Barry Green
Forum Replies Created
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[pom_boarder] “To summarise he explains that DVCPROHD at 24fps comprises of 60% redundant frames which effectively makes the 100mbps stream into a 40Mbps stream, only marginally better than HDV at 35Mbps.”
That’s a very inaccurate summarization though.
First, 1080 DVCPRO-HD is always 100 megabits. If you shoot 1080/24p (with 3:2 pulldown), 1080/25p, 1080/30p, 1080/50i, or 1080/60i, it’s always 100 megabits. In the specific case of 1080/24pA, most editing programs can strip out the duplicated “padding” frames and end up with a pure 1080/24p data stream with a net data rate of 80 megabits.
In 720 mode, each frame is stored discretely and takes up 1/60th of 100 megabits, so 24p does take up 40 megabits.
When you say “only marginally better than HDV at 35Mbps” there’s several misconceptions there. First, HDV is not 35mbps. XDCAM-HD or XDCAM-EX are, but HDV is not. HDV comes in two varieties, either 720 (at 19 mbps) or 1080 (at 25mbps). So to make a proper comparison you’d have 720/24p DV100 vs. 720p HDV, which means 40mbps vs. 19 mbps. Or you’d compare 1080/24p DV100 vs. 1080/24p HDV, so you’d have 80 mbps vs. 25mbps. Or you’d have 1080/24p DV100 vs. 1080/24p XDCAM-HD, which would be 80 mbps vs. 35mbps.
Even then, you’d have too many other variables to compare. DVCPRO-HD is always 4:2:2, HDV and XDCAM-HD are always 4:2:0, so DVCPRO-HD stores twice as much color information. But in the case of 720p, DVCPRO-HD prefilters to 960×720, whereas HDV stays at 1280×720. But, HDV uses long-GOP compression which is susceptible to variable performance depending on the situation being shot, whereas DVCPRO-HD uses consistent reliable intraframe encoding.
In short, it is impossible to compare them by the numbers. You simply cannot say that one’s number here is better than another’s number there. It ain’t that easy.
So one way you could look at it is via the manufacturer’s rankings. Sony has several flavors of HD recording systems, and they rank them like this:
#1: HDCAM-SR
#2: HDCAM
#3: XDCAM-HD
#4: HDVHDV is their lowest form of recording an HD signal. They classify XDCAM-HD as falling between HDV and HDCAM.
DVCPRO-HD is Panasonic’s direct competitor to HDCAM. It can be more fairly compared “on the numbers” to HDCAM because both are intraframe compression codecs; DVCPRO-HD records 4:2:2 color (vs. HDCAM’s 3:1:1, which means DVCPRO-HD records 50% more color info) but HDCAM has a larger bandwidth (135 megabits vs. 100 megabits). So in the end they are basically comparable.
And by that type of comparison, one can easily see that DVCPRO-HD is far superior to HDV, and is a more professional and overall better codec than XDCAM-HD. The BBC has just standardized on DVCPRO-HD for all their productions at Factual Studios and is expected to convert entirely to P2 very shortly.
Now, to confuse issues even further: the recording format is only one element in the total imaging chain. The lens, the chips, the DSP, everything all work together to produce the final image. If you chained a little $300 Handycam to a DVCPRO-HD deck and recorded straight DVCPRO-HD, and then compared that to a Sony F350 XDCAM-HD camcorder, my bet is that the XDCAM-HD recording would look much better. The final image is determined by more than just the recording format. Canon also must have believed that DVCPRO-HD was better than HDV; when they did their “watchmaker” demo footage for the XLH1, they chose to record directly through HD-SDI to an external DVCPRO-HD deck rather than use the XLH1’s own HDV deck.
So you cannot judge DVCPRO-HD just by one particular camcorder. For example, Discovery HD has certified DVCPRO-HD as an acceptable production, editing, mastering, and delivery format, whereas they restrict HDV to only 15% of a program’s total content and will not accept HDV as an editing, mastering, or delivery format. However, they also put the same 15% restriction on the HVX200, even though the HVX200 shoots to one of their unrestricted acquisition formats! Why? Because there’s only so much performance one can get out of a 1/3″ camcorder, and Discovery classifies all the 1/3″ camcorders together; none of them are accepted for unrestricted acquisition.
But the format does still come into play. A 2/3″ DVCPRO-HD camcorder would be accepted for unrestricted acquisition. A 2/3″ HDV camcorder would not.
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[mark cookman] “But why do you ( Barry ) suggest the 1080pA rather than 1080pN format? I believe in this scenario 6 redundant frames would be recorded – maybe its for compatibility with more edit systems?”
There is no 1080pN mode in DVCPRO-HD. There’s 24P mode (which is using 3:2 pulldown) and there’s 24pA mode (which uses a different type of pulldown, called 2:3:3:2, but all it really means is that one frame out of each group of five gets repeated to pad out the sequence). Most editing programs know how to strip out that “padding” frame, thus returning you to the original pure 24P sequence.
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[Raymond Motion Pictures] ” film cameras run at half the speed of projectors”
But — they don’t. The projector feeds the film through at exactly the same speed as the film camera does. The projector displays 24 frames per second. It just flashes each frame twice (or three times) to even out light/dark flicker. It has nothing (nothing nothing nothing) to do with motion.The projector cannot run faster than the film camera, or everything would be playing at double speed, of course.
Theatrical film projection is done at 24 frames per second. A film projector flashes the image multiple times only to even out the light/dark transition from when the shutter is closed. Using a bowtie/butterfly shutter lets them even out the open/closed timing moreso than using a half-moon shutter would, while still maintaining the same amount of overall shutter-open time.
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[doka15] “The one reason that I shoot 720p is because of the progressive mode”
1080/24p and 1080/30p are also progressive.
[doka15] “I think many people might think the way I do that 1080i is an interlaced format and you are shooting frames to interlaced”
They may think that, but it doesn’t make it true. The 1080 is recorded in an interlaced wrapper, but it’s progressive footage (basically the same as how an F900 HDCAM camera records 1080/24p but records as 1080/24psF.) The editing programs know how to remove the interlace pulldown and give you a pure original 1080/24p sequence.[doka15] “I would be worried about interlacing compression artifacts even though it is a single frame.”
If you’re using FCP, EDIUS, or Raylight, you have nothing to worry about. All of them know how to remove the pulldown and give you a true 1080/24p image (but you have to have shot in 1080/24pA). If using Avid, you can’t edit true 1080/24p — Avid doesn’t know how to remove the pulldown. For Avid users, it may be best to stick to 720p mode.
[doka15] “Also the nice thing about shooting 720 is the over and under cranking of the footage”
Yes, and that can only be done in the 720 mode. You could always use that footage in a 1080 sequence by uprezzing the 720 footage.
[doka15] “I would think I might end up with a product that won’t look as nice as the 720p format.”
Well, the choice is yours of course. 1080/24p from an HVX is sharper, more detailed, and less compressed than 720/24p. If I was planning to do something for the big screen, there’s no doubt that I’d shoot it in 1080/24pA mode, and only swap to 720 for those sequences where I needed overcranking or undercranking.
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Glad to help, and thanks for ordering — I hope you find them useful! 🙂
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You’re viewing high-def analog component. HD signals can be sent via component, or also digitally (via HD-SDI or HDMI, etc). So you are seeing a high-def signal.
(Unless you’ve gone into the menus and told it to downconvert everything to 480/60i, which is an option that’s available to you).
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[Raymond Motion Pictures] “So, when it goes to film print for projection it’s 48fps”
But it’s not 48 fps. It’s 24 frames per second. You only see 24 frames. Yes each one gets flashed twice (or three times), but 24 frames move through the projector each second.
Transfer that 24fps to DVD and watch it on a progressive-scan DVD player connected to a progressive-scan TV and you’ll see exactly 24 frames per second, no repeating, no flashing, no pulldown, no anything.
The multiple-flashing repeat frames thing is a concession to the mechanical shutter of a film projector, and not to the actual motion of 24fps material.
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I should add — if choosing 1080, always go for 1080/24pA. FCP, EDIUS, and Raylight can all strip out the pulldown and let you work with straight 24P with no interlacing. Don’t use the 1080/24P mode, use 24PA.
If you’re on Avid, you’re kind of hosed. Avid doesn’t support pulldown removal at all from HVX 1080 footage, IINM.
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[tommazzvideo] “no I mean inside the camera, how do you clear clips all at once”
Format the card.
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There will be a difference. A “big” difference? Well, the 1080 is going to show around 20% higher resolution, and quite milder compression. I’d go for 1080 if planning for the big screen. 720’s enough, but if you have the storage space available, why not go for the best you can get?