Your SYSTEM can't play back uncompressed let alone the RAM. The data stream of uncompressed media is (30,375) 27 MB per second, nearly 10 times that of DV.
720x480x24
/8, /1024 to get the formula.

I've yet to see a desktop that can playback uncompressed at 720 x 480 or 640 x 480 at 29.97fps without hardware assistance.
That's why there is DV.

Spot, but isn't a Dynamic RAM preview supposed to be generated in DV format, regardless of what's on the timeline?

27MB/s is nothing for the RAM. The RAM preview should work for uncompressed too, it does for me.

Perhaps your project setting is at 19 for some reason?

Yes, the RAM is be able to playback 27 MBPS, but the comment was playback wasn't constant through the file, suggesting that there isn't enough RAM to play the file, or that the RAM is fragmented.
My point above is that the system can't sustain 27MB via the drives for INTERNAL view, and to be previewed externally at full frame/rez it needs to be rendered to DV.

My interpretation was that theigloo fully understands what the RAM preview does and doesn't do, but that it doesn't give him 29.97fps when playing back his RAM preview timeline selection. On my system it works (P4 2.8MHz, 1GB RAM).

I get 29.97 fps as well, but note, it still reads from the hard drive, even though it's Ram preview.

CORRECTION: I don't get 29.97, between 23-29.
The RAM preview is for rendering effects and layers, maybe that's why this is happening. Use selectively prerender video, but this will take more time.

theigloo, do you know what your hard drive throughput is? There's a utility at the canopus website called raptortest (or raptest?) that will measure the throughput of your hard drives.

Also be checking that drives are defragged, in DMA and not PIO mode, be sure that the drive being used is not the boot drive or the drive where Vegas lives.

Spot, but isn't a Dynamic RAM preview supposed to be generated in DV format, regardless of what's on the timeline?

That's exactly what I think it shoud do too. Vegas should take whatever is on the timeline and 'render' it to whatever format it natively likes best and stick that in RAM. The whole purpose of the RAM preview is to get a real-time look at what you're doing.

There should be no difference when RAM previewing footage from my DV cam versus footage at the same resolution that is uncompressed. Each frame should be converted to the same thing in both cases.

It would be great if the Sony EPM would chime in with the official word.

Also be checking that drives are defragged, in DMA and not PIO mode, be sure that the drive being used is not the boot drive or the drive where Vegas lives.

No. The drives have nothing to do with RAM preview. That is the purpose of the RAM preview - to get the hard drive and effects generation out of the equation. You are 'flattening' the timeline and storing it in the machines most responsive mass storage. Your hard drive, no matter what kind or how defragemented, is the slowest part of your computer.

Having a unkept or poorly setup drives will slow the creation of the Preview. But once the preview is built, the HD is out of the equation.

I've yet to see a desktop that can playback uncompressed at 720 x 480 or 640 x 480 at 29.97fps without hardware assistance.

You should come over to my house. I'll show you realtime playback of 1080p uncompressed footage.

After Effects' RAM preview will do it no problem. That is because the feature actually works.

What black magic is Vegas doing? Again, I think this is a bug.

I should aslo add that Windows media player plays the file back off the HD at what appears to be 29.97 fps. If it's not, it's much higher than what Vegas gives post RAM preview.

I think the inability of Vegas to do as good or better than WMP disqualifies it from being called a proffesional application.

Then there must be something wrong with your settings in Vegas.

What do you mean? My RAM allocation in the prefs is 700 Mb. I am not new to Vegas.

Other people are repeating the issue. That rules out settings.

I've been playing with a bit, and here's my thoughts...

Set resample to disable and turn off unnessary updates (like the scopes). This seems to help out with the framerates. The problem I think is that the project is set to DV, and Vegas is trying to redraw from uncompressed to DV. And that's why the previews aren't keeping up. There's no project setting for uncompressed.

Even with Ram preview, Vegas is still accessing the hard drive. Not sure why...

Just a guess/opinion.

I don't know if you remember this but there's a tiny difference in the framerate of an AEFX file and what Vegas plays at. AEFX makes a 29.97 fps file while Vegas runs at 29.97002997. So there'll be a calculation running.

People noted quite a while back that avi files rendered in AEFX would have an occasional doubled frame in vegas. I think the period between these was something like 9 minutes but the first would occur very early.

So, I'd look for a difference between an uncompressed file created by Vegas and one created by AEFX.

Rob Mack

But, once again, this shouldn't matter because once you've generated the RAM prerender it should be at the proper Vegas project frame rate, regardless of what the source was.

Yah. You know, I tried a few experiments just before heading home. I took some footage in vegas and rendered uncompressed to a new track. That played back on-screen at about 19-21 fps. Then I did a ram preview and it played back at about 29.97 with a little hitting of the hard drive (huh?). Then I took that uncompressed clip int AEFX and rendered a new uncompressed clip. This new one actually played a little better that the one vegas had created but then it had no audio in it. It actually played at 29.97 without ram preview Oddly, it was 2 frames longer than the vegas-made clip.

I'm not really that familiar with aefx and I was in a hurry but still...why better playback, and why the extra frames?

And why is theigloo's playback worse while mine is better.

And why, when I ram preview on the first clip does it just render half the clip while the AEFX clip renders 100% to ram? The AEFX clip was created from the Vegas clip. Both are about 450 MB.

Wierd. Must be loose nuts behind the wheel.

Anyway, I can reproduce the exact opposite of what theigloo is seeing.

Rob Mack

Yes, you are right. However, if RAM is getting hiccuped information for whatever reason, then it could well be related to other issues.
Regarding playback of uncompressed on a desktop system, I'll clarify then. A few thousand people have seen me playback uncompressed HD as well, from RAM on the VASST tours and Sony press events. That DOESN'T equate to playing back uncompressed on a desktop in my mind. Playback of uncompressed (in my view) is playing back full rez, full frame, with no rendering to anything. It's either got to be rendered to RAM, or nothing. Hard drives can't manage the thruput of uncompressed media on a non-hardware assisted desktop at this point in time. Certainly RAM will. But that's not the same thing. You're still rendering.

theigloo:

Here's how it was explained to me by the lead video engineer for Vegas:

The RAM preview function does not store frames that the video engine was able to produce "quickly" (slightly faster than needed to keep up with realtime).

What is happening is that some frames (probably those that happen to be in the hard disk's cache) read quickly enough on the RAM preview build pass that it doesn't store them. Unfortunately, upon playback of the RAM preview, the frames are not reading as quickly as they did on the build pass, and your playback rate drops below realtime.

We might add a keyboard modifier to bypass this logic and store every frame, but in the meantime, a workaround is to apply a no-op video effect to the video (to slow down the video engine, of all things), or composite an empty text overlay over the video, so that the RAM preview doesn't "skip" any frames during the build. Then, the playback should be full rate.

You could also Prerender the segment to a fast format like DV, although that would be lossy compared to uncompressed.

///d@

Dennis, thanks for the explanation. That makes a lot of sense.

Yes, thanks. That explains a lot. I was getting a bit confused. To restate:

Vegas does an optimized ram preview, rendering just enough to get full playback. Sometimes Vegas is wrong about how much needed to be rendered and doesn't do enough.

Rob Mack