View Full Version : Frame Rate Mystery


Graham Jones
August 7th, 2004, 07:35 PM
I have posted this elsewhere in the forum, but guess this is the best place for it.

I am using the JVC GR-PD1 to shoot a low budget feature which will finish on 35mm. I selected the PD1 over the HD1/HD10 because of frame rate. I explored frame rate conversion programmes to convert the HD cams 30p to 24p but didn't feel confident from the tests I saw that I would be protected...

The PD1 shoots a nice image in true 16:9 at 25p.

I just have one query. The component Y/Pb/Pr output has two settings, both of which are 50 frames per sec. To quote the manual

'576/50P: signals are output in progressive scan mode (FACTORY PRESET)'

576/50i: signals are output in interlace mode.'

That's it.. no 25p output.

I haven't made a mistake and shot at 50p - which is indeed possible - I am definitely shooting at 25p, but irrespective it outputs at 50p/50i depending on how I set it. There's no other option.

It's even articulated by the manual which says that HI-RES mode:

'records signals in the progressive scan mode (625 scanning lines at 1/25th of a second for recording and 1/50th of a second for playback at one time).'

I have experienced some MPEG2 NLEs getting confused by this and playing footage too fast and saying it's 50p... though not the bundled NLE MPES PRO - it knows that it's really 25p.

I assume that 50p playback doesn't truly affect frame rate - that the frame rate is still 25p: as there are only 25 differences a second?

However, I am transferring to 35mm, where 25p will be vital, and I just wondered if anyone had any idea whether the fact that technically it's coming in at 50p will matter.

I'm doing a test in less than a month, so will find out... but I just wondered whether anybody had anything to say in advance.


G

Graham Jones
August 7th, 2004, 07:39 PM
I should also clarify: I don't have any editing difficulty. I am using the bundles MPES PRO and find it very satisfactory. I am exporting the results back to Mini DV at virtually 100% quality.

It's just that when I transfer them from cam via the said component output, it will technically be 50p, even though my work is a very deliberate 25p.

Maury McEvoy
August 8th, 2004, 10:57 AM
<<<-- Originally posted by Graham Jones Senior :

That's it.. no 25p output.

I haven't made a mistake and shot at 50p - which is indeed possible - I am definitely shooting at 25p, but irrespective it outputs at 50p/50i depending on how I set it. There's no other option. -->>>

My guess is that every 25p 'camera' frame is output twice (i.e. 50p).

You may need to convert your output from 50p to 25p (i.e. remove every other frame).

My GR-HD1 duplicates output frames if the shutter is set to 1/15.

Daniel Moloko
August 8th, 2004, 11:23 AM
i think you lost the chance to shot with the HD10u, cause for sure you can transfer to 24p with good results:

http://www.dvinfo.net/conf/showthread.php?s=&threadid=27888


you can even use the TWIXTOR PRO to archive some good motion

ciao

Graham Jones
August 8th, 2004, 11:46 AM
I clicked on that link, Daniel, but found no sample clips of HD10u 29.97 -- 24 conversion?

Just a debate about it and some other things. I have viewed such samples elsewhere and been unhappy.

You talk a lot about shooting your first feature on Super 16mm rather than HD. Well, I shot my first feature on Super 16mm and blew up to 35mm and am shooting this, my second on PD1 and transfering to 35mm.

Each project has it's own requirements. It's never just technical. There are always production considerations which have a huge effect.

What I mean is: I would shoot o Super 16mm or HD if that was appropriate... it's not, Pal 25p is.



I'll see how the test comes out - but I think I probably do have 25p.

Daniel Moloko
August 8th, 2004, 12:03 PM
theres a sample made by LES DIT if you look at the replies.

it is great!

tell me what samples have you seen? i want to check it out.

have you seen any sample at the theatre?

ciao

Graham Jones
August 8th, 2004, 12:21 PM
Yeah, that's the clip I've already seen. Sorry, I didn't notice there was more than one page!

Daniel, it's terrible. The frame rate conversion has fuzzed it. Transfer that very clip to 35mm and I think you will be unhappy.

I could be wrong.

Les himself says:

'Tell me your opinion of the artifacts from converting 30fps to 24. In motion, like a real audience would see it. Not paused, movies don't pause. I'm curious what you think. Please don't comment on the crappy hand held camera work, I was just testing the camera out !'

I appreciate all of this... my opinion is that it's quite poor. You can feel the power of HD but it's discounted and fuzzed and transfering that to 35mm? Nah.

Again, I could be wrong.

If I found a way to go from HD10u - 35mm I would switch to HD10 immediately. I tried for months and couldn't. The frame rate is too big an issue for the folks who do the 35mm transfers... and my eye can see why.

Daniel Moloko
August 8th, 2004, 01:43 PM
Maybe i dont know nothing about anything.

cause i think the footage looks good. i think its better to have a 35mm footage that looks like that one, cause i just cant stand DV transfered to 35mm. looks like junk.

so, if i have to choose from two kind of junk, id prefered the junk from HDV. that's my guess.

ciao

Graham Jones
August 8th, 2004, 02:20 PM
nobody's talking about transfering DV

Graham Jones
August 8th, 2004, 03:39 PM
Best of luck - just make sure to test the process in it's entirety (HD10u - Frame Conversion - 35mm) before prinicipal photography begins!

Daniel Moloko
August 8th, 2004, 06:44 PM
yeah
im not talking about DV transfer.
im just talking about in what format i can film. and i cant afford to film in another high-end format. im talking about 3k cameras.

so, if im working in that budget, i only have two choices, one is DV and the other is HDV.

HDV has the "problem" of frame convertion.

DV is the problem itself - very bad image.

i prefer to get the look of HDV in the post.

what about you if you had to choose between DV and HDV?

ciao

thanks!

Graham Jones
August 9th, 2004, 01:55 AM
'what about you if you had to choose between DV and HDV?'


Well, 28 Days Later was shot on DV. It's a good example of what can be achieved - and a reminder that it's not only about camera resolution, but also lights and post production processing.

The PD1 I'm using has a DV mode, like the HD1 and HD10 but I don't use it

I use HI-RES mode, which is a lower resolution version of HI-DEF mode on the HD1 and HD10 but with 25p not 29.97p.

Graham Jones
August 9th, 2004, 02:06 AM
Every project is different - but testing is vital.

Testing your proposed process always throwns up unexpected surprises.

That's why I'm testing PD1 to 35mm, to see if the 50p output matters. I don't think it matters - as it's still 25p - but I will only know when I see them do it. When I look at the cinema screen and see my footage playing.

You have to do that too, otherwise you might be very surprised down the line!

Daniel Moloko
August 9th, 2004, 02:43 AM
i think 28 days later looked terrible, on the cinema screen.

my project dont support that kind of bad tasting image provide by DV, i mean, ANY DV. im seen a lot of dv footage tranfered to 35mm, nothing was good at all. it is a resolution problem, for sure.
(not even robert rodriguez like the DV format printed on 35mm)

but yes, you are right i got to see by myself the printed 35mm version of HDV 30p footage.

but i do believe in LES DIT. who said its good for most audiences.

anyway, have you seen any HD10U footage printed to 35mm at a cinema?

ciao

Graham Jones
August 9th, 2004, 03:00 AM
so you think 28 days later looked terrible on the cinema screen, but that skateboarding footage will look good?

beauty's certainly in the eye of the beholder.

if we all saw the same thing - films would be boring.

best of luck

Graham Jones
August 9th, 2004, 03:01 AM
no, i haven't seen hd10u 35mm transfer - but we need people like you to pioneer that!

Chris Hurd
August 9th, 2004, 06:16 AM
Having seen "28 Days Later" on both the big screen and DVD, I will definitely say that it looked worse in theaters. It looked much better in my living room on my 31" consumer television.

Graham, the 50p / 50i thing is just a matter of conventions. There is no accepted standard of 50p, the manufacturer simply miswrote it in the manual. The reference is of course to 25p. Whoever wrote the manual (most likely it is a translation from Japanese anyway) is most likely unaware of the accepted convention of describing that particular frame rate as 25p, as opposed to 50p as it's printed.

Basically it all boils down to your choice of either interlace (50 fields / sec.) or progressive (25 frames / sec.) -- that's all that's really going on here. The manual has been written in an unintentionally confusing manner is all.

Graham Jones
August 9th, 2004, 06:33 AM
that would make me happy Chris, but I'm not convinced it's a typo.

See this parallel thread, where i go into a little more detail

http://www.dvinfo.net/conf/showthread.php?s=&threadid=30192

Moderator note: other thread link removed and correct one inserted. -Rob

David Newman
August 9th, 2004, 09:35 AM
I just posted this into the other thread also:

It is not an issue. 50p analog output is simply so that the frame doesn't flicker like crazy. Even 24p film is displayed at 48Hz, with each frame being flashed on the screen twice. You are shooting 25p, if you are editing from the IEEE1394 signal you are editing 25p.

However, the PD1's MPEG transport stream does indicate 50 discrete frames -- this is where some software is getting confused. The MPEG stream marks repeat frames, just the same way 24P film is encoded onto 30fps only NTSC DVDs. The repeat frames do not take a significant slice of the bit-stream, but editing software does need to be aware of it.

Graham Jones
August 9th, 2004, 10:54 AM
that's illuminating... i'm going to leave this thread now and continue in the othe thread at http://www.dvinfo.net/conf/showthread.php?postid=210238#post210238