Is HVX true 4:2:2

smelni

smelni

Veteran
I heard a rumor and first i must say very clearly that it is just a rumor that i wanted to check out.

I heard that the HVX is not true 4:2:2 - I am not sure why or how. I have actually heard this a couple of times and recently from someone "in the industry".

I just wanted to see if anyone has heard this and if it is true then what does that mean and especially what does it mean for quality and keying?

I do not mean to start a rumor so if this is completely untrue then I apologize in advance.

thanks
 
There are people trying to claim that the HVX is 3:1.5:1.5, which just shows that they clearly do not know what they're talking about (nor do they know how to do the math, because the ratio of 3 to 1.5 is exactly the same as the ratio of 4 to 2, so 3:1.5:1.5 is the same as 4:2:2)!

The HVX is true and genuine 4:2:2. Two color samples for every four pixels, on each and every line.

The discrepancy comes about in them trying to equate horizontal luma subsampling with the number 4. And you can't. You don't. That's not what the "4" means.

For example, HDCAM is 3:1:1. These people who are spreading the fibs are trying to say that the "3" in this case represents a subsampling of 1920 down to 1440. But it doesn't. It has nothing to do with that. The 3 shows the ratio of luma to chroma samples IN THE SUBSAMPLED LINE. So HDCAM is 3:1:1, meaning there's one chroma sample for every three pixels, on every line. The way it works is HDCAM is 1440x1080 in luma, and 480x1080 in chroma. 1440 / 3 = 480. 1/3 as much chroma as luma. 3x as much luma as chroma. So it's 3:1:1. Has nothing to do with the number of luma samples per line; it could be 1920x1080 and still be 3:1:1 if the chroma sampling was done at 640x1080.

They then try to claim that HDV 720p is 4:2:0, because it doesn't subsample luminance at all, it retains a full 1280x720 luminance grid, so they try to claim that that's what entitles that format to use a "4". Which is nonsense. HDV 720p is 4:2:0 because there are two chroma samples for every four luminance samples, on every other line. See, where they fall down in their tilting-at-windmills quest is that they conveniently forget to point out that 1080i HDV is also 4:2:0, and 1080i HDV also subsamples from 1920 down to 1440. So shouldn't HDV 1080i be limited to a maximum first value of 3, if they're going to claim that that's why HDCAM is measured as 3:1:1? And wouldn't that make HDV 1080i 3:1.5:0? Preposterous. 1080i HDV is 4:2:0.

It just shows a complete misunderstanding of 4:x:x terminology. Charles Poynton explains it rather well, and so does Graeme Nattress. The sampling notation of 4:x:x is applied to the final ratio of chrominance to luminance, AFTER subsampling.

DVCPRO-HD is 4:2:2 in all modes. Yes there's subsampling. Yes there's subsampling in 1080i HDV and in HDCAM too. That doesn't change what 4:2:2 and 3:1:1 and 4:2:0 mean.
 
Right! As you well explained, Barry, it was a obvious misunderstanding of the ratio meaning, BTW, concerning 720p and not 1080i/p, wasn't it?

And about HDCAM, if it is the same ratio method but 3:1:1 (480x1080 in chroma), does it mean an inferior ratio, that is, a DVCPRO-HD chroma advantage? 640x1080 in 24p/60i and 720x1080 in 25p/50i?
 
Hi,

HDV 720p:__________Frame res 1280x720, 4:2:0, Y sample: 1280x720, Cr,Cb Sample 640x360
DVCProHD 720p:_____Frame res 1280x720, 4:2:2, Y sample: 960x720, Cr,Cb Sample 480x720

JVC gives the full scan 1280x720 without subsampling/shifting so the final frame follows the spec listed above.
 
Emanuel said:
Right! As you well explained, Barry, it was a obvious misunderstanding of the ratio meaning, BTW, concerning 720p and not 1080i/p, wasn't it?
Click to expand...
Yes, this argument is always applied against 720; for some reason the detractors always seem to forget that DVCPRO-HD also offers 1080i and 1080p (wonder why they leave that out? Hmmm...) I mean, do they really expect that 1280x720 with 640x360 chroma can stand against 1280x1080 with 640x1080 chroma? 50% more luma and 3 TIMES as much chroma res?

And about HDCAM, if it is the same ratio method but 3:1:1 (480x1080 in chroma), does it mean an inferior ratio, that is, a DVCPRO-HD chroma advantage? 640x1080 in 24p/60i and 720x1080 in 25p/50i?
Click to expand...
Yes, in 1080 DVCPRO-HD records substantially more chroma than HDCAM does.
 
stephenlnoe said:
Hi,

HDV 720p:__________Frame res 1280x720, 4:2:0, Y sample: 1280x720, Cr,Cb Sample 640x360
DVCProHD 720p:_____Frame res 1280x720, 4:2:2, Y sample: 960x720, Cr,Cb Sample 480x720

JVC gives the full scan 1280x720 without subsampling/shifting so the final frame follows the spec listed above.
Click to expand...

Those numbers are correct, yes, but it leaves out that DVCPRO-HD supports twice as much temporal resolution as HDV 720p does. HDV 720p in its current configuration is limited to a maximum of 30p, DVCPRO-HD delivers 720/60p.
 
Barry_Green said:
The HVX is true and genuine 4:2:2. Two color samples for every four pixels, on each and every line.
Click to expand...

This really puzzles me, how an earth the horizontal chroma resolution is visibly so acceptable?
If we compare full hd 4:4:4 horizontal resolution and dvcprohd1080p, we notice that there are only one chroma sample in dvcprohd per 3 samples in full hd.
At the same time vertical resolution in dvcpro has the same chroma resolution than full hd.

Clearly this is because of legacy reasons of interlaced television, but that's something we should get away from.

In progressive picture, I see no logical reason for 3x1 chroma pixels (or even 4x1 in hdcam), so instead of getting 640x1080, I'd prefer 960x540.

So I'll hope that next dvcpro codec we'll get is 1920x1080@4:2:0.
It should give better quality than 1280x1080@4:2:2 at least with natural content.
 
Barry - thank you so much for clearing this up - a great explanantion as always - now i understand what i was being told and I can give the explanation back.

thanks for your time
 
Barry_Green said:
Those numbers are correct, yes, but it leaves out that DVCPRO-HD supports twice as much temporal resolution as HDV 720p does. HDV 720p in its current configuration is limited to a maximum of 30p, DVCPRO-HD delivers 720/60p.
Click to expand...

Barry,

Just keeping the apples with the apples. 720p24 to 720p24. Frame for frame.

Of course there is a cornucopia of datarate and resolution math, however with the JVC offereing you know you're getting full1280x720p24@3.51MB per uncopressed TGA frame and Y sample: 1280x720, Cr,Cb Sample 640x360. That's nice to know.

A Hi8 beat us all out of a 48hour film project win because the story was excellent, not because of their technology. I mention the 48hour specifically because there is such a mixed bag of cameras all in one place.

It's all good isn't it?
 
wait - now i am a little confused. So is the HDV format better at the luma sampling when recorded at the same frame rate as DVCProHD?
 
smelni said:
wait - now i am a little confused. So is the HDV format better at the luma sampling when recorded at the same frame rate as DVCProHD?
Click to expand...
The short answer is yes.

When you compare apples to apples (ie 720p24 HDV1 to 720p24 DVCProHD)

HDV 720p:__________Frame res 1280x720, 4:2:0, Y sample: 1280x720, Cr,Cb Sample 640x360
DVCProHD 720p:_____Frame res 1280x720, 4:2:2, Y sample: 960x720, Cr,Cb Sample 480x720

The formats are much closer than people think.

Barry's right when you get into different resolutions though (1080i and 1080p). We'll see what NAB brings to the table for HDV and 1080p.
 
So then, considering this - it seems that DVCproHD's biggest winning attribute is the intraframe compression - while HDV is highly interframe compressed. Cause the YCrCb numbers work out to be very close - about 10 percent different if you multiple all the numbers
 
smelni said:
wait - now i am a little confused. So is the HDV format better at the luma sampling when recorded at the same frame rate as DVCProHD?
Click to expand...
At the same frame rate? No, because at 24P you could record in 1080 and get 1280x1080, vs. 1280x720 in HDV. You'd get 50% more luma, and three times as much chroma, in DVCPRO-HD.

The HDV1-to-DVCPRO-HD comparisons always try to limit DVCPRO-HD to its very most limited mode. DVCPRO-HD can do far more than HDV can even think about.

It's like if you were going to play basketball against Shaquille O'Neal, but you decided that because you're 5'6", the artificial constraint is that both players can be no taller than 5'6". So Shaq has to play on his knees. Would you stand a pretty good chance against him in that case? Sure. Maybe. Heck, Shaq'd probably still beat most of us, but yes you'd have the best chance you'd ever have. But why would Shaq ever agree to that? Unleash the man, let him play, and you'd never stand a chance.

If you want to stick to 24P, shoot 1080/24P on the HVX, and get 50% more luma res and 3 TIMES as much chroma resolution as HDV1. If you want to stick to 720P, let the HVX's full 60P frame rate come into play, where you get a comparable resolution picture (25% less luma than HDV1 but 50% more chroma than HDV1), but you also get variable frame rates and up to twice as many frames per second.

No contest.
 
smelni said:
So then, considering this - it seems that DVCproHD's biggest winning attribute is the intraframe compression - while HDV is highly interframe compressed. Cause the YCrCb numbers work out to be very close - about 10 percent different if you multiple all the numbers
Click to expand...
Hardly. DVCPRO-HD's biggest attributes are:

intraframe compression for a complete avoidance of all motion artifacts;

substantially superior chroma resolution (in 720p mode it has 50% more chroma than HDV, in 1080 mode it has about 90% more than HDV);

true progressive scan in 1080 mode, which no HDV2 product offers;

constant, predictable compression performance on a frame-for-frame basis, vs. HDV's bit-starved nature which can cause significant image degradation if the codec gets overloaded;

imperviousness to dropouts, where HDV can punt an entire 15-frame GOP (1080 mode) or 6-frame GOP (720 mode); or, in the JVC version, you can get massive scrags that stay on the screen for 1/4 to 1/5 second (depending on whether you're recording 24p or 30p mode);

variable frame rates;

the ability to record 60p in 720 mode;

MUCH milder compression than HDV in all circumstances;

bitstream compatibility with existing DVCPRO-HD products that are already established in the marketplace, such as the AJ-HD1200A deck and the VariCam, as opposed to the nearly universal incompatibility of the three various flavors of HDV;

much better editing integration (FCP5 has been working in native DVCPRO-HD for 18 months now, since April 2004) and depending on your Mac you can edit nearly a dozen streams of DVCPRO-HD in real time (something that just isn't gonna happen when editing an MPEG-2 transport stream!);

the ability to do a firewire preview of DVCPRO-HD data, something HDV cannot now nor ever do. Not sure if the HVX supports realtime firewire scrubbing/preview in HD or not, but it works on the 1200A deck.

There are probably more reasons, these are just the ones that I can think of off the top of my head.

The 720/24p variant of HDV is probably the most robust, best implementation of HDV. I have said many times that if I had to shoot HDV, that would be the flavor that I would strongly prefer (although Canon's new 1080/24F is not bad at all). That doesn't put it in the same ballpark, class, or league as DVCPRO-HD though. It's a whole class up from HDV. Maybe two, if you follow Sony's logic:

DVCPRO-HD is a direct toe-to-toe competitor to HDCAM. Sony produces four HD formats, HDCAM-SR at the top, then HDCAM, then XDCAM-HD, and then HDV at the bottom. Sony classifies XDCAM-HD as "between HDV and HDCAM." That puts HDCAM two levels above HDV. And by extension, DVCPRO-HD two levels above HDV. And that sounds about right to me.
 
Barry - i understand all that and see that the hvx is superior in that way. Clearly superior especially in the addition functions available.

but in an apple to apple test - 720 24p on both - theoretically the hdv should look nearly the same - or will the interframe compression lose all the gains in the luma?

EDIT - thanks barry - beat me to it
 
If you want to make Shaq play on his knees, then yes, the HDV1 720/24p will be quite competitive with 720/24p DVCPRO-HD. The chroma res vs. luma res will probably come close to cancelling each other out. It will definitely be the most competitive that HDV will look against DVCPRO-HD, yes.

Of course, we're talking strictly about codecs here too. There's far more going on that will affect your image than just the codec! The lens, the chips, the latitude, the sensitivity, the noise, the DSP processing, the gamma curves, all those things will play a big role in how the overall image looks.
 
smelni said:
So then, considering this - it seems that DVCproHD's biggest winning attribute is the intraframe compression - while HDV is highly interframe compressed. Cause the YCrCb numbers work out to be very close - about 10 percent different if you multiple all the numbers
Click to expand...
Not exactly, If the codec carries a clean signal then once it's in the NLE it can be uncompressed from the transport stream (whether HDV or DVCProHD) and worked with in it's uncompressed state. The hangup is not on HDV or DVCProHD as a transport but on what gets uncompressed.

I wrote this on some other threads somewhere around here but I'll write it again. With HDV you can work in 1 of 4 modes. Those being: Native MP@HL, RGB(AVI), Uncompressed (2VUY), or intermediate codec (Cineform and the like). If working in uncompressed you get the full rez 1280x720, 4:2:0, Y sample: 1280x720, Cr,Cb Sample 640x360 @ 3.51MB per TGA frame (uncompresssed). Once the data is uncompressed then the transport stream (whether HDV or DVCProHD) have nothing to do with working the frames and frame sequences.

Then it comes down to how well the original codec handled the motion estimation and the DCT compression. With HDV1 you know exactly what you're getting 1280x720 without interpolated pixels. I offer These uncompressed frames (Click here) for you to bring into photoshop and check out. With any DCT compression you can push the image to seeing the 8x8 blocks (DVCProHD or HDV). Try working with the TGA's to see how much HDV uncompressed can take.

I tell you, splitting hairs over 8 bit formats get's old and I should have left it alone. Let me write this, both HDV and DVCProHD are much better than what we had and certainly both are worthy of film transfer if the story is good enough.

take care amigos...
 
stephenlnoe said:
Let me write this, both HDV and DVCProHD are much better than what we had and certainly both are worthy of film transfer if the story is good enough.
Click to expand...

Completely agreed (as far as HDV1/720/24p goes!)
 
HVX-200 Questions

HVX-200 Questions

Hello:

Does anyone have answers to the following HVX questions:

1. Can this camera record 4:2:2 color onto DV tape at 480P?

2. Can this camera record the 720P to "DV tape" with variable frame rates (slow motion, ect.)?

3. What is the most cost effective portable hard drive to record 720P variable frame footage with? Any recommendations?

4. What is currently the best NLE to edit 720P 24fps, HD DVCpro footage with? In other words, with a Powerful PC how can you easily edit with this 720P 24fps content as source?

5. HVX-200 vs. DVX-100b for 480 24P footage, any difference?
Does the HVX capture better 480P image quality then DVX-100b?

Thanks Friends
 
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