Is an iMac i7 not fast enough for HD Multiclip edits?

[David Cleverly]

Hi there,

I am getting my head around this multicam/multiclip editing thing.

I am using an iMac i7 27" with 4gb RAM, as it came. Not the current model, the previous one.

I am working with a 6-camera shoot, all shot in XDCAMHD. I have ingested the material and now have setup a multiclip sequence.

Because I have 6 cameras, I need to switch the viewer to a 9 angle setup, but I am finding that the playback of each camera is jerky...so much so that it would be impossible to switch properly.

By the way - and as an addition since having a bit more of a look around the net - all my clips are on the one FW800 Hard Drive.

So:

1) Seeing as I have 6 cameras, should each camera has its own drive as some here have suggested?

2) Do I need more RAM?

3) Is this purely showing the limitations of the computer?

4) I automatically set my timeline up as XDCAMHD...should I not set the timeline up as an XDCAMHD settings? Is there a better (say, ProRes setting) that I should use for the timeline?

Cheers and thanks in advance...

David

[Kevin Spahr]

I would think your main problem is getting all that data off your hard drive. I think you may need a Raid 0 array and have it connected via eSATA. I don't know if there is a way to hack an eSATA connection on an iMac. Even then you might have jerkyness, six streams of HD is a lot of data!

A cheaper solution is may be to work with proxies that would have a much lower data rate for editing.

[Paul R Johnson]

on my Premiere System, I have solved it to a large degree with one interbal drive having some of the cameras, an external firewire with more and then a USB drive with the rest - drawing files from more than one source seems to help no end, Still not perfect if you push it, but it works for me.

[Andrew Hughes]

Also note that not all hard drives are the same speed. You should make sure that your FW hard drive is 7200 rpm and has a decent amount of cache.

The firewire spec allows for a maximum of 800mps for FW800 and 400mps for FW400. But you're not going to get anything like that with anyhard drive. Also, and I think this is still true, if you connect a FW400 device to a FW800 port, all firewire devices are going to slow down to FW400 speed.

Pulling this from memory, but tests on my firewire drives gave me something like 30-50mps. When I upgraded to esata this basically doubled.

But Paul's suggestion is right on--when trying to read that much data simultaneously, if you can split off to different sources, you'll get much better performance. No matter how fast the drive is, if you're making it skip around constantly between 6 different files, you're gonna really slow it down. This is kinda worst-case scenario for speed.

Unfortunately, this is where the iMacs limitations as editing stations become apparent because with a desktop you have more ports and (better) can install more internal hard drives.

[David Cleverly]

Great, thanks for the suggestions. It appears when, dealing with this project anyway - (ie: XDCAM HDCAM with 6-streams) - I might have bitten off more than I can chew...

:-(