Slow Render again, tried most suggestions, looking for more

[Brad Leigh]

I don’t Get it, the render times seem ok. This test is 3 clips HDV with dissolves, takes about 7 minutes for a 1:24 clip. I just wonder if it could be faster. Program seems to edit fine, I’m very happy there.

And to show disk

i7 2600 3.4 Ghz 8Gig Ram , Win 7 Pro, Vegas Pro 10

[Brad Leigh]

One correction, Re Checking settings I realized that Render had switched back to GPU, I switched back to CPU I played with Ram settings and I seem to be up to 40% or so.
I give up, system seems to work pretty good despite low CPU usage.
B

i7 2600 3.4 Ghz 8Gig Ram , Win 7 Pro, Vegas Pro 10

[Dave Haynie]

I hadn’t noticed that before… you’re using an i7 2600, 3.2GHz, four core, in hyperthreading mode (eight virtual cores). Just a question: how many renderning threads do you have set (Preferences/Video/Maximum number of rendering threads:)?

So you’re not seeing any core terribly busy… numbers 6 and 8 are downright sleeping.

There can be some weirdness with too many threads on such systems… the virtual cores eat up the on-chip cache twice as fast as regular cores alone (makes sense — same hardware, twice the program context).

It’s possible to get all those cores fighting each other — cache thrashing. Can’t be sure that’s it, but seeing as how none of your cores are all that busy and neither is the I/O, unless you’ve got some 1980’s Fast-Page-Mode DRAM in that rig, I can’t think of another obvious bottleneck.

What you want to have happen: program runs, rendering starts. The very carefully tuned rendering code plus data fits entirely in the CPU’s L1 cache for critical sections, L2 cache otherwise. Things go fast, life is good.

What happens when you “thrash” the cache: core 1 is rompin’ along, core 2 needs a different chunk of code or data that’s not in the cache… but until grabs that stuff, but it has to toss out the stuff core 1 was going to start using pretty soon. So core 1 gets to that part of the code, and has to wait for its stuff to get loaded.

Now, if you’re running a hyperthreaded processor, that was actually core 1a stalled waiting for a memory fetch… that lets core 1b on the bus (they’re a virtual pair)… and now it’s also contending for resources on the chip. And it gets worse if there’s much task swapping.

You show plenty of free memory, so I don’t think that’s the problem.

So here’s my advice. First, find the Options/Preferences dialog. Go to the Video tab, look at “Maximum number of rendering threads”. I’d set this to eight, one for each processor, to start with. Definitely no more… that will help with the possibility of cache thrashing.

Also, while it doesn’t seem related, try setting Dynamic RAM Preview max (MB) to 1000MB (1GB)… you can spare it. I have a theory that Vegas will use this otherwise useless memory during rendering to better chunkify the disc access (eg, larger disc reads deliver better throughput, since there’s less seeking between files on the same disc for the same amount of data loaded over time).

-Dave

[Brad Leigh]

Dave
Wow Thanks so much! I love this. I was embarrassed to post last night that I got CPU percentage UP and ram usage up when I increased my Dynamic ram preview. Everything I had read on this forum said drop it down to min. I have tried different thread numbers. It started to get interesting because I experimented with different Dynamic ram preview settings and cpu percentage, and ram usage went up, at a certain point it didn’t help render times with this simple test. Rendering this test with 1 minute 24 second split screen, and a single dissolve HDV footage to AVCHD I could get down to about 5 minutes @ 40- 45 % cpu.
Buy increasing ram preview I could get CPU up to 60% and RAM usage up to 6 or 7 GIGs but render time started to fall off. I left my system last night at 1024 Ram preview. That decreased my render time from 7:30 to 5:30 and my cpu % from about 14% up to 40%. I figured I would leave it there until I threw some AVCHD files in the mix. Thanks I thought I was loosing my mind.
Brad

i7 2600 3.4 Ghz 8Gig Ram , Win 7 Pro, Vegas Pro 10

[Dave Haynie]

[Brad Leigh] “Wow Thanks so much! I love this. I was embarrassed to post last night that I got CPU percentage UP and ram usage up when I increased my Dynamic ram preview. Everything I had read on this forum said drop it down to min. I have tried different thread numbers. It started to get interesting because I experimented with different Dynamic ram preview settings and cpu percentage, and ram usage went up, at a certain point it didn’t help render times with this simple test.”

The stated purpose of Dynamic RAM Preview is just that — preview rendering using RAM while editing. But Vegas does seem to statically allocate this… so it’s claimed during a render as well. That of course means that you don’t want this number set too high during a render, particularly if you’re on a multi-core CPU. If you think about it, even if all the code fits in cache and doesn’t need to be replicated, for each thread you add, you have a full image rendering pipeline, which means a number of uncompressed HD images in RAM at the same time. If there’s too much memory doing other things, you’ll start paging — virtual memory — and that’ll become your bottleneck. You want every render to take place entirely in RAM.

However, I’ve seen that setting this to zero can actually slow down a render, and I’ve heard others offer evidence of the same thing. This makes sense — if Vegas has some memory of its own pre-allocated, why wouldn’t the programmers use it for buffering. This was actually one annoyance I had with Vegas, from the start, coming in from the music world. In the day, audio programs like Cakewalk let you define RAM buffers, which essentially let you add speed and thus tracks, at the expense of latency. I never quite figured out how Vegas figured out what I wanted it to do in this. Once you get to video, maybe it’s too complex to leave to the user, but then again, if it can be left to the user — and by that I mean me — I might be able to solve a performance problem that Vegas can’t solve automatically.

-Dave

[Josh Bowren]

Just before rendering I have been setting the Dynamic Ram Preview to 0mb.

I have noticed much faster renders with little to no bottle necking.

just my two cents.

josh

[Brad Leigh]

Dave
Thanks again. I had gone from the default in vegas of 350mb to 0, Life seemed to improve when I went up to 1 gig. Curious to see what happens when I throw some AVC files in the mix.
Thanks Again
B

i7 2600 3.4 Ghz 8Gig Ram , Win 7 Pro, Vegas Pro 10

[Dave Haynie]

I had a new marketing animation to render tonight.. so I decided to get all sciencey on it and see how tweakables affect performance. Here are the results:

System
3.2GHz AMD 1090T 6-core processor
16GB DDR3 DRAM
nVidia GeForce 8800GT GPU (runs CUDA, fairly ancient)

Project
1920×1080 59.94 fps progressive
32-bit floating point (full range) pixels
Best quality
Gaussian motion blur

Source video
1920×1080 59.94 progressive MPEG-2 at 50Mb/s.
Total time: 1:42:15
No video effects
Four fairly sparse audio tracks, applying some audio
effects (reverb)

Target video #1
1920×1080 29.97 fps progressive AVC at 10Mb/s.
Total time: 1:42:15
Sony AVC at Baseline, CAVLC

Trial Threads Preview GPU CPU RAM(GB) Time Size (kiB)
1 8 2GB yes 76% 7.96 12:26 126,829
2 8 1GB yes 75% 7.01 12:38 126,829
3 8 0GB yes 57% 6.12 15:52 126,829

4 8 2GB no 94% 7.90 10:10 112,335
5 8 1GB no 94% 6.95 10:12 112,335
6 8 0GB no 80% 6.21 13:20 112,335

7 6 1GB no 93% 6.87 10:41 112,335
8 12 1GB no 94% 7.13 10:27 112,335

Target video #2
1920×1080 59.94 fps progressive AVC at 20Mb/s.
Total time: 1:42:15
Sony AVC at High, CABAC

9 12 1GB no 80% 7.04 13:14 208,543
10 12 1GB yes 80% 7.00 12:33 228,431

Notes
It’s pretty clear, on my system, the GPU render isn’t always
helpful. Part of the problem of using alternate processors is
ensuing the overhead of the communications, the weird way you
have to structure the math, etc. actually yields a payoff.
And yeah, probably need a GPU update.. but which one?
Hopefully, Vegas 11 answers that question.

It’s clear they’re using a slightly different algorithm on
the GPU vs. non-GPU render. This is not a shock.

It’s also clear that “Preview” RAM is being used
constructively during render, as was my contention. And kind
of what you’d hope, but nothing I’ve seen documented.
If you don’t have crazy amounts of RAM, though, you have to
be careful with this, or you might slow rendering down in
other ways.

-Dave

[Don Cobble]

Dave I was having the same problem ( U R A Jean Yus) for me it was boris Light wrap When I took that off it rendered at 100% when I use light wrap 18-20% CPU! and no GPU? I dont know the cause but will look for a way to do without light wrap in boris!
Thank U
don

PC
I7 2.8 Ghz 8GB Ram
Win 7 Pro 64bit OS
PNY Quadro 4000

3-4 TB HD
Vegas Pro 9 32bit & Vegas Pro 9 64bit & Vegas 10 32bit & Vegas 10 64Bit

Camera
Sony EX1 shoot in 1920×1080 30P

[Brad Leigh]

Dave
Thanks again. I still yet don’t understand why I’ve never seen above 60% and usually it’s around 40%, but my sessions are simple at this point as I get deeper into it maybe i’ll bog it down a bit more.
But I am happy that for the first time in my life I bought a new computer, and upgraded my software, and experimented with it BEFORE I started my project. So my blood pressure is pretty low. I guess some wisdom does come with age.
Thanks
Brad

i7 2600 3.4 Ghz 8Gig Ram , Win 7 Pro, Vegas Pro 10