Going to try that next. I'm wondering if anyone else is doing this and what their workflow is. If you're using proxies, could you tell me how long they take to build? Was hoping that I am not the first person using Vegas to do this. Always better to have someone else light the path forward.... ;-)
I also am about ready to tackle a new system, as this was purchased in 2009, and wondering if there is a way to build a system and perhaps RAID, that can handle 2-3 cam 4K multicam shoots.
Btw, I tried these clips in FCPX as well and got the same playback.
And the clips are fine for editing without it being multicam. I think I'm just running up against technological limitations here.

I know this is going to initiate a firestorm of RAID discussion, but 100 mbps should not tax a 7200 RPM drive. With multiple input streams, you might consider multiple physical spindles to reduce the possibility that seek time might become a factor if the data was spread all over the disk. If seek time really was an issue, a $100 SSD would solve that problem with little muss or fuss.

Your current limitation is almost certainly processor core clock speed and/or memory buss bandwidth. I was going to launch into a long technical dissertation on the subject but you're looking at a forklift upgrade. Then there are proxies...

John

I have tried editing 3cam 4K also from AX100 from a RAID 5 with 7200rpm disks and it just doesn't do it. I believe that the RAID overhead is a bigger issue. Even a RAID 0 with SSDs has issues compared to a single or multiple single drives, one for each camera stream. While a single file or a longer cut plays fine, the problem is after straight cuts or transitions where data needs to be pulled from different locations at the same time.

A 4-core CPU certainly doesn't cut it and yes, core clock is very important too. As you said, a forklift upgrade is necessary if one wants to use the XAVC-S files natively. Building time for proxies depends on the render speed of the system and the codec used. I use Vegasaur to build proxies, its more flexible then Vegas build in function.

Even a Gen1-i7 can edit 4 cams of 1080 XDCAM-EX with a good GPU. If the proxy feature is not working well for you. You could just manually create proxies of your own, and switch back and forth.


I also think getting out of that XAVC-S format into XAVC-I would perform better.

Multicam 4K without proxy, I would think would require a system well beyond the minimum Sony 4k requirements.

100mbs is not that much HDD bandwidth, but I would do a drive for each camera to avoid IO contention. Maxing your memory within reason would be good too, since Windows builds a huge disk cache. Mine for example with 32GB of RAM is at 22.1GB. Accessing from memory will always be faster than making a disk call.

You can watch your disk IO in resource monitor. If you are not seeing high utilization, and disk queue depth, then HDD IO is not your playback problem. Decoding the footage, mixing the streams, and throwing the pixel to screen is more than likely the issue.

I also think getting out of that XAVC-S format into XAVC-I would perform better.

Yes, it does perform better and it does smart render if I remember that correctly.

Thanks for the input guys! Just what I was looking for. John, I think you're right about a system upgrade being in order. Since posting, I tried moving the second camera files folder to a completely separate drive, deleting the file folder from its original location to be sure. Both drives were internal, 7200 RPM SATA drives. It made no difference at all. Still got 1-5 FPS playback. This would tell me a RAID wouldn't even help.
I'm trying to avoid proxies, and my plan is to use the AX100s, which I picked up for $1,000 each, as B and C cams, so replacing them is not in the cards. Going to XAVC-I for my main cam is a promising idea though.
I would love to hear the full system specs of anyone who is pulling off 4K multicam 2 or 3 camera edits with 24 FPS playback.

Try and use Catalyst Browse or Prepare to convert the AX100 XAVC-S files to XAVC-Intra; it did make quite a difference on my system. You can also try and set the project properties to 1080 24p instead of the full resolution. And switch of "smart resample" on all files.

I also think I'm crippled by the age and specs of the system. I've upgraded the GPU to a Radeon HD7950 and maxed the RAM to 16 GB but it is old - an Intel Xeon W3520 Bloomfield 2.66 GHz 4 x 256KB L2 Cache 8MB L3 Cache LGA 1366 - copied and pasted specs there.
It's actually a 2009 Mac Pro - you get the idea.

Time to build a Skylake Windows 10 system I'm thinking.

Hey Old Smoke - project properties are set at 1080p 24FPS - I use the 4K for reframing on occasion and for the great 1080p quality of final files.
Thanks though.
And I tried all the Catalyst products on trial but at the price Sony is asking.... um, no. Don't think so.
Thanks again though. Really appreciate the feedback.