Ummm...Direct to Disk Question

braw

braw

Well-known member
I know this has been covered a while back, but I'm unclear about this direct to hard drive situation. So, if you have P2, you can dump the cards to a standard off the shelf HDD with no need for an intelligent device. I can get an external enclosure and dump straight to it right?

But to capture directly to disk, I need a Firestore that is an active intelligent device. The reason for this is that the camera doesn't have the ability to control the external HDD. Yet it can control it enough to dump footage at what I assume faster than real time.

What am I missing here? It treats the P2 cards like a HDD, and recognizes a HDD plugged directly into it to dump off the P2. Yet it can't stream directly to it.

So to have fun with this, I am calling that someone designs a PCMCIA card that plugs into the P2 slot, connects to an external HDD and the HVX sees it as a P2 card. In my limited understanding, the only limitations would be the LSI interface, and if the HVX has some sort of cap on how big a P2 it can see.

Phony P2, "Hi, I'm a 200GB P2 card."

HVX, "Shut the f@ck up, no way you are, get out of me!"

I'm seriously not trying to rehash an old argument; I just never got this one worked out in my head.
 
braw said:
I know this has been covered a while back, but I'm unclear about this direct to hard drive situation. So, if you have P2, you can dump the cards to a standard off the shelf HD with no need for an intelligent device. I can get an external enclosure and dump straight to it right?
Click to expand...

I don't think "without an intelligent device" is correct here....
 
the problem is that you can't send HD (or SD for that matter) in real time through firewire (400 mbps) you need a device with some sort of protocol or acceleration that can take the HD information coming from the camera through firewire(similar concept found in AVID DNA products like Mojo). a standard off the shelf Hard Drive would be like a bottleneck situation - video info coming through too small of a passage.. at least i think this is what would happen.
 
ullanta said:
I don't think "without an intelligent device" is correct here....
Click to expand...

So what makes the Firestore work and not an off the shelf drive? Doesn't the Firestore go through firewire?

What I mean by intelligent is a drive with some control circuit built in. A device that tells the HDD what to do.
 
troypod said:
the problem is that you can't send HD (or SD for that matter) in real time through firewire (400 mbps) you need a device with some sort of protocol or acceleration that can take the HD information coming from the camera through firewire(similar concept found in AVID DNA products like Mojo). a standard off the shelf Hard Drive would be like a bottleneck situation - video info coming through too small of a passage.. at least i think this is what would happen.
Click to expand...

So is it that it sends the info over firwire too fast and can't go slower?

I guess where I'm confused is that DVRack works through firewire correct? Also, does the HVX dump to an off the shelf through USB or Firewire, or both? Doesn't it dump this faster than realtime?

I understand that the HDD would be the bottle neck, but there are drives fast enough to do it.
 
I'll try and see if I can explain anything here...

There are two protocols used by firewire: AV/C and SBP2. SBP2 is also used by USB2. AV/C is a data-streaming protocol, it's the protocol used by tape decks and cameras. And that is the protocol that the HVX uses when it's in camera mode -- it streams data out the firewire port. If you connect an AV/C-aware unit on the other end (such as a tape deck, or a FireStore, or HV Rack, etc) then that device can monitor and capture the streaming data. AV/C is, as far as I know, a synchronous (clocked) data transfer system.

SBP2 is a file-transfer protocol. It's totally unrelated to AV/C. SBP2 is what a firewire drive would use to connect to a computer, allowing the computer to take control of it. SBP2 sends packetized info; I believe USB2 is asynchronous, and I think firewire transfer is probably asynchronous as well. This is the method used for having the camera offload P2 cards to external drives.

Now, SBP2 is asynchronous. It's not "clocked". So it doesn't matter how fast, or how slow, the drive is... the camera offloads info as fast as the drive can take it, and if the drive slows down or pauses, well, that's okay -- the camera will wait for it. But in streaming that's a HUGE NO-NO. In streaming the bits keep coming and coming and coming. If the drive can't keep up, bits fall and frames get dropped and data gets corrupted. So SBP2 devices are not suitable for streaming. You have to have an AV/C-compliant device to handle streaming.

So the FireStore is some sort of AV/C-compatible device, which also has some sort of internal file system for communicating with the hard disk. Off-the-shelf hard disks have no clue what AV/C streaming is. But for live video capture, they would *have* to support AV/C. Yet they don't. Which is why the FireStore has reason to exist.
 
troypod said:
the problem is that you can't send HD (or SD for that matter) in real time through firewire (400 mbps) you need a device with some sort of protocol or acceleration that can take the HD information coming from the camera through firewire(similar concept found in AVID DNA products like Mojo). a standard off the shelf Hard Drive would be like a bottleneck situation - video info coming through too small of a passage.. at least i think this is what would happen.
Click to expand...

Sorry, but this is not correct as an answer to the question at hand. The camera's firewire output is not raw HD but DVCProHD, which has a maximum data rate of 100Mbps... which should be easily handleable by the firewire bus and most FW drives.

The issue is indeed one of needing "intelligent control" for the drive.
 
Barry, you friggin rock. Thank you for that. I knew I was missing something important.
 
Oh man, the sticky about established info maybe should be updated to specify these situations as well. The less important threads, that cover old news, should be avoided, new curiousity for P2 came after IBC and Resfest and old questions got posted.
 
bibo said:
Barry,
Could a device like this be useful to dump footage from the HVX?

http://www.supergooddeal.com/ProductDetails.asp?ProductCode=HS40OTG-BK&Click=1727
or
http://www.cooldrives.com/usbotgshcou2.html
Click to expand...

Either one of those products look like they can act as a regular external USB2 hard disk, so yes they'd work fine to copy footage from the P2 cards to those drives. Remember, we're not talking about streaming live capture to them, we're talking about recording to the P2 card, and then (after the fact) plugging in a USB2 drive and offloading the P2 card footage down to the USB2 drive.

As long as it's a USB2-compliant SBP2-aware external hard disk, it'd work with the HVX for offloading footage.
 
Barry_Green said:
Either one of those products look like they can act as a regular external USB2 hard disk, so yes they'd work fine to copy footage from the P2 cards to those drives. Remember, we're not talking about streaming live capture to them, we're talking about recording to the P2 card, and then (after the fact) plugging in a USB2 drive and offloading the P2 card footage down to the USB2 drive.

As long as it's a USB2-compliant SBP2-aware external hard disk, it'd work with the HVX for offloading footage.
Click to expand...

Thanks Barry.
That's what I thought - those devices should be good to keep offloading footage from the P2 cards.
 
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