From: Kevin in Fort Davis <fsm79734@gmail.com>

Date: July 4, 2015 9:22:27 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Naming Cameras?

Thanks so much for that analysis, Milton, I appreciate it!  I've somewhat verified that empirically, and have found it safer to sometimes run at 3.750 fps.  Would the video preview screen's freezing be a likely effect of a lack of FireWire bandwidth?  Also, is there any advantage of using the FMT7 modes of the camera in terms of bandwidth?

-Kevin

On Fri, Jul 3, 2015 at 6:52 PM, Milton Aupperle maupperl@gmail.com [Astro_IIDC] <Astro_IIDC@yahoogroups.com> wrote:

Hi Kevin;

Okay, I had a look at the IIDC tables. In a "perfect" world, you can use up to 8 kilobytes of data per packet for FireWire. With a single camera running, that's fine but when multiple cameras are running, you have to be more conservative on usage.

At 1600x1200 in 8 bit mono with 3 cameras, the best you can reliably do is 7.5 fps in FireWire 800. Each camera uses 2 kilobytes per packet for data, so 3 cameras will  use up 6 kilobytes per packet, leaving you 2 kilobytes for headroom.

At 800x600 in 8 bit mono with 3 cameras, the best you can reliably do is 30 fps in FireWire 800. Each camera uses 2 kilobytes per packet for data, so 3 cameras will  use up 6 kilobytes per packet, leaving you 2 kilobytes for head room

If your Mac had a FireWire expansion card (i.e. Cardbus, PCI, Express etc.) installed, then you could run more cameras or at higher frame rates because each card has it's own bus and bandwidth. Apple has never produced any Mac model that has multiple FireWire controllers, so even if a Mac had 3 built in FireWire ports they would still be sharing bandwidth.

HTH..

Milton Aupperle

On 2015-07-03, at 2:10 PM, Kevin in Fort Davis fsm79734@gmail.com [Astro_IIDC] <Astro_IIDC@yahoogroups.com> wrote:

[Attachment(s) from Kevin in Fort Davis included below] 

Thanks, Milton, that's what I thought.

By the way, regarding our FW800 bandwidth/camera recognition issues of late, I've rearranged things in our dome to try and alleviate that.  I have 1m cables from the three Flea3 cameras to the FW800 hub, and then a 4.5m (soon to be a 3m cable as soon as it arrives) cable from the hub to the computer.  I tested it all day yesterday without a hitch, but today we had some video previews freezing.  My question is, of the available video formats in the larger frame sizes, which one would consume the least FW bandwidth?  Please see the attached screen shot for the formats in question.

Thanks as always!  -Kevin