DVD & DVD-RECORDERS
(Digital Versatile Disc) -a brief overview
The ordinary play-only type of DVD disc which we use for watching movies (called DVD-VIDEO) is only one type of DVD. As its name suggests, the DVD format is very versatile so can be used for many purposes and hence there are a number of different formats in use. There are also physically different types, e.g. single sided and double sided, and discs with an extra layer under the surface, called double-layer discs. Technically a DVD single-side can hold 4.7Gb of data, about 7 times that of a CD.
Apart from video DVDs, play-only DVDs can also hold computer-data, or a mixture of both. Thats why DVD/CD drives are now replacing CD-only drives in computers.
Then there are DVDs which you can record on yourself. You can buy DVD-recorders which work much like vhs video recorders, some with hard-drives and even vhs-decks in as well. Also many computers are fitted with recorder-drives, called DVD-writers, and they are are a popular upgrade to a PC. However the DVDs these all make are not identical to DVD-video used for movies you rent or buy. Manufacturers have tried to design dvd recorders and writers which make discs that are compatable with existing players, but because of the complex technology involved there are compromises, so at present we have 5 broad types each with different characteristics:
1) DVD+R ("DVD PLUS R") (originally specific to Philips, Sony, and LG) has good compatability with DVD players, but you can record on it only once, can't erase. Recordings are made in a continuous fashion on the disc, like on a CD. You could imagine the recording being in a continuous spiral groove like on a vinyl LP record (remember those?). You can record a bit and then add more later, building up until it is full. You can make a section 'invisible' afterwards which is skipped when played, but cant do much else with it once its recorded. Its ideal for 'archiving'. To play a DVD+R disc on ordinary DVD players (see below for info on compatability) you have to 'FINALISE' it first, an easy procedure which takes a few minutes, but stops you from adding any extra recordings to the disc. Its very similar to finalising an audio CD-R.
2) DVD+RW has many similarities to DVD+R but importantly you can erase recordings and re-record. So they are re-usable like a video-tape. They are also quite compatable, and have a nice feature with many machines that you dont generally have to finalise them so a part-used disc will often play in other players, and then can be added to later. (The disc is updated or 'finalised' automatically). Overall a very easy-to-use format.
3) DVD-R ("DVD MINUS R") (originally specific to Panasonic, Pioneer, JVC and others) has many similarities to DVD+R including finalising for compatability. This format has been the most common for producing compatable video-DVDs using a computer, but as most computer drives (writers) can use both plus and minus formats DVD+Rs are also used for this. DVD-R has one important feature over DVD+R, in that recodings made in widescreen format are 'tagged' as such so TVs usually select the correct format to show automatically. DVD+R will playback without any 'tag' to tell the TV what format it is so you have to manually set the TV each time. But these issues do depend on the dvd player's design as well as the TV.
4) DVD-RW is re-writable like +RW but has some important differences. Firstly, a new blank disk you must 'FORMAT' first. This is a way of preparing the disc for recording, and you choose one of two ways. Either 'VR mode' or 'Video mode'. VR is not really compatable with most existing players, Video mode is. However VR-mode does have more editing features so if you dont need to play the discs in other players its a useful format. Also unlike +RW when used in most machines, the -RW Video mode needs finalising to make compatable, after which you cannot add any extra recordings. So if you want to partially record a disc and then play it in an ordinary player, you have to finalise it and more recordings cant be made. However with some machines you can 'unfinalise' it later and start again, and add more recordings.
5) DVD-RAM records quite differently on the disc so cannot be played on ordinary play-only players. This is because you can erase any part of a recording and re-use that bit again, so recordings eventually get all jumbled-up on the disc (ordinary players expect the recording to be continuous). A DVD-RAM recorder knows where things are on the disc (because its clever) so it doesnt matter. This system makes it possible to do clever editing and because the laser-pickup is happy skipping about all over the disc you can even be playing one part back while recording on another. This is very much how a hard-drive records in a computer ('fragmented') and very similar indeed to the audio Minidisc with its versatile editing. Its a much less common format nowadays, and blank discs are more expensive.
CONFUSED? -just go back and read all the above again before continuing!
There are lots of other issues to make the world of recordable DVD a complex one, e.g. different digital compression techniques and ratios, billingual issues, disc-menu options, copy protection systems, & DVD-ROM used in PCs.
Also to make matters more complex, different makes and models record on the discs slightly differently, so sometimes you cant record more programs on a disc which has already had recordings made on another make and model of player, even if its meant to be compatable, and the features on a given format of disc are not always the same on different makes and models.
HARD DRIVES are often combined with a DVD-recorder in the same unit. The hard-drive (= HDD) is used to record things initially (like timer-recordings from TV) which can then be transferred (at a faster speed) to DVD later as a more permanent form of storage.
TWIN TUNERS some DVD-recorder + VHS or HDD combinations have two tuners so you can record two different programs at the same time, one on dvd, the other on vhs or hdd.
The length of time you can record on a dvd you chose when you set up the recording (like SP-LP on vhs), recorders have lots of different 'speeds' giving times from around 1hour to 6hours. You can mix 'speeds' on one disc. You may wonder why bother using 1hour, well its because a shorter time means higher quality. 1hr is very high quality indeed, 2-3hrs is pretty good (better than vhs) while the longer playing times you can see 'digital artefacts' which show up mainly on movement, or the picture is less sharp. Thats because to get a lot video on one dvd a lot of the data (or 'information') has to be removed, this is called compression. Its a common feature of modern digital television and you may have seen these problems on news broadcasts, even perhaps on normal Tv programs.
Digital TV systems like DVD, SKY-digital, Freeview, Freesat and cable are all 'compressed', unlike our old-fashioned conventional 'analogue' TV. However the main reason for compressing digital is you can get far more 'programs' down one 'channel'. But digital (including the excellent 'DV' tape format for camcorders) is also the only easy way the home-user can record high quality pictures and sound and maintain that quality (with care) when making copies or editing. Also digital video and sound are particularly compatable with a PC, so editing video and 'burning' the result on to a DVD (or a CD) is popular (and easy).
MULTICHANNEL SURROUND SOUND. ("5.1 or 6.1 or 7.1") An important difference to note between pre-recorded DVD-video discs and DVD-recordable is the inability to record surround-sound on a recordable. In contrast to DVD-video, which usually carries 6 independant soundtracks, all DVD recorders we know of to date are 2-channel stereo, but who knows what the future holds! Surround sound is one of the key features of pre-recorded DVDs. There are subtly different techniques used, like DTS and Dolby Digital, but generally movies have one system or another. Many DVD plyers are integrated in a complete surround-sound system, sold with all the speakers as a package, but also the surround-sound commonly is a digital signal fed out of a socket on the rear panel of a DVD player. Connect this to a decoder/amplifier and feed that to at least 5 speakers around the listening area, usually with a sub-woofer to get the bass-end moving (the ".1" bit), and this will help to re-create the sound of a good cinema sound-system.
MANUFACTURERS and FORMATS. It used to be that manufacturers only used certain formats, but generally now they are all pretty compatable.
Not long ago it used to be like this:-
Panasonic used DVD-RAM, DVD-R , Pioneer used DVD-R, DVD-RW, JVC used DVD-RAM, DVD-R, DVD-RW, Sony and LG use DVD-R, DVD+R, DVD-RW, DVD+RW
BLUE-RAY has now appeared specifially for HD (high definition). This is another format of DVD. It packs far more data (i.e. time) on to a disc by using a blue laser (normal ones are infra-red). Blue-ray DVDs will NOT play in standard players, only Blu-ray players. But these will of course play existing format DVDs, so are backwards compatable. There are a few Blue-Ray DVD recorders available now, and computer drives, thus slowly the world of HD home video is becoming a reality.
In general terms the write-once formats (+R & -R) are the most compatable with existing dvd-players, particularly the older ones. The RW formats are said to be about 80-90% compatable. In practise they play on almost all modern players (1-2 yrs old) but not many of the early players. There are always exceptions of course! Compatability with DVD-recorders using other formats is also an issue for RWs, generally ok with Rs. But the situation is getting better all the time as new recorders and players will play more, if not all, formats.
However DVD-RAM will NOT play in the majority of dvd-players (except some Panasonics), only in RAM-recorders, but this situation will also improve with new models coming out this year.
We aim to give accurate impartial advice about the products we supply, but as manufacturers sometimes change specifications without warning and new products appear overnight, it is not possible to guarantee our advice is always up-to-date. Always phone us or call in to our shop to get the latest info.
We are always pleased to hear from customers about their own experiences of products, good or bad!