Barry Green
Forum Replies Created
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If you’re shooting 24p, shoot in 1080/24pA. Don’t set the detail level too high, try -3 or so, and I wouldn’t use Cine-D or HIGH gamma, you want the lower-noise gammas like B.Press or Cine-V.
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The HPX500 is a new 2/3″, interchangeable-lens, HD-SDI/Genlock/TCIN & TC-OUT camera that has all the features of the HVX200, so you get variable frame rates, 1080 & 720 & DV50 & DV, etc. Should be shown in April at NAB, with a price of “under 200,000 Yen” (okay, so all I’ve seen on it is the Japanese press release, and that’s what they called it). So figure around $15,000 or so.
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It includes P2 Maker, which lets you render back out to the P2 Card (or, to hard disk to make a P2-compatible MXF file on the hard disk).
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I’d love to, but every time I post the name or a link, the post gets held in a queue for approval… I guess they don’t like that other forum over here all that much, or don’t like redirecting COW browsers to look at a competing forum.
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[doka15] “I guess the question is why can’t Panasonic just create that?”
Panasonic can’t modify Quicktime, only Apple can do that. Apple could make Quicktime on the PC compatible with DVCPRO-HD immediately if they wanted to, and they wouldn’t have to pay any licensing fees or worry about patents or anything like that. Panasonic distributes a free DVCPRO-HD codec for Windows already; just install the P2 Viewer and you have a free codec. All Apple would have to do would be to program Quicktime to tie into that and they would completely avoid all licensing issues or hassles, as well as avoid having to write a codec for the PC platform.
Will they do it? You’ll have to ask Apple that question. Nobody can modify Quicktime except Apple.
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[Brooks] “How does it have twice as much bandwidth when they are both at 100mbit
Thanks”I’m talking about at equal frame rates. At 24p you have effectively 40 megabits in 720/24p mode, and 80 megabits in 1080/24p mode.
Put a simpler way: every frame of 720p is allocated exactly the same amount of space, 1.67 megabits (100/59.94 = about 1.67 megabits). 720 stores up to 60 frames per second, and the amount of space allocated per frame is constant.
And every “frame” of 1080 is allocated a fixed amount of space, being about 3.34 megabits (100 / 29.97 = 3.34 megabits). 3.34 is twice as much as 1.67, so on a frame per frame basis, 1080 has twice as much bandwidth allocated per frame. And in the matrix of pixels, 1080 has twice as many pixels to encode per frame too (each frame of 1080 encodes 1280×1080 pixels = 1,382,400 pixels; each frame of 720 encodes 960×720 pixels = 691,200 pixels per frame). And 1,382,400 = 2 * 691,200.
So you have twice as many pixels in half as many frames, so it all nets out at the same 100 megabits. And, because the same number of pixels per second are being encoded in 100 megabits (1,382,400 x 29.97 = 691,200 x 59.94) you end up with the same compression ratio, 6.67:1.
Which would be all fine and dandy, except that the HVX doesn’t deliver enough pure resolution to fully saturate the 1080 frame size. It does on the horizontal, but on the vertical it only musters about 800 lines of detail. It’s more than enough to fully saturate the 720 frame, but not quite enough to fully saturate the 1080 frame.
So you end up with twice as much bandwidth (3.34 megabits per frame) but only having to encode about 30% more detail. The result is that a 1080 frame is less “taxing” to the compression engine, and you get milder compression and fewer compression artifacts. We’ve demonstrated it over on our other forum, search for posts by Jim Arthurs; 1080 delivers more resolved detail than 720 with milder compression.
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[jimbrodie] “Anyway, I wonder if next time I should adjust the core detail to avoid these visual vibrations.”
That may help a little, but mainly just zoom in or zoom out a little. Changing focal length can greatly minimize the problem.[jimbrodie] “Is 24p the culprit or should I use 30p and forgo the film look?”
Definitely not, it happens in all modes.
[jimbrodie] “Also, I’ve noticed that the exposure changes in 24p when I zoom out – is this the shutter automatically adjusting – I’ve heard that in 24p mode you have no control over this, eventhough I’m in manual exposure and the shutter control is off.”
It has nothing to do with the shutter, or 24p. What’s happening is that the lens maximum aperture is smaller at the telephoto end of the scale. So at full telephoto the best it can do is f/2.8, but at full wide angle it can be as wide-open as f/1.6 so, as you zoom out, it’s possible for the lens to open more and more. If you set a fixed aperture of f/2.8 or smaller (meaning, somewhere between f/2.8 to f/16), then no exposure change will happen.
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Yes you will get a better key with 1080/24p than you will with 720/24p. There’s more detail retained in the frame (about 20% more), but the big benefit is that the HVX’s 1080 image is much less compressed than its 720 image. The 1080 frame has twice as much bandwidth, but only about 20% more detail to deal with, so it has a lot more bandwidth per pixel available and accordingly it delivers less-compressed footage. You have 20% more detail and 100% more bandwidth.
The downside is, of course, that you’ll be taking up 2.5x as much space on the P2 cards. But assuming that ultimate quality is your goal, 1080 should be your choice.
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[gary adcock] “The playback on any HD Monitor is at 48i it cannot be anything else.”
Not from the HVX. From the HVX playback is at 60i. It cannot play back 48i, it doesn’t record 48i, 48i never enters into the equation. It records its 24p signal embedded in 60i.If you export footage back to a card and play it back from there, it’ll be 60i.
[gary adcock] “The 1400 deck does allow for monitoring of HD content over the FW connection with out stuttering.”
Yes, but that output is not going to be 48i. It’s going to be 60i. Anyone working with FCP or EDIUS or Avid in a DVCPRO-HD sequence is going to be sending a 60i signal to their monitor. That’s what the codec supports, that’s what the transport stream is.
Maybe if you’re transcoding away from DVCPRO-HD, using an uncompressed suite such as one built for HDCAM, then maybe you’d run into 48i, but it would have nothing to do with the HVX or with the native editing of its footage.
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[gary adcock] “Specs for the 1080 format call for PsF, or progressive segmented frame, playback devices render this content as 48i according to the read out my BTW1700 Panasonic display. It is my understanding that the only devices that can playback a true 24p image as progressive are D5, SRW, and highend DDR’s like Stwo, HDRave etc.”
Playback to what though? I’m talking about how the footage is treated and edited. It is not split into fields, it’s handled as 24p footage, progressive frames.
If you have some sort of monitoring card installed and are piping it out to a monitor, then maybe 48i would come into the equation, but that has little to nothing to do with how the footage is handled by the editing system.
If it was truly 48i, then when you rendered motion graphics or titles over your footage you’d see a “disconnect” and field separation. You don’t, because the footage is treated at all times like 24p.
It may be getting converted to 48i for display on a 24fps interlaced monitor, but then again it’d get converted to 60i for display on a conventional CRT too. But that’s a conversion that’s handled in the after-the-NLE stage, not anything to do with how the footage is recorded or stored or manipulated.
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