CD-Recordable FAQ


Q. Can I just copy files onto a CD-R like I would to a floppy?

A. The process of writing to a CD-R can be a bit more involved than copying files to a floppy. Burning a CD-R requires CD-R burning software. Some CD-R writer comes with bundled CD-R burning software (such as the PrimoCD Plus). With "packet writing" software, and a writer that supports it, you can treat a CD-R disc like a floppy. For CD-R, you can only write to each part of the disc once, and you cannot reclaim the space used. There are other limitations in writing to a CD-R as well. With common software, it usually ends up writing everything to the disc all at once, if you want good compatibility. Also, when the writing is in progress, you cannot interrupt the drive, otherwise it will be un-readable. If you want to write your files in smaller bunches, a fair bit of space will be lost every time you stop and start again.

Q. What are the methods of writing to a CD-R?

A. There are three basic methods for writing to a compact disc: Track-at-Once (TAO), Disc-at-Once (DAO), and Packet Writing.

Track-at-Once In Track-at-Once recording, the recording laser is turned off after each track is finished, and on again when a new track must be written, even if several tracks are being written in a single recording operation. Tracks recorded in Track-at-Once mode are divided by gaps. If a data track is followed by an audio track, the gap is 2 or 3 seconds. The gap between audio tracks is usually 2 seconds. There is nothing that can be done by the software to suppress or reduce the gap, unless both recorder and software support variable-gap Track-at-Once. All current CD recorders support Track-at-Once.

Variable-Gap Track-at-Once Some newer recorders allow you to set the size of the gap between tracks in Track-at-Once mode. For example, Toast uses variable-gap Track-at-Once to allow the setting of the size of the gap, from near-zero (2 sectors, or 2/75 of a sec) to 8 seconds, before each audio track on an audio disc.

Disc-at-Once Opposite to Track-at-Once (TAO) that allows writes to be made in multiple passes one track at a time, Disc-at-Once (DAO) writes the entire disc in one pass. The entire writing must completed with out interruptions. In Track-at-Once mode, there is additional overhead due to the area required for laser stops and starts. In Disc-at-Once recording, one or more tracks are recorded without ever turning off the recording laser, and the disc is closed. Disc-at-Once recording requires a blank disc, and cannot be used for multisession. Not all CD recorders are designed to support Disc-at-Once recording, and some which are supposed to support it need firmware upgrades. For example, the CD Copier included with Easy CD Creator does not currently support Disc-at-Once. Toast 3.x does not support Disc-at-Once; Toast 4 and Jam do. Disc-at-Once is primarily needed to record audio discs with a variable (or no) gap between tracks.

Session-at-Once Session-at-Once is used primarily for CD Extra. In Session-at-Once recording, a first session containing multiple audio tracks is recorded in a single pass, then the laser is turned off, but the disc is not closed. Then a second (data) session is written and closed.

Packet Writing Packet writing is a method of writing data on a CD in small increments. Not all CD recorders support packet writing. Not all current CD-ROM drives can read packet-written discs. Packet writing is a feature which must be built into the recorder's hardware.

Fixed-Length and Variable-Length Packets There are two kinds of packets: fixed-length and variable-length. Fixed-length packets are more suitable for CD-RW in order to support random erase, because it would be daunting (and slow) to keep track of a large, constantly-changing file system if the packets were not written in fixed locations. The down side is that these packets, with a length of 32 KB (UDF standard), take up a great deal of overhead space on the disc. The normal data capacity of a CD-RW disc formatted for writing in fixed-length packets is about 500 MB. Variable-length packets save space, because the size of the packet can vary with the size of the data being written. This is more useful when writing to a standard CD-R disc, because these are write-once media, and it is not necessary to track and allocate free space when files are made invisible.

Q. What is a multisession disc?

A. A session is a recorded portion of a disc and it's TOC (Table Of Contents). A multisession CD is made by adding an additional session to a CD which already has a session on it. You can burn multisession CDs with linking to previous sessions so that all sessions can be accessed. If the sessions are not linked, the disc allows only the last session to be read.

Q. What is incremental writing?

A. Incremental writing is making a disc in multiple writing sessions but the disc is not closed after each session and cannot be accessed. The disc is closed when writing to it the last time, at which point the TOC (Table Of Contents) are written.

Q. What is disc fixation?

A. Disc fixation is the process of writing the TOC (Table Of Contents).

Q. What are subcodes?

A. There are eight subcode channels (P, Q, R, S, T, U, V, W). Each channel can hold 4MB of data. Channel P does not have many applications. Channel Q includes ISRC (International Standard Recording Code), position information, and media catalog numbers. Channels R-W are used for text and graphics. The other channels are generally not used.

Q. How long does it take to record a CD-R and CD-RW disc?

A. The amount of information being recorded will affect the time required. 650MB of data takes 74 min at 1x (150KB/sec), 37 min at 2x (300KB/sec), 19 min at 4x (600KB/sec), 13 min at 6x (900KB/sec) and 9.3 min at 8x (1200KB/sec). Total time needed should include additional time for writing the TOC (Table Of Contents) which is typically between 1 to 5 min.

Q. What is the difference between physical and virtual image?

A. The physical image is an exact copy of the data on the hard drive, the virtual image is a software pointer to the data. The physical image requires more HDD space but is more reliable as a rule because of the time saved when gathering the information during the recording process.

Q. I burned an audio CD but have some pops and problems with it. What is the cause?

A. The quality of the audio copies is usually affected by the way in which the master is read in. First you should make sure you have a good quality master, a Disk-at-Once recorded master that has been final fixated is the best way to go. Next be sure to read in the audio disc at a slower speed than data discs are read in, usually 2x or 4x at the most, to insure a good quality read.

Q. I have a problem when trying to verify audio CD and video CD?

A. Because of the way Audio and Video CDs are recorded, CDs containing Audio or Video tracks cannot be verified.

Q. Can I download MP3s from the Internet and make an audio CD?

A. Yes. You can download MP3s, write them to a CD. Many popular CD recording programs will also decode MP3s. It's also possible to take songs from a CD and convert them to MP3s for use in an MP3 player. See PlayWrite MP3 Pro.

Q. What is the difference between cynanine and phthalocyanine CD-R Media

A. Cyanine dye is the de facto standard. The Orange Book was written based on the original cyanine dye discs from Taiyo Yuden. Most CD writers are optimized for cyanine dye. As a result, cyanine discs are compatible with a wider range of laser powers. Phthalocyanine dye has performed better than cyanine dye in accelerated age testing, and may work better in situations that requires higher laser powers, e.g. higher speed recording. In most situations, the two types of discs perform essentially the same.

Q. What is BurnProof?

A. BurnProof is a Sanyo trademark. It comes the phrase "Buffer Under RuN-Proof." Recorders using the BurnProof technology can record data past the end of a recorded point where the recording was stopped due to the underrun. When used with the recording software, Sanyo's chipsets that support BurnProof, monitors the CD-R drive buffer. When it anticipates a buffer underrun, it puts the recorder into suspend mode, waits for more data from the source to fill the buffer. Since the address where recording was suspended is known, the controller can find that exact spot on the disc when restart. Once found, the recorder will then position the head on that spot and start recording again. Starting and stopping in response to a potential buffer underrun results in a data gap of 40 to 45 milliseconds. This is well within the Orange Book specification that states that the data gap cannot be more than 100 milliseconds. During reading, CD error correction will deal with the data gap, and the user will not notice the existence of the gap. More testing will tell if this technology is proof against all forms of buffer underrun.

Q. How do I prepare data for making a CD?

A. CD-ROMs must conform to specific standards that make it possible for a computer to read them. These standards include the CD-ROM volume label and the file system standard.

Volume Label This is for the identification of the disc. It is the equivalent of a book title and is electronically stored on the CD. The label can anything you wish to identify the CD . The volume label is limited to eleven characters, using A-Z (upper case letters only), the numbers 0-9, and the _ (under score).

File System Standards You should considered what file system to use before planning to make a CD. Use a ISO 9660 standard for CD's that play on all platforms.

If you are planning to use your CD on both DOS and Mac platforms, your data must meet ISO 9660 (level 1) requirements. File names meeting the ISO 9660 (level 1) standard are restricted to the characters A-Z, 0-9, and the _ (underscore). If you use any other character or space, it would be converted into an underscore. File names, (including extensions) may contain 11 characters, the eight dot three, convention. In the hierarchy of folders or directories, they cannot go more than eight levels deep.

If you need long file names, you may create an ISO 9660 (level 3) an ISO 9660 (Joliet Standard) CD-ROM:

  • The ISO 9660 (level 3) is an extension of the ISO 9660 Level 1 standard. It allows up to 32 characters in a filename and does not require a dot-three extension.
  • The ISO 9660 (Joliet Standard) is an extension of the ISO 9660 Level 1 standard. It allows up to 64 characters in a filename and does not require a dot-three extension.
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