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The Perfect Audio Rips





v-d-online
HowTo: Create Perfect Audio RIPS that are reversible to the original CD

It was suggested that a PRIMER on AUDIOPHILE QUALITY RIPPING would be a good idea. The following is presented in an effort to satisfy the above requirement.

Objectives:
* To identify the benefits of accurate ripping over default, Wizard-style, ripping from commonly used software.
* To present step-wise instruction for configuring your system and suggested software to acheive the best quality audio source files from a rip.
* To provide current links to available public use audio ripping software and audio codec converter software. All programs included are FREE and are commonly accredited as Best-Of-Breed throughout the Internet.


At the conclusion of this article
* you will be able to explain the difference between lossy and lossless audio compression codecs and be familiar with current formats available.
* you will be able to configure your system to acheive the most accurate audio rip files
* you will be able to setup and run FLAC to create the best possible Audio Torrents
* you have an idea of what a quality audio torrent might include


AUDIO COMPRESSION:
For a [Mostly] Comprehensive Guide to Audio Compression Codecs, Their uses, Pros/Cons see: hxxp://www.uk-t.org/forums.php?action=viewtopic&topicid=2753

Audio compression is a form of data compression designed to reduce the size of audio data files. Audio compression algorithms are typically referred to as audio codecs (enCOde-DECode). As with other specific forms of data compression, there exist many "lossless" and "lossy" algorithms to achieve the compression effect.


:- Lossy compression

Note: Actually this is not a compression (i.e. redundancy reduction = reversible), but an irrelevance coding (i.e. an irrelevance reduction).

As opposed to lossless compression, where information redundancy is reduced, most lossy compression reduces perceptual redundancy; sounds which are considered perceptually irrelevant are coded with decreased accuracy or not coded at all.

In order to determine what information in an audio signal is perceptual irrelevant, most lossy compression algorithms use transforms such as the modified discrete cosine transform (MDCT) to convert sampled waveforms into a transform domain. Once transformed, typically into the frequency domain, component frequencies can be allocated bits according to how audible they are. Audibility of spectral components is determined by first calculating a masking threshold, below which it is estimated that sounds will be beyond the limits of human perception.

The masking threshold is calculated using the absolute threshold of hearing and the principles of simultaneous masking - the phenomenon wherein a signal is masked by another signal separated by frequency - and, in some cases, temporal masking - where a signal is masked by another signal separated by time. Equal-loudness contours may also be used to weight the perceptual importance of different components. Models of the human ear-brain combination incorporating such effects are often called psychoacoustic models or "psycho-models" for short.

Other types of lossy compressors, such as the linear predictive coding (LPC) used with speech, are source-based coders. These coders use a model of the sound's generator (such as the human vocal tract with LPC) to whiten the audio signal prior to quantization. LP may also be thought of as a basic perceptual coding technique; reconstruction of an audio signal using a linear predictor shapes the coder's quantization noise into the spectrum of the target signal, partially masking it.

Due to the nature of lossy algorithms, audio quality suffers when a file is decompressed and recompressed (generational losses). This makes lossy-compressed files unsuitable for audio engineering applications, such as sound editing and multitrack recording. However, they are very popular with end users (particularly MP3), as a megabyte can store about a minute's worth of music at adequate quality.


:- Lossless compression

Compared with image compression, lossless compression algorithms are not nearly as widely used in audio compression. The primary users of lossless compression are audio engineers and those consumers who disdain the quality loss from lossy compression techniques such as Vorbis and MP3.

First, the vast majority of sound recordings are natural sounds, recorded from the real world, and such data doesn't compress well. In a similar manner, photos compress less efficiently with lossless methods than computer-generated images do. But worse, even computer generated sounds can contain very complicated waveforms that present a challenge to many compression algorithms. This is due to the nature of audio waveforms, which are generally difficult to simplify without a (necessarily lossy) conversion to frequency information, as performed by the human ear.

The second reason is that values of audio samples change very quickly, so generic data compression algorithms don't work well for audio, and strings of consecutive bytes don't generally appear very often. However, convolution with the filter [-1 1] (that is, taking the first difference) tends to slightly whiten (decorrelate, make flat) the spectrum, thereby allowing traditional lossless compression at the encoder to do its job; integration at the decoder restores the original signal. More advanced codecs such as Shorten, FLAC and TTA uses linear prediction to estimate the spectrum of the signal. At the encoder, the estimator's inverse is used to whiten the signal by removing spectral peaks while the estimator is used to reconstruct the original signal at the decoder.

Lossless audio codecs have no quality issues, so the usabilty can be estimated by

- Speed of compression and decompression
- Compression factor
- Software support

Some Lossless Formats:

- FLAC (Prefered)
- SHN
- APE
- LPAC


For a truly excellent article with more information about Lossy Vs. Lossless Audio Compression, including proof that FLAC is completely lossless, see hxxp://www.bobulous.net/misc/audioFormats.html


ACCURATE AUDIO RIPPING
There are a great many software programs capable of RIPping (Copying) an audio CD. The trouble is that most all take no pains to account for the differences inherent in every Disc Drive manufacturer's product. Many also use either proprietary or OS specific data transfer libraries. While you or I may not be able to tell the difference between a Pioneer or a Plain Vanilla Disc Drive ripped wav file, you better believe there are differences!

These inconsistencies can, and do, introduce artifacting into your copied source files. If you plan to edit or remaster or just burn the files again you will not be working with a true and faithfull source - and your burn process will likely add more errors to the file in the process.

To date - and to the best of my knowledge - there is only one program on the market that is revered by Audiophiles the world over for its ability to create ABSOLUTELY accurate audio rips: EAC, Exact Audio Copy. This essentially free program (classed as "Thank-Ware" because the author would just like you to drop him a howdy-do) allows you to quantatatively 'tune' it to your hardware. Not only that, but there are support forums that contain the combined (and growing) list of CD and DVD drives and their correct/verified read/write offsets to simplify your work setting up.

Once you know how to use EAC properly you will be able to RIP and BURN digitally identical copies of your audio CDs.


HOW TO: Use Exact Audio Copy
Download EAC from here : hxxp://www.exactaudiocopy.de/ or hxxp://www.exactaudiocopy.org

{Linux users can run EAC via Wine.}

Before installing EAC you will probably want to install an ASPI layer for your computer.
If your machine has SCSI hardware, and/or built in CD burner, get the one from Adaptec (hxxp://www.adaptec.com/)

If you have Firewire or a USB/USB2 external burner you will want to use the ASPI from Nero (copy this file to the system32 folder on your computer or put it in the directory where you install EAC and reboot). (ftp ://ftp6.nero.com/wnaspi32.dll)

========================================
EAC MUST BE CONFIGURED TO WORK CORRECTLY!
========================================

Recommended EAC Settings:

Most important: uncheck on "Tools tab" Activate beginner mode... option !!!

Extraction tab:

* Check: Synchronize between tracks
* Check: Fill up missing offset samples with silence
* Leave the remaining checkboxes unchecked
* Select: Error recovery quality - High

Tools tab:

* Check: 1st to 4th checkboxes

Normalize tab:

* Do NOT use Normalize

Filename tab:

* Naming Scheme = %A - %C - %N - %T Example: Artist - Album - 01 - Song.wav FLAC will read this filename and attempt to create a proper tag.


Recommended Drive Settings:

Extraction Method tab:

* Secure mode - NOT Paranoid, Synchronized or Burst mode!
* Check: Drive has 'Accurate Stream' feature
* Check: Drive caches audio data
* Do Not Check: Drive is capable of retrieving C2 error information

Offset/Speed tab:

* Select: Use read sample offset correction. Please test and check your offset!
Tutorial: hxxp://pages.cthome.net/homepage/eac/setup.htm
For a list of offsets you can use: hxxp://www.accuraterip.com/driveoffsets.htm
* Check: Overread into Lead-In and Lead-Out (if EAC generates [Sync Error] on last track - uncheck)
* Check: Allow speed reduction during extraction

HOW TO CREATE CUE FILE?

Select tracks to extract and press F6 (to Test & Copy the tracks).

Don't forget to check the CRCs after each rip, because unlike other errors they do not generate a There Were Errors message (the log doesn't warn you).


Do's and DON'Ts
DO NOT rip the CD to one large file in ANY format.


USING FLAC TO CREATE LOSSLESS COMPRESSED FILES

Download FLAC codec and frontend from hxxp://flac.sourceforge.net/download.html

Recommended FLAC Frontend Settings:

* Level: 8
* Check: Verify (only)
* Do Not Check: Replaygain
* Encode and make Fingerprint


If you don't/can't use the Windows-only flac frontend you can create the fingerprint file on the commandline:
metaflac --with-filename --show-md5sum *.flac >fingerprint.txt
Files


TORRENT STUFF...

Please include the following files:

* EAC log file (or other file if not using EAC) in ENGLISH!
* A short album name.nfo text file with a description of tracks, recording, performers and any other information
* A .cue sheet to facilitate the burning of the disc [EAC will do this for you]
* A thumbnail of the album cover no smaller then 100x100
* If possible, please include any artwork from the album at 300 to 600 dpi descreened (pattern removal).

Suggested Torrent Naming Scheme
Performer's Name - Title of the Recording year of issue [format] (additional info: MFSL, XRCD, gold etc)

* Example: Rush - 2112 (1976) [FLAC] (MFSL)

Do NOT use things like ~ or ` in foldernames or filenames, some people can not download these files due to the nature of these characters...
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