4.2.2. versus 4.2.0
 

My situation is unique and maybe someone can enlighten me a bit. I come from a background as a 35mm film shooter, without having edited or managed the end use/workflow. I'm moving to HD and have learned a ton of new technical information already. But what is the difference between 4.2.2 and 4.2.0? I understand the soon to be released Sony XDCAM EX Cinealta will deliver 4.2.2 under a certain workflow.

I chiefly produce very high end stock footage, destined for my agent, Getty Images, who distributes and markets my material worldwide. It needs to be the highest quality possible to be intercut into movies, commercials, and documentaries.

Chris.. I see you're in San Marcos. I'm in Austin. Any chance for a beer/coffee to talk tech sometime?

4:2:2 has half the colour resolution of the luma for any given resolution, 4:2:0 (and 4:1:1) have only quarter the colour (Chroma) resolution.

For most footage, 4:2:0 looks pretty good to the human eye, however if you need to do heavy manipulation, like blue screen etc, 4:2:0 can produce visible jagged edges around coloured objects. It is also noticeable with high contrast coloured areas such as coloured graphics and titles.

For high end stock footage, clients may demand more than 4:2:0 but it isn't always possible to drag a 35mm camera and rolls of film everywhere.

The EX outputs 4:2:2 over HD SDI which would require a separate recorder, such as a computer or high end HD VTR, however I'm not sure if this 4:2:2 output is "real" 4:2:2 or just upscaled 4:2:0 - can someone confirm?

All footage recorded on board will be 4:2:0 (even if bumped up to 4:2:2 and played back through the HD SDI) because that is limited by the camera's recording codec.

Initial reports suggest the EX picture quality may be unrivaled for it's size but if you need the best quality possible, you may need to spend a bit more.

Chroma resolution relative to luminance. With 4:2:0, chroma is half that of luminance both horizontally and vertically. With 4:2:2, it's half horizontally, but the same vertically.

It's much more significant with interlaced video than progressive, as the alternation of samples then takes place on a field basis, so in frame terms you get two adjacent chroma samples, then two gaps.

There's a lot more to it than that, especially when motion gets involved, but the advantages of 4:2:2 over 4:2:0 are far more pronounced with interlace than progressive.

http://www.dvinfo.net/conf/attachmen...0&d=1159424266

http://en.wikipedia.org/wiki/Chroma_subsampling

It might be easier to see what is going on other then reading about it.

It's worth noting here that the EX1 uses 4:2:0 color across a full 1920 x 1080 image (in HQ mode), which works out to 960 x 540 chroma samples per frame. That's a decent amount of color information compared to any other HD camera under $10,000.

The absolute number of color samples isn't a good metric.

You need a ratio of color samples to luma samples, which is why we use ratios to describe color in video... i.e. 4:2:2 or 4:2:0.

This won't often matter to the viewer, but it matters a lot if the footage is to be used for VFX work or extensive post.

For a client like Getty I'd be concerned about 4:2:2. After all if you've been turning in 35mm, then Getty has been getting 4:4:4 images from you in video terms. Check with their engineering staff though.

I wrote about this before here:

http://dvinfo.net/conf/showpost.php?...3&postcount=35

The HD SDI output direct from the camera head is 10 bit 4:2:2 uncompressed. (SMPTE 292M)

It is the XDCAM codec which discards color information, not the camera head.

So, if you play back media from the SxS cards, you get upscaled 4:2:0 video.

As far as field capture of 4:2:2 footage goes, one worthy workflow is HD-SDI to the AJA ioHD, and then Apple ProRes 4:2:2 direct to disk. This is "do-able" with a Macbook Pro and an external drive setup over eSATA. That's three more gadgets on set.

So, you are trading a somewhat larger film cam and mag for a small camera that has to be tethered to a video village. It is hard to choose.

If you can justify another $5K USD and want the best out of your EX1, go with Convergent Design's upcoming XDR Flash

If the EX1's camera head is as good as we believe, just imagine shooting full raster to 422 @160Mbps I-Frame.

Man, I really want one of these!
Well, actually I want the camera first. LOL

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

I am not entirely convinced on that unit. It seems promising, and I'd like to be convinced. I am extremely excited by the prospects.

My first concern is that I haven't heard of Convergent Design, which may be my own fault. I have to be convinced about them as an engineering facility. Do they make solid products? For that I can turn to the community- what has been the experience of people here with Convergent Designs products?

By comparison AJA is a known quantity. I know their engineering, I've used their products, I've seen dozens of my peers using their stuff. I even see Apple talking about and working with them.

I need to see more information on workflows for their capture format on Final Cut and Avid. Can it use the built in Logging and Transfer option in FCP? Do we need additional software? I'd love to see a whitepaper talking about the capture format in detail.

Hopefully there will be more answers as the promised ship date draws near.

That said the Convergent Designs product is a bit high, but in the right ballpark price wise, and it provides some innovation and potentially great utility.

I'm eager to get the opportunity to test a Flash XDR and to hear from those of you that do get to test one.

Thanks Thomas - good link.

They do mention 4:1:0 : "This ratio is possible (indeed, some codecs do support it), but not widely used. It means half the vertical and quarter the horizontal color resolutions......"

Whilst it may not be chosen by choice, it can effectively become the colour space if material is originated in a 4:1:1 system and then coded for release in 4:2:0 - which is exactly what happens if material is shot NTSC DV25 (4:1:1) and then used to make an NTSC DVD (4:2:0). I understand it is one very valid reason why 4:2:2 codecs like DVCPro50 have more takeup in the US than in 50Hz countries.

In PAL the problem only comes up with DVCPro - both DVCAM and DV PAL are 4:2:0 - and may be one reason why DVCAM is far more popular than DVCPro over here.

AFAIK 4:1:1 is not used for any HD codec, so the problem shouldn't arise for HD.

Yeah 4:1:1 was a pretty bad color format. I hate the fact that NTSC users have to make DVD's with such bad decimated color. This is one of those things I try to explain to people why homemade DVD's don't look as good as Hollywood DVD's. NTSC 4:1:1 to DVD is really murdering the color. This is one of the main reasons why HDV down converted in software to DVD looks so darn good. Sure it has over sampled resolution to help but it also has over sampled color which helps a lot and the color starts as a native 4:2:0. In a world where every single other video standard works in 4:2:0 or 4:2:2 I will be glad when DV is gone and 4:1:1 right along with it. I don't think we will ever see 4:1:1 ever again. Now if we could only get rid of interlaced video forever along with 4:2:0 field based color spaces and just stick with the more natural looking progressive flavor of 4:2:0.

Yes - 4:2:2 and 4:1:1 really are engineered to be most relevant for interlaced systems. (And in NTSC, I believe 4:1:1 was chosen over 4:2:0 for DV25 more because digital devices were then seen as islands in an analogue world - all i/p, o/p being analogue.) In the progressive world, 4:2:0 and 4:4:4 are much more suitable.

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 may be missing the mark here.

Can't the EX1 'record' 4:2:2 on the SxS cards? OR does one NEED to 'record' into a computer using the HD/SDI ports via external hardware (say Blackmagic).

I thought it was possible to record in a 4:2:2 colourspace in the field using the SxS cards and then dumping the media from the cards into a computer?

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.

The image I attached is a key from the jpeg Thom linked to here:
http://www.dvinfo.net/conf/attachmen...0&d=1159424266

I took that image and did a quick key with Primatte RT. You'll notice some desaturation... ignore that. I upped matte density too much. Just notice the edges.

The result file is a PNG, and it has transparency enabled so drag it over whatever background you like when you get it on your computer.

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

Consider that these are computer generated files- the easiest to composite.

A real image of say a person with this stuff called hair might present additional challenges.

Sometimes more data is good data.

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.