Confused about XH-A1, AJA I/O and 4:2:2 Output?

tverhaar

tverhaar

Active member
I'll ask forgiveness up front on two counts here - first, I searched and browsed for info on this topic but didn't find anything. Second, I may not have found anything because I am probably a little weak on understanding precisely what I am asking... so here goes ...:)

I know that the XH-A1 records HDV to tape but I also know (think) that with the jackpack on the XH-G1 you can send an uncompressed signal out via the HD-SDI jack. This implies (?) that the camera itself captures this uncompressed signal but just doesn't record it on board. Assuming I am correct on this, does it mean that one can capture a higher quality signal from the A1 either (or both) of these ways:
1) through a PCI card into a laptop, (via FireWire?) or
2) into the new AJA I/O box introduced at NAB (does this give me uncompressed or just the ProRes 422 output?)

My questions arise from this: I am planning on buying an XH-A1 but would really like the option of capture a signal in the 4:2:2 color space (ProRes 422 would be fine, I think). I could upgrade to the XH-G1 but for not much more I could get either the AJA unit or a laptop with a capture card (as I say this I actually am not sure there are capture cards for a MacBook Pro(?).

I will continue to research this but any help or enlightenment would be much appreciated.

Regards,
TVH
 
Not via firewire, no -- only the compressed 4:2:0 HDV signal goes through the firewire. But if you were to use an analog component capture board then yes, you could capture the full uncompressed HD signal from an XHA1 (or any other HD camcorder).
 
Barry_Green said:
Not via firewire, no -- only the compressed 4:2:0 HDV signal goes through the firewire. But if you were to use an analog component capture board then yes, you could capture the full uncompressed HD signal from an XHA1 (or any other HD camcorder).
Click to expand...

The Canon literature suggests that a component out jack is only available on the G1 (looks like an RS-422 jack?), in addition to the the HD/SDI out (BNC) connector on the jackpack. Would these be the only way to get a signal out that is uncompressed? That would mean I can't do any of this with the A1, just the G1?

(Sorry to be so thick - I have been working with FireWire out on my GL1. It's all so simple that way!) :(

Thanks again for the help. And especially a thanks to Barry. Is there anything you don't know?:beer:
 
A1 has a component out. It's just that a setup required for capturing via component is expensive (at least $1000 for the card alone plus a decent RAID system).
 
And now, just to make things more interesting, some further research on the Canon site (specifically in their XH-A1 Product Tour, it states unequivocally the following... "with the new Digic DV II digital processor the XH-A1 has an output with 4:2:2 color sampling..."

How does one actually output this 4:2:2 from the A1? Is this the same question I have been trying to ask?

*sigh* :huh:
 
jade8472 said:
A1 has a component out. It's just that a setup required for capturing via component is expensive (at least $1000 for the card alone plus a decent RAID system).
Click to expand...


Jade - Thanks. You were replying just as I was posting the last question...

So I get that the A1 outputs 4:2:2 via the component output but one needs a capture card and a RAID. OK - so far so good.

Now - I have looked on the AJA site but it doesn't look like there is a capture card/device that will hook up to a MacBook Pro/laptop. Is there such a card? Will the new AJA I/O introduced at NAB do this then? I know, it is $3500 (and not available) but it's not much more than paying up for a G1 and would appear to add more capability?

I am just trying to figure out an upgrade path here. Is anyone who already has an A1 thinking these thoughts? Am I too obsessed with the 4:2:2 thing? I am just thinking about working with chromakeys and with the new Color app...


Hmmm...
 
How does one actually output this 4:2:2 from the A1?
Click to expand...
Well, you can't, because 4:2:2 is a digital notation and the XHA1 doesn't have a digital output. You can output an analog signal that probably has color bandwidth that would be appropriately sampled as 4:2:2 though. (this is probably falling in the category of "a difference that makes no difference" but still... you're talking about an analog output; you'd have to capture that into a digital system, the digital capture would sample the chroma at 4:2:2; the question is whether the XHA1's analog output has high enough chroma bandwidth to require 4:2:2 sampling. I believe it does but don't know for sure.)

Short answer is: if you want HD-SDI, then yes you'd need the G1 (or XL-H1). But if you just want uncompressed high-def, you can get that through the component (or HDMI) ports available on all of these HD camcorders.
 
Barry_Green said:
Well, you can't, because 4:2:2 is a digital notation and the XHA1 doesn't have a digital output. You can output an analog signal that probably has color bandwidth that would be appropriately sampled as 4:2:2 though. (this is probably falling in the category of "a difference that makes no difference" but still... you're talking about an analog output; you'd have to capture that into a digital system, the digital capture would sample the chroma at 4:2:2; the question is whether the XHA1's analog output has high enough chroma bandwidth to require 4:2:2 sampling. I believe it does but don't know for sure.)

Short answer is: if you want HD-SDI, then yes you'd need the G1 (or XL-H1). But if you just want uncompressed high-def, you can get that through the component (or HDMI) ports available on all of these HD camcorders.
Click to expand...


So just to make sure I get it...

It would seem the Canon site is sort of "playing games" regarding their representation of 4:2:2? (Cuz the thing I quoted above was an exact quote.) Except that their claim would be that the analog signal can be sampled at 4:2:2? I guess they know that since the G1 creates the same signal as the A1 but actually outputs it (but isn't that also an analog/component out - or is the BNC connector on the G1 jackpack a digital out?).

And, the component out mentioned by jade above puts out the analog signal that you are referring to? And THAT is the signal that could be input into a capture card or perhaps the AJA I/O? (Which does have a component in.)

But the bottom line is that you suggest I can effectively get just as much color space out of the digital/HDV signal?

I know... so many questions. :dankk2:

Thanks again...
 
I haven't read that quote; what I'm saying is that an analog signal doesn't get represented as "4:2:2" or "4:1:1" or whatever; it's incorrect nomenclature.

But, it's also a difference that probably doesn't make much difference, one that will probably disappear under a blanket of "common use"; just like people refer to European HD cameras as "PAL HD"; that's completely wrong usage of the term PAL but it'll probably be co-opted into common use.

The internal signal processing is almost certainly being done at 4:2:2, and then converted for analog output. So in that sense, a digital card that samples at 4:2:2 is probably adequately capturing the analog output, so it probably doesn't really matter.

The XHG1 has an HD-SDI output port on it, and that outputs a digital signal. The component output port is analog. But it's still uncompressed HD, just analog instead of digital.

And yes, the component output mentioned by Jade outputs the analog component uncompressed HD signal, which could be captured by an AJA I/O.

And no, you certainly can't get as much color space out of the HDV signal; the digital output through firewire has had its color information chopped in half (to 4:2:0) from what it could have been and what the internal processing was.
 
You must log in or register to reply here.
Back
Top