4.2.2. versus 4.2.0

[Piotr Wozniacki]

Originally Posted by Alexander Ibrahim

SxS records only 4:2:0 Long GOP XDCAM.

The EX1 requires some sort of outboard system for 4:2:2 recording.

AJA's ioHD with a laptop and Convergent Design's Flash XDR seem to be the most popular outboard systems proposed right now.

While I am excited about the EX1, not including 4:2:2 recording could become a serious oversight with the indie crowd this camera is aimed at.

How do you record from AJA ioHD to a laptop - through the FireWire? If so, is the 400 mbps version enough?

[David Heath]

Originally Posted by Alexander Ibrahim

Uh... no.

4:2:2 matters a bit to poor folks that need to actually work with footage before we output it.

Clearly there isn't anything I can say to convince you, so take a look for yourself.

No - I am convinced, and maybe the "largely" in what you quoted from me is being overlooked, I'm certainly not saying that 4:2:0 is every bit as good as 4:2:2, period. Just saying the subject has more to it than often made out, especially when referring to straightforward footage with no keying etc.

One thing your image does reinforce (and which is often overlooked) is the difference between progressive and interlace 4:2:0 - 4:2:2 is unquestionably the best of the three, but the difference is less marked between it and the prog 4:2:0 sample than it and the interlace sample.

Sometimes more data is good data.

Undoubtably. So why draw the line at 4:2:2? Why not insist on 4:4:4?

I suspect that if the enlargement of the image had been done on a nearly vertical edge just above the three o'clock position we'd have a very different result, and that whilst the 4:4:4 result would be very similar, there would be much less difference between 4:2:2 and progressive 4:2:0.

Thanks for clearing that one up. Looks like I have to recalculate some things relating to this camera. A big oversight to not have 4:2:2 recording onto the cards.

I am looking at a camera to use for indy filmmaking and I would definetely need to use with greenscreen. The EX looks pretty nice on paper for everything except not getting 4:2:2. If I can't get the 4:2:2 coloursampling recordiong onto the EX1's cards.. what is the cheapest method of getting the 4:2:2 into my computer via the HD-SDI? Thinking of price point here.

In this case should I consider the HVX over the EX?

By the way I will be stepping up from DV. So i feel a little bit in the woods when it comes to HD. I have used many (A1, HVX200, fx1, z1) and really see the difference in quality and resolution. But I haven't yet had the opportunity to use an HD camera for greenscreen work.

[Kevin Shaw]

Originally Posted by Alexander Ibrahim

Clearly the 4:2:2 image shows a marked improvement in key quality when compared to the 4:2:0 progressive image.

Makes sense, but if you had to choose between 4:2:0 with full 1920x1080 image resolution or 4:2:2 with 1280x1080 resolution, which do you think would produce the better key?

[Alexander Ibrahim]

Originally Posted by Kevin Shaw

Makes sense, but if you had to choose between 4:2:0 with full 1920x1080 image resolution or 4:2:2 with 1280x1080 resolution, which do you think would produce the better key?

4:2:2 1280 definitely.

Now, if I determine the the image is "unkeyable" then I prefer to have the highest resolution image I can for rotoscope and tracking mattes.

[Alexander Ibrahim]

Originally Posted by Ben Allen

I am looking at a camera to use for indy filmmaking and I would definetely need to use with greenscreen. The EX looks pretty nice on paper for everything except not getting 4:2:2. If I can't get the 4:2:2 coloursampling recordiong onto the EX1's cards.. what is the cheapest method of getting the 4:2:2 into my computer via the HD-SDI? Thinking of price point here.

In this case should I consider the HVX over the EX?

By the way I will be stepping up from DV. So i feel a little bit in the woods when it comes to HD. I have used many (A1, HVX200, fx1, z1) and really see the difference in quality and resolution. But I haven't yet had the opportunity to use an HD camera for greenscreen work.

Well Ben as a fellow indie I am buying into the EX1. I like the HVX, but I really want the 1/2" sensors, focus marks and full raster 1080p image.

The cheapest way to get 4:2:2 into a PCI Express desktop is BlackMagic's Decklink HD Extreme. $995 MSRP That unit is single link HD SDI, but it has analog and digital i/o. (The HD Pro models are SDI only.)

http://www.blackmagic-design.com/products/hd/

The best way to get 4:2:2 into a laptop right now is AJA's ioHD. $3495 MSRP.

http://www.aja.com/html/products_Io_IoHD.html

You output via HD SDI to the ioHD, and then it pipes into your Mac via firewire. It works over Firewire 400Mbps, but the ioHD comes with a 800Mbps connector on its casing.

That footage is in Apple's ProRes 4:2:2 codec in 10 bit color.

Alternatively there is the Convergent Design Flash XDR. That is MSRP $4995. It uses compact flash drives and records a 4:2:2 intraframe codec at 160Mbps. It also offers 50Mbps and 100Mbps 4:2:2 with Long GOP. That might come out a bit cheaper if you have to buy a Mac and external drives for the purpose.

http://www.convergent-design.com/dow...%20XDR.pdf

There is also V3HD, which captures to DVCPRO HD. It retails for $2750, making it the cheapest solution possible for a laptop.

DVCPRO HD limits you to 1080i or 720p capture. That may be better for keying than the SxS 4:2:0 footage, but the camera does so much more, I'd rather spend the extra cash and get the full performance.

http://www.v3hd.com

In any case I'd recommend an external SATA RAID 0 disk array for capture. It should work though on even a single USB connected drive. It should work on some of the 7200RPM laptop internal drives, but I've never seen that tested.

The main reason these solutions are rejected is that its a lot of cabling and hassle. For film style work I see that as a non-issue because my cameras are always tethered to video village for video monitoring (yes even on dolly and steadicam shots!) if nothing else.

With these solutions I get 4:2:2 video, and I can use the Mac as a waveform|vectorscope. In a pinch I could use the Mac for monitoring video too.

As a note I think I am going to go the AJA ioHD route.

[Alexander Ibrahim]

Originally Posted by David Heath

No - I am convinced, and maybe the "largely" in what you quoted from me is being overlooked

Maybe I misread that. Sorry.

Undoubtably. So why draw the line at 4:2:2? Why not insist on 4:4:4?

Only one reason: $$budget$$.

4:4:4 means HDCAM SR or uncompressed data on the drives.

Uncompressed 10 bit 4:4:4 is only available with RED and higher priced cameras. The only ones "readily" available are the Thomson Viper and Sony's F950 & F23.

Also we are talking dual link HD SDI, at about 3Gbps. Thats about a Terabyte every five minutes.

Thats a lot of disk space and it has to be FAST. Four disk RAID 0 at minimum. A 14 drive RAID 0 SATA array can give 12TB or about 60 minutes of recording. (That's real binary TB not the popular trillions (10^12) of bytes) That's two fully loaded Xserve RAID's.

HDCAM SR recorders can alleviate the disk space issues- at the meager cost of $95,000 USD. (Base configuration)

Eventually- but not yet. When I do start working with 4:4:4 the EX1 will be B cam or smaller roles.

I suspect that if the enlargement of the image had been done on a nearly vertical edge just above the three o'clock position we'd have a very different result, and that whilst the 4:4:4 result would be very similar, there would be much less difference between 4:2:2 and progressive 4:2:0.

Well they become more similar, but not the same, 4:2:2 holds the advantage.

By the way, 4:2:0 with a circular subject like this looks almost exactly like a 90 degree rotation of 4:1:1

[Kevin Shaw]

Backing up for a moment here, what were the cameras and recording modes used for the circular images example? Not all video is created equal for any given chroma format, so one example of each format isn't informative without more background detail. Was the 4:2:0 example from the EX1, or some other camera?

I'm not convinced that having 960x540 square chroma samples spaced evenly across an HD image (e.g. from the EX1) is dramatically different from having 640x1080 non-square samples (e.g. from the HVX200).

Interlaced versus progressive is another matter, which raises the question whether the EX1 has a decent progressive recording mode?

Great information Alexander!!

The BlackMagic looks like the cheapest but the AJA solution offers allot more -but- obviously more $. Capturing into ProRes is another bonus.

The 1/2 inch sensors, lens and 1080p are what's attracting me to this camera. As many others as well! Alot to think about and a budget to be made.

thanx,

Ben

[David Heath]

Originally Posted by Kevin Shaw

Makes sense, but if you had to choose between 4:2:0 with full 1920x1080 image resolution or 4:2:2 with 1280x1080 resolution, which do you think would produce the better key?

Mightn't the answer depend on a lot of other factors, most importantly whether they are both interlace or both progressive?

Originally Posted by Alexander Ibrahim

Only one reason: $$budget$$.

4:4:4 means HDCAM SR or uncompressed data on the drives.

I think any confusion might be that I am speaking theoretically, you are speaking here and now, so yes, for present practical purposes I agree.

But for the future, and the ideal progressive only world we all long for, 4:1:1 and 4:2:2 are colour spaces conceived for the interlace world. Their non symmetry matched the non symmetry of interlace. Progressive images are symmetrical, and much better suited in theory by 4:4:4 or 4:2:0.

[Thomas Smet]

Originally Posted by Kevin Shaw

Backing up for a moment here, what were the cameras and recording modes used for the circular images example? Not all video is created equal for any given chroma format, so one example of each format isn't informative without more background detail. Was the 4:2:0 example from the EX1, or some other camera?

I'm not convinced that having 960x540 square chroma samples spaced evenly across an HD image (e.g. from the EX1) is dramatically different from having 640x1080 non-square samples (e.g. from the HVX200).

Interlaced versus progressive is another matter, which raises the question whether the EX1 has a decent progressive recording mode?

Kevin I created that image in 3D Studio Max. I rendered with a softer form of anti aliasing to somewhat simulate low pass filtering in cameras. I rendered out a 4:4:4 RGB sample and then used After Effects to convert to other decimated formats. I then took still images of each format and put together the image you see.

So it is computer generated but really that means it has a lot more raw detail then what most cameras can do. Real world fotoage also tends to be softer and the details are blended together a little bit more. This means even if you have 4:2:0 the chroma samples are a little bit more blended. If you usually shoot VFX stuff softer without any electronic edge sharpening this helps even more. In this case the edges are so naturally soft that the difference between 4:2:2 and progressive 4:2:0 becomes pretty small. Video is never 1 pixel accurate like a computer image is.



Alexander, Sure the straight keying looks better with 4:2:2 but your example doesn't show any chroma upsampling or softening. The key to good keys is upsampling the chroma to try to get back to a 4:4:4 format. Sure it isn't perfect but it does help a lot. I use Shake and I always soften the two chroma channels and relink the three channels back together before I do a key. In this case the super small edge you gain with 4:2:2 gets even smaller to the point where it gets really hard to tell on moving footage without inspecting a still image up close on a computer.

There are even ways of fixing interlaced 4:2:0 by reshfting just the chroma samples and then upsampling them. This still isn't as good as progressive 4:2:0 but it does help a lot. This is not something that can be done in Shake however and special plugins or processing tools have to be used. Nattress makes great plugins for FCP that help upsample the color.

Sure progressive 4:2:0 isn't perfect but it is not bad either. You can tell from the keyed image that other then slight pixelized edges it looks very clean. If you are downsampling to SD for your final project it will look almost perfect. Even if you do not it is going to be very hard sitting back on a ocuch to notice these single pixel sized edges. If you add chroma softening you get rid of the problem. Yes 4:2:2 is better but that is a no brainer. The question is by how much and is it really worth it to everybody. To me and you it is worth it but not to everybody else. In fact I see some people pulling off some pretty amazing stuff with progressive 4:2:0. With the proper processing it is going to look pretty darn clean.

[Thomas Smet]

It should also be pointed out that HDCAM tape uses 3:1:1 color and only samples 1440x1080 pixels. This give you chroma channels that are 480x1080 pixels in size and yet a lot of people pull great keys from this tape format and the tape format is regarded as the industry standard. I have worked with keying HDCAM footage and while it wasn't perfect I got some very good results from it. I also studied at the Academy of Art college under Jay Cooper who was one of the leading compositors for Star Wars Episode 2. He supplied us with some great ILM material to work with and gave us a great rundown on how much they hated working with HDCAM. ILM upsampled chroma on the footage however and ended up with some great results. A lot of it they also captured tied to a capture station so that helped a lot.

So if 3:1:1 was good enough for ILM and Episode 2 I'm sure the rest of us can make great use of other decimated chroma formats.

[James Huenergardt]

Alexander,

Quoted from Alexander Ibrahim
"Alternatively there is a Cineform Flash XDR. That is MSRP $5995."

I'm familiar with the Convergent Design product, but didn't know it was Cineform based.

Where did you hear that it was Cineform based? That would be very exciting for me anyway.

[Ken Hodson]

Originally Posted by David Heath

The main point I wanted to bring out was that 4:2:2 is largely (and justifiably) seen as so desirable in the NTSC world is not because it *is* 4:2:2 - but because it avoids an eventual effective 4:1:0. Keep 4:2:0 throughout - as with PAL DVCAM/DV - and there is less advantage to a 4:2:2 system for origination, even more so with progressive systems.

I once belived the same thing. I assumed that PAL's 4:2:0 would give an advantage over NTSC as far as DVD conversion would go, because of mpeg2 DVD's 4:2:0, but it was explained to me that is not the case. I am not an expert on this but I was told that PAL's 4:2:0 does not equate to DVD's 4:2:0. Therefor PAL is of no advantage.

[Alexander Ibrahim]

Originally Posted by James Huenergardt

Alexander,

Quoted from Alexander Ibrahim
"Alternatively there is a Cineform Flash XDR. That is MSRP $5995."

I'm familiar with the Convergent Design product, but didn't know it was Cineform based.

Where did you hear that it was Cineform based? That would be very exciting for me anyway.

I didn't that would be a brain fart. Or wishful thinking if you like. In either case it isn't true.

Please read that as, "Alternatively there is the Convergent Design Flash XDR. That is MSRP $5995."

I'm gonna edit the original too.