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 | ||||
| 1.33:1 | ||||
| 1.66:1 | ||||
| 1.78:1 | ||||
| 1.85:1 | ||||
| 2.35:1 |
| Key |
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 higherspatial 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.
資料來源:http://www.michaeldvd.com.au/articles/palvsntsc/palvsntsc.asp
NTSC is used with a fps of 60i or 30p, so theoretically offers very slightly smoother motion than PAL, which is generally used with 50i or 25p.
Progressive scanning (alternatively referred to as noninterlaced scanning) is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used in traditional analog television systems where only the odd lines, then the even lines of each frame (each image called a video field) are drawn alternately. (p-逐行掃描/播放, i-隔行掃描/撥放)
以NTSC電視機為例, 在工作的時候, 把衣幅525行圖像分成兩場來掃, 第一場稱奇數場, 掃描奇數行, 而第二場掃描偶數行, 透過兩場掃描完成原來一圖像掃描的行數
NTSC is used with a fps of 60i or 30p, so theoretically offers very slightly smoother motion than PAL, which is generally used with 50i or 25p.
Progressive scanning (alternatively referred to as noninterlaced scanning) is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used in traditional analog television systems where only the odd lines, then the even lines of each frame (each image called a video field) are drawn alternately. (p-逐行掃描/播放, i-隔行掃描/撥放)
以NTSC電視機為例, 在工作的時候, 把衣幅525行圖像分成兩場來掃, 第一場稱奇數場, 掃描奇數行, 而第二場掃描偶數行, 透過兩場掃描完成原來一圖像掃描的行數
PAL broadcast systems
This table illustrates the differences:
| PAL B | PAL G, H | PAL I | PAL D/K | PAL M | PAL N | |
|---|---|---|---|---|---|---|
| Transmission Band | VHF | UHF | UHF/VHF* | VHF/UHF | VHF/UHF | VHF/UHF |
| Fields | 50 | 50 | 50 | 50 | 60 | 50 |
| Lines | 625 | 625 | 625 | 625 | 525 = NTSC | 625 |
| Active lines | 576 | 576 | 582** | 576 | 480 = NTSC | 576 |
| Channel Bandwidth | 7 MHz | 8 MHz | 8 MHz | 8 MHz | 6 MHz | 6 MHz |
| Video Bandwidth | 5.0 MHz | 5.0 MHz | 5.5 MHz | 6.0 MHz | 4.2 MHz | 4.2 MHz |
| Colour Subcarrier | 4.43361875 MHz | 4.43361875 MHz | 4.43361875 MHz | 4.43361875 MHz | 3.575611 MHz | 3.58205625 MHz |
| Sound Carrier | 5.5 MHz | 5.5 MHz | 6.0 MHz | 6.5 MHz | 4.5 MHz | 4.5 MHz |
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