizer Cmy_extracted_file.wav
Note that anyway it will never be possible to recover the track as "hi-fi" in that case...
(It will sound quite like an FM radio recording)
- My source file has clipped audio signals which causes ugly crackling. What can I do ?
Unfortunately, you can do nothing.
- I processed a terribly trebbleless audio track. The result is better but trebbles sound bad,
metallic, or almost scratchy.
In case of drastically attenuated high frequencies (eg. low encoding bitrate in source file), it
will never be possible to recover them correctly, by any existing way.
- Can norqualizer be used to correct stereo asymetries ?
Yes, it does. Especially for recordings from cassette tapes where channels are often different in
terms of volume and bandwidth. It will not alter true stereo quality since it does not compress
and usual true stereo recordings are not based on bass/trebble discrimination.
- When I "norqualize" WAV files recorded from analog audio inputs, the "norqualized" file has no
more trebbles at all !
Probably you recorded from your analog source with improper parameter settings for your recording
software (eg. 32 bits format with a 16 bits input). This has resulted in a right-left swap on each
sample, causing a very high amplitude unaudible high frequency component in your soundtrack. Note
that anyway you must solve this problem to keep your amplifier and tweeters in good conditions,
whatever you use or not norqualizer. You can check for this in an audio editor (e.g. Audacity)
by zooming on a very small part of the track.
- Does norqualizer uses some psycho-acoustic well known theories, as used in MP3 algorythms ?
No. Norqualizer performs a time domain peak and quasi-peak analysis on 3 channels containing
prefiltered bands (Low, medium and high). Considering this levels monitored on the whole track,
it applies a correction factor for each channel before re-mixing. This level analysis principle
results from experience and observation and has not been justified by any theoretical work,
although the use of quasi-peak detection as one of the normalization criteria could be compared
to one of the well known perception phenomenons explained by theories of psycho-acoustics.
V.P. Paris, FR.
Version 1.2 of the 20th of December 2013