Mostly venting about rendering – 40+ hours for a 53-minute show

[John Rofrano]

[Scott Simpson] “My board is an Asus P7P55D-E — it’s an 1156.”

That board support a Core i7 so it is possible that you could just upgrade the processor.

[Scott Simpson] “I’m running an i5-750.”

That processor is not multi-threaded. So you have 4 cores and 4 threads. The Core i7 is multi-threaded so it has 4 cores with 8 threads. That means a processor upgrade to an i7 should double your processing power with 8 threads vs 4 threads.

This is the part that gives people a false sense of security. They say, I have a 4-core Core i5 it should be just as good as a 4-core Core i7 but they loose the fact that their 4 cores have only 1 thread per core and the Core i7 has 2 threads per core for twice the processing power for multi-threaded tasks like rendering video.

[Scott Simpson] “At this point, I’m best off replacing ………everything except the drives and case, probably.”

That depends. You want your system to be well balanced. So it doesn’t make sense, for example, to upgrade just the CPU and leave slow memory because then the memory becomes the bottleneck. But if you have relatively fast memory, you might look into just upgrading the CPU.

Rendering is CPU bound. If you want to increasing rendering speed, increasing your CPU power is the single biggest change you can make.

~jr

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

[Norman Black]

[John Rofrano] “That processor is not multi-threaded. So you have 4 cores and 4 threads. The Core i7 is multi-threaded so it has 4 cores with 8 threads. That means a processor upgrade to an i7 should double your processing power with 8 threads vs 4 threads.
“

I disagree. The extra logical threads only give you 0-35% better performance. It varies by application. In can be negative!, but in this situation, typically at most 1 percent slower.

In a hyper-threaded processor two separate logical threads share the physical resources of a single “real” CPU core. Therefore each thread really only runs at around half speed on that core. You can get better performance than that since the CPU core has more execution units than a typical single thread can fully saturate. Also, a given thread pipeline will stall due to memory access and for that period of time the other thread gets full access to the CPU core execution units.

So how can it sometimes be slower? Most commonly due to cache thrashing.

[Scott Simpson]

Now my newest computer feels very old. Are you looking to part with it? Reckon it’d be a significant performance jump?

—
Radio guy in a TV world. Bigasssuperstar.com

[Barry Hull]

Scott,

I too render some long videos, 45 minutes to over an hour. I find that the effects I use have a HUGE influence on render times.

One of the worst offenders is composites, green screen brings renders to a crawl.

I’ve had three camera VEG files with track level effects such as Beauty Box that took three full days to render and I have a latest/greatest computer setup… if that makes you feel any better when you’re twiddling your thumbs.

Yeah, you need a fast computer, but get rid of those effects unless you really need them. Just sayin…

Barry W. Hull

[Dave Haynie]

[Norman Black] “[John Rofrano] “That processor is not multi-threaded. So you have 4 cores and 4 threads. The Core i7 is multi-threaded so it has 4 cores with 8 threads. That means a processor upgrade to an i7 should double your processing power with 8 threads vs 4 threads.
”

I disagree. The extra logical threads only give you 0-35% better performance. It varies by application. In can be negative!, but in this situation, typically at most 1 percent slower.”

That’s correct. And yeah, it varies by application. What happens in the i7 is the each core has a second set of CPU registers. Any time there’s a pipeline stall for one CPU context (you’re reading memory, for example, which is much slower than CPU internal stuff), the other set, which defines a second thread, is swapped in. So you’re keeping that CPU core busy pretty close to 100% of the time. Without the hyperthreading, it might have been kept busy only 70-80% of the time. That difference is the speedup you get with the dual threads per core.

Not so much anymore, but certainly in the past, and even today on some problems, hyperthreading can slow things down. It’s possible. Why? Caching. You’re running twice as much code through the same sized on-chip caches. If you don’t exceed their capacity with those extra threads, things go faster. But if one thread is kicking out stuff the other thread needs, then you have cache thrashing and the system runs slower. Today’s caches are large enough that you rarely see this. And if the two threads are doing mostly the same thing, even better chance things go faster… for example, when an MPEG or AVC render is on all cores… same code, different data, good chance it all fits. Also a good chance since after all, Sony’s writing the code for an i7… that’s pretty much a given. No telling if they do much testing on lesser processors, but every company doing pro video work is developing with recent higher-end processors.

-Dave

[Dave Haynie]

[Barry Hull] “One of the worst offenders is composites, green screen brings renders to a crawl.”

Yup. I did one animation some years ago, with probably 40-50 animated layers, all in green-screen (I hadn’t figured out how to do alpha stuff in Vegas back then). The two minute video took about 4-5 hours to render on my best PC back then. Ouch!

The other thing to consider is that GPU acceleration can really help here, for compositing and some plug-ins, even when there’s no GPU acceleration in the particular CODEC. Obviously, it’s only helpful with it’s stable on your system. It’s been nothing but stable on mine, even back in Vegas 11. Not so for everyone, sadly. GPGPU is still a pretty new thing, as they say, you can tell the pioneers by the arrows in their backs.

Another thing here, when you’re CPU only… just benchmark, for a minute, how much CPU power your PC uses even just playing back a single AVC stream (CPU-only, of course, no video acceleration). Vegas decoding an AVC stream will take more CPU than that. Per stream. It’s not necessarily a small thing. So you have three video tracks, and you’ve discovered that Vegas takes 50% of your CPU to decode each 53 minutes video just for playback, you can be certain that you’re spending as much as 80 minutes per render JUST ON THE VIDEO DECODE! If it’s just pure cuts, no compositing, it would represent over 27 minutes of your render.

-Dave

[John Rofrano]

[Dave Haynie] “So you’re keeping that CPU core busy pretty close to 100% of the time. Without the hyperthreading, it might have been kept busy only 70-80% of the time. That difference is the speedup you get with the dual threads per core. “

Point taken, but the bottom line is that a hyper thread quad core can get more work done than a non-hyoperthread quad core so 4-cores is not always equal to 4-cores. Even at 30% that’s a pretty good boost.

~jr

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