CD Audio F.A.Q.

1. What is the difference between track-at-once and disc-at-once?
2. What does the term “jitter” mean?
3. What is finalizing and what does it do?
4. Can you copy DTS encoded CDs?
5. How do you copy tracks from an audio CD?
6. How can I make MP3 files from CD audio tracks?
7. How can I get rid of clicks and hisses on my CD?
8. How can I make a CD from my tapes and records?
9. How can I transfer my DAT to CD?
10. Is there a way to put data and audio on the same disc?
11. How can I record audio without the 2-second gap?
12. How do you record and play MP3 files onto a CD-R?
13. Will my audio quality suffer by recording at fast speeds?
14. How do you create a hidden track?
15. Is it possible to record live audio directly to a CD?

1. What is the difference between track-at-once and disc-at-once?

Track-at-once is when the CD burner writes the disc one track at a time. This creates a gap in between tracks. This is caused due to the laser turning on and off during the process. This feature is best used when you know you need gaps in between the tracks. These gaps are 2 seconds in length.

Disc-at-once means you write the entire disc at one time. The laser does not turn on and off for multiple tracks. You will still have multiple tracks, but the space between the tracks will be as long or as short as you make them to be within your recording software. If you have tracks that flow into each other, you will want to write disc-at-once. A good rule of thumb is anytime you are copying a disc or recording audio, record the session disc-at-once. This will give you the best chances of playing in most players.

2. What does the term “jitter” mean?

Jitter is defined as “a time-based error caused when digital samples are converted back into an analog signal.” Audio data consists of the data, as well as the address information for the audio blocks. When the audio data is fed into the buffer, the address information is fed into a different part of the controller. Thus, the data and the address info are separated. Jitter comes into play when the two are inaccurately put back together. This glitch sounds like tiny, repeated clicks. This usually occurs only with audio extraction. To compensate for this, you will want to use jitter correction software, which is performed by most digital audio extraction programs.

3. What is finalizing and what does it do?

When you burn a CD-R, you have a choice to either burn the disc as an open session or a closed session. As an open session, you are able to add to the disc at a later time. However, open session discs cannot be played on an audio CD player. For playable audio, you need to close the disc, a process that is called “Finalizing.” Once closed or finalized, you cannot add any more information to the disc. When you finalize, you are creating the TOC (table of contents) within the lead in. The lead out is also created, thus closing the disc. You are also finalizing the disc when you use disc-at-once recording.

4. Can you copy DTS encoded CDs?

Yes you can. Writers will copy CDs with DTS encoding the same as they would copy regular 16 bit stereo audio. But in order to play the CD correctly, you will need to play them in a player that is hooked up to a DTS receiver. Most DVD players currently will play these discs.

5. How do you copy tracks from an audio CD?

This process is called track extraction. There are burning software titles on the market that allow you to extract audio from another CD and make a compilation disc. In this case, you would drag the files from the master CD and drag them into your burning software. It will also allow you to place the songs in the order of your choosing. If you do not want to go the computer route, there are many consumer grade CD burners on the market that allow you to make compilation discs. You will find these burners at your local electronics superstore. Remember, these types of recorders only use special CD-R media that is not able to be duplicated and tends to cost more. If you are looking for something a little more professional, contact Optical Resources at 1-800-646-8881 for more information.

6. How can I make MP3 files from CD audio tracks?

You need to get conversion software or an encoder of some kind. These programs will allow you to take the files from the master CD, encode them to the specifications of your choosing, and store them on your hard drive for later use. If you are going to be posting your music on the Internet, make sure you use a high quality encoder so your audio will not suffer.

7. How can I get rid of clicks and hisses on my CD?

The first step is singling out where the sound came from. Listen to your WAV files to see if your extraction process could be redone. After that, extract your audio from the disc you just burned and compare the audio to the WAV that you have on your hard drive. Also listen to make sure that you are not clipping the audio. This occurs when the recorded sound level is too high. If none of these tests work for you, the last place to check is your burning software itself. You may need to get a newer or updated version of the software you currently use. Make sure that your CD-R media is certified for recording at the speed you are trying to record at. Also try playing your CD in different players to see if the clicks and hisses are still there.

8. How can I make a CD from my tapes and records?

The basic idea here is to connect the audio outputs from the tape or record player to the audio inputs of the CD recorder. If you own a stand-alone CD recorder, just connect it to the source player using either RCA or 1/4 inch plugs, whichever you need. If you only have a computer CD burner, you will need to connect the output of the source player to the audio input jack on your computer’s soundcard.

With the stand-alone unit, you just hit record on the recorder and play on the player. Press stop when finished and you’ll have your tape or vinyl collection on CD. When recording to the computer recorder, you will need to record to an audio recording software. You can find this type of software in computer stores or in music stores. Then just hit record in the recording software and hit play on the player. Remember, you need to make sure your recording level is loud enough or your CD will be too quiet. If you are in need of a quality conversion that utilizes sound restoration and the work of an experienced sound engineer, you should contact a local service bureau that specializes in audio restoration and conversion.

9. How can I transfer my DAT to CD?

This can be done in a similar manner as tapes and records. With a DAT, there are analog and digital outputs on the back. You will want to connect those outputs to the inputs of your CD recorder or your sound card in your computer. If you are using a digital connection like S/PDIF, make sure your input source has these types of inputs. Higher end sound cards and CD recorders usually have these types of inputs. If your DAT player is an older unit that only has audio at 48 kHz, you’ll need to convert the audio to 44.1 kHz for it to play on a CD. This should be done on your computer. Whether you are transferring the audio in analog or digital format, press record on the CD recorder or the recording software and press play on the DAT.

10. Is there a way to put data and audio on the same disc?

Yes, there are actually 2 ways to do this. The first way is to put the data on track 1 and put the audio on the rest of the tracks. The other way is to put the audio in the first section of the disc and the data in the second section of the disc. For this to work, you need to use CD recording software that allows you to record the audio disc-at-once, but also allows the disc to be unfinalized. Then, you add the data in the second section and finalize the disc.

11. How can I record audio without the 2-second gap?

You need to record your disc using the disc-at-once format. This can be selected within the burning software and it usually asks you right before it starts the burning process. By using disc-at-once writing, you are writing the disc as a whole, not per track. If you are using more advanced CD burning software, you may be able to set your PQ subcodes and designate when each track starts. You can create a gap at any length or create no gap at all.

12. How do you record and play MP3 files onto a CD-R?

Whatever the audio file, it needs to be converted into an uncompressed, red book standard audio file like a WAV or an AIFF. Only these types of files can be played on a conventional CD player. Many of the current CD recording software programs will convert the MP3 to WAV or AIFF for you when you try to record the MP3s to a disc. However, there are newer devices on the market that allow you to play MP3’s from a CD-R, not having been converted to WAV or AIFF. By going this route, you are able to fit much more than 74 minutes of audio on a disc, though it still has to fit within 650MB. Depending on how you compress your MP3 files, you can fit up to 99 tracks on a disc.

13. Will my audio quality suffer by recording at fast speeds?

To answer this question, there are several factors that need to be addressed. First, is the CD burner you are using of professional standard? There are many brands of CD burners on the market, but there are a limited few that would be considered a quality recorder. These professional standard recorders include Plextor, Teac, and Sanyo to name a few. The next factor to look at is what is the quality of the CD-R media you are using? As with recorders, there are some good manufacturers and there are some bad manufacturers. I recommend Taiyo Yuden as the best quality piece of media on the market. Some other notable brands include Mitsui and Verbatim. Assuming you are using a professional recorder with professional media, there should not be a noticeable difference in your audio quality. Some have claimed to hear audible differences between discs burned at lower speeds and those burned. Many times, this is due to poor quality media, a low-end recorder, or both. If you have a pair of the greatest ears, along with a tweaked out room, you may hear a difference between recording speeds. The question to ask is not do you hear a difference, but will your listeners? Even people with good stereo systems cannot match an acoustically pleasing mixing room, not to mention a pair of good ears is hard to come by. For all practical purposes, there will be no audible difference between 1X and 16X recorded CD-Rs.

14. How do you create a hidden track?

On a CD, the start of the first track is labeled at “index 00.” The audio starts at “index 01.” The gap in between these two indices is called the pre-gap. This pre-gap must be at least 2 seconds in length to make it Red Book standard. In order to make a hidden track, you need to find burning software that will allow you to change index times. First, you need to combine the two songs that will become the hidden track and track 1. This can be done with any digital audio editing software. Select this “combined” song to be track 1, setting “index 00” to time zero. Then set “index 01” to a point right after the “hidden track” is complete. What will happen is when this disc is played on a CD player, the player will automatically go to “index 01” which is where the audio is supposed to start. You then will have to rewind back to listen to the “hidden track.”

15. Is it possible to record live audio directly to a CD?

Yes, but you will need the proper equipment to do so. There are products on the market that allow you to record direct from a powered source like a mixer or an amplifier. It is not feasible to record direct to CD via your computer. You would first have to record to some kind of audio recording software, then save the file as a WAV, then burn it to a disc. If you are looking for a product that will record audio, Optical Resources makes a product called the StartREC. This product allows you to record audio directly from a source like a mixer, and then burn multiple copies of the finished recording.