Is using HD-SDI on HPX170 worth the expense?

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lawyerjim

Member
I have an HPX 170 and have seen recent posts that a nanoflash will get little, if any, improvement over recording to the P2 cards. I thought the HD-SDI output on the HPX 170 was a big selling point over the HVX 200.

I had been looking at an AJA Ki Pro to record to via HD-SDI. I was under the impression that there would be a noticeable difference in the uncompressed footage versus the DVCPRO-HD.

Is the difference in recording via HD-SDI worth the expense and hassle?
 
One advantage of HD-SDI is the ability connect with many live camera systems for tv and such. As for recording, dvcprohd is pretty good. Your not going to get much better by using another recording medium.
 
Well, you'd have to look at what it is you're trying to accomplish, and what you're working with.

The appeal of an outboard recorder is typically that it is a) higher resolution, or b) more color sampling (4:2:2 instead of onboard 4:2:0), or c) 10-bit instead of 8-bit, or d) using a high-quality codec instead of a lame codec like HDV or something.

In the case of the HPX170, you're dealing with a camera that already has the highest-quality onboard codec of anything in its price bracket, so ...

a) the outboard recorder will record 1920x1080. The onboard DVCPRO-HD records 1280x1080 (in the US/NTSC) or 1440x1080 (in PAL). So it seems like the outboard could record higher res, but ... the problem is, the chipset in the camera only generates about 1440x810 worth of detail in the first place. So the onboard recorder is already recording just about all the detail the camera can give it. You might see a tiny bit of increase from an external recorder, but I'm betting the difference would be slight or even minimal.

b) the onboard recorder is already recording 4:2:2, so you're not going to gain anything by going to an external.

c) the HPX170's onboard recorder is 8-bit, but so is its SDI output. So if you connected it to a 10-bit recorder, you wouldn't get anything additional; it only feeds 8-bit data out the SDI port, so nothing to gain here.

d) the HPX170's onboard codec is already a very robust intraframe 100mbps codec. It's not like some underpowered long-gop thing, it's a top-class codec that is approved for unlimited acquisition, editing, and mastering by Discovery HD and the BBC. So while you might get 220mbps of ProRes out of a Ki Pro, I seriously doubt you're going to see much if anything in the way of actual image improvement vs. the onboard DVCPRO-HD.

For all those reasons, I do think that an external recorder with an HPX170 is a waste of money and an unnecessary hassle. But, I haven't tested that particular combination; if someone does run such a test and shows substantial differences, let's see them; until then, on paper at least, it really doesn't make any sense to go spend thousands of dollars to get an external recorder for this camera.
 
Barry_Green said:
For all those reasons, I do think that an external recorder with an HPX170 is a waste of money and an unnecessary hassle. But, I haven't tested that particular combination; if someone does run such a test and shows substantial differences, let's see them; until then, on paper at least, it really doesn't make any sense to go spend thousands of dollars to get an external recorder for this camera.
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Agreed... but I have always thought about how going to a Nano could possibly end up being cheaper than using P2 cards... You can always hook up your nano to your next camera... your P2 investment kinda limits you to other P2 cameras... but if you plan to upgrade cameras or have multiple cameras with HD-SDI ports and dont want to invest in the media for the native recorder on each camera, some of these HD-SDI recorders (especially some of the newer less expensive offerings) could really be the way to go.

But yea, I agree that from a quality standpoint there is nothing to gain... the DVCPROHD is almost overkill on the HPX, the codec is almost more robust than the information the camera puts out.
 
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Thanks for all the info. I was looking into getting an SDI recorder now because I am going to need an external recorder in a couple of months for a "reality" type project where I will be recording for much longer than I currently have the cards for. I was thinking that it might benefit me now if there was a noticeable difference in the footage. Based on what I read here, I will wait until I have to have it. I like the idea of the HyperDeck Shuttle because of the cost and SSD drives but it looks like it would be more at home on a desk than carried on a camera.

By the way, would your answers be different if it was an AF100? Am I understanding correctly that the AF100 records in 4:2:0 to the cards but with an AJA Ki Pro, (or similar), it would record in 4:2:2 to the hard drive? Would the difference be worth it then?
 
You will pick up some benefit with an AF100; it still isn't 10-bit so it can't take 100% advantage of an external recorder (and neither could an FS100 or XLH1 or practically any other sub-$10k camera), but you would at least get 4:2:2 from the external recorder. The image would also benefit from reduced compression artifacts, at the expense of the footage taking up 10x as much space.

External recorders don't really offer much benefit in the way of longer record times; the onboard recorder on an AF100 or FS100 or EX1 or whatever takes up much much less space than an external recorder. About 1/8th to 1/10th as much space as a ProRes recorder. And the Black Magic Hyperdeck Shuttle takes up unholy amounts of space. It's more like, what, 10 gigabytes per minute... the AF100 could record six continuous hours on a 64GB memory card, you'd only be able to record for six minutes on a 64GB SSD with the HyperDeck.

If you're really looking for long record times, the Nano has the ability to hot-swap compactflash cards for long continuous recording, assuming you have enough CF cards. And the AF100 can record for six hours on an internal card, and you can have two cards loaded, so it'd deliver twelve hours of continuous recording on two 64GB SDXC cards.
 
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