HV20/BM Intensity Pro/RAID - Confusion at DVinfo.net

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Old April 13th, 2008, 01:21 PM   #1
Join Date: Apr 2008
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HV20/BM Intensity Pro/RAID - Confusion


This will be by necessity a bit long-winded, but I figure the more you know up front the fewer questions you will have of me. I have two Canon HV20s that I have been using to record a documentary of a 90-year-old lady. The project is a labor of love and I expect it will never have any commercial distribution. It’s mostly of her talking in a relaxed manner in her living room. I’ve chiefly used available light. When I first started the project I only had one SD camera. Since the time I bought and began using the HV20s I’m guessing that the project is now about half SD and half HD – and it will eventually be an overwhelming majority in HD – although I do have plenty of very valuable footage in SD.

I have a few broad questions as I go forward – especially as my hardware has just changed and I need to make a couple of decisions. One regards the use of a Black Magic Intensity Pro card (and if it makes sense to even use one for my needs) and the other whether to RAID or not. I have seen differing opinions and I certainly need more help.

I have a new 8 proc Mac Pro with 10 gigs of RAM and I’m running FCP 6.0.3. Both questions arise because I bought a Black Magic Intensity Pro card. I bought it because I thought it would be good to bring in my footage in true 1920 X 1080 format rather than the compressed 1440 X 1080 format of HDV. After all, the HV20 can capture at that resolution…so why not get the best picture. HDMI instead of FW. Made sense…on the surface at least.

Well, after I bought the BM card I read on their web site (quoted below) that to use it in HD one needs a massive (at least 8 disks) raid – which I don’t have.

“When you’re working with uncompressed HD video, the internal hard disk will not be fast enough. You need a high-speed disk array. These can be purchased pre-built, or you can build your own using two hard disks for SD or at least eight hard disks for HD.”

Further reading elsewhere indicated that working exclusively in HDV may not necessitate a RAID – but I guess if I am using the BM Intensity Pro I’m outside the spec of HDV as from what I understand, HDV by definition is no more than 1440 X 1080. So that brings up a couple more questions…pardon me if they’re not the brightest ones. One is, I was under the impression that I could use the BM card as the device to bring in 1920 from tapes I have already recorded. That may be half-witted right there…but then some further reading indicated that to be able to capture via HDMI it had to be in real time, with the computer adjacent to the video taping with the camera going out via HDMI into the computer directly – bypassing the tape.

So you can see one point of confusion…does indeed using the HDMI interface (and 1920 goodness) of the BM card require that one goes directly, during recording into the computer for capture? If so, then that’s a moot point as I cannot bring my Mac Pro to the lady’s tiny apartment. I guess I’m not sure if recording onto tape means that 1440 is locked onto the tape itself thereby meaning that going out later on via HDMI would not be any better picture.

Another question is, even if I can use the BM card for capture, would it really make a significant difference for me given that I have low production standards. Maybe it’s best to just sell the card? If that’s the case then there’s no need for a RAID of even a limited size as I’ve been able to easily capture from the HV20 onto the internal hard drives without any difficulty.

However, if the BM card were a possibility, would using a couple of internal drives suffice for a RAID? I could set up a RAID 5 using three internal terabyte drives – leaving the fourth drive as my boot drive.

So, suggestions? Questions? Thanks in advance,
John Page is offline   Reply With Quote
Old April 13th, 2008, 03:19 PM   #2
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1) Once the signal has been recorded to tape, it's been compressed to the HDV spec. There is no quality benefit to using the Intensity after the fact.

2) You don't have to record uncompressed from the Intensity (necessitating a fast RAID) you could record to any number of CODECs that are better than HDV (Apple's ProRes, for one.)

3) Judging the quality benefits versus the hassle of lugging a giant (and heavy!) Mac Pro around with you is a tough call. Bypassing HDV compression does yield a notably better image (especially color resolution) but it is a giant PITA. For a talking head shoot without saturated colors and fast motion, I'd find it hard to justify. If you were doing a green screen shoot or other work that was prone to compression break-up, then it might make more sense.
Joseph H. Moore is offline   Reply With Quote
Old April 13th, 2008, 06:35 PM   #3
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It would be hard to justify the amount of time, money and effort for a distinguishable difference at this level of quality when there are much more capable cameras now available.
Mike Thomann is offline   Reply With Quote
Old April 16th, 2008, 12:55 AM   #4
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to use the intensity, you need to have the PC nearby (within the range of the hdmi cable)

so that probably rules it out for you, but heres a few things on using it:

- to capture you need a sustained 120MB/s write rate on your hard drive. with typical 3.5" 7200rpm drives, that will mean at minimum 3 drives in raid 0, ideally 4 or 5. alternatively 5 drives in raid 5 will work, and give you security.

- the black magic can capture and compress in its own codec which can easily record to a single drive. it only needs 13MB/s.

- you can also choose other formats, like cineform HD (purchased separately) to compress as you capture. cineform has several datarates to balance size and quality.

- as mentioned, once recorded to tape, theres zero point to the hdmi card, just use firewire for that. the beauty of the card is that it bypasses compression and scaling before it goes to tape.

hope thats useful to you :)
Terence Krueger is offline   Reply

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