DVD Recording and Disc Writing Speed - Important Facts

What disc writing speed means in DVD recording

Different kinds of blank recordable DVDs

Robert Silva

Commercial DVD and home-recorded DVD share some commonalities, but there are differences. One major difference is how DVDs are designed to be used for home DVD recording.

For home DVD recording, blank DVDs come in several formats and both single and double layers.

A standard, single layer, recordable DVD disc has 4.7 GB of storage space and holds up to 2hrs (120min) of video at DVD quality. All commercial movie DVDs hold about 5GB per layer — with each layer holding about 133 min. DVDs can have one or two layers on each side. However, most DVDs use just one side with one or two layers. If you buy a movie DVD that has a 2-hour movie, plus an hour or so of extra features, this means that the disc has more than one layer.

All types of DVD players and recorders can play back commercial discs with more than one layer. However, some older players (pre-1999) may not be able to in all cases.

DVD Recording Modes

Unlike VCRs, DVD recorders do not have recording speeds. A recordable DVD disc rotates in a set manner, either at constant static rotation rate or at a constantly accelerated rotation rate throughout the recording process (depending on disc format).

Instead of changing speeds, when you want to record a program longer than 2 hours the DVD recorder has to compress the video at a higher ratio in order to fit more time on the disc.

By compressing the video, you can fit more recording time (4, 6, or 8 hours) on the same, 4.7 GB disc. The process of recording longer times on a DVD is referred to as record modes. Typically, DVD recorders have 1, 2, 4, and 6-hour record modes, but some also feature 1.5, 3, 8, and even 10-hour modes.

The ability to record up to 10 hours on a DVD sounds like a great idea, but recordings made at a longer mode length will be lower in quality due to the increased compression. The increased compression not only affects the video quality but can also affect playback on some DVD players as the disc is harder to read, causing skips and freezes.

How Disc Writing Speed Factors Into DVD Recording

When you buy a blank recordable DVD, on the label it not only refers to the disc size and base record mode time (usually 120 min) but also refers to writing speed. The disc label may indicate a 2x, 4x, 8x, or higher writing speed capability.

What the term writing speed refers to is the how fast video or other types of computer data can be written to the DVD disc from a hard drive or another disc. This is not the same as live, real-time, recording.

In the case of a PC or Mac, this means you can copy a video or data file that you have previously recorded on your hard drive to a particular DVD disc, or, from one disc to another, that you have placed in your DVD-writer, at a high rate of speed.

For example, you can copy a 2-hour long video that you have recorded on your hard drive to a DVD in 15 minutes if the DVD writer and DVD disc supports an 8x writing speed. By the same token, if you have a DVD recorder that also has a hard drive, you would be able to copy the same 2-hour video to a DVD disc at the same 8x speed, provided the DVD recorder and disc support it.

In other words, both the DVD recorder and the DVD disc have to support specific disc writing speeds. Just because a disc might support up to an 8x writing speed doesn't mean that the DVD recorder can also write to the disc at that speed. For details, it is best to consult your DVD recorder user guide.

DVD writing speed is analogous to the high-speed dubbing functions on most dual-well audio cassette decks, audio cassette/CD recorder combos, or dual-well CD recorders that allow the user to copy from tape and/or CD to another tape and/or CD at a 2x or 4x higher-than-normal speed. This also applies to making copies of CDs on a PC — the faster the writing speed of the drive and the disc, the quicker you can copy from one disc to the next. This is also commonly referred to as tape or disc dubbing speed.

Writing Speed capability varies from product to product (if this feature is offered) — so take note of all DVD recorder and recordable disc specifications in the user manual or disc packaging label — the same goes for audio CDs.

The Bottom Line

DVD recorders do not have recording speeds, like a VCR, but recording modes. DVD recording modes can be used when recording with a built-in tuner, or outside sources, such as a VCR or camcorder. The DVD recording modes enable the user to put more video time on a DVD disc by increasing the amount of compression in the video signal, not changing the rotation speed of the disc.

The downside to putting more video time on a DVD disc is a loss of quality in the recorded video and possibly decreasing playback compatibility on other DVD players.

Disc writing speed, on the other hand, has no relation to how much time you can put on a DVD disc but refers to how fast you can dub from a computer or DVD recorder hard drive, or from another disc to a recordable DVD disc. Disc Writing Speeds are used when making copies of video or data from internal pre-recorded sources, residing on a PC, DVD recorder hard drive, or another disc.

DVD record modes determine how much video time you put on a DVD, Disc writing speed is how fast you can copy already recorded video or data from a DVD or a hard drive onto another DVD.