Direct to External HD

[Galahad]

Does anyone have experience in recording DV to externals via laptops?

I'm looking to record long 4 hour+ sessions for a couple of weeks and convert them and would rather not use my laptop's internal drive for that purpose. I'm currently looking at basic consumer USB 2.0/firewire solutions as they are cheap, but if performance/failure is an issue I could invest in faster and tougher esata enclosure from someone like firmtek.

[edDV]

Does anyone have experience in recording DV to externals via laptops?

I'm looking to record long 4 hour+ sessions for a couple of weeks and convert them and would rather not use my laptop's internal drive for that purpose. I'm currently looking at basic consumer USB 2.0/firewire solutions as they are cheap, but if performance/failure is an issue I could invest in faster and tougher esata enclosure from someone like firmtek.

Yes.

Better to use a large internal drive or if possible eSATA (via PC card hard disk controller?)

Older laptops have IEEE-1394 to USB2.0 frame drop issues during capture. The problem is USB2 uses a software disk controller which drops frames when interrupted by OS activity. Newer faster laptops may have more immunity to interrupt but a hardware hard disk controller offers more safety. eSATA has bandwidth equal to an internal drive.

None of this is a problem if you use a tower computer with multiple hardware disk controllers and PCI bus mastering.

[Galahad]

Thanks for the reply,

Yeah that's what made me concerned. The laptop is a Macbook Pro(2.16 core 2 duo, 3 gig ram) but I'm still worried about USB CPU usage and streaming issues.

The eSATA solution I found involves an express card to an external enclosure with active cooling. It's quite pricey (300) but I'm wondering if a cheap express card would have the same issues as a software controller or that a cheap enclosure would cause heat issues.

[edDV]

Thanks for the reply,

Yeah that's what made me concerned. The laptop is a Macbook Pro(2.16 core 2 duo, 3 gig ram) but I'm still worried about USB CPU usage and streaming issues.

The eSATA solution I found involves an express card to an external enclosure with active cooling. It's quite pricey (300) but I'm wondering if a cheap express card would have the same issues as a software controller or that a cheap enclosure would cause heat issues.

Ask in a video Mac Pro forum if this card provides a hardware safe path for DV capture. A good design would isolate the hard disk path from OS disk activity.

[srenaud]

I've captured about 12 hrs of video this way. (A long comedy fest my son was in)

External ide hard drive. PCMCIA firewire card.

Worked like a charm.

[2Bdecided]

IIRC WinDV implements a large buffer (in memory) which guards against this problem. It's really quite hard to make it drop frames, though I don't use the PC for anything else when capturing. I suspect a Virus checker kicking in on a system that can only just keep up would cause problems.

Cheers,
David.

[edDV]

IIRC WinDV implements a large buffer (in memory) which guards against this problem. It's really quite hard to make it drop frames, though I don't use the PC for anything else when capturing. I suspect a Virus checker kicking in on a system that can only just keep up would cause problems.

Cheers,
David.

I see occasional drops even on Core2 Duo desktops when capping DV from my Canopus AVDC-100 to a USB2 drive while running or encoding other heavy video tasks to other drives. If you copy or cap a second file to the same USB2 drive the probability of a drop rises. None of this happens if the target is an internal PATA, SATA or external eSATA drive.

If you do much of anything heavy on a laptop primary drive while capping DV to USB2, you get a drop.

It's all about probabilities and consequences. For Pro work I'd consider the laptop PC card eSATA route for external drives but test it thoroughly before doing a serious project. I'd feel more comfort with a microATX lunchbox with multiple PATA/SATA hardware disk controllers.

[2Bdecided]

To be fair, if I was rendering or encoding video while capturing DV, then the capturing would be useless on my PC (lots of dropped frames) with the internal drives. It's an old slow machine. I also wouldn't dream of trying to capture two streams at once.

Despite this, external USB2 HDDs have proven more than fast enough for capturing one DV or HDV stream reliably.

If it fails on a given machine, something else may be wrong which may not be solved by choosing an even faster interface or internal drives.

Cheers,
David.

[edDV]

If it fails on a given machine, something else may be wrong which may not be solved by choosing an even faster interface or internal drives.

Cheers,
David.

USB2 drives are good for up to 30MB/s sustained transfers (e.g. a file copy) so are more than adequate for 3.8MB/s DV transfers, but dropped frames come from something else. A DV/HDV capture is a data stream, not a file copy so is subject to drops if the USB software disc controller is interrupted by other OS activity such as large writes to the internal drive, virus checking or indexing*. A faster or dual core laptop CPU may have a lower probability of a drop but is still less safe than a desktop with multiple hardware disc controllers and PCI bus mastering.
http://www.pcguide.com/ref/mbsys/buses/types/pciMastering-c.html


* DV capture programs can set a stream buffer to memory but at 3.8MB/s inflow, such a buffer can quickly overflow.

[2Bdecided]

Someone has claimed WinDV seems to use a buffer of about 16MB, which is enough for your PC to go and do something else for over four seconds without causing problems.

I don't find it anywhere near that reliable, but good enough, given that I'm not going to let the OS do anything stupid while capturing if I can help it.

Cheers,
David.