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Discussion in 'Archived Threads 2001-2004' started by Ted Todorov, Aug 22, 2002.
From another thread that was going way off topic:
PAL is a standard, and that standard states 50Hz
PAL is run at 720x576 at 25fps, which is created by speeding 24fps film up 4%. It is indeed stored on the DVD at 25fps. PAL speedup bothers enough people that studios have started pitch correcting the tracks. It doesn't help the timing issues, but it does at least de-chipmunk them.
NTSC is 720x480 29.97fps, which is created by 3:2 pulldown (3 frames, repeat 1, 2 frames, repeat one and so on) and runs at 60Hz. 24fps material destined for NTSC is most often these days stored in the native 24fps, and the DVD player does the 3:2 pulldown calculations
Jeff, I am happy to be corrected, but it is my understanding that PAL DVD's of film are encoded at 24fps. This information is based on knowledge gained from folk working in this area of DVD mastering whom I used to work with.
Your comments are further welcomed.
BTW, there is one experiment that can be performed to see who is right:
Play a PAL film on a Malata with the output set to PAL -- time it with your trusty stop watch.
Play the the same DVD with the Malata's output set to NTSC -- time it with your trusty stop watch.
If the two times are equal Jeff is correct. If the two times differ by 4% Stephen is correct.
A further point Ted, as you are probably well aware, with modern telecine processes films are transfered to tape at 1080/24p. Thus each film frame has an unique and complete MPEG frame. Obviously to view this is impossible without some frame rate increase. Infact what happens is that the 1080/24p signal is feed to special monitors that frame triple to 1080/72p for viewing. To own one of these babies (and the sony ones are only 24") you will most likely need to modify your mortage arrangements!
When 24fps film is converted to PAL, a 4% speed-up occurs before the disc is encoded. In other words, a PAL master is created, which is then MPEG-2 encoded 'as is' and authored onto the DVD. The soundtrack follows suit, so it is already sped-up when it reaches the DVD. All of this means, that without special software and a PC to view it on, you can't watch a PAL DVD at the correct speed (unless you demux the VOB files to your hard disk, and convert them yourself).
When 24fps film is converted to NTSC, no conversion to the media is really necessary, other than a slight tweak to make it 23.98fps (don't ask). 'Flags' accompany the MPEG-2 video on the DVD, which tell the player which of the 48 fields to repeat (it's every 3rd field twice, hence 3:2 pulldown, which gives the slightly jerky motion).
PAL = 25fps stored on disc ->interlaced (each frame = 2 fields, with each field being shown once) = 50 fields per second, which can be displayed on 50Hz/100Hz displays
NTSC = roughly 24fps stored on disc ->interlaced (each frame = 2 fields, with every third field being shown twice) = 60 fields per second, which can be shown on 60Hz displays
So, even with progressive scan etc., PAL DVDs will always be sped-up. Better change the FAQ!
I am aware of very, very few PAL DVDs which are pitch corrected. The Lord of the Rings (at least the R4 version) is the most recent example (probably at the insistence of Jackson, who lives in a PAL territory), but there are few others that I am aware of. I am also not aware of a material number of complaints to distributors about this issue sufficient for the Studios to start pitch correction as a matter of course - people who have been brought up with PAL television all their lives usually don't notice it at all, unless they have very good pitch, are musicians etcs. Indeed, the vast number of consumers would be completely oblivous to the PAL speed up issue.
As for the "chipmunk" effect, perhaps Americans (who are not familiar with PAL as they are not its intended market) think that a PAL transfer sounds like this, but I certainly think that is a gross exaggeration of the results of speed up.
I agree with Simon. PAL DVDs are encoded at 25 fps. When you demux the video from a PAL DVD you get a MPEG2 file that is 25 fps. I have tested this, and the video files are 25 fps.
Yes Ted, I have seen the Apple monitor at an IT show recently, very nice, but still out of my price range for such an item according to my personal administrator and house cleaner.
Seems my understanding of film on DVD may be incorrect, but there we go. That said, I have never seen the Malta in action but it must have some terrible temporal side effects if is does infact convert all 25fps material to 30fps, or even 25 to 24 then adding 3:2 pulldown. Must hunt out the chip set white papers and see.
Luck you, like I have multistandard sets
I'm actually not surprised at the number of people who are not concerned by the PAL speedup. In fact, the majority of people are not concerned by the audio portion of DVD at all. My cousin, for instance, has a collection that's 5 times the size of mine, and claims he's a 'DVD collector'. He loves movies, and is studying film. However, he's not got the first idea about PAL speedup, 3:2 pulldown etc. It's like my friend Andy, who will happily listen to tapes in his car that sound truly awful, because the car stereo pumps them out too fast! When I mentioned it to him, and suggested he should get it fixed, he was genuinely surprised! No wonder the majority of people can't notice PAL speedup. Maybe they're wandering round in a dream or something, because to me its painfully obvious.
Of course he's a film lover, like myself. We wouldn't buy DVDs otherwise!
I didn't mean anything buy it, other than it that it surprises me how few people really know the differences between formats, even when they have shelves full of movies from all over different parts of the world. It's like he buys tonnes of R1 titles all the time, and he's saying "Get the R1, it's great!", while I'm saying "Why, because you get to hear the soundtrack at the correct speed and pitch?", to which he would reply "Wha - ?"
Oh, and my cousin and I DO get along well ...