The V8 default is 128 I believe.
JJK

I had big issues with V5/V6 with dynamic RAM set to 16-64, I think 16 was the default at the time. I think the default setting changed in V7 install to be outside this range.

Yes, we have tested that in Septemer 2007, both for Vegas 7 and Vegas 8. Render time decreased dramatically with increasing size of the dynamic ram preview, as reported in our German forum.

http://www.vegasvideo.de/forum/thread.php?postid=78526#post78526

Vegas 7:
4:31 Minuten bei 750 MB
4:27 Minuten bei 511 MB
7:30 Minuten bei 256 MB
9:16 Minuten bei 0 MB

Vegas 8:
5:11 Minuten bei 750 MB
5:07 Minuten bei 511 MB
7:11 Minuten bei 256 MB
9:32 Minuten bei 0 MB

Footage used was an HDV2 1080 50i project, with huge PiP effects, using a Q6600, based on XP and 2 GB recognized RAMs..

The recommendation was to adjust the dynamic ram size to 500 MB.

Sony has never recommended that you set the preview RAM to zero

Devil's advocate: Actually, they do. From the Using Dynamic RAM section of the manual / online help: "To turn off dynamic RAM previewing, enter 0 in the Dynamic RAM preview (max) box on the Video tab of the Preferences dialog."

Just sayin'.

Rob

It's not a recommendation, they're just telling you how to do it if you should wish to do so.

Maybe Sony didn't, but as I recall several users here have recommended setting the RAM preview to 0, in order to fix a "black frame" bug when rendering HDV. In my case, that seemed to work sometimes but not always.

This was a very timely thread. I just had 2 GB of RAM arrive via UPS today. I have a very minimal system for editing AVCHD files, so I bumped up my RAM to 3 GB. After installing the RAM, I bumped up my preview RAM amount to 512 MB. Vegas opens much faster with the extra RAM, but I have not rendered anything yet to test that out.

I've never noticed any rendering speed difference caused by the Preview RAM setting. What i have noticed occasionally is that if i have most of my available RAM allocated to Vegas' preview function then other programs may start swapping in and out of RAM and that will dramatically slow down Vegas' rendering speed. So, in my case, i get the best performance by leaving Preview RAM set at 0.

Preview RAM affects enough things that Sony could publish a small white paper on it. Yes, as Vegas consumes memory it'll force other programs into the page file, and if it consumes too much memory it has (in past versions) triggered nearly constant page file churning. This doesn't mean Vegas itself gets swapped but it doesn't matter--if swapping is happening it slows the system down overall.

As to what specifically Vegas uses the preview RAM for during a render? Don't know but I'd think at the barest minimum if you had 500MB of frame data cached in RAM when you started to render then that part would render like lightning.

Rob Mack

I suspect that one of the things we'll all like about Vegas64 will be the ability to throw 4 or 5 or 6 gig at the RAM Preview and be able to render up a pretty good sized chunk of HD to see it in real time with transitions and the like.

John

One thing I wonder is how a larger ram preview allocation affects longer renders. For example, if you're rendering a half hour program does it give you the same proportional improvement as it does a 3 minute program?

If you get a much better bang out of the shorter progam I'd think it was because you started the render with a greater proportion of it being cached to ram.

Rob Mack

I tested this in Vegas 7 on my XP x64 machine with 4GB RAM.

I found that the rendering process actually slowed down with more than 256Mb set.

At the bottom end I found that it had to get below 16Mb before slowing down significantly.

So now I leave it at 128Mb.

This is the issue. Somehow you've got to get it from the disk to the CPU. Fast disk arrays along with the mobos with the i/o bandwidth to match are the answer. Throwing more RAM at the problem just creates the temporary illusion that things are better.

Bob.

Well, findings seems to be quite different here. But a short test on a specific pc will give a fast answer, how render time behaves. Given the huge differences I listed above, I think it is worthwile to test that out on a specific pc.

Keep in mind that if your preview settings don't match the render settings then Vegas can't use the cached RAM preview data for the render. The only way to ensure that the preview data is useful is to have the preview size set at Full and the good/best switch set to match what you use for the render. I wonder how many of us normally run with those settings? Or do most of use use Good/Auto or even less in order to maximize frame rate while previewing?

Well, at least I usually match the project and the render settings in term of pixel size - and use full preview for HDV, given the huge preview power of a Q6600 for HDV material, and the support via an Intensity Pro on a full-HD HDTV.

But I do not know what other user are doing here.

It's a good point. KennyMusicman's post last night got me wondering about this so I tried a few things and, yes, RAM preview is dependent on your preview window settings. So it stands to reason that you'd get a quick render burst if your preview and render quality settings match (Good/Good or Best/Best) and probably Full.

This is not to say that Vegas isn't continuing to use Preview RAM in a different way after it uses up cached frames. Just because one can show that Vegas does a specific thing with cached frames doesn't mean it's not doing more than that.

Rob

So what is the optimal dynamic ram setting, "0", "128" or "500"?
There are recommendations for all of the above in different posts here.
Just stopped a long (9 hour) render to reset dynamic ram setting.
Only 2% in.
But what do I change it to.
Anybody else confused?
Somebody's got to be right here.
I feel like I'm on a game show staring down three doors.
In the menatime time I'll try 128.
Mine was set at 250.
here's goes!

Just test it! Time a render at 128, 256, 512 or whatever then make your choice.

I've really been playing with this recently... I think the "sweet spot" is going to vary from machine to machine for several reasons. Firstly, the actual storage in physical ram vs pagefile is different, depending especially on how much ram you have, as well as its speed, read, write, access times etc. Likewise, this is linked to the HDD for the same reasons. Then you have the sustained speeds of the ram - I've noticed that my ram tails off in speed the more full it gets. Link this to the cpu, and overtime of a ram preview build, the CPU utilisation starts off nicely at 100%, but over time decays down to about 56%. So a longer ram preview gets slower the larger it becomes. Next factor in your page file. My 32bit os starts paging to HDD once ram files to 74%, giving me a limited physical ram allotment (more testing due on the 32bit world for this). In 64bit, the ram just kept filling up to my alloted amount, without referring to the HDD (FWIW, I run 8GB ram). Also, if depends on where you page file is, since if it's being used, that's another read/write to HDD, in addition to the r/w for the render destination, and source. So you could be involving 3 HDD (not counting raids) in the read, page and write process for the render.
Therefore, if you work with ram preview, using a 64bit OS has clear advantages, if you have the ram. Also, for info. If I render-test without allowing any ram builds to occur naturally by vegas, nor making any myself, I get an average of 0.5 (half) second different in render times between 32 and 64 bit OS's. If I allow some time for naturally ram generation, potentially, (and worth more research) there could be some time saving within the render process.

So if you want the long answer. THere is is. If you want the short anser, look above at Nicks post :)


[edit: render after ram preview for render test = < 3s..!]

Nick,
My intent was not to get someone else to do my homework.
I was puzzled at how render speed can be so varied.
So what we're saying here as regards dynamic RAM settings is, it depends on the machine.
My small test shows a "0" setting increses render time by about 2 fold over 128, and 512 turns our to be only a tad faster.

Was meant politely Peabody.

I just tested this again in Vegas 8.0b.

Xp x64, Q6600, 4GB RAM, rendertest.hdv.veg

Restarted Vegas each time and a few small apps were running on the computer.

16MB 2:24
32MB 2:23
64MB 2:22
128 MB 2:22
256 MB 2:22
512 MB 2:22
1024 MB 2:25

So basically in my case RAM preview size is making no difference to render speed.

Wolfgang, can you tell us what your system specs are? I'm curious how you're getting the render speed increase, especially from 256MB to 511MB.