DVD recorders: Disc formats
DVD-R is one of the most common formats
There are 7 formats of DVD recordable discs available at present. No one DVD recorder can record on all formats.
The different blank media formats offer different facilities, however, not all recorders implement these fully and so there are differences between the features that are accessible on the different types of the discs.
A list of the features of the different types of disc is given below.
DVD-R
One of the most available formats. The DVD discs can be used for recording in either stand alone DVD recorders or in DVD drives on computers. The discs are cheap write-once-only discs.
The video is recorded onto the disc linearly from start to finish. They support multi-session - new recordings can be added later to the remaining blank section.
Recordings cannot be erased although unwanted titles can be hidden by deleting them from the table of contents. The recorded disc has to be ‘finalised’ to be able to play in most modern DVD players.
DVD-RW
These are re-recordable versions of the DVD-R system. The DVD discs can be used for recording in either these stand-alone DVD recorders or in DVD drives on computers. DVD-RW has 2 different modes of recording:
DVD-RW video mode
In its original configuration ‘DVD-RW video mode’, the recordings are recorded onto the disc linearly from start to finish. They support multi-session - new recordings can be added later to the remaining blank section.
Individual recordings (titles) can be deleted and replaced with new recordings. But if subsequent recordings are put in the space left by an erased title care must be taken to ensure the recording is no longer than the space so it doesn't continue copying over the next title. In this sense they are similar to replacing a recording on to cassette tape.
However, it is not possible to erase and replace part of a title. It’s possible for the whole disc to be erased and re-used. The blank disc has to be formatted before use and the recorded disc has to be ‘finalised’ to be able to play in most modern DVD players.
The compatibility is less reliable than DVD-R due to the different optical properties that some players cannot cope with. Once finalised chapters can’t be erased or re-recorded unless the disc is ‘un-finalised’ first.
DVD-RW VR mode
A newer mode for the DVD-RW discs is the ‘DVD-RW VR mode’. This gives the disc greater versatility for replacing and adding new recordings over old ones.
If a chapter is deleted and replaced with a new recording, the new recording will utilise the available space as normal but if the recording is longer than this gap, the recorder jumps to the next available blank space. This recording is still ‘linear’ but makes the disc appear more like a ‘random access disc’.
This format also allows more editing features to be used, such as join, crop and playlists. The discs can be finalised but the drawback is that the VR mode recorded disc is not compatible with other standard DVD players except for a few recent models that specifically support VR mode playback.
VR mode also allows the disc to be ‘read’ at the same time as it is recording (such as ‘time slip’) but these are less versatile than a hard drive PVR.
DVD+R
A rival system to the -R/-RW format. The DVD+R discs capabilities are very similar to the DVD-R discs, however the + recording systems is considered to be more a robust recording format and so less likely to produce errors.
The DVD discs can be used for recording in either stand alone DVD recorders or in DVD drives on computers. The discs are write once only discs. The video is recorded onto the disc linearly from start to finish.
They support multi-session - new recordings can be added later to the remaining blank section. Recordings cannot be erased although unwanted titles can be hidden by deleting them from the table of contents.
The recorded disc has to be ‘finalised’ to be able to play in most modern DVD players.
DVD+RW
These are re-recordable versions of the DVD+R system. The DVD discs can be used for recording in either stand alone DVD recorders or in DVD drives on computers.
The recordings are recorded onto the disc linearly from start to finish. They support multi-session - new recordings can be added later to the remaining blank section.
Individual recordings (titles) and parts of titles (A-B erase) can be deleted and replaced with new recordings. However, subsequent recordings cannot be longer than the space left by an erased title or A-B space.
In this sense they are similar to replacing a recording on to cassette tape. It is possible for the whole disc to be erased and re-used.
The blank disc is formatted automatically before use and the recorded disc is automatically ‘finalised’ so able to play in most modern DVD players although the compatibility is less reliable than DVD+R due to the different optical properties that some players cannot cope with.
Once finalised chapters cannot be erased or re-recorded unless the disc is ‘un-finalised’ first.
Dual layer discs
Is a recent addition on the market, and dual layer discs in R and RW formats may also become available. Commercial DVD films are recorded onto 2 layers giving 2 x 4.7GB capacity. Normal recordable DVDs only record on a single layer giving 4.7GB.
However, as dual layer blank DVD+Rs are now available there are several consumer computer DVD drives that can record on these. There are currently no standalone DVD recorders with the built in TV tuner that can record dual layers as yet known by the laboratory.
The finalised discs should be playable on modern standalone DVD players; however, in practice the switching to the second layer of the disc can cause some DVD players to freeze up.
The laser beam reads the data by focusing on spots imprinted on the disc
DVD-RAM
A true random access disc, the video is not recorded linearly (from start to finish) and available blank space is consolidated. In this sense DVD-RAM operates similarly to a computer hard drive or MiniDisc.
These discs sometimes come in a protective square caddy; this is to prevent damage to the surface of the disc, which is delicate.
The discs in the caddies can be removed and the discs put into DVD players without the caddy. Some DVD players have a disc tray shaped to be able to accommodate the caddy.
These discs are not compatible with most DVD players and DVD recorders, the exceptions being all Panasonic DVD players from the last 2 years.
Being true random access they offer a variety of title erase and edit facilities. They also allow the disc to be ‘read’ at the same time as it is recording (such as ‘time slip’) but these are less versatile than a hard drive PVR.