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I have a decent enough grasp of the differences overall in how films are handled for different areas, so I'm not looking for a primer per se; however, I would like some clarity on how this works and have some examples to share.

Background: For some reason I've had the desire to watch the "Creating the World of Harry Potter" documentary that was an exclusive of the "Ultimate" editions of the home releases in the US. Given that I owned a few of the blu-rays already I balked at repurchasing these overpriced editions. I did stumble across a listing in the UK Amazon store for a Region-Free version of the entire 8-film collection and the documentary for approximate $40 USD. This is a good $100 cheaper than I could find in the states and so I made the purchase.

Thinking I got a good deal, I started to hunt for other region-free sets that were incredibly priced and I bought Battlestar Galactica, Star Trek TNG and a 6 movie collection of Kubrick films before I stumbled across this thread:

Farscape Blu-Ray forum

As discussed here there seems to be dialog surrounding 25fps vs. 24 fps, pitch correction, and ever more dialog in this thread surrounding NTSC vs. PAL playback.

NOW, given all this, my question is:

How are films that are supposed to be different FPS or formats prepared for region-free versions and do those versions have concerns that should be investigated when importing to an NTSC region?

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The most important point to note about DVD regional formats is that it has little or nothing to do with how the video is actually encoded. Regional locks are designed not for different television formats but for marketing purposes: distributors want the freedom to control regional marketing.

The actual regional lock matches a code on the disk with a code in the decoding device and refuses permission to decode a disk from a different region. Many computers enforce this in software (you are asked the first time you insert a disk which region you are in and a difficult-to-alter code is set in the DVD reader to enforce the lock).

The worry about different frame rates is a legacy of the days when everything was analogue. In Europe, for example, analog TV was 25 fps to match the mains electricity frequency of 50 Hz. Analogue movies on TV were sped up from their 24 fps on film to 25fps for TV broadcast to avoid nasty artefacts cause by the frequency mismatch. in the USA where mains is 60hz and TV is 30fps, more complex schemes had to be used.

None of this matters in a digital world especially when the DVD signal is transmitted via a digital interface and never needs to go via an analogue TV signal. If you watch DVD on your computer this has always been true and the display frequency will have no relation to the mains power in your region.

In practice, DVD decoding still accommodates older TV technology but does so in software or hardware. But much of this is irrelevant with digital outputs. The encoding on the DVD contains information to allow the decoding to be adjusted to local frame rates, if required. As wikipedia explains:

...the content can be encoded on the disc itself at one of several alternate frame rates, and use flags that identify scanning type, field order and field repeating pattern. Such flags can be added in video stream by the H.262/MPEG-2 Part 2 encoder. A DVD player uses these flags to convert progressive content into interlaced video in real-time during playback, producing a signal suitable for interlaced TV sets. These flags also allow reproducing progressive content at their original, non-interlaced format when used with compatible DVD players and progressive-scan television sets.

What this means is that the local standard problem is now solved in software and DVD encoding doesn't need to take into account the local TV standards. This is also why region-free releases work anywhere with no adjustment.

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