Burning Audio CDs

One of the top reasons for buying a CD burner is to compile music CDs. Imagine the annoyance of having to carry 15 CDs on a road trip just so that you can have all 17 of those favorite songs on hand. With a CD burner, you won’t have to. All you have to do is copy those 17 favorite tracks onto a single CD and bring that along. The best part of it is that it’s fairly easy to do with Easy CD Creator.

The first step to compiling a music CD is to pre-record all the tracks you want into WAV Files, and store it on the hard drive. So what is a WAV file? And what do I mean by pre-record? And why do we need to pre-record? A WAV file is a type of file format used by the computer to store audio data. It is a standard file format that every audio program supports. The music you hear from your music CDs is really just special forms of WAV files. The main advantage to WAV files is that it stores audio data without loss of quality. A WAV file recorded at 16bit Stereo and 44KHz is perfect CD Quality. Yikes!! Look at all those terms!! 16Bits, 44Khz, what the heck are those? 44KHz refers to how many samples the WAV file takes per second. So 44Khz means that when you are recording the WAV file, the system takes 44,000 samples (actually 44,100 samples to be precise) for every second of audio data. This is analogous to a video camera.

A video camera captures 30 frames per second, and turns that into a movie. The 16bit refers to how detailed each sample is. 16 bits means that it takes a series of 16 zeros and ones to describe each sample. Obviously, the higher the bit rate, the better the sound. Think of a song as a movie with different scenes. Each second, 44,100 scenes are played. Now, think of the bits as the number of words used to describe each scene. So 16 bits means it takes 16 words to describe each scene. A lower bit rate, say 8 bits, means only 8 words are used to describe each scene. So take a scene, and let’s describe it. In 16 words, I can say “A dark-haired, fair complexioned man is standing in a room filled with a bustling crowd.” Now, cut that down to 8 words. “A man is standing in a crowded room.” Needless to say, the 16 bit description yields a much more vivid image, just as 16bit audio yields a much more vibrant and realistic audio experience. Finally, stereo just means it records two channels of audio, each one at 44Khz and 16 bits.

Ok, so we know what a WAV file is. But why do we need to convert the audio track from the CDs into WAV files first? I have two CD-ROMs. Why not just record from one to the other, just like the way I dub tapes? There are several reasons for doing this. The first reason is something called buffer underrun. When the computer is writing to a CD, it first reads the source data into a part of memory called a buffer, and from there, it records the data onto the CD. As data is written from the buffer to the CD, that data is removed from the buffer. Thus, it is critical that the data is fed into the buffer at approximately the same rate it is being written to the CD. If the data is being fed into the buffer slower than it is being written to disk, buffer underrun occurs. When buffer underrun occurs, the CDR laser is left waiting for new data. This wait could cause the CD you are burning to be ruined. Buffer underrun happens if the source medium cannot transfer data quickly enough to the buffer. With hard drives, this rarely ever happens. But with CD ROM drivers, especially older IDE based drives, it happens more frequently. Some people make the assumption that since they have CD ROM drives that run at 36X, and their CDR only burns at 4X, that they won’t have this problem. That is not necessarily the case. Sometimes the problem occurs not because the drive can’t read the data fast enough, but because the data can’t be transferred to the buffer fast enough. This is analogous to saying that sometimes you can’t get to work fast enough not because your car can’t go fast enough, but because the highway is too clogged.

Another problem with doing a CD to CD copy is distortion. With newer CD-ROMs that spin at 36X or higher, the CD is spinning so quickly that it tends to vibrate in the drive. This vibration is known as jittering. With data CDs, it’s not a big deal. But with audio CDs, what happens is that you may get distortions in the form of clicks. So to prevent the problem, pre-record the WAV file using your CDR drive, which tends to compensate for the problem.

And the last is the hassle. If you were to compile songs from 10 different CDs, you would need to sit around and wait for the song from each CD to be written, and then insert the next CD. This process quickly becomes tiresome. It’s much easier to just pre-record all the songs to the hard drive.

After the WAV file is recorded to disk, the rest is easy. Now start a new CD layout by choosing New from the File menu. Once you start a new CD Layout, find the directory where you stored all your pre-recorded WAV files and drag them into the lower pane in the order you want the tracks to be burned. As you drag more tracks into the lower pane, you will notice an indicator bar at the bottom of the screen that displays how much more time there is available for additional tracks. Be sure not to go over the 74 minute limit. Once you have finished designing your CD Layout, it’s time to burn. But before you click the record button, you should be aware of a problem known as the 2 second gap. Basically, the audio track ends two seconds earlier, and you hear a 2 second silence between tracks. To fix the problem, you will need to write the CD in disc-at-once mode. During a normal CD writing process, the laser is turned off between tracks, which causes the 2 second gap problem. But in disc-at-once mode, the CD is written in one turn, without ever turning off the laser. This will effectively eliminate the 2 second gap problem. To write in disc-at-once mode, do the following:

  1. Click on the red Record button in the toolbar.
  2. Next, click on the Advanced tab
  3. In the Advanced tab, choose Disc-at-once

Note, however, that there is a slight disadvantage to using disc-at-once, and that is disc-at-once will prevent you from making further additions to the CD. This really isn’t a problem with audio CDs, since most compilations are one time deals. The advantages, in my opinion, outweigh the drawbacks. For one, disc-at-once eliminates the 2-second gap problem. Disc-at-once also ensures higher compatibility with older CD players (because it closes the disc after the write. More on that in the advanced guide to CD burning). So, whenever possible, use disc-at-once to write your audio CDs.

And as a teaser, if you think writing normal CDs are fun, wait till you see the advanced guide. In there I will show you how to encode an AC3 compliant Audio track onto a CDR disc that will play in normal home theatres.

Page 1: Basics of CD Burning
Page 2: This page: Compiling music CDs
Page 3: Writing data CDs

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