LossyWAV

2008-01-03T21:31:48Z

Halb27:

LossyWAV

2008-01-03T21:30:25Z

Halb27:

2008-01-03T20:14:47Z

Halb27: /* Presets */

{{title|lossyWAV}}
{{Codec Infobox
| name = lossyWAV
| logo =
| type = lossy
| purpose = lossy pre-processor
| maintainer = [http://www.hydrogenaudio.org/forums/index.php?showuser=42400 Nick.C]
| recommended_encoder = lossyWAV
| recommended_text = latest
| website = [http://www.hydrogenaudio.org/forums/index.php?showtopic=56129 Hydrogenaudio]
}}

lossyWAV 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 to maintain [[transparency]] with a high degree of confidence when processing any audio data.

==History==
lossyFLAC is an idea started by [http://www.hydrogenaudio.org/forums/index.php?showuser=409 2Bdecided], utilising the wasted bits feature of the FLAC lossless codec with the aim of transparently reducing audio bit depth (making some lower significant bits (LSB's) zero), consequently taking advantage of FLAC's detection of consistently zeroed lower significant bits within each single frame and significantly increasing coding efficiency.[http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=55522&view=findpost&p=498179]

Nick.C ported the original [[Wikipedia:MATLAB|MATLAB]] implementation to [[Wikipedia:Borland Delphi|Delphi]] (Many thanks [[Wikipedia:CodeGear|CodeGear]] for your free Turbo Explorer!!), and lossyFLAC proved itself to work with other lossless codecs, so the application name was changed to lossyWAV.

Since then, Nick.C has heavily developed and built upon lossyWAV, with valuable tuning performed by [http://www.hydrogenaudio.org/forums/index.php?showuser=25015 halb27].

==Naming==
lossyWAV-processed WAV files are named with a double filename extension, .lossy.wav, to make them instantly identifiable. e.g. ".lossy.flac" would indicate an audio file which was processed using lossyWAV, and subsequently encoded using FLAC.[http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=55522&view=findpost&p=498559]

Combinations of lossyWAV with each specific encoder are referred to as lossy'''X''', where '''X''' is an abbreviation of the lossless codec name. Combination names are listed in the "[[LossyWAV#Known supported codecs|known supported codecs]]" section below.

==File Identification==
From v0.5.9, lossyWAV inserts a variable length FACT chunk immediately after the FMT chunk. This takes the form:<pre>fact/<size>/lossyWAV beta vx.y.z : dd/mm/yyyy hh:mm:ss
-2 -cbs 512 -nts 0.00 -snr 21.00 -skew 36.00
-spf 22224-22235-22336-12347-12358 -fft 10101</pre>Where the version, date & time and user settings are copied. Additionally, if a lossyWAV FACT chunk is found in a file, the processing will be halted (exit code = 16) to prevent re-processing of an already processed file.

The -check parameter can be used to determine whether a file has previously been processed without trying to process it, exit code = 16 if already processed; exit code = 0 if not.

==Presets==
*-1: Highest quality preset, disc space-saving alternative to lossless archiving for large audio collections.
*-2: Default preset; a compromise between -1 and -3.
*-3: High quality preset for usage on a compatible [[Wikipedia:Digital audio player|DAP]], approx. 370kbps for "normal" music. [http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=56129&view=findpost&p=531316]

All tuning has been performed on quality preset -3 with -2 and -1 being more conservative. Quality preset -3 is generally accepted to be (and from testing so far is) transparent. If you find a track which -3 fails to achieve transparency after processing, please post a sample (no more than 30 seconds) in the development thread.

Presets are, of course, not limited to these example uses. Currently, command line parameters exist to allow the user to tune the processing to personal requirements. This may not always be the case.

'''It is up to the user to decide which preset to use for their own purposes.'''

==Supported input formats==
*[[WAV]]: 16-bit, 24-bit; sample rate ≥ 32kHz [[Pulse Code Modulation|PCM]]. Very high sample rates (>48kHz) have not been extensively tested. Tunings have been focussed on 16-bit, 44.1kHz samples (i.e. [[Wikipedia:Red Book (audio CD standard)|CD]] PCM).

==Known supported codecs==
{| class="wikitable" style="text-align:center"
|+ '''Recommended settings'''
|-
!Codec
!lossyWAV parameters
!Encoder parameters
!Combination name
|-
![[Free Lossless Audio Codec|FLAC]]
| —
| -'''3''' -'''m''' -'''e''' -'''r''' 2 -'''b''' 512 --'''keep-foreign-metadata'''[http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=56129&view=findpost&p=533689]
|lossy'''FLAC'''
|-
![[Wikipedia:Lossless Predictive Audio Compression|LPAC]]
| —
| -'''b'''512
|lossy'''LPAC'''
|-
![[Wikipedia:Audio Lossless Coding|MPEG-4 ALS]]
| —
| -'''l''' -'''n'''512
|lossy'''ALS'''
|-
![[TAK]]
| —
| -'''fsl'''512
|lossy'''TAK'''
|-
![[WavPack]]
| —
| --'''blocksize'''=512
|lossy'''WV'''
|-
![[Wikipedia:Windows Media Audio#Windows Media Audio Lossless|WMA Lossless]]
| -'''wmalsl''' (same as -'''cbs''' 2048)
| —
|lossy'''WMALSL'''
|}

There is also [http://www.hometheaterhifi.com/volume_8_4/dvd-benchmark-part-6-dvd-audio-11-2001.html#Meridian%20Lossless%20Packing%20(MLP)%20in%20a%20Nutshell evidence] — so-called "Bit Shifting" — to suggest that lossyWAV may work with [[Wikipedia:Meridian Lossless Packing|MLP]], but this remains untested due to prohibitive prices of encoders.

==Known unsupported codecs==
*[[ALAC]]
*[[Lossless Audio|LA]]
*[[Monkey's Audio]]
*[[OptimFROG]]
*[[TTA]]

==lossyWAV application settings==
<pre>
lossyWAV beta v0.6.0 : 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 settings [4xFFT] (-cbs 512 -nts -3.0 -skew 36 -snr 21
-spf 22224-22225-11235-11246-12358 -fft 11011)
-2 default settings [3xFFT] (-cbs 512 -nts 0.0 -skew 36 -snr 21
-spf 22224-22235-22346-12347-12358 -fft 10101)
-3 compact settings [2xFFT] (-cbs 512 -nts +3.0 -skew 36 -snr 21
-spf 22224-22235-22347-22358-2246C -fft 10001)

Standard Options:

-o <folder> destination folder for the output file
-nts <n> set noise_threshold_shift to n dB (-48.0dB<=n<=+48.0dB)
(-ve values reduce bits to remove, +ve values increase)
-force forcibly over-write output file if it exists; default=off
-check check if WAV file has already been processed. default=off;
errorlevel=16 if already processed, 0 if not.

Codec Specific Options:

-wmalsl optimise internal settings for WMA Lossless codec; default=off

Advanced / System Options:

-shaping enable fixed shaping using bit_removal difference of previous
samples [value = brd(-1)/4]; default=off
-snr <n> set minimum average signal to added noise ratio to n dB;
(-215.0dB<=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
-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).
-fft <5xbin> select fft lengths to use in analysis, using binary switching,
from 64, 128, 256, 512 & 1024 samples, e.g. 01001 = 128,1024
-cbs <n> set codec block size to n samples (512<=n<=4608, n mod 32=0)

-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.</pre>

==Indicative Bitrate Reduction==

Conversion using lossyWAV beta v0.5.8, FLAC -8
<pre>
|=======================================|=========|=========|=========|=========|
|Album | FLAC -8 | lW -1 | lW -2 | lW -3 |
|=======================================|=========|=========|=========|=========|
|AC/DC - Dirty Deeds Done Dirt Cheap | 781kbps | 468kbps | 417kbps | 366kbps |
|B52's - Good Stuff | 993kbps | 476kbps | 421kbps | 376kbps |
|David Byrne - Uh-Oh | 937kbps | 464kbps | 413kbps | 363kbps |
|Fish - Songs From The Mirror | 854kbps | 451kbps | 399kbps | 357kbps |
|Gerry Rafferty - City To City | 802kbps | 468kbps | 416kbps | 366kbps |
|Iron Maiden - Can I Play With Madness | 784kbps | 486kbps | 437kbps | 387kbps |
|Jean Michel Jarre - Oxygene | 773kbps | 538kbps | 475kbps | 422kbps |
|Marillion - The Thieving Magpie | 790kbps | 473kbps | 421kbps | 373kbps |
|Mike Oldfield - Tr3s Lunas | 848kbps | 491kbps | 436kbps | 389kbps |
|Scorpions - Best Of Rockers N' Ballads | 922kbps | 492kbps | 437kbps | 378kbps |
|=======================================|=========|=========|=========|=========|
|Average | 850kbps | 480kbps | 426kbps | 376kbps |
|=======================================|=========|=========|=========|=========|
|53 sample "problem" set | 784kbps | 543kbps | 491kbps | 434kbps |
|=======================================|=========|=========|=========|=========|</pre>

Large Batch Conversion: (lossyWAV -3; FLAC -3 -m -e -r 2 -b 512)
<pre>
|=======================================|=========|=========|=========|=========|
|3283 Tracks; 258 Discs; 87.2GB>36.8GB | 880kbps | ###kbps | ###kbps | 371kbps |
|=======================================|=========|=========|=========|=========|</pre>

==Example Foobar2000 Converter Settings==
[[Image:Foobar2000_Converter_Settings.PNG]]

Example flossy.bat file called from above converter settings.
<pre>
@echo off
c:\data_nic\bin\lossyWAV %1 %3 %4 %5 %6 %7 %8 %9 -below -nowarn -quiet
c:\data_nic\bin\flac.exe -8 -f -b 512 "%~N1.lossy.wav" -o"%~N2.flac"
del "%~N1.lossy.wav"
</pre>

==Frequently asked questions==
*'''Question:''' Is it [[Variable Bitrate|VBR]]?
*'''Short answer:''' Yes.

*'''Question:''' Is it [[transparency|transparent]]?
*'''Short answer:''' Almost certainly.

*'''Question:''' Is it [[lossless]]?
*'''Short answer:''' No.

*'''Question:''' Why should I use this?
*'''Answer:'''
:*high quality
:*extremely low chance of audible [[artifact|artefacts]]
:*reasonable [[bitrate]]s
:*usable with unmodified, established lossless formats.

==Current Test Settings==
No current test settings

==External links==
*[http://www.hydrogenaudio.org/forums/index.php?showtopic=56129 Current development thread] You will find the latest version and last stable version in post #1 of this thread.
*[http://www.hydrogenaudio.org/forums/index.php?showtopic=55522&st=0 Original lossyFLAC thread] Where David Robinson (Replaygain developer) introduces the method and a Matlab implementation.