# Audio CDs

### From Audacity Manual

## CD Format

The vast majority of music CDs are encoded according to the Red Book Standard. The Red Book standard is a 16-bit, 44.1KHz PCM audio signal. This is very similar (though not directly compatible with) WAV and AIFF files encoded at 16-bit, 44.1KHz. The sound quality is identical across those formats, but the data is organized differently/// i.e. a data stream not a file which is why most OSes can't open it///

## CD-audio and Audacity

Audacity cannot read CD-audio directly. In order to edit audio from a CD using Audacity, the audio data must first be extracted from the CD and converted to a format that Audacity can read. This process is known as ripping. Audacity cannot rip CD-audio, other software must be used.

## CD creation

Just as Audacity cannot read CD-audio, it also cannot be used to create audio CDs directly. Software that can is called CD-burning software.

### Preparing Audio Files

The best way to prepare your audio for the CD-burning process is to export to the WAV or AIFF format at 16-bit, 44.1KHz. It may be possible to use other formats if your CD-burning supports them, but they may not give the best quality.

Once you have these files prepared, your CD-burning software can use them to burn a disc.

### Common Pitfalls

- Wrong sample rate. Most CD-burning software expects all files to be at 44.1KHz.
- 2-second gap added to the end of each track. Your CD-burning software should provide an option to remove this gap.
- Unsupported formats. Some CD-burning software does not support compressed formats such as MP3, Ogg, or M4A/AAC.

RIPPING

Audacity does not contain any function for importing (ripping) audio from CDs. This can, however, be achieved by using other programs to extract the data into a file format Audacity does support.

## Introduction

Users new to audio editing are often surprised to find that they cannot import the audio from CDs into Audacity with the Project > Import Audio command. In fact, most operating systems don't actually allow the import of data from the CD tracks into applications, because audio CDs don't have files or a file system like computer media, but consist essentially of a stream of bits on the disk. That is why when you look at an audio CD in a file manager like Windows Explorer, each CD track will appear only as a small .cda "file" 44 bytes in size, which is merely header information for the stream.

So in order to import tracks from an audio CD, you must first usually extract (or "rip") the tracks to a .WAV or .AIFF audio file using CD extraction software. Then you can import that .WAV or .AIFF into Audacity with the usual Project > Import Audio command. You can also extract CDs to the much smaller .MP3 format, but this is not recommended if you want to edit the audio in Audacity, because every time you encode to MP3 you lose audio data. On the other hand .WAV and .AIFF are lossless. You can always export your audio from Audacity to .MP3 after you've edited it, but to save un-necessary losses, import the audio in the first place as .WAV or AIFF.

## Windows

For users on Windows, Audacity recommends CD-EX as a fully featured CD extraction program which can extract to the .WAV format you need for editing the audio in Audacity.

In the CD-EX window, simply select the CD tracks you want to extract to .WAV and press F8 or Convert > Extract CD track(s) to .WAV. Normally, every CD track will be extracted to its own audio file, but CD-EX also has a nice feature that lets you extract any range of audio (including all of it) to a single file. So if you want to extract a sample of two CD tracks that starts in the middle of one track and ends in the middle of another, you can. To do this, right-click on any of the tracks > Extract partial CD Track, or press F10.

Make sure you know where to look for the exported .WAV files when you import them into Audacity. By default CD-EX saves the .WAV to one of your Documents and Settings folders for whatever account you are logged into at the time. If in CD-EX you click Options > Settings > Filenames tab and look in the second text box from the top (marked ".WAV --> MP3"), you will see the location where it saves its output files from CD extraction or file conversion.

You can also extract audio CDs to .WAV with Windows Media Player 11 (click Tools > Options > Rip Music and choose "WAV (Lossless)" in the Format dropdown in "Rip Settings"), or to .WAV or .AIFF with the Windows version of iTunes (see below). Earlier versions of Windows Media Player are not recommended for extracting CD audio for editing in Audacity, because they are unable to extract to .WAV.

## OS X

iTunes is the built in media player for Mac computers.

To extract CD audio in iTtunes, set the "conversion format" in its Preferences at Advanced > Importing: Import using .WAV or .AIFF encoder. Under that, choose the "automatic" setting. Then insert your CD in the computer and click "Audio CD" on the "Source" pane on the left. Select the tracks you want to extract and right-click or control-click on them and then click the option "convert selection to .WAV" (or ".. to .AIFF").

OS X users do have an additional quick way to import CDs, because when a CD is put in the drive, the .cda tracks are mounted as .AIFF files in the Finder. It's thus possible to either drag the .AIFF files from the Finder into Audacity, or use the Project > Import Audio command, instead of extracting the audio. Note however that if you import CD tracks into Audacity from Finder and save them as a Project, the CD must be present next time you open the Project, unless you set Audacity to make a copy of the data. To do this, go to the File Formats tab of Preferences and where it says "when importing uncompressed audio....", check the radio button "make a copy of the file before editing".

Another possibility is to use Max, a free software CD-ripping and encoding application. It has full support for encoding into the FLAC loss-less audio format, which is rather tricky to set up in iTunes.

## Linux

If you are on Linux or other Unix-like systems you can use K3b or Grip for Gnome desktops.

## BURNING

Audacity does not enable you to burn CDs directly, so you need to export an audio file (usually a .WAV or .AIFF) from Audacity, then burn that file to a CD with burning software such as Windows Media Player (built into Windows) or iTunes (built into OS X). Either of these applications will require you to add the files for burning to a playlist before you can burn them. You can do this by simply dragging the files from the location you exported them to, into the playlist. Real Player is different and requires you to add files to "My Library" with its File > Add Files to My Library command before you can burn them to CD. If you have not yet created a Real Player library, see this link and for help burning to CD on Real Player go here.

You can also use a standalone burning program like Nero or Toast to burn your exported files. If you do this, it's always best to open the files from within that software, not drag and drop them from your file manager.

Hint: Windows Media Player 11 will not accept .WAV files for burning if they are dragged straight into a burn list, but have not previously been played in Media Player. You will see a red symbol and a "length of file cannot be determined" error. To solve this problem with a .WAV that has never been played in Media Player, drag the file into the Media Player Library or into a playlist, then from there into a burn list. Also, this version of Windows Media Player does not accept .AIFF files for burning, so you must export as .WAV. Neither of these problems affect previous versions of Media Player.

## Burning different types of CD

There are two main types of CD - an "audio CD" and a "data CD". An audio CD (sometimes called a "music CD") will play on any standalone CD player, as well as as in your computer and in DVD players. A data CD (sometimes called an MP3 CD where the data it contains are MP3 files) will not normally play on standalone CD players. It will play on computers, most DVD players and in MP3 CD players. So if you want to play your CD on a standalone player, or give it to others and be sure they'll be able to play it, you need to tell your burning software to burn as an audio CD. For example, to set iTunes up to burn an audio CD, you go to the Advanced tab of its Preferences, click the Burning tab, and at "Disc Format", select the "Audio CD" radio button.

### Audio CDs

Audio CDs always contain high quality uncompressed PCM stereo data at 44 100 Hz sample rate, 16 bit resolution. So if you want to burn an audio CD, you should always export the file you want to burn as a 44 100 Hz 16 bit stereo WAV or AIFF file. To configure Audacity to do this:

1. At the bottom left of the Audacity window, set the Project Rate to 44 100 Hz.
2. If you are using a 1.2.x version of Audacity, go to the Preferences > File Formats and in the "Uncompressed Export Format" dropdown, choose WAV (Microsoft 16-bit PCM) or AIFF (Apple/SGI 16-bit PCM).
3. If your Project does not already contain a stereo track, click Project > New Stereo Track (or in Audacity 1.3.3, Tracks > Add New > Stereo Track). It does not matter that this track is empty, its purpose is just to make Audacity export your recording as a stereo file. This step is not needed if you are burning to CD with iTunes.
4. Click File > Export as WAV or File > Export as AIFF. If using 1.3.3, click File > Export and choose "WAV, AIFF and other uncompressed types" in the "Save as type" box, then click the "Options" button and choose "WAV (Microsoft 16 bit PCM)" or "AIFF (Apple/SGI 16 bit PCM)".

Be sure to tell your burning software to burn an "audio CD" or "music CD" (not a "data CD" or MP3 CD"). Always use a high quality CD-R disc, as some standalone CD players may refuse to play CD-RW discs properly.

Because audio CDs must always contain uncompressed 44 100 Hz 16 bit stereo audio, they are necessarily limited on a 650 MB ("Red Book Standard") or 700 MB audio CD to 74 - 80 minutes playing time respectively. If you need more playing time (e.g. to try and accommodate a C90 cassette or two LPs onto one CD), some CD burners will let you "overburn" into the blank CD space so as to extend the playing time by a further few minutes, so giving you the possibility of up to 80 minutes' playing time on a 650 MB disc or up to 86 minutes on a 700 MB disc. Overburning (if your burning software and burner supports it) is always done using Disc at Once (DAO) mode in which the tracks are burnt continuously without turning the laser off. It is also theoretically possible to overburn using "90 minute" (790 MB) or "99 minute" (870 MB) CD-R discs. However there is no guarantee whatsoever that your CD burner will accept such CD-R discs, or that your CD player will play anything other than a Red Book Standard 650 MB disc burned with 74 minutes of audio.

### Data CDs/data DVDs

For burning really long files to optical media, you must burn either a "data CD" or a "data DVD". For example if you burn MP3 files to a 700 MB "data CD" (which your burning software may call an "MP3 CD"), using Audacity's default 128 kbps MP3 export bitrate, this gives you over 11.5 hours' playing time on the CD. If you went to "MP3 Export Setup" in the File Formats tab of Audacity Preferences and reduced the MP3 bitrate to 64 kbps, you would reduce the quality of the exported audio but could then fit about 23 hours of audio on the CD. If your DVD player can read data DVDs containing MP3 files, then you could get for example nearly 80 hours of 128 kbps quality MP3 audio on a 4.7 GB data DVD.

## Burning separate CD tracks from a long file or recording

If you have a file or recording from an LP or cassette and want to burn separate CD tracks from it corresponding to each track on the LP or cassette, see Splitting recordings into separate tracks.

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