How is PAL converted to NTSC these days?

hello_hello · 22nd July 2017, 22:22

How is PAL converted to NTSC these days?

I ask, because I was looking at an NTSC DVD of classic Doctor Who recently (the new series is dead to me now), and it doesn't appear to use field blending or pulldown. I'd be happy to assume it'd always been NTSC if I didn't know better.

The film parts appear to be field blended, but I can't seem to work out how the video was converted or find any specific information.

For anyone who knows how it's done.... would there be a way for a mere mortal to reverse the conversion process for 50i? Not that there's any particular need because it looks fine the way it is after de-interlacing.

Here's a small sample. It's not from an episode as such, but footage from the original video tape included as a DVD extra.

Doctor Who.ts (18MB)

Sharc · 23rd July 2017, 11:10

It looks like a native 29.97i production, true interlaced, no telecine.....
If the original is 25i they might have used a professional interpolator for conversion.
I don't think you can restore the 25i "original source" (?) without damaging this version.

One could try to produce 50p with

Code:

tdeint(mode=1,type=2,order=1)  #or a bobber of your choice
srestore(frate=50.0)  #50p

Watch out for dropped frames (jerky playback) though!

Then re-interlace if needed for 25i

Code:

spline36resize(720,576)   #for "PAL" compliance
separatefields().selectevery(4,0,3).weave()   #25i TFF

Perhaps someone has a better proposal.

hello_hello · 23rd July 2017, 16:20

Thanks Sharc.
I figured there was no going back to 25i or deinterlacing to 50fps. I'll try your suggestions though as neither are identical to anything I've tried, and you never know....

I'm not worried about any sort of compliance so I've encoded a few as variable frame rate, but there's no automatic way to output combinations of 25fps and 59.94fps with a timecodes file (that I know of), and doing it all manually quickly becomes mind numbingly boring.

I think I was somewhat impressed the interpolation looks so good, especially as it's interlaced to interlaced, so I was just curious to learn a bit more about how it's done if anyone knows. I looked through some more of the DVD today, and every now and then I spotted an artefact that appeared to be interpolation related, but fairly minor stuff you'd probably have to be looking for to notice most of the time. As far as interpolation goes, it's pretty good.

manolito · 23rd July 2017, 17:54

Excuse me if this post should reveal my complete ignorance about standards conversions...

But are you sure that this conversion from 25fps interlaced to 29.97 interlaced has been using any interpolation at all? Couldn't it have been done using the old and trusted method I have learned (XSDeeni) here many years ago?

Quote:

AssumeTFF() # Specify source field order
Your Bob Deinterlacer
Resize(720,480)
ChangeFPS(59.94)
AssumeTFF() # Specify target field order
SeparateFields()
SelectEvery(4, 0, 3)
Weave()

Cheers
manolito

Blue_MiSfit · 23rd July 2017, 22:22

Professional motion compensated standards converter like an Alchemist box or a software solution like Cinnafilm Tachyon?

Sharc · 23rd July 2017, 23:13

Quote:

Originally Posted by manolito

...But are you sure that this conversion from 25fps interlaced to 29.97 interlaced has been using any interpolation at all? Couldn't it have been done using the old and trusted method I have learned (XSDeeni) here many years ago?

Applying your script to a 25i video would produce a sequence of 1 clean (p) and 2 combed (c) frames, like ... p c c p c c p c c ....
In the clip of the OP all frames are combed (true interlaced) which would exclude that it was produced with your method, I think.

kolak · 24th July 2017, 11:02

Quote:

Originally Posted by manolito

Excuse me if this post should reveal my complete ignorance about standards conversions...

But are you sure that this conversion from 25fps interlaced to 29.97 interlaced has been using any interpolation at all? Couldn't it have been done using the old and trusted method I have learned (XSDeeni) here many years ago?

Cheers
manolito

This is used very often, but recently motions adaptive conversion also, as engines are getting better. Alchemist OD and Tachyon can do fairly good job even for 25p sources. It still can also go slightly bad depending on the source nature.
If it looks like real interlaced source then it most likely was Alchemist or Tachyon conversion: 25p/25i to 29.97i.

kolak · 24th July 2017, 11:05

Quote:

Originally Posted by Blue_MiSfit

Professional motion compensated standards converter like an Alchemist box or a software solution like Cinnafilm Tachyon?

Alchemist box is obsolete- new software version (but heavily GPU based) is much better.

hello_hello · 24th July 2017, 14:13

It's possibly the first conversion of that type I've seen, at least where I have no doubt the source was originally PAL.
I did wonder why only the video parts were converted that way. I'm reasonably sure the film parts were field blended. I probably should look again.

Thanks for the info everyone.

22nd July 2017, 22:22	#1 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	How is PAL converted to NTSC these days? How is PAL converted to NTSC these days? I ask, because I was looking at an NTSC DVD of classic Doctor Who recently (the new series is dead to me now), and it doesn't appear to use field blending or pulldown. I'd be happy to assume it'd always been NTSC if I didn't know better. The film parts appear to be field blended, but I can't seem to work out how the video was converted or find any specific information. For anyone who knows how it's done.... would there be a way for a mere mortal to reverse the conversion process for 50i? Not that there's any particular need because it looks fine the way it is after de-interlacing. Here's a small sample. It's not from an episode as such, but footage from the original video tape included as a DVD extra. Doctor Who.ts (18MB)

23rd July 2017, 11:10	#2 \| Link
Sharc Registered User Join Date: May 2006 Posts: 3,997	It looks like a native 29.97i production, true interlaced, no telecine..... If the original is 25i they might have used a professional interpolator for conversion. I don't think you can restore the 25i "original source" (?) without damaging this version. One could try to produce 50p with Code: tdeint(mode=1,type=2,order=1) #or a bobber of your choice srestore(frate=50.0) #50p Watch out for dropped frames (jerky playback) though! Then re-interlace if needed for 25i Code: spline36resize(720,576) #for "PAL" compliance separatefields().selectevery(4,0,3).weave() #25i TFF Perhaps someone has a better proposal. Last edited by Sharc; 23rd July 2017 at 11:43.

23rd July 2017, 16:20	#3 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	Thanks Sharc. I figured there was no going back to 25i or deinterlacing to 50fps. I'll try your suggestions though as neither are identical to anything I've tried, and you never know.... I'm not worried about any sort of compliance so I've encoded a few as variable frame rate, but there's no automatic way to output combinations of 25fps and 59.94fps with a timecodes file (that I know of), and doing it all manually quickly becomes mind numbingly boring. I think I was somewhat impressed the interpolation looks so good, especially as it's interlaced to interlaced, so I was just curious to learn a bit more about how it's done if anyone knows. I looked through some more of the DVD today, and every now and then I spotted an artefact that appeared to be interpolation related, but fairly minor stuff you'd probably have to be looking for to notice most of the time. As far as interpolation goes, it's pretty good. Last edited by hello_hello; 23rd July 2017 at 16:24.

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23rd July 2017, 22:22	#5 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	Professional motion compensated standards converter like an Alchemist box or a software solution like Cinnafilm Tachyon?

24th July 2017, 14:13	#9 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	It's possibly the first conversion of that type I've seen, at least where I have no doubt the source was originally PAL. I did wonder why only the video parts were converted that way. I'm reasonably sure the film parts were field blended. I probably should look again. Thanks for the info everyone.