Rendering time

[John Rofrano]

It’s probably the compositing of 30 tracks instead of 20. Yes empty tracks add to rendering time because Vegas still has to check every track to see if there is a frame of video that needs to be rendered. I did a test once and I was very surprised by this but that’s how Vegas Pro works.

One thing you might be able to do is combine multiple tracks into a new project and then nest that project in the main project. While this won’t immediately cut down the rendering time, it does give you he option of rendering that project separately and then using the rendered file in your final project which will reduce the number of tracks. Knowing your show format, I would say that Sarah’s interviews are a good candidate for this.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Roger Bansemer]

Thanks John. This forum is great. I can always count on an answer from it’s members.

Roger Bansemer – PaintingAndTravel.com

[Steve Rhoden]

Yeah, empty tracks do takes up a considerably amount of render time,
but its not necessarily a bad thing.

Steve Rhoden
(Cow Leader)
Film Editor & Compositor.
Filmex Creative Media.
https://www.facebook.com/FilmexCreativeMedia
1-876-461-9019

[Stewart Bourke]

Steve,

Could you elaborate please? Why would spending time rendering nothing, but adding to an overall render time not be a bad thing?

Thanks,

Stewart

[Dave Haynie]

I think any track that’s complete empty or muted may not be a huge burden, but any track that’s somewhat occupied still has to be factored in, it can’t be ignored. Obviously, the there’s some time to deal with things being on a track vs. not being on a track, and some time spent dealing with the specifics of what’s on the track. So a blank part isn’t going to use up as much as a different part of that same track with a video clip on it. But there can still be global effects, envelopes, etc. that Vegas has to work out even if there’s no clip.

Having done animations with 50+ tracks, you can buy a little more performance when it’s possible to include multiple unrelated things on the same track. I haven’t measured the actual effect recently, but given that back in those days I was seeing 3-4 hour render times for a 30-60 second animation, every little bit helped.

There may be other things at work, too, that conspire to make things slower than you’d expect. Vegas is doing a great bit of work dealing with multiple tracks, the aforementioned indvidual per-track overhead, the media on each track, etc. I suspect that some of these are ideally kept in cache (per-track data, for example) while other data may be sortly cached or not at all (the media, as it streams through). It may very well be that once you have a certain number of tracks on your system, you all of a sudden start “thrashing” you CPU’s caches. This is worse, too, as you add more processor cores and hyperthreads (each of which can be working on something else) all hitting that same set of caches (CPU, L2, L3) at the same time.

Translated to English, that means that as you add tracks of low complexity, you may find a point that’s more “falling off the wall” than simply adding one more track. You might even find this point yourself. Take that “still fast” project and add, one-by-one, a simple track… not empty, but also not doing much… eg, you’re not expecting to have to decode a whole AVC track (that’s one of the most CPU intensive things done in a typical render, that AVC decoding… at least until we get to HEVC decoders being used for regular video). Track some rendering times and see if this just goes on linearly, forever, or whether it hits some kind of wall.

-Dave

[Stewart Bourke]

Dave,

Thanks for the detailed answer.

However, my question was to understand why Steve felt that having slower render times due to completely empty tracks was not necessarily a bad thing. This does not seem to make sense to me.

Stewart

[Dave Haynie]

Yeah, I wasn’t trying to address that. I think it may well be an unavoidable thing, but I’ve never quantified just how slow it gets. Certainly no slowdown that I know of is an advantage.

-Dave