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RE: High-end standards conversion

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Dave Chapman
RE: High-end standards conversion
on Oct 14, 2008 at 3:11:39 pm

Hi -

At our company we deliver a lot of HD features, most of them shot 25fps, some shot at 24p. All digital.

Most of these deliverables consist of HD-CAM SR master, and then a selection of Digi's - 16:9 FHA PAL Digi, 16:9 FHA NTSC Digi, 4:3 Pan & Scan PAL Digi and a 4:3 Pan & Scan NTSC Digi.

For the following case, lets pretend our original format is Uncompressed 10-bit HD 1080 25.
Creating a HD master is pretty simple, outputting through our Final Cut Pro Mac, and Kona 3 Video card straight onto SR. Creating the SD PAL deliverables is also pretty simple in that we use the HD-CAM SR deck to down-convert the signal to SD straight into the PAL Digi deck. We use the SR deck - an expensive option, I know - to d/c because the Kona 3 card does not d/c very well at all. Its creates very odd ghosting around white text on picture, which would completely fail any decent QC. So PAL Digi tapes are not a problem.

When it comes to creating NTSC deliverables we would export a full uncompressed QT movie of the film, and change the frame rate to 23.98 in Cinema Tools. This does slow the film down, and because of this it also creates a 'pitch shift' in the audio, which we sometimes deal with by creating a new sound mix at 23.98 with a corrected pitch shift. It also makes the film longer, which we always warn our clients about, but has never been a problem.

Then we play out through the HD SR deck (set to 4:2:2 29.97 psf) onto a NTSC Digi recorder. Our Kona 3 card creates a 2:3:2:3 pull-down which plays out at 29.97 from a 23.98 sequence. This has passed QC before and is all good and well until....

...we need to do some insert edits!

Trying to insert edit from our 23.98 sequence onto our new 29.97 Digi master is nearly impossible. Assembling from the start of our clock and playing the film out is usually fine, it creates new T/C on the tape and unless it drops frames the master is mostly spot-on. However, if there is a new shot, or correction that needs to be inserted it becomes a total mission, which usually results in us having to create whole new master.

I have considered assembling the shot I need to insert onto a fresh tape (with the pull-down), digitising it at 29.97 and inserting onto my master, but it would lose too much quality and take too long.

I was wandering whether people here had any experience in this - or whether there is a better solution to creating NTSC tapes from a 25fps HD source, WITHOUT resorting to the use of an Alchemist, which counts as a Standards Conversion, that is usually unacceptable in delivery.

We are Xsan based, with Mac Pro machines and Kona 3 video cards.

Thanks in advance for any help in this matter!

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Gavin Gourlay
Re: RE: High-end standards conversion
on Oct 14, 2008 at 7:14:24 pm

why is an Alchemist output unacceptable for delivery ?

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Dave Chapman
Re: RE: High-end standards conversion
on Oct 15, 2008 at 8:42:24 am

Because is specifically says on the delivery sheet for most of these films: 'Alchemist conversion unacceptable'.

Also, even if we could use an Alchemist, that would not solve the 'insert edit' issue, which is probably the most annoying part of this.

Some of use here were thinking that if there was any way to play out 23.98 through the SR deck, making the deck do the 2:3:2:3 pulldown onto the Digi tape at 29.97. Somehow 'locking' the decks, so second for second they would match, and we could insert through the SR. Not sure how plausible that is, but I know that Sony SR deck is pretty clever!

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Ian Liuzzi-Fedun
Re: RE: High-end standards conversion
on Nov 27, 2012 at 5:14:58 pm

Ever figure this shit out?

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