any ideas how jvc's new camera will output 50i 25p @ 720
by Kaspar Kallas
on
May 30, 2005 at 6:06:12 pm
Hi
Best to my knowledge there is no standard @ 720 for 50i or 25p only 60p (at least most hardware is compliant with those specs)
if I am wrong please slap side of yer monitor, say bad boy and tell me this (also what should I consider for getting live output from analog outputs to sdi converter because aja HD component to HD-SDI converter supports 720 @ 60p only)
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by dino on May 30, 2005 at 7:28:29 pm
Yea, I've been wondering about the whole thing with their 720/24P as well. They probably output as 60P (actually 59.94P) as there is no official spec for 720 at 24fps. The same problem we've all been fighting with the Varicam. I believe it also scales to 1080/59.94i but no 1080/23.976P as we would actually want. Why is it so hard?
It seems JVC is simply not addressing the PAL based market. If you go to jvc.co.uk, there are no "pro" products listed. The closest they get is a variant of the original single chip HDV camera that records as SD only. Oy.
I hope when this camera is actually released they make available a detailed paper on the intricacies of what exactly ProHDV is.
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by Barry Green on May 30, 2005 at 9:18:26 pm
In America, the ATSC television standard does provide for 720/24p, 720/30p, and 720/60p broadcasts. 720/24p is a totally legit HD broadcast standard.
In the HDV format announcement of 9/2003, they list 720/25p, 720/30p, 720/50p and 720/60p as appropriate HDV formats.
There is not now, nor will there ever likely be, any form of 720/50i or 720/60i. If you want that "reality" look (i.e., "live video") when shooting 720, that's what you use 720/60p (or 720/50p) for. Shooting and displaying 60p or 50p will give you the "live" look.
How the JVC actually records 24p is debatable. Steve Mullen wrote an article saying that it actually recorded 24 frames per second in a GOP of 6 frames. Doing so would make it incompatible with HDV. Steve Gibby reported that the Lumiere people had some actual footage from the camera, and that the 24p was actually recorded within a 60p data stream. That would make it potentially compatible with HDV, but raises another question, which is: if it can encode 60p, why does the camera not offer 60p recording? Adam Wilt explained that the NTT MPEG-2 encoder chip in the camera simply cannot handle a data rate of 720/60p -- so how could it encode the 24p to a 60p stream? Perhaps the duplication of frames allows it to keep the data rate low...
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by Dino on May 31, 2005 at 12:29:03 am
Quoting: "In America, the ATSC television standard does provide for 720/24p, 720/30p, and 720/60p broadcasts. 720/24p is a totally legit HD broadcast standard."
Broadcast standard yes, production standard no. ATSC only covers what will be decoded by an ATSC compliant tuner. It has no bearing on how the image is acquired, edited or even displayed.
Production standards are defined by the Society of Motion Pictures and Television Engineer's standards SMPTE-274M and SMPTE-296M. These recognize 720P signals at either 60 or 59.94 progressive frames per second, not 24. This is why, even though it acquires at 24, the Panasonic Varicam always records 60 fps.
In a little twist on the intention of the standards, HDV uses ATSC as it is essentially a way to store an MPEG transport stream, the same stream that is carried in a broadcast.
Quoting: "the 24p was actually recorded within a 60p data stream. That would make it potentially compatible with HDV, but raises another question, which is: if it can encode 60p, why does the camera not offer 60p recording?"
The HDV standard only allows for recording at 30p at 720. I believe you are correct in calling it a bandwidth limiting measure. I'm guessing it is wrapped as 60P for compatibility with both HDV and absolutely any editing package that may attempt to edit it as in the non-linear world we obviously have provisions for 60P and in many cases 24P but not 30P.
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by Graeme Nattress on May 31, 2005 at 1:33:08 am
Yes, it's a 60p MPEG2 stream, but the duplicate frames are flagged as duplicates of the real 24p frames, so they don't take up any extra data space in the stream. It's quite clever really.
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by Kaspar Kallas on May 31, 2005 at 4:10:50 am
All this leads me to another stupid question:
what kind of pull-up/down is used to get 24 to 25fps so if I want to give out PAL DVD or any brodcast copy?
Re: any ideas how jvc's new camera will output 50i 25p @ 720 by David Roth Weiss on May 31, 2005 at 11:01:38 pm
Pretty bad Jiri. Reality TV shows are doing well, but nothing of substance is paying well. If HDV can be made to work like the professional post we're used to, maybe there's hope for those of us who make docos...
