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Mac Pro and Video Encoding Speed

A

all-in-my-head

macrumors member
Original poster
Oct 25, 2003
69
0
UK
Hi,

I have a Mac Pro running Dual 2.8 Quad Core with 6Gb Ram, what I'm intrigued by is what governs the speed of a task like encoding video?

For instance, I'm compressing a video that was originally in H.264 940x540 res and is about 350mb in size, down a notch to H.264 with a medium quality and the same res. To do this I'm simply using Quicktime Pro and the basic settings. (I've also tried exporting for web, desktop setting)

This is taking some time, but what i don't understand is why looking at system performance, the cpu usage never goes above 50% and with other apps open I still have 1.8GB of free ram.

So is the slowness really down to hard drive read/write speed, and/or data transfer within the computer? (It's encoding to/from the same internal HD)

I'd be grateful to anyone who understands these things to explain a bit more about what is happening. In my logic i would understand the slowness if the Ram or Cpu was maxed out, it's obviously doing a hard job.

thanks
 
Great question as I am also wondering the same things.

I record 4GB of data to my 1080p video cam, import it to Final Cut Express, then trim it to 30mins of video and export it to a .264 .mov file at 1280x720 with a max data rate of like 5Mb/s. This whole process takes ages up to like 7 hours or time and the same issues only 400MB of main memory is used while I have 8GB free, 250% processor used -vs- the 800% I think i have on my 8 core MAC pro so the cpu is like 30% used and there is hardly any HD activity.


Seems like this is very inefficient.
 
I think it just has to do with apple's quicktime. I do a lot of DVD to ipod touch, or sony's psp .h264 medium to high quality.

I know when I try to use my quicktime pro for converting. It takes 3 to 4 times longer than Visualhub or isquint. Quicktime even takes longer than ffmpegx which is a free converter for the mac.

I think quicktime is crippled on purpose by apple, so it won't hog all your resources.
 
I always assumed it was that quicktime is only threaded for up to 4 cores. Hence..using only around 50% of an 8 core MP. seems pretty reasonable to me. BUT..i do hope it is changed for more cores.
 
Same problem with other software

I'm doing a fair amount of video editing using Final Cut Studio 2 as well as exporting vids from KeyNote into a Quicktime format. I've got my activity monitor up full-time on an alternate screen and I've noticed that my 8 core processor never gets fully utilized. I'm not doing anything else and everything shows the RAM and CPU are not being maxed... not even close. What's the key to getting this $5K machine to really use it's hardware the way I thought it would?

Comon you MacPro experts out there, tell us the key to get this machine speeded up.

WW
 
Idk..i really think it's because w/e software you are using, isn't threaded enough for 8 cores. I just do multiple things at once and I have seen cpu usage in the 98% range.

Like handbrake, i forget what cpu % use it gets. But it isn't threaded enough to use all of an 8 core. so..you can just run two instances and use more/all of your resources.

Hence, why apple is making Snow Leopard, which is supposed to better use all cores. Hence, why intel stressed the need to better write applications.
 
You need to use compressor to utilise all 8 cores when encoding video.


Ensure you use Apple Qmaster and are sharing services. Export a self-contained QT movie from Final Cut first. Then import that file into Compressor. Select the cluster and compressor.

I halved my encode times.
 
Great to hear I'm not the only one who experiences this. And it sounds like there is an obvious answer in the multi-core thing.

I guess we have to wait for Snow Leopard then to get are Pro's running at 'Pro' speed. In the meantime I'll try getting to grips with FCS's Compressor.

Is it just FCS 2 that is suited to using 8 cores? I've got FCS with FCP version 5.x, the first revision that supported HD, and possibly before multi-cores (ie more than 2) started being used in Pros!?.

Hoping I don't have to upgrade, again!
 
kingkezz said:
You need to use compressor to utilise all 8 cores when encoding video.


Ensure you use Apple Qmaster and are sharing services. Export a self-contained QT movie from Final Cut first. Then import that file into Compressor. Select the cluster and compressor.

I halved my encode times.
Click to expand...

Well if I have to export the self-contained QT movie then what's the point. At that point I'm done. It's exporting the QT movie that's taking the majority of the time. Is there a way to take the raw FCP project and use compressor to make the initial QT movie?

Thanks
WW
 
The ResQ Shop said:
Well if I have to export the self-contained QT movie then what's the point. At that point I'm done. It's exporting the QT movie that's taking the majority of the time. Is there a way to take the raw FCP project and use compressor to make the initial QT movie?

Thanks
WW
Click to expand...

Exporting a self contained QT movie (using current settings) takes no time at all. I can export a 20 minute sequence in like 2 minutes.

I then use Compressor to encode into .m2v or h.264 etc.

The idea is that you export a .mov using your current sequence settings, then import that file into compressor to encode into whatever you want, for web etc.

There is a documented issue within compressor that produces problems if you export directly from FCP timeline to Compressor.

Theres a thread on this in the Digital Video forum.
 
kingkezz said:
You need to use compressor to utilise all 8 cores when encoding video.


Ensure you use Apple Qmaster and are sharing services. Export a self-contained QT movie from Final Cut first. Then import that file into Compressor. Select the cluster and compressor.

I halved my encode times.
Click to expand...

Is Apple Qmaster useful when you aren't on a network with other Mac to share resources? I thought that's the only way it benefited.

I would be very happy to hear that I am wrong :)
 
MatchFrame said:
Is Apple Qmaster useful when you aren't on a network with other Mac to share resources? I thought that's the only way it benefited.

I would be very happy to hear that I am wrong :)
Click to expand...

You don't have to be on a network. You just set up your cores as a virtual cluster and tell compressor to use it and away you go.
 
Alican said:
You don't have to be on a network. You just set up your cores as a virtual cluster and tell compressor to use it and away you go.
Click to expand...

That is absolutely fantastic news. Can't wait to set it up when I get home from work. Just bought my new Mac Pro last month and FCS2 last week.

Is there a little guide somewhere to setting this up, or will it be pretty straightforward when I take a look at it?
 
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