Cd/dvd Formats. Conversion From Analogue to Digital and the Future of Digital Media Storage

Digital data is different from analogue data, because there is usually very little data loss that occurs. Compare cassette tapes and audio CDs, the analogue tape has a series of frequency curves that tell the speakers what sounds to emit through an amplifier. CDs do much the same except data is contained in binary form (i.e. zeros and ones) the device or player recognises these zeros and ones and arranges them into a frequency pattern which is then transferred through to the speakers. Basically it is the same process as with a tape except with one extra step – converting from binary code into frequency curves. So while tapes get stretched and damaged, the frequency curves embedded on the film deteriorates. Whereas this hardly ever occurs with CDs because the data is stored behind Perspex and it’s hard to change a zero to a one (and vice-versa.)

But what is binary? As I said before, it is either a zero or a one – but how is this done I hear you ask. Well binary code is generated most commonly with lasers or magnets and is why we call media “digital.” Digital media encompasses all CDs, DVDs, Hard Disc Drives (computers), iPods etc. For CDs, a laser will burn a microscopic “dot” in the media which a device will identify as a “one.” All other sections that the laser does not burn are read as a “zero.” Hence binary code is made! Magnetic media works in a similar way except instead of burning dots, the drive will change the magnetic field at a particular segment to make a “one.”

So what does this all mean to you? Not much really, except that it helps to conceptualise the differences in formats each media possesses...

Audio/Video vs. Data

CDs come most commonly in CD-R, CD-RW, CD-ROM and VCD format and can fit 700MB on a disc as a data CD or 80 minutes as an audio CD. The confusing part is how do audio CDs and data CDs differ? Firstly is not the actual media that is different, but the way in which the data is written on the disc. Audio CDs have to be readable by a CD player, so there was a standard made so that all audio CDs would be created in such a way that a player anywhere in the world could understand. This differs from Data CDs where any type of file can be copied to a CD, including word documents, images, music etc. What! Music on a data CD? Yes it’s true; remember when you decided to back up your old CD albums onto your computer? – Well you probably used a program like Windows Media Player or iTunes to “rip” the songs to your computer from the CD. When this happens, the audio from the CDs is converted to a format on your computer that minimises space requirements. Popular formats (or codec’s) include MP3, WMA, OGG and AAC. So instead of storing a whopping 700MB per album, you can decrease the amount to as low as 50MBs per album without too much reduction in sound quality. The difference with copying music onto a data CD is that the music will still be in one of the audio formats you used such as MP3 and hence unreadable by conventional CD players.

DVDs are much the same deal except with a video component: DVD players (like CD players) will only read DVD Video files that are arranged in a way it can understand. Data DVDs can store any type of file you want. Popular DVD formats are DVD-R, DVD-RW and DVD-RAM which store about 4.7GB on a Data DVD or 60 minutes on a DVD video. However you can increase the number of minutes on a video DVD by reducing its quality (which you cannot do for an audio CD.) So it still arranges the files for a DVD player except the size (aspect ratio-wise) of the video becomes smaller and hence blurry when viewed. Manufacturers have made a DVD that has 2 layers called DVD-DL (or DVD – Dual Layer) which doubles the capacity of conventional DVDs so you can fit more video onto a disc without the need to decrease the quality. Almost all DVDs that are sold today are on DVD-DLs. You can also copy videos onto a data DVD, except these will be in a compressed format such as an AVI or MPEG – comparable to an MP3 or WMA file for music.

So what’s the future of digital storage? Blu-ray is a new type of disc which is just starting to become popular it makes use of a blue laser (which has a smaller wavelength) to write data onto its surface hence increasing the disc capacity up to 25GB and 50GB on a dual layer disc. Ideally, this type of disc should have been made instead of regular DVDs for its obvious benefits – but when DVDs were first invented there was no need of a 25GB disc so the current DVDs were the cheaper and the most obvious choice. Blu-ray will eventually succeed DVD as DVD did VHS and CD did to cassette.

CDs will likely remain common as they are roughly the amount of space needed to fit a song album on. If manufacturers decided to increase the capacity of audio CDs, then there would be compatibility issues with existing players and lots of space would go to waste as most artists will not produce albums that would exceed audio CD capacity anyway.

Interesting sidenotes:

MP3 CDs are CDs that are a cross-between audio CDs and Data CDs. A relatively new CD player can support MP3 CDs but all files on the disc must be converted to MP3 format first. This increases the amount of songs you can fit on one CD.

CD quality – this means the CDs you buy from an outlet – is considered to be infinite. However when you rip CDs to your computer you lose quality by reducing the space it requires; so when you convert these files and burn them to an audio CD again, it is not the same quality as the original. Likewise for DVDs. The only way to keep the original quality is to actually copy CD to CD using burning software such as Nero or rip using a lossless encoder and burn from there.

For high quality conversion and duplication visit Benarama Productions We offer premium grade conversion from cassette tapes to CD, and VHS tapes to DVD – locking your files digitally for years to come and cleaning any imperfections from the original copy. We also offer video editing to make your memories memorable servicing corporate videos through to birthday parties. No matter what the size – capture it properly with Benarama Productions! Go to www.benarama.com.au and follow the links.