Re: Converters to for UK electrical appliances in USA
 

I don't get it..:huh:

Re: Converters to for UK electrical appliances in USA
 

:) Well, what I know "pointing a finger" to mean is to blame/criticize someone else. So I read your quote as if you point a finger at someone else, it actually gets pointed back at you three-fold. But, maybe you mean it in some other way. Don't know! :p

Re: Converters to for UK electrical appliances in USA
 

It has been a long time since I dug into this (I used to convert UK/PAL DVDs for use in the US before off-the-shelf players could do it), but I think the answer is this: TVs use the frequency of the local AC power supply to determine the rate at which 'frames' (individual pictures that make up the moving image) are presented on the screen. Since the national power frequency in Europe is 50 Hz, and in US 60 Hz, PAL video is 50 fields/sec (25 frames/sec) and NTSC is 60 fields/sec (30 frames/sec) - a field is half a full frame, and the difference relates to interlacing, which is too complicated for this discussion... suffice to say, from now on, PAL is 25 frames/sec and NTSC is 30 frames/sec.

So to play material recorded in one system on the player of the other system, you have to convert between these two frame rates.

To play an NTSC signal (30 frames/sec) on a PAL TV (designed for 25 frames/sec), you can simply drop every 6th frame and thus, convert 30 frames/sec to 25 frames/sec (over-simplification, but good enough). But to play a PAL signal on an NTSC TV, you have to increase the number of frames, and that requires some kind of 'frame buffer' ("hold that last frame you just got and repeat it") which adds cost and complexity - it's generally easier to discard information than it is to introduce information. These days, though - most NTSC TVs can handle it.

Note that professional converters (what studios would use to prepare UK material for the US market, etc) take a much more sophisticated approach, analyzing adjacent frames, looking for changes, etc.

That required a lot of cobwebs to be cleared from info I haven't thought about since 2003 but I believe it's correct!

Re: Converters to for UK electrical appliances in USA
 

Have you ever had one of those moments when you read something and it's like the universe suddenly aligns itself... and your understanding of things becomes crystal clear? Wow! I just had one of those moments!

Ian

Re: Converters to for UK electrical appliances in USA
 

Yep, quality. Makes a lot of sense, I don't doubt that that's correct.

Re: Converters to for UK electrical appliances in USA
 

Sounds like it makes good sense to me too thanks!

Re: Converters to for UK electrical appliances in USA
 

That's the clearest explanation I've heard. Cheers. :thumbsup:

Re: Converters to for UK electrical appliances in USA
 

This web page has a good deal of techno-babble detail on the whole process, with some good diagrams (diagrams REALLY help with this topic) at this sub-section.

Another piece of technical trivia that my notes jogged my memory on is that all movies, regardless of country of origin (at least, movies shot on celluloid - some new movies are done without film these days), are shot at 24 frames/sec, which is neither PAL nor NTSC compatible. So going from a movie to TV is a challenge that has to be faced by both PAL and NTSC folks. When converting a movie to DVD, you don't want to convert from 24 frames/sec to 30 frames/sec 'on' the DVD, because space is at a premium and you want to optimize the storage usage. So what the MPEG-2 spec (the 'way' movies are encoded on DVD) allows for is a 'flag' that says "repeat every 'n'th field during playback" to convert 24 frames to 30 frames (or 25 frames). This is called 'pulldown'. If you've ever watched a movie and noticed that motion is not 'smooth', it's probably caused by this. A movie on DVD is stored differently from a 'TV show' on DVD (recorded originally on video equipment). This page has a few nice diagrams to explain it.

I got started on this back in 2002 when my family sent me a copy of "the office" on PAL DVD and I could not play it on my equipment here (this was before cheap 'region free' players, and cheap pal/ntsc tv's). Back then, the conversion process would run 24 hours non-stop on my PC for a high quality conversion.