PAL vs NTSC
or, Which DVD Do I Buy?
There has been endless debate on the relative merits
of the quality of PAL images versus the quality of NTSC images. In this
article, I want to present you with the arguments for and against both
PAL and NTSC on DVD so that you can make an informed decision when purchasing
your DVDs in regards to the best version to buy. As you will see in this
article, it is not necessarily the case that PAL is always better or that
NTSC is always better. However, I aim to point out the reasons why you
should prefer one format over the other, and in which circumstances you
should prefer one format over the other.
As an aside, if you are not familiar with the concept
of 16x9 enhancement, I strongly recommend that you read
my article on this topic, as your understanding of the remainder of
this article will be significantly enhanced if you understand 16x9 enhancement.
As a further aside, if you have a Region 1 DVD player you in all likelihood
cannot play PAL DVDs both for reasons of Region locking and because the great
majority of Region 1 DVD players have had their PAL playback ability disabled,
not to mention the fact that most NTSC display devices cannot display PAL
images.
They're Not Really PAL or NTSC
The first thing I need to clarify about DVD is that
PAL and NTSC are words and formats that are applied to DVD for convenience,
and because of historical convention. There is nothing fundamental about
a DVD which makes it either PAL or NTSC, but for simplicity and brevity,
I will continue to use these terms throughout this article.
At their heart, DVDs are merely carriers of data
files with compressed audio-visual information contained therein. This
information can be placed on DVD in one of two resolutions; 720 x 576 pixels
(PAL DVDs), or 720 x 480 pixels (NTSC DVDs), and with various frame rates
(24, 25, and 30 frames per second are common). The DVD player itself takes
this data file and formats it appropriately for display in either PAL or
NTSC.
The Issue Of Resolution
In principle, PAL DVDs have a compelling advantage over
NTSC DVDs. PAL DVDs have 576 pixels of vertical resolution versus 480 pixels
of vertical resolution. That's a 20% increase in resolution for a PAL DVD
as compared to an NTSC DVD. Increased resolution translates into a better
looking image. However, this is an overly simplistic way of looking at
the whole PAL vs NTSC issue as there are other factors that need to be
taken into account.
Active Pixels & 16x9 Enhancement
Because programming can be presented on DVD in various
aspect ratios, it is useful to consider the active pixels in a given
image when considering the overall resolution of a DVD. For a widescreen
image, not all of the pixels available on a DVD are actually used for the
image. Some of them make up the black bars above and below the image. The
format that provides the most overall active pixels for a given aspect
ratio will in theory be the best possible format. Complicating the issue
is the difference in active pixels when a DVD is 16x9 enhanced.
The following table illustrates the common aspect
ratios presented on DVD along with the total active pixels presented in
each possible DVD format. I have highlighted the best formats in green.
Aspect Ratio |
4x3 PAL
|
16x9 enhanced PAL
|
4x3 NTSC
|
16x9 enhanced NTSC
|
1.33:1 |
720 x 576 = 414,720
|
538 x 576 = 309,888
|
720 x 480 = 345,600
|
538 x 480 = 258,240
|
1.66:1 |
720 x 461 = 331,920
|
671 x 576 = 386,496
|
720 x 384 = 276,480
|
671 x 480 = 322,080
|
1.78:1 |
720 x 430 = 309,600
|
720 x 576 = 414,720
|
720 x 358 = 257,760
|
720 x 480 = 345,600
|
1.85:1 |
720 x 414 = 298,080
|
720 x 554 = 398,880
|
720 x 345 = 248,400
|
720 x 461 = 331,920
|
2.35:1 |
720 x 326 = 234,720
|
720 x 436 = 313,920
|
720 x 271 = 195,120
|
720 x 363 = 261,360
|
Key |
Best
|
Second Best
|
Third Best
|
Worst
|
Widescreen Movies
For widescreen movies, 16x9 enhanced PAL DVDs provide
the highest resolution image, and are theoretically the version of choice.
If the PAL version of a widescreen movie is not 16x9 enhanced, then the
version of choice is a 16x9 enhanced NTSC DVD.
Frame and Field Rates
The consideration of which version is best is complicated
by the issue of source material. In the case of movies, the choice is simple
- pick the disc which has the highest possible image resolution, all else
being equal. In the case of video-sourced material, the choice is less
simple.
Movies
Movies the world over are shown at a frame rate of 24
frames per second. That is, 24 images are projected onto the cinema screen
every second. Movie film is a very high resolution format, far higher in
resolution than the DVD format. Accordingly, the movie itself is not the
limiting factor in deciding between PAL and NTSC format DVDs, as the same
source material is usually used to create both the PAL and the NTSC versions
of a particular DVD. Therefore, the limiting factor in resolution is the
DVD itself, with PAL inherently higher in resolution than NTSC.
Video
With video-based source material, there are two predominant
worldwide formats; PAL and NTSC, which differ in both resolution and in
frame rate. PAL is higher in resolution (576 horizontal lines) than NTSC
(480 horizontal lines), but NTSC updates the on-screen image more frequently
than PAL (30 times per second versus 25 times per second). What does this
mean in practice? NTSC video is lower in resolution than PAL video, but
because the screen updates more frequently, motion is rendered better in
NTSC video than it is in PAL video. There is less jerkiness visible. When
video source material is transferred to DVD, it is usually transferred
in the format it was created in - PAL or NTSC, and the subsequent image
has either higher temporal resolution (more frames per second -
NTSC) or higher spatial resolution (more lines per image - PAL).
Conversions between the two video formats are possible,
and are indeed frequently carried out, as it seems to be far more
acceptable to sell PAL transfers in PAL countries and NTSC transfers in
NTSC countries, even if the source material did not originate in the respective
format. Conversions between these formats is problematic, however, as compromises
need to be made in order to accommodate the source material, and visible
artefacts can be introduced by the conversion process.
Converting NTSC to PAL
When converting from NTSC to PAL, two things need to
be accomplished. 480 lines of resolution have to be upconverted to 576
lines of resolution, and 30 images per second have to be downconverted
to 25 images per second.
The resolution upconversion does not actually add
any real picture information to the image, as you cannot create real picture
information where none existed before. It does, however, make the picture
viewable on a PAL display, and often results in a superficially better-looking
image.
The frame rate conversion actually results in a loss
of temporal resolution, as PAL has a lower frame rate than NTSC.
Converting PAL to NTSC
The converse situation applies to PAL to NTSC conversions.
576 lines of resolution are downconverted to 480 lines of resolution, and
frames need to be inserted to go from the 25 frames per second of PAL to
the 30 frames per second of NTSC. Once again, the resultant image is of
less actual resolution than the original image, as information is discarded
spatially and made up temporally.
Implications for Video Programming On DVD
The best format to record and play back video programming
on DVD in is the format in which the programming was originally created.
If it was videotaped in the NTSC format, then the NTSC DVD will be the
version of choice. If it was videotaped in the PAL format, then the PAL
DVD will be the version of choice.
Higher Definition Source Material
Complicating this issue is the fact that more and more
programming is being created in higher definition video formats these days,
and these high definition formats can usually be converted down to PAL
or NTSC equally well, with both formats having their respective disadvantages.
So, Which Version Do I Choose?
As a general rule, video programming sourced from PAL-based
countries is likely to look better in PAL, and video programming sourced
from NTSC-based countries is likely to look better in NTSC, since these
are the likely native formats that they have been created in.
Other Factors To Consider
If all of the above issues aren't enough to consider
when deciding whether to purchase a PAL or an NTSC version of a particular
title, there are several other factors which are also worth taking into
consideration.
Compression Ratio
Previously, it has been established that a PAL DVD has
20% more resolution than an NTSC DVD. This does not necessarily translate
into a superior image. The DVD format relies on a lossy video compression
format (MPEG-2) to allow a reasonable length of programming to fit onto
a single DVD. The longer the programming, the higher the compression ratio
needs to be, and the more likely it is that visible compression artefacts
will be present. If an additional 20% of resolution needs to be compressed,
then this can potentially result in a lesser quality image if the programming
is overcompressed. Fortunately, many PAL DVDs are being produced as dual
layer discs, whereas their NTSC counterparts are being produced as single
layer discs, thus providing the necessary room for both versions to look
their best.
Censorship
There are times when programming can be censored for
display in PAL countries and uncensored in NTSC countries. GoldenEye
and Tomorrow Never Dies
are specific examples of DVDs where the PAL versions of the DVDs have been
censored in comparison to the uncensored NTSC versions. The converse also
sometimes applies, as is the case with Eyes
Wide Shut, the DVD of which was digitally censored in the USA but uncensored
in Australia.
It is exceedingly difficult to find out whether a
specific DVD has been censored in one part of the world or another. Two
specific Internet resources that are helpful in this area are;
-
The Internet Movie Database, at http://www.imdb.com.
This lists cuts and alternate edits to specific movies under the Alternate
Versions subheading, and
-
Melon Farmers, at http://www.melonfarmers.co.uk/dhhits.htm.
This is predominately a listing of UK cuts to DVDs, which is generally
not applicable to the Australian version of the DVD. However, on occasion
we receive the same disc as the UK, and subsequently suffer the same censorship.
-
The Cut List, at http://www.dvdfile.com/software/cut_list/index.html.
This is a listing of US cuts and alternate DVD edits.
PAL's 4% Speed Up
Movies on PAL DVDs play back 4% faster than their NTSC
counterparts. The great majority of people will never notice this, but
for a small minority, this is an intolerable artefact. For more details
on why this speed-up occurs, please refer to my
article on this topic.
NTSC's 3:2 Pulldown
Movies on NTSC DVDs play back at the correct speed,
but they achieve this by utilizing a process called "3:2 pull-down". A
detailed discussion of this process is beyond the scope of this article,
but the net effect of this is that any image pan is not smooth, but takes
place in a series of uneven steps, an artefact known as judder.
As with PAL's 4% speed-up, the great majority of people will never notice
this artefact, but for a small minority, this is intolerable. Personally,
I find this artefact all but intolerable and find it very hard to watch
a movie on an NTSC DVD because of it.
Extras
Often times, the extras on one version of a DVD are
not found on another version. It is most disconcerting when you have purchased
a DVD to find out that another version is available which has far more
extras than the one that you have just paid good money for.
Remastering
Sometimes, a DVD will be produced from restored or remastered
source elements in one region and from non-restored sources in another
region.
Conclusions
-
PAL is a higher resolution format for DVD than NTSC. All else being equal,
a PAL DVD of a movie should look significantly better than the equivalent
NTSC DVD.
-
If a PAL version of a movie DVD is not 16x9 enhanced and the NTSC version
is 16x9 enhanced, then the NTSC version will be the preferred version,
all else being equal.
-
For video-based material, it is generally better for the DVD to remain
in the same format as the source material.
-
Do your homework before purchasing a DVD! Check as many resources as you
can in order to determine which version of a particular DVD is the most
appropriate one to purchase.
© Michael Demtschyna
7th July 2000