LossyWAV
lossyFLAC is a lossy pre-processor for audio. It reduces bit depth of the input signal, which, when used in conjunction with certain lossless codecs, reduces the bitrate significantly compared to unpreprocessed compression. lossyWAV's primary goal is too maintain transparency with a high degree of confidence when encoding any audio data.
History
lossyFLAC was an experiment started by 2Bdecided with the aim of transparently reducing audio bit depth (making some lower bits zero), thereby taking advantage of FLAC's detection of consistently zeroed lower sample bits within each single frame, increasing coding efficiency.[1]
Nick.C ported the original MATLAB implementation to Delphi, and has since heavily developed and built upon the original methods of lossyWAV. Fine tuning has been performed with the help of halb27.
lossyWAV processed files are usually named with a double filename extension, to make them instantly identifiable. e.g. ".lossy.flac" would indicate an audio file which was processed using lossyWAV, and subsequently encoded using FLAC.[2]
Presets
- -1: Disc space-saving alternative to lossless archiving for large audio collections.
- -2: General usage; a compromise between -1 and -3.
- -3: High quality preset for usage on a FLAC or wavPack enabled DAP.[3]
Known supported codecs and optimal settings
| Codec | lossyWAV parameters | Encoder parameters |
|---|---|---|
| FLAC | -b 512 | |
| TAK | ||
| WavPack | ||
| WMA Lossless | -wmalsl (equiv. to -cbs 2048) |
Known unsupported codecs
lossyWAV application settings
lossyWAV beta v0.5.1 : WAV file bit depth reduction method by 2Bdecided.
Delphi implementation by Nick.C from a Matlab script, www.hydrogenaudio.org
Usage : lossyWAV <input wav file> <options>
Example : lossyWAV musicfile.wav
Quality Options:
-1 extreme quality [4xFFT] (-cbs 512 -nts -2.0 -skew 36 -snr 21
-spf 22224-22225-11235-11246-12358 -fft 11011)
-2 default quality [3xFFT] (-cbs 512 -nts +1.5 -skew 36 -snr 21
-spf 22224-22235-22346-12347-12358 -fft 10101)
-3 compact quality [2xFFT] (-cbs 512 -nts +6.0 -skew 36 -snr 21
-spf 22235-22236-22347-22358-2246C -fft 10001)
-o <folder> destination folder for the output file
-nts <n> set noise_threshold_shift to n dB (-18.0dB<=n<=+6.0dB)
(-ve values reduce bits to remove, +ve values increase)
-force forcibly over-write output file if it exists; default=off
Codec Options:
-wmalsl optimise internal settings for WMA Lossless codec; default=off
Advanced / System Options:
-snr <n> set minimum average signal to added noise ratio to n dB;
(0.0dB<=n<=48.0dB) Increasing value reduces bits to remove.
-skew <n> skew fft analysis results by n dB (0.0db<=n<=48.0db) in the
frequency range 20Hz to 3.45kHz
-cbs <n> set codec block size to n samples (512<=n<=4608, n mod 32=0)
-fft <5xbin> select fft lengths to use in analysis, using binary switching,
from 64, 128, 256, 512 & 1024 samples, e.g. 01001 = 128,1024
-overlap enable conservative fft overlap method; default=off
-spf <5x5hex> manually input the 5 spreading functions as 5 x 5 characters;
These correspond to FFTs of 64, 128, 256, 512 & 1024 samples;
e.g. 22235-22236-22347-22358-2246C (Characters must be one of
1 to 9 and A to F (zero excluded).
-allowable select allowable number of clipping samples per codec block
before iterative clipping reduction; (0<=n<=64, default=0).
-window select windowing function n (0<=n<=6, default=0); 0=Hanning
1=Bartlett-Hann; 2=Blackman; 3=Nuttall; 4=Blackman-Harris;
5=Blackman-Nuttall; 6=Flat-Top.
-clipping disable clipping prevention by iteration; default=off
-dither dither output using triangular dither; default=off
-quiet significantly reduce screen output
-nowarn suppress lossyWAV warnings
-detail enable detailled output mode
-below set process priority to below normal.
-low set process priority to low.
Special thanks:
David Robinson for the method itself and motivation to implement it in Delphi.
Dr. Jean Debord for the use of TPMAT036 uFFT & uTypes units for FFT analysis.
Halb27 @ www.hydrogenaudio.org for donation and maintenance of the wavIO unit.
Frequently asked questions
- Question: Is it VBR?
- Short answer: Yes.
- Question: Is it transparent?
- Short answer: Almost certainly.
- Question: Is it lossless?
- Short answer: No.
- Question: Why should I use this?
- Short answer: High quality, extremely low chance of audible artefacts, reasonable bitrates.