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Ok, I have to do a report/project on the compact Disc for a communications/technology class. ... And theres got to be some computor nerds out there that have some info to share with me about this.

 

I have done searches on Wikipedia and stuff already, but plz, one question I'm having trouble answering is...

 

Seeing how a compact disc can normally hold around 80 min. of music, how come in lets say a ps2 or other video game, they cram gigabites of data onto this disc that can barely hold 80 min of sound? Especially if the video game is music based and there are hours upon hours of songs on the disc.

Is the disc different than a normal compact disc, is the data in a different format, wats going on???

 

Plz only post here if u have relevant information and you know what your talking about because this is a serious class and a serious grade, I don't want to be getting false information.

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Theres a big difference between high quality music on audio CD's and compressed MP3's and such.

 

MP3 cuts frequencies off you arent able to hear, the usual audio CD you can buy in a shop has all those frequencies too.

 

Further MP3 compresses the music data, usual audio CDs have uncompressed music data.

 

And the music files used in games may even be a lower quality, meaning smaller size, than MP3 is.

 

Piper

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ooo... So usually when you would burn a cd or something the data is uncompressed, but in a music cd, an mp3 or other kinds of discs that you buy at stores with tons of data on them, its all compressed so that they can fit more on it? Is that correct, I'm gona put that on my paper.

 

Also, is it true that that many CD's would put data on the front and back or on multiple locations on the cd, if so how does that work exactly because the laser that reads the disc is specifically placed to only read data in 1 location i think...?

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Also, is it true that that many CD's would put data on the front and back or on multiple locations on the cd, if so how does that work exactly because the laser that reads the disc is specifically placed to only read data in 1 location i think...?

 

If the informtion is on both sides of the Cd this will work like a doudle sided DVD and has to be manually flipped over but most Cds/DvD's are multi layered nowadays , how the laser reads the differant layers and knows which layer to read then personally i havent a clue ( I know how a DvD works but not that technically), Im sure a Web search on how the laser works/reads discs would help

 

 

Howstuffworks.com

Edited by conavar

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ooo... So usually when you would burn a cd or something the data is uncompressed, but in a music cd, an mp3 or other kinds of discs that you buy at stores with tons of data on them, its all compressed so that they can fit more on it? Is that correct, I'm gona put that on my paper.

 

Its the format, that counts. Usual audio CDs you just put in your CD player and listen to, have uncompressed music, limited to 76 mins or such.

 

If you burn such a CD (which is highly illegal, of course), its still an audio CD with uncompressed data.

 

If you burn a CD containing MP3 files, its a data CD. A usual CD player without MP3 support cant play it. But your comp can play such a CD when you use a media player to decode and play the MP3 files.

 

Its the MP3 format which causes the data reducion.

 

A CD is still a CD which can hold like 700MB of data.

 

If a song is in audio format, like 50-60 MB, or its compressed to MP3-format, like 2-5 MB, you can of course store more SONGS on one CD, but its still limited to 700MB.

 

Here is a link for MP3: http://en.wikipedia.org/wiki/MP3

 

There are other formats, like ogg, which compress music data, its not limited to MP3: http://en.wikipedia.org/wiki/Ogg

 

Or WMA http://en.wikipedia.org/wiki/Windows_Media_Audio

 

And, and, and.

 

But its up to you to find that out :)

 

Piper

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Seeing how a compact disc can normally hold around 80 min. of music, how come in lets say a ps2 or other video game, they cram gigabites of data onto this disc that can barely hold 80 min of sound? Especially if the video game is music based and there are hours upon hours of songs on the disc.

Is the disc different than a normal compact disc, is the data in a different format, wats going on???

Your question is nothing to do with MP3/ogg/any other format, but in data storage.

 

A PS2 disc (as in your example) is to all intents and purposes a slightly modified DVD.

 

The capacity of an 80 minute CD is around 700MB of information, a single layer DVD can hold approximately 4.7GB of information, or 500 minutes of CD quality audio.

 

CDs and DVDs are built in basically the same manner, but CDs have much larger pits and grooves to store the data when compared with a DVD, so the DVD has more room on a disc.

 

I did a google search for cd dvd differences - lo and behold the first link: http://www.imation.com/products/dvd_media/differences.html

Insights: The Differences Between CD & DVD Media

 

Did you know...?

Recordable CD & DVD drives have become a must-have for home computers. More and more machines are including CD or DVD writer drives as a standard feature, and fast, affordable drives are easily available for machines without.

 

However, there's some question about new recordable DVD formats. There are no fewer than seven DVD formats, each with different specs and drive requirements — and not all of them are intended for computing.

 

Still, one common question is how any of these DVD formats varies from the writeable CD formats. Although DVD and CD media and drives have the same form factor (media size and shape), that's where the similarities end. DVD media has at least seven times the capacity of CD media — a feat partially accomplished by using multiple recording layers and recording on both sides of the media. The write method also helps boost the capacity of DVD.

 

Data pits & lasers

Like CDs, DVDs store data in microscopic grooves running in a spiral around the disc. All DVD drive types use laser beams to scan these grooves: Minuscule reflective bumps (called lands) and nonreflective holes (called pits) aligned along the grooves represent the zeros and ones of digital information.

 

DVD technology writes in smaller "pits" to the recordable media than CD technology. Smaller pits mean that the drive's laser must produce a smaller spot. DVD technology achieves this by reducing the laser's wavelength from the 780nm infrared light used in standard CD drives to 625nm to 650nm red light.

 

Smaller data pits allow more pits per data track. The minimum pit length of a single layer DVD-RAM is 0.4 micron as compared to 0.834 micron for a CD. Additionally, DVD tracks are closer together, allowing more tracks per disc. Track pitch-the distance from the center of one part of the spiral information or "track" to the adjacent part of the track-is smaller. On a 3.95GB DVD-R, track pitch is 0.8 microns; CD track pitch is 1.6 microns. On 4.7GB DVD-R media, an even smaller track pitch of 0.74 microns helps boost storage capacity.

 

These narrow tracks require special lasers for reading and writing — which can't read CD-ROMs, CD-Rs, CD-RWs, or audio CDs. DVD-ROM drive makers solved the problem by putting two lasers in their drives: One for DVDs, the other for CDs.

 

Layers

To facilitate the focusing of the laser on smaller pits, DVD media uses a thinner plastic substrate than do CDs. This reduces the depth of the layer that the laser must pass through to reach the pits to record or read data. This reduction originally resulted in disks that were 0.6mm thick — half the thickness of a CD.

 

Even single-sided DVDs have two substrates, even though one isn't capable of holding data. Double-sided discs with two data surfaces must be turned over (much like old vinyl records!) to read data on each side.

 

Data access speeds

DVD accesses data faster than CD and uses more robust error correction. In fact, the speed of DVD demands a new unit of measure. CD drive speeds are expressed as multiples of that format's original data transfer rate "X," or 150KB per second. A 32X CD-ROM drive reads data at 32 times 150KBps or 4MBps. DVD's 1X is a blistering 1.38MBps. That's faster than an 8x CD drive.

 

Universal Data Format (UDF)

Another big difference between DVD recording and CD recording is the recording format. DVD recording uses UDF — Universal Data Format. UDF makes it possible to store data, video, audio, or a mix of all three within a single physical file structure. This file structure ensures that any file can be accessed by any drive, computer, or consumer video. UDF includes the CD-standard ISO 9660 compatibility, but CDs do not comply with UDF.

 

 

If your course doesn't teach you about these (extremely basic) things and just expects you to know, you are on the wrong course or have an incompetent lecturer, consider changing classes or colleges.

 

If however you just can't be bothered looking then please don't come asking for coursework help.

 

I'll be watching with interest..

 

Regards

 

An extremely competent ex computer sciences college lecturer.

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If your course doesn't teach you about these (extremely basic) things and just expects you to know, you are on the wrong course or have an incompetent lecturer, consider changing classes or colleges.

 

If however you just can't be bothered looking then please don't come asking for coursework help.

 

I'll be watching with interest..

 

Regards

 

An extremely competent ex computer sciences college lecturer.

 

Lol yeah, ist for a Highschool course, and my teacher is a complete dumbass, I hate him but alot of my friends are in the class so I'm gona stick with it. And its supposed to be a research project but I figure this game has enough computer people to just tell me all about it.

 

Thnx for all the posts.

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Just a smartass post, labrat, he was asking for COMPACT DISC, and not for DVD's.

 

Of course, CD's are different from DVD's, one can hold 700MB of data, the other one 4.7 GB of data, but to answer the question, why you have only 12 songs on an audio CD but can have a CD with a game, which contains lots of game data + music, the answer still is compression. like MP3 and others :P

 

<smartass mode off>

 

(yeah, labrat, you know, that im joking, right? :D )

 

Piper

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google the terms

 

lossy --> Mp3 (very compressed) - extensive algorhythmic compression of the music track

lossless -->AIFF (CD tracks) - bit by bit fullscore electronic representation of the music track

Edited by Ikaris

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Just a smartass post, labrat, he was asking for COMPACT DISC, and not for DVD's.

 

Of course, CD's are different from DVD's, one can hold 700MB of data, the other one 4.7 GB of data, but to answer the question, why you have only 12 songs on an audio CD but can have a CD with a game, which contains lots of game data + music, the answer still is compression. like MP3 and others :P

 

<smartass mode off>

 

(yeah, labrat, you know, that im joking, right? :D )

 

Piper

Yeah I know you was joking, but he asked why a PS2 disc can hold more data than a CD, I answered him - PS2 is DVD not CD.

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Just a smartass post, labrat, he was asking for COMPACT DISC, and not for DVD's.

 

Of course, CD's are different from DVD's, one can hold 700MB of data, the other one 4.7 GB of data, but to answer the question, why you have only 12 songs on an audio CD but can have a CD with a game, which contains lots of game data + music, the answer still is compression. like MP3 and others :P

 

<smartass mode off>

 

(yeah, labrat, you know, that im joking, right? :D )

 

Piper

Yeah I know you was joking, but he asked why a PS2 disc can hold more data than a CD, I answered him - PS2 is DVD not CD.

 

PS2 are both some games are DVD some are CD depending on game size and age

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Yeah so I presented my project on Friday, It didn't go so well... Oh well, It's kind of a class that it really doesn't matter if I get a good grade in it or not. But I will get my grade for it on monday all the same.

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Hey! Every class is important! Heck with the school, it's the learning and understanding that is the main thing, once you get curious and can express the answers to others, then school is a piece of cake. This, you see, is why Yankee fans excel..... :omg:

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Lol... no I mean this class doesn't matter because it's not an academic class, whether I pass or not makes absolutly no difference on my collage aplication whether i get an F or an A, but I have A's in all my other classes, and the teachers really is a complete clueless idiot.

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yup... great, I got a C+ on the project cause the teacher thought I didn't know wat I was talking about in my presentation... I SPENT 20 MINUETES EXPLAINING IN FULL DETAIL EVERYTHING ABOUT THE COMPACT DISC!!! yeah anyway, hes a horrible teacher and doesnt even know where the on button on a dell computor is... seriously, he tried to push in the dell logo part and then through a fit cause it wasnt working.

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