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19th May 2005, 12:24 | #1 | Link |
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"4,7 GB = 120 min." - why?
On the cover of single-layer DVD-R's / DVD+R's it says "4,7 GB / 120 min"
- why is that? I know on CD-R's it says "700 MB / 80 min" because that CD-R has 360,000 sectors, and..: Data capacity: 360,000 sectors * 2048 bytes/sector data track = 737,280,000 bytes data (737,280,000 bytes) / (1024 bytes/KB) = 720,000 KB (720,000 KB) / (1,024 KB/MB) = ca. 703 MB So it can store ca. 703 MB data. Audio capacity: 360,000 sectors * 2,352 bytes/sector audio track = 846,720,000 bytes audio 44,100 samples/second * 2 bytes/sample * 2 (stereo) = 176,400 bytes/second (846,720,000 bytes) / (176,400 bytes/second) = 4,800 seconds (4,800 seconds) / (60 seconds/minute) = 80 minutes So it can store exactly 80 minutes of audio. But when it comes to the amount of sectors on DVD-R's / DVD+R's... According to OSTA there are some different numbers.. http://www.osta.org/technology/dvdqa/dvdqa6.htm DVD+R: DVD+R Specification Version 1.2 - 2,295,104 sectors (4,700,372,992 bytes) DVD-R: DVD-R (General) Specification Version 2.0 - (2,294,922 sectors) 4,700,000,000 bytes Although this is the minimums, most manufacturers are using 2,298,496 sectors (4,707,319,808 bytes) The reason for the "4,7 GB" stamp is because they use decimal 10-base notation - 1 GB = 1,000 KB = 1,000,000 bytes instead of the usual binary 2-base notation (like Windows use) - 1 GB = 1,024 KB = 1,048,576 bytes So.. how does those 2,295,104 / 2,294,922 / 2,298,496 sectors gets translated to "120 minutes"...? 120 minutes * 60 seconds/minute = 7,200 seconds (2,295,104 sectors) / (7,200 seconds) = 318,764444444..... sectors/second (2,294,922 sectors) / (7,200 seconds) = 318,739166666..... sectors/second (2,298,496 sectors) / (7,200 seconds) = 319,235555555..... sectors/second Clearly, any rigid "sectors/second" specification - like the "75 sectors/second" from CD's - is not used for DVD-R's or DVD+R's. Some manufaturers, like BenQ, thinks that 120 minutes of digital audio will take as much as 4,7 GB: http://www.benq.com.au/HomeProductList.asp?bc=30 "Offering the storage capacity of 4.7GB of data or 120 minutes of digital audio, BenQ's DVDR media enables you..." (I don't think I'll ever by any media from BenQ..!) Let's use the 2,298,496 sectors (4,707,319,808 bytes) DVD size. 4,707,319,808 bytes * 8 bits/byte = 37,658,558,464 bits 37,658,558,464 bits / 7,200 seconds = ca. 5,230,355 bits/second (ca. 5,230,355 bits/second) / (1,024 bits/Kbits) = ca. 5,108 Kbits/second. As far as I know, the DVD bitrate is variable. How can they set "120 min" on the cover? Could it be some old typing error, that it should say "120 mm" (the diameter of the DVD) instead..? |
19th May 2005, 14:29 | #2 | Link | |
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4.7 GB is a nicer number than the exact number of bytes or GB that are on the disc. CDs you'll find have maybe 79 mins 57 seconds, which is as near as dammit 80 mins. 703 MB is also as near as dammit 700 MB. The reason is it's very difficult to engineer a CD to exactly the "White Paper" specs. Doing so would also drive the cost up a lot. Making something to within "reasonable limits" is more cost-efficient and also allows for discrepencies within the manufacture process. 120 mins for the DVD recording is the average time you'll get. That particular notation is the standard time you'll get with a DVD recorder (standalone). With different recording modes you can extend the recording time (LP is 240 mins, EP is 360 mins). In short, it's just a standard that's been adopted, and stuck with out of convenience. Live with it.
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20th May 2005, 03:42 | #3 | Link | |
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According to the IEC 60027-2 standard, a gigabyte really is 1,000,000,000 bytes! A gibibyte is 1,073,741,824 bytes.
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21st May 2005, 13:09 | #5 | Link |
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MPEG-2 is VBR, so running time is utterly meaningless.
however, if you assume a constant (or average) bitrate of about 5000 kbps, then you'll get about that long on a DVD-5. it is all marketing after all, though. i would never put that much video on a DVD-5 - you just can't guarantee it'll look good at that bitrate. of course, you could fit heaps of video on a DVD-5 if it were in h.264...
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21st May 2005, 19:19 | #7 | Link | |
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Its always fun to hear people moaning about being cheated about a few 'GB' when they format their brand new hdds |
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22nd May 2005, 04:39 | #8 | Link | |||
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well i was not going to bother saying anything but what the hell, may aswell play a little devils advocacy. as such these comments are just meant to show you the other side of the story and should not be taken personally.
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as i said at the start, this is just to encourage people to think and see both sides so please dont try and flame me, i wouldnt take that kindly.
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22nd May 2005, 05:29 | #9 | Link | |
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To ease confusion, there has to be some rule that everyone will agree to. The IEC attempted to set a standard in 1998, so you would think Microsoft had enough time to incorporate the new math into Windows XP. Yet they didn't. The IEC standard is clear and concise (though I confess "gibibyte" doesn't roll off the tongue as fluidly as "gigabyte," LOL). So if/when Microsoft finally adopts it (and perhaps only then), I think it's pretty much guaranteed to become global law. Until that happens, or until a more agreeable standard comes along, Windows users remain mired in confusion. I have wondered if Microsoft's failure to implement the IEC standard is due to backwards compatibility issues. But I find it difficult to rationalize, considering that many of my old DOS games and programs don't work correctly under XP. As a user, it seems that I gave up "backwards compatibility" when I upgraded from Win98 in the first place...
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22nd May 2005, 12:13 | #10 | Link | |
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Re: "4,7 GB = 120 min." - why?
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but now also a movie of 90 min. is double layered, usually they fit about 70 min. in one layer... Anyone up to compare DVD and vhs tapes? How many vhs240 is a DVD? |
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22nd May 2005, 13:25 | #11 | Link |
interlace this!
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interesting... i wonder how much footage in half-d1 could be squeezed on a DVD before the quality falls below that of VHS...
i'm sure you could fit around 8 hours quite comfortably on a DVD-5 if you're only aiming for VHS quality.
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22nd May 2005, 14:00 | #12 | Link | |
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for example how many ram manufacturers are sticking kibi on their stickers ? none i have seen. is Mac using kibi (as in on screen, reporting hd and/or ram size etc)? i dont know. are Linux distros using kibi (again screen)? i know it was added to the kernel several years ago and there was complaints then about it causing confusion. couldnt find anything more about it though. how about third party software manufacturers(for any platform) ? have they started using kibi in their displays ? cant say i have seen this happening either. so this is not just a MS thing but a much wider spread non-acceptance.
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Narrator: And of course, with the birth of the artist came the inevitable afterbirth - the critic. (History of the World part 1) Last edited by dragongodz; 22nd May 2005 at 14:03. |
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22nd May 2005, 21:21 | #13 | Link | |
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Half d1 you mean 352x576/480? 8 hours on a dvd is 159kb/s, this is the mpg1 bitrate, 352x288. but using lp a svhs can play 8 hours on a tape with better quality than mpeg1 but still using xvid we can put 10 hours of movies on a dvd with better quality respect to the svhs.... Last edited by movmasty; 22nd May 2005 at 21:28. |
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23rd May 2005, 01:56 | #14 | Link |
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I'm with dragongodz on this one. There isn't a computer user alive (much less a programmer or hardware engineer) that would be CAUGHT DEAD using those crappy IEC terms. That was the stupidest thing ever conceived, and you can bet the IEC didn't consult a single computer expert while making this 'standard'. It's just jealous mathmeticians trying to embarass software programmers making ten times their salary.
I won't ever use those units in anything I write, and neither will anyone I know. They're just plain stupid. Who did they consult when making up those units? The director's three year-old? I have an idea - the base-10 camp can use the following units: 10e3 - kissy 10e6 - missy 10e9 - gissy 10e12 - tissy Have fun getting magazines to print THOSE units! |
23rd May 2005, 02:17 | #15 | Link |
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Well, how about:
Killer-byte Miller-byte Godziller-byte Thriller-byte In all honesty, I agree the IEC terms sound like baby talk. Big hunky macho programmers don't want to talk like that. I didn't exactly say it in my previous post, but I kinda alluded to a similar misgiving on my part. But is that the only reason people won't adopt them? Because if it is, don't you think it's kind of a silly reason? I'm sure we'll get over it once everybody is using the terms (if that ever happens).
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23rd May 2005, 05:33 | #16 | Link |
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You have to give people a compelling reason to change or they won't. So, name one reason to change - the IEC is TELLING you to. Is it compelling? Not in the slightest.
Now name a reason to NOT change - tradition, confusion, the IEC picked stupid sounding terms, and finally, all current computer science materials (books, etc.) would have to be rewritten, republished, and repurchased. Is it compelling? You bet your posterior. Hell, they couldn't get the US to go metric, and metric terms sound pretty cool. What in God's green Earth makes them think they could push that 'standard' when it makes you sound like an idiot? |
23rd May 2005, 06:14 | #17 | Link | |
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but thats another topic I agree though, atleast make the stuff sound smart, not lieka 3y/o's baly-rish |
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23rd May 2005, 06:51 | #18 | Link |
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@Joe Fenton:
The IEC isn't "pushing" it on anyone. They are publishing an international standard (that's their job) which the industry will either accept or reject. IMHO "the terms sound stupid" is not a compelling reason to reject it, but some of your other points are certainly valid. If all computer science materials will have to be rewritten, well, it's only because they were wrong to begin with. For example, the prefix "Kilo" (borrowed from the Metric system) is universally understood to mean 1000 units, and it's been that way for 200 years. What has screwed us up now is the fact that the computer industry adopted the same prefix, but redefined it as 1024 units! The IEC's standard will eliminate this confusion once and for all, and to me that is an overwhelmingly compelling reason to adopt it. But, like your example of the U.S. going metric, it just ain't gonna stick unless everyone agrees, especially the big players. I think Microsoft could set a tremendous example by adopting the standard in their next OS. Will we sound like infants when we talk? Sure! But at least we'll agree on what we're talking about. Remember the term "googol" (from which "Google" gets its name) was invented by a 10-year old child. Do people of today feel stupid saying the word "Google"? Absolutely not!
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23rd May 2005, 07:09 | #19 | Link | |
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anyways, yeah getting this stupid 10/2-base crap sorted out would be nice, much less math in hte long run converting this crap to that crap |
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