Well I can understand the Vegas Preview working better on transitions, titles, effects modified tracks, etc, but my prerender is the same format as the files that are being prerendered. The playback performance should be the same in those parts as far as I can see. If I put a single Cineform clip on the timeline, and use exactly the same format for my prerender, why should one play back any better than the other? After all, it's smart-rendering the prerender. They should be exactly the same shouldn't they? Well they're not. The pre-render plays back WAY smoother!

Yes Laurence. I did understand that, so what is it you are REALLY implying? Hmmm . . ?

Let us take a very simple example:
You have just 2 still pictures on the time-line and they are crossfading over 1 second.
If you preview this, Vegas has to do the rendering "on the fly" i.e. make both pictures more or less transparent and merge this result.
Often your CPU has not the power to do this at 30 fps and you will loose some frames.
If you prerender the area around the crossfade then Vegas takes the necessary time to render this into one video file in the RAM or on disk.
-And when you then preview the whole thing Vegas is so clever, that when it comes to the part, that is prerendered, it does not bother to prerender on the fly for the preview, but it simply - and without that you notice anything - shows the all ready rendered videostream from RAM or HD.

Above all this Vegas is so smart, that if you change anything concerning the prerendered area then Vegas discards the prerender done and will again atempt to render on the fly when you preview the next time.

This is a clever program - right?

OK . . without the thin veil of "wit", and being coy - just WHAT is being suggested here? - And yes I got all the above, but will somebody please say what they think?

It depends on the template you choose for the pre render files.

If you aren't seeing the preview files rendering, you probably need to turn on 'Show preview while rendering' in the general tab of the preferences.

If you use Dynamic ram preview, that will render at the current preview quality.

Andrew

I think what's being said is what's been said many times over the years. Vegas will discard the prerenders way too easily. Make any change and even though it doesn't in anyway affect the prerender Vegas insists on doing it all again.

Some allowance for intelligent human control over the discarding might reduce the angst over this.

Bob.

Okay, so you have footage on the timeline that won't play at full framerate. You <shift+m> to prerender and you set up the prerender to use the same codec. Vegas then blips through the prerender as if there was nothing to do and you see a black preview screen for the seconds this takes to happen (as you should if nothing is being rendered)

Now, even though nothing was really rendered, your playback has improved to full frame rate.

These are wild guesses. Maybe Vegas cached frames to ram as you were doing this and this has improved the playback, OR maybe Vegas has cleared it's cache of frames. Hard to know but if you were to change the preview window settings that would clear out cached frames. You might be able to get some clue by doing that.

Rob Mack