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Q: DVD ( Answered 5 out of 5 stars,   0 Comments )
Subject: DVD
Category: Computers
Asked by: sulafa-ga
List Price: $4.00
Posted: 08 Nov 2003 11:52 PST
Expires: 08 Dec 2003 11:52 PST
Question ID: 273878
I have a DVD movie and when i put it on my laptop it says that the DVD
is 7.42GB, i thought DVD were something like 4.7GB how could this be?

Note that there is no problem i just want to know how this DVD is more
the 5GB, th emovie works fine.
Subject: Re: DVD
Answered By: clouseau-ga on 08 Nov 2003 12:04 PST
Rated:5 out of 5 stars
Hello sulafa,

Thank you for your question.

I know that for me, all of the DVD "standards" are confusing still and
when I need info, I trot over to the DVD FAQ (Frequently Asked
Questions) as this seems to be the gospel according to DVD:

Searching a bit, I found:

"...[3.3] What are the sizes and capacities of DVD?

There are many variations on the DVD theme. Discs come in two physical
sizes: 12 cm (4.7 inches) and 8 cm (3.1 inches), both 1.2 mm thick,
made of two 0.6mm substrates glued together. These are the same form
factors as CD. A DVD disc can be single-sided or double-sided. Each
side can have one or two layers of data. The amount of video a disc
can hold depends on how much audio accompanies it and how heavily the
video and audio are compressed. The oft-quoted figure of 133 minutes
is apocryphal: a DVD with only one audio track easily holds over 160
minutes, and a single layer can actually hold up to 9 hours of video
and audio if it's compressed to VHS quality.

At a rough average rate of 5 Mbps (4 Mbps for video and 1 Mbps for two
or three tracks or audio), a single-layer DVD can hold a little over
two hours. A dual-layer disc can hold a two-hour movie at an average
of 9.5 Mbps (close to the 10.08 Mbps limit).

A DVD-Video disc containing mostly audio can play for 13 hours (24
hours with dual layers) using 48/16 PCM (slightly better than CD
quality). It can play 160 hours of audio (or a whopping 295 hours with
dual layers) using Dolby Digital 64 kbps compression of monophonic
audio, which is perfect for audio books.

Capacities of DVD:
For reference, a CD-ROM holds about 650 megabytes, which is 0.64
gigabytes or 0.68 billion bytes. In the list below, SS/DS means
single-sided/double-sided, SL/DL/ML means
single-layer/dual-layer/mixed-layer (mixed means single layer on one
side, dual layer on the other side), gig means gigabytes (2^30), BB
means billions of bytes (10^9). See note about giga vs. billion in
section 7.2.

DVD-5 (12 cm, SS/SL) 4.37 gig (4.70 BB) of data, over 2 hours of video 
DVD-9 (12 cm, SS/DL) 7.95 gig (8.54 BB), about 4 hours 
DVD-10 (12 cm, DS/SL) 8.74 gig (9.40 BB), about 4.5 hours 
DVD-14 (12 cm, DS/ML) 12.32 gig (13.24 BB), about 6.5 hours 
DVD-18 (12 cm, DS/DL) 15.90 gig (17.08 BB), over 8 hours 
DVD-1 (8 cm, SS/SL) 1.36 gig (1.46 BB), about half an hour 
DVD-2 (8 cm, SS/DL) 2.47 gig (2.66 BB), about 1.3 hours 
DVD-3 (8 cm, DS/SL) 2.72 gig (2.92 BB), about 1.4 hours 
DVD-4 (8 cm, DS/DL) 4.95 gig (5.32 BB), about 2.5 hours 
DVD-R 1.0 (12 cm, SS/SL) 3.68 gig (3.95 BB) 
DVD-R 2.0 (12 cm, SS/SL) 4.37 gig (4.70 BB) 
DVD-R 2.0 (12 cm, DS/SL) 8.75 gig (9.40 BB) 
DVD-RW 2.0 (12 cm, SS/SL) 4.37 gig (4.70 BB) 
DVD-RW 2.0 (12 cm, DS/SL) 8.75 gig (9.40 BB) 
DVD+R 2.0 (12 cm, SS/SL) 4.37 gig (4.70 BB) 
DVD+R 2.0 (12 cm, DS/SL) 8.75 gig (9.40 BB) 
DVD+RW 2.0 (12 cm, SS/SL) 4.37 gig (4.70 BB) 
DVD+RW 2.0 (12 cm, DS/SL) 8.75 gig (9.40 BB) 
DVD-RAM 1.0 (12 cm, SS/SL) 2.40 gig (2.58 BB) 
DVD-RAM 1.0 (12 cm, DS/SL)  4.80 gig (5.16 BB) 
DVD-RAM 2.0 (12 cm, SS/SL) 4.37 gig (4.70 BB)* 
DVD-RAM 2.0 (12 cm, DS/SL) 8.75 gig (9.40 BB)* 
DVD-RAM 2.0 (8 cm, SS/SL) 1.36 gig (1.46 BB)* 
DVD-RAM 2.0 (8 cm, DS/SL) 2.47 gig (2.65 BB)* 
CD-ROM (12 cm, SS/SL) 0.635 gig (0.650 BB) 
CD-ROM (8 cm, SS/SL) 0.180 gig (0.194 BB) 
DDCD-ROM (12 cm, SS/SL) 1.270 gig (1.364 BB) 
DDCD-ROM (8 cm, SS/SL) 0.360 gig (0.387 BB) 

* Formatted DVD-RAM discs have slightly less than stated capacity. For
example, the contents of a completely full DVD-R will not quite fit on

Tip: It takes about two gigabytes to store one hour of average video.

The increase in capacity from CD-ROM is due to: 1) smaller pit length
(~2.08x), 2) tighter tracks (~2.16x), 3) slightly larger data area
(~1.02x), 4) more efficient channel bit modulation (~1.06x), 5) more
efficient error correction (~1.32x), 6) less sector overhead (~1.06x).
Total increase for a single layer is about 7 times a standard CD-ROM.
There's a slightly different explanation at

The capacity of a dual-layer disc is slightly less than double that of
a single-layer disc. The laser has to read "through" the outer layer
to the inner layer (a distance of 20 to 70 microns). To reduce
inter-layer crosstalk, the minimum pit length of both layers is
increased from 0.4 um to 0.44 um. To compensate, the reference
scanning velocity is slightly faster, 3.84 m/s, as opposed to 3.49 m/s
for single layer discs. Longer pits, spaced farther apart, are easier
to read correctly and are less susceptible to jitter. The increased
length means fewer pits per revolution, which results in reduced
capacity per layer.

Note: Older versions of Windows that use FAT16 instead of UDF, FAT32,
or NTFS to read a DVD may run into problems with the 4 gigabyte volume
size limit. FAT16 also has a 2 gigabyte file size limit, while FAT32
has a 4 gigabyte file size limit. (NTFS has a 2 terabyte limit, so
we're ok there for a while.)

See 4.3 for details of writable DVD. More info on disc specifications
and manufacturing can be found at Disctronics, Cinram. Panasonic,
Technicolor, and other disc replicator sites..."

So most likely, you have a Single Sided / Dual Layer DVD-9 in your
case, which is actually quite common. DVD Recordable, currently is
limited to 4.7GB, but even that will be changing as Dual Layer
recordabales become available later this year.

Search Strategy:


I trust my research has provided you with the answer you desired. If a
link above should fail to work or anything require further explanation
or research, please do post a Request for Clarification prior to
rating the answer and closing the question and I will be pleased to
assist further.


sulafa-ga rated this answer:5 out of 5 stars

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