Barry Green
October 1st, 2005, 06:00 AM
At ResFest I was able to get some footage from the XL H1 in 24F mode, recorded on tape. I was also fortunate enough to have Nate Weaver along (a very talented shooter well-known from his posts about the HD100, as well as an ex-XL1 owner) so I let Nate do the shooting.
I was going to post the clip here for all to see, but there's a hitch -- a big one. It turns out that apparently, Canon has implemented their own, completely incompatible recording format! 24F footage won't play on any existing HDV equipment -- won't play on an HD100, won't play on an HD1, won't play on an FX1, won't play on an HC1. Won't play on the cameras themselves, and it won't play through firewire to HDV Rack from those cameras. On the Sony cameras the timecode display updates, but there's an error message on the LCD screen that says (IIRC) "incompatible tape format."
It seems like the only device that can play 24F footage is: an XL H1.
This also helps explain why, at RESFest, Canon was showing their footage off of DVCPRO-HD tape. There is no HDV deck that could play 24F footage! It's a new, third incompatible format of HDV. They had to use a non-HDV deck in order to be able to play it at all.
I talked at length with the Canon representative at the show, and he predicted that this would be the case -- that 24F won't play on existing HDV equipment. He'd seen the file coming out of the firewire port and he said it was a 24-frame file (which, of course, Sony HDV isn't -- all Sony HDV is recorded as a 60i or 50i file). And a 24-frame file doesn't make sense within the context of a 15-frame GOP either -- how do you fit 24 frames into a 15-frame GOP? You can't. He also said the CCD is clocked to 24fps, which CF24 isn't.
So, based on what the Canon rep told me, and what has been reported here, plus my firsthand experience with 24F, I think we can now make some educated guesses as to what 24F actually is, and what it isn't.
We know it isn't actual progressive scan, again verified by the Canon rep. And we know it isn't CineFrame 24 (thank goodness), because if it was CF24 it'd play in a Sony camera or deck. And, although I was only able to observe the 24F footage in the Canon's viewfinder (they didn't have a monitor at RESFest while I was there), the motion rendition didn't have the CF24 mode's characteristic herky-jerky movement. It looked consistent on consistent-speed objects. That's not a scientific observation, because I can't view the footage on a monitor or frame-by-frame, but that's a casual observation made of what was in the viewfinder.
Based on all this, I feel confident in making an educated guess as to what 24F actually is. I believe CF24 will likely prove to be a 48hz version of Sony's CF25. I think they clock the CCD at 48hz (instead of 50hz like CF25), and they capture one field (540 lines). They probably use the Digic II chip to synthesize the missing field, which will probably lead to a vertical resolution actually a bit higher than CF25. And, I am guessing that this stream is then encoded using a 12-frame GOP without pulldown -- a 12-frame GOP would work quite nicely with a 24-frame data stream.
Clocking the CCD at 48hz and using one field would give you a motion rendition identical to 24P shot at 48hz. It'll be only half the theoretical maximum vertical resolution, but then again the news isn't all bad: the Sony has about 775 lines of vertical res, but CF25 mode skips the low-pass filtering that lowers interlaced-footage res, so CF25 delivers a legit 540 lines rather than the 380 you'd expect from straight de-interlacing. So if the Canon employs the same process, it should offer at least 540 lines, and maybe a tad more depending on how good Digic II is at synthesizing/up-rezzing the "missing" field.
So, while Nate and I thought we would have a nice "scoop" for DVInfo readers, by posting the first 24F clip to the world, it turns out that it just isn't possible. It can't be captured (from any other HDV device). Maybe Kaku will be able to capture some footage if he tries to digitize directly from the XL H1, although I'm pretty sure that if he's using FCP it'll probably be a no-go (FCP doesn't support JVC's 24P mode, I'm guessing it won't support the Canon mode either without an update). I'll be sure to ask him to try this.
I was going to post the clip here for all to see, but there's a hitch -- a big one. It turns out that apparently, Canon has implemented their own, completely incompatible recording format! 24F footage won't play on any existing HDV equipment -- won't play on an HD100, won't play on an HD1, won't play on an FX1, won't play on an HC1. Won't play on the cameras themselves, and it won't play through firewire to HDV Rack from those cameras. On the Sony cameras the timecode display updates, but there's an error message on the LCD screen that says (IIRC) "incompatible tape format."
It seems like the only device that can play 24F footage is: an XL H1.
This also helps explain why, at RESFest, Canon was showing their footage off of DVCPRO-HD tape. There is no HDV deck that could play 24F footage! It's a new, third incompatible format of HDV. They had to use a non-HDV deck in order to be able to play it at all.
I talked at length with the Canon representative at the show, and he predicted that this would be the case -- that 24F won't play on existing HDV equipment. He'd seen the file coming out of the firewire port and he said it was a 24-frame file (which, of course, Sony HDV isn't -- all Sony HDV is recorded as a 60i or 50i file). And a 24-frame file doesn't make sense within the context of a 15-frame GOP either -- how do you fit 24 frames into a 15-frame GOP? You can't. He also said the CCD is clocked to 24fps, which CF24 isn't.
So, based on what the Canon rep told me, and what has been reported here, plus my firsthand experience with 24F, I think we can now make some educated guesses as to what 24F actually is, and what it isn't.
We know it isn't actual progressive scan, again verified by the Canon rep. And we know it isn't CineFrame 24 (thank goodness), because if it was CF24 it'd play in a Sony camera or deck. And, although I was only able to observe the 24F footage in the Canon's viewfinder (they didn't have a monitor at RESFest while I was there), the motion rendition didn't have the CF24 mode's characteristic herky-jerky movement. It looked consistent on consistent-speed objects. That's not a scientific observation, because I can't view the footage on a monitor or frame-by-frame, but that's a casual observation made of what was in the viewfinder.
Based on all this, I feel confident in making an educated guess as to what 24F actually is. I believe CF24 will likely prove to be a 48hz version of Sony's CF25. I think they clock the CCD at 48hz (instead of 50hz like CF25), and they capture one field (540 lines). They probably use the Digic II chip to synthesize the missing field, which will probably lead to a vertical resolution actually a bit higher than CF25. And, I am guessing that this stream is then encoded using a 12-frame GOP without pulldown -- a 12-frame GOP would work quite nicely with a 24-frame data stream.
Clocking the CCD at 48hz and using one field would give you a motion rendition identical to 24P shot at 48hz. It'll be only half the theoretical maximum vertical resolution, but then again the news isn't all bad: the Sony has about 775 lines of vertical res, but CF25 mode skips the low-pass filtering that lowers interlaced-footage res, so CF25 delivers a legit 540 lines rather than the 380 you'd expect from straight de-interlacing. So if the Canon employs the same process, it should offer at least 540 lines, and maybe a tad more depending on how good Digic II is at synthesizing/up-rezzing the "missing" field.
So, while Nate and I thought we would have a nice "scoop" for DVInfo readers, by posting the first 24F clip to the world, it turns out that it just isn't possible. It can't be captured (from any other HDV device). Maybe Kaku will be able to capture some footage if he tries to digitize directly from the XL H1, although I'm pretty sure that if he's using FCP it'll probably be a no-go (FCP doesn't support JVC's 24P mode, I'm guessing it won't support the Canon mode either without an update). I'll be sure to ask him to try this.