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Old 07-10-2004, 13:29   #1
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Question DVD Compression

Hi,

I just have a quick question about compression. When reading the excellent reviews of the Star Wars Trilogy on this site they mention compression being excellent. My questions is this. Some decent movies like these, how much data would they take up if they were uncompressed. Curious thats all?

Thanks

T

Last edited by Theriomophic; 07-10-2004 at 13:30.
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Old 07-10-2004, 14:23   #2
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Somewhere around 30mb per second. So for a 2 hour film, you're taking around 220gb.
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Old 07-10-2004, 18:56   #3
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Well, you can do the maths yourself, really, if you like. An NTSC DVD's typical resolution is 720x480 pixels. Now with 3 bytes per pixel (for true colour) that works out to 1,036,800 bytes per frame. NTSC films play at 24fps so with's 25,920,000 bytes per second, it works out to 1,492,992,000 bytes per minute (~1.5Gb).

Obviously that doesn't take audio into account, though, so for nice quality 5.1 (assuming equal 48Khz 16bit sound for each channel) that's an additional 6x2x48,000 bytes per second (576,000) or 34,560,000 (~34Mb) per minute.

So assuming Star Wars to be 125 minutes (special edition) for the US cinema release (and probably therefore the DVD version, too) it's:

(1,492,992,000 + 34,560,000) * 125
= 190,944,000,000 bytes
= 186,468,750 KBytes
= 182,098 MBytes
= ~178 GBytes

I hope that answers your question.

Btw, I've probably screwed up the maths somewhere so don't trust my figures.
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Old 07-10-2004, 21:01   #4
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Quote:
Originally Posted by ajm
Somewhere around 30mb per second. So for a 2 hour film, you're taking around 220gb.
Can't wait for the day when we have 220gb video discs
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Old 08-10-2004, 00:06   #5
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Quote:
Originally Posted by Dr Derek Doctors
Obviously that doesn't take audio into account, though, so for nice quality 5.1 (assuming equal 48Khz 16bit sound for each channel) that's an additional 6x2x48,000 bytes per second (576,000) or 34,560,000 (~34Mb) per minute.
Sorry to be pedantic, but it's 5.1 x 2 x 48,000 = 489,600 which is about 29Mb per minute

The 0.1 channel AFAIK does carry 1/10 of the sound range
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Old 09-10-2004, 07:41   #6
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Quote:
Originally Posted by Marz
Sorry to be pedantic, but it's 5.1 x 2 x 48,000 = 489,600 which is about 29Mb per minute

The 0.1 channel AFAIK does carry 1/10 of the sound range
I refer the learned gentleman to my "Btw, I've probably screwed up the maths somewhere so don't trust my figures." disclaimer which protects me from indemnity in this matter.

Ah, I always kinda' wondered why it was called "5.1" instead of "6, but with one of those loud buggers included"
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Old 09-10-2004, 18:47   #7
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hold on though, I thought that uncompressed D1 standard definition video was 270 mbps!

I'm sure this is the figure given by Steve Roberts of the BBC.

Thats one hell of a lot of data!

Last edited by Duncan Harvey; 09-10-2004 at 18:47.
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Old 09-10-2004, 18:53   #8
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Quote:
Originally Posted by Duncan Harvey
hold on though, I thought that uncompressed D1 standard definition video was 270 mbps!
I suspect that's measured in "bits" not "bytes", then it sounds about right.
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Old 10-10-2004, 01:37   #9
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Quote:
Originally Posted by Marz
Sorry to be pedantic, but it's 5.1 x 2 x 48,000 = 489,600 which is about 29Mb per minute

The 0.1 channel AFAIK does carry 1/10 of the sound range
The .1 is only symbolic, but it's true that if you take account of the limited frequency range of the LFE channel and bear in mind Nyquist's theorem, then you wouldn't need to sample at 48 kHz. That would be serious overkill. I can't recall exactly what range the LFE channel carries, but I'd imagine it's only up to around 120Hz-200Hz or so, which is much less than 1/10th of the entire range. You'd need a sample rate of at least 240Hz-400Hz to capture those low frequencies accurately (Nyquist).

Last edited by Squirrel God; 10-10-2004 at 03:20.
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Old 10-10-2004, 15:58   #10
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Quote:
Originally Posted by KeyserSoze
Can't wait for the day when we have 220gb video discs
http://news.bbc.co.uk/1/hi/technology/3696306.stm




I have to say I am surprised that MPEG-2 appears to be the standard codec for Blu-Ray and the next generation of DVD, I was expecting an MPEG-4 based codec.
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Old 10-10-2004, 16:05   #11
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DVDs are one of the most successful consumer products in history. Most DVDs have two layers and can hold up to 8.5GB.
Either they're misinformed, or that's very misleading (if they're on about each layer)
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