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  #1  
Old 09-13-2005, 10:56 PM
David Sandwisch David Sandwisch is offline
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Default PAL to NTSC speed change?

What is the speed change when a show originally shot on PAL is transfered to NTSC? I believe it should be .1%. I do understand that going from PAL to 24fps is a 4% slowdown and that going from 24fps to NTCS is .1% and I see in ProTools that there is a 4.1% pulldown / pullup option. Is that suggesting that going from PAL to NTSC speed you actually go from PAL to 24fps then to NTSC speed? It seems to me that the easiest way to convert PAL to NTSC would be to go from 25fps to 30fps (just repeat every 5th frame) and then slow it down .1% to 29.97. I am not sure what else you need to know from me to answer this question but I am happy to provide more information if you need it. I have PTHD2. Thanks
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Old 09-14-2005, 01:55 AM
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Default Re: PAL to NTSC speed change?

Hi David,
I had a similar post a few weeks ago. Go to my post record to check it out.
My situation was a bit different. I had done a 5.1 mix in PAL. The Digi Beta master was then shipped off to the States for conversion to NTSC. The converted NTSC Digi Beta was then sent back to me. The conversion that was made luckily was a second = second version which means there was no change in the length or sync or pitch. I then made a QT DV NTSC from the Beta and was able to work with that.(Originally I was worried because our DVD guy was having problems with sync, but that's because he had a panic attack, what fun!))

If the conversion was not done properly you will have a definite change in pitch when you change the pull rate.

We use USA Dubs in New York. They did a great job and they are the only ones in the country that have an Alchemist Platinum system for proper second=second conversion.

If I remember correctly the pull rate from going from PAL 25 fps video to NTSC 29.97 fps is actually +4.167. Trust me you don't want to go there.

I would highly recommend making a proper conversion before getting yourself into the muddy waters of sync issues.

I'm sure there are plenty of people on the DUC that will help you.

All the best,
Mitch
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  #3  
Old 09-14-2005, 07:05 AM
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Default Re: PAL to NTSC speed change?

as MusPro says, find out FIRST how the conversion of the movie was or will be done.

if they do "a second = a second" then there is no speed change or pitching necessary. make a second copy of your session, import the new video and let it rip. it if runs in sync, then you are good to go.

if they do not do it this way, then this may help... first off PT is a bit misleading, i have learned, when doing true conversion transfers.

the PAL 25 to NTSC 29.97 transfer varispeed is -4.096%, or clock at 46034

for NTSC-PAL, transfer is actually +4.272% up from NTSC speed. or clock at 50050.

ProTools addresses this as Up 4%, Up .1%, which is a bit incomplete, but close.. when you do the math and it beomes clear.

hope this helps.
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Old 09-14-2005, 08:57 PM
David Sandwisch David Sandwisch is offline
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Default Re: PAL to NTSC speed change?

I should have said that the project is finished and we mixed to PAL quicktime and then the director took a PAL DVCAM to a transfer house for the conversion. I know the video will be slowed down and the pitch will be adjusted to compensate. I am just curious by how much and more specifically, I actually want to see the math that you use to come up with the 4% number. I would like all the messy details if you would. Thanks.
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Old 09-14-2005, 09:34 PM
Eric L Eric L is offline
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Default Re: PAL to NTSC speed change?

This thread may help. Just a search away...

29.97 to 25 etc
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  #6  
Old 09-15-2005, 10:43 AM
Richard Fairbanks Richard Fairbanks is offline
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Default Re: PAL to NTSC speed change?

Eric, that link doesn't go anywhere useful!

You can calculate the percentage of change if you know the original sample rate, and the final sample rate. The thing to keep aware of is that 24fps and 30fps involve a picture change, not an audio change, so in the formula I give, do not use 30 or 29.97. Instead use 24 or 23.976.

% change = (Final - original) / original x 100

If you want to speed up 23.976fps audio to match 25fps playback (25 fps runs faster) follow these math steps:

A. (25 minus 23.976) equals 1.024. Take this value and plug into the next step:
B. 1.024 divided by 23.976 equals .042709376. Multiply this by 100:
C. .042709376 times 100 equals 4.2709376 percent faster.

If you had worked with a 29.97 version of the 23.976 picture, you would use the exact same numbers. If you worked with a 29.97 original picture that is transfered to 25 with a 2:3 telecine process, which speeds up realtime, use the exact same numbers in the calculations.

Another example, lets shoot at 25fps, post it, and project at 24. How much will the audio slow down?

(24 - 25) / 25 * 100 = -4 percent. That is negative four percent slower.

Pitch change is by the same percentage. Cents are 100s of a semitone, the same as percentage, so the change of pitch in cents equals the percent of change.

Most people gloss over when the math comes in, but this is relatively straight forward. The real confusion is because not all conversions from one picture rate to another work the same way, so without knowing exactly what was done there is no way to know what numbers to plug into the formula.

I hope this helps.
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Old 09-15-2005, 02:10 PM
Eric L Eric L is offline
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Default Re: PAL to NTSC speed change?

Quote:
Eric, that link doesn't go anywhere useful!
I'm sorry, Richard. Do you mean the link does not work, or that the thread it links to is not appropriate for this discussion?

Your math is very similar to the math on that thread. Am I missing something? Again I apologize if my contribution is not "useful".
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  #8  
Old 09-15-2005, 02:35 PM
CharlesL CharlesL is offline
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Default Re: PAL to NTSC speed change?

Hi guys,

I too have almost the exact same situation now.

Situation is this, Original programme is from PAL Digital Beta. Done, fully dubbed and mixed in Germany.

Then, we need to do Mandarin dubs and mix.

Mandarin dubbing was done in Taiwan, and the Digial Beta tapes were converted to NTSC and recorded in Pro Tools settings with 29.97 DF.

The Taiwanese studio supplied me with the original NTSC (29.97DF) ProTools Session, a PAL ProTools sesison (done with SRC, I thnk), DA-88s and AIFF bounced audio of the dubs for safety (SRC-ed to PAL too)

Final Mix will be done in Singapore and the "complication" is, Final Mandarin mix need to have a PAL and NTSC version. Video for PAL & NTSC will be different too (different subtitles..etc)

However, when I opened the "PAL" ProTools session and imported my Quicktime movie (in PAL), audio ends much much earlier than video!! Same thing happened with the bounced safety AIFF "PAL" files.

I tried all PULL up/down settings for audio and video in ProTools, and it still doesnt sync up. Then I finally opened up the original 29.97DF NTSC Pro Tools session, changed the time format to PAL/25fps and everything synced up fine (almost..)

So, I think I can just switch the fps settings of the sesison and then do a PAL MIX.

Only question is, can the PAL's final audio mix be used to stripe both the PAL & NTSC Digital Beta decks?

Thanks & Regards,
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  #9  
Old 09-15-2005, 02:37 PM
José Luis Díaz José Luis Díaz is offline
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Default Re: PAL to NTSC speed change?

Hi Richard,

I use another method that does not need any math at all.

a) Select an empty space in a track in the time line of 239,760,000 samples.
b) Open the plugin that expand/compress the time that you like.
c) In the destination time box write 250,000,000 samples.
d) Save this setting as "23.976 to 25fps".

This method means: 23976 samples must be converted to 25000 samples, right? In the same way (increasing 10,000 times the time) 239,760,000 must get 250,000,000 samples.
You can do all the resting standard tranformations:
240,000,000 to 239,760,000 samples -> Save it as "24 to 23.976fps"
240,000,000 to 250,000,000 samples -> Save it as "24 to 25fps"
250,000,000 to 240,000,000 samples -> Save it as "25 to 24fps"
250,000,000 to 239,760,000 samples -> Save it as "25 to 23.976fps"
239,760,000 to 240,000,000 samples -> Save it as "23.976 to 24fps"

Next time you need to do any standard time compresion/expansion just go to the presets and you are done.

Jose Luis
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  #10  
Old 09-15-2005, 02:53 PM
Richard Fairbanks Richard Fairbanks is offline
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Default Re: PAL to NTSC speed change?

Eric, I've clicked the link you provided on two systems but what I see is a page that has all the usual forum stuff, but without the thread. There is nothing to read. I thought maybe the link was broken or there was some other technical problem so I posted a quick formula to give an answer. That's all I meant and it was my mistake to not say so.

SonidoA&D, that is really quite clever! I never thought about it that way. Good one! Since you are really just entering a ratio into your time compander plugin, why do you need to multiply by 10K? Why not just enter 23967 and 25000? The ratio is the same either way, isn't it?

Charles, what do you mean the NTSC version syncs up "almost"? How does it NOT sync up? To answer your question, if the picture conversion was done so that the program time remains the same it should not matter if you mixed against the PAL or NTSC version. All video decks want 48Khz audio so all you need to do is change the timecode setting of the session, find your offset to the master, and you're all set. "Almost" scares me.
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