3:2 pull down equivalent of PAL

[lord loh.]

I read an article on the internet about converting cinema 24 frames per second into 60 fields per second for the NTSC telivision.

The 24 frames were divided into 4 ses of 6 frames each. (4X6=24)

Now in each set, the first frame is displayed thrice and the second twice the third thrice and the fourth twice....
so a total of 3+2+3+2+3+2=15 fields are produced from 6 frames.

Thus 60 fields are produced from 24 frames.

How can this process be carried out for PAL which has a refresh rate of 50Hz ?

 

[Nigel Goodwin]

I read an article on the internet about converting cinema 24 frames per second into 60 fields per second for the NTSC telivision.

The 24 frames were divided into 4 ses of 6 frames each. (4X6=24)

Now in each set, the first frame is displayed thrice and the second twice the third thrice and the fourth twice....
so a total of 3+2+3+2+3+2=15 fields are produced from 6 frames.

Thus 60 fields are produced from 24 frames.

How can this process be carried out for PAL which has a refresh rate of 50Hz ?

A couple of points!.

Firstly, American NTSC provides 30 pictures per second (not 60), consisting of 60 interlaced 'half pictures'. Likewise European PAL provides 25 pictures per second, consisting of 50 interlaced 'half pictures'.

So PAL is actually easier to do, as you only need to gain an extra picture per second - so how about showing every picture twice (to account for the interlacing), and show the last picture four times.

You can actually buy chip sets that do all this for you, they were used in standards conversion VCR's - the only ones I've seen were by panasonic, and Aiwa.

 

[lord loh.]

The place I read about the 3:2 pull down termed pictures per second as frames per second and half pictures(even or odd) as fields.

so NTSC has 60 fields per second (according to that tutorial)

So PAL is actually easier to do, as you only need to gain an extra picture per second - so how about showing every picture twice (to account for the interlacing), and show the last picture four times.

If Chip sets have been using this, then I think it works... But doesn't it cause jitters? (lip movement - video) or is it too fast to see....

Thanks a lot Nigel, you are always helpful. The last picture 4 time was not a very intutive technique.

 

[Nigel Goodwin]

The place I read about the 3:2 pull down termed pictures per second as frames per second and half pictures(even or odd) as fields.

Although I've been repairing TV's for 34 years, I can never remember which is which between frames and fields :lol:

But to be honest, it has no bearing on servicing TV's.

so NTSC has 60 fields per second (according to that tutorial)

So PAL is actually easier to do, as you only need to gain an extra picture per second - so how about showing every picture twice (to account for the interlacing), and show the last picture four times.

If Chip sets have been using this, then I think it works... But doesn't it cause jitters? (lip movement - video) or is it too fast to see....

It was just a guess :lol:

You've got to add an extra frame to give 25 rather than the 24 used by film (and I wonder why 24 was chosen for film anyway?), so adding it at the end is as good as anywhere?.

 

[lord loh.]

It was just a guess :lol:

You've got to add an extra frame to give 25 rather than the 24 used by film (and I wonder why 24 was chosen for film anyway?), so adding it at the end is as good as anywhere?.

So I am still to find the standard method....

**broken link removed**

tells me that PAL converted movies are 4% short on run time :lol: . Sounds strange. What about the voice track??? Chop it? :shock:

 

[Nigel Goodwin]

It was just a guess :lol:

You've got to add an extra frame to give 25 rather than the 24 used by film (and I wonder why 24 was chosen for film anyway?), so adding it at the end is as good as anywhere?.

So I am still to find the standard method....

What makes you think there is a 'standard' method?. I doubt it makes much difference where you add the extra frame?.

**broken link removed**

tells me that PAL converted movies are 4% short on run time :lol: . Sounds strange. What about the voice track??? Chop it? :shock:

I've never heard any suggestion like that?. But certainly the sound could easily be processed so the tone is correct - and 4% difference probably wouldn't be noticed?.

 

[evandude]

4% difference probably wouldn't be noticed

It would if by the end of a 2 hour movie, the audio was almost 5 minutes behind :lol: