[Dixielandjazz] US vs UK DVD's

[Ulf Jagfors]

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;

  a.. The Internet Movie Database, at http://www.imdb.com. This lists cuts 
and alternate edits to specific movies under the Alternate Versions 
subheading, and
  b.. 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.
  c.. 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
  a.. 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.
  b.. 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.
  c.. For video-based material, it is generally better for the DVD to remain 
in the same format as the source material.
  d.. 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