Putting Display to Sleep during Sharing, has now started slowing the encoding speed?

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Putting Display to Sleep during Sharing, has now started slowing the encoding speed?

I normally Put the Display to Sleep via a Hot Corner whilst Sharing or generally transcoding as it reduces electricity consumption and puts less wear on the monitor.

Yesterday I was surprised to notice that when doing this, the encoding speed was at least halved.

Assuming it was some temporary aberration, I did some further tests this morning only to discover that whilst the display slept, the encoding crawled along and once the display was awakened the encoding sped up.

I have been putting the display to sleep over the past few years with no problems whatsoever, so I am completely baffled by this sudden change in behaviour.

Incidentally, every other process was switched off and there was always plenty of Free RAM.

The project properties are irrelevant as the performance of the encoding varied according to whether the display was on or off, but here they are:-

1080i25 optimised to ProRes 422

63 minutes of family clips with cross dissolves, 21 chapter markers and no other effects.

The project was being Shared to an H.264 Master File.

Another oddity I noticed was that on this occasion whilst creating the Master File, the progress indicator went up to 100%.

Usually with Master Files it is completed at 50%

I haven't done such a long encode for many weeks and wondered whether upgrading to 10.0.8 might have caused either of these changes?

iMac, OS X Mountain Lion (10.8.4), Little knowledge... many opinions.

Posted on Jun 21, 2013 3:53 AM

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Answer 1

Jun 21, 2013 4:01 AM in response to Ian R. Brown

This is interesting. Maybe sleeping the display also sleeps or somehow slows down the GPU also? Considering that FCPX uses the GPU extensively, that might explain it. I wonder if just turning brightness all the way down, or most of the way down, would be a better alternative then.

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Answer 2

Ian R. Brown Author

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24,503 points

Jun 21, 2013 4:07 AM in response to Luis Sequeira1

Your second sentence sounds credible except for the fact that I have been sleeping the display for years with no reduction in encoding speed .......... theoretically you would even expect it to be marginally faster as there is one less item drawing power from the iMac.

I almost always work with the brightness set to minimum as it is still light enough to see clearly.

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Answer 3

Ian R. Brown Author

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Jun 21, 2013 5:09 AM in response to Ian R. Brown

I am getting even more baffled.

I created a 20 second project and exported it to a Master File using multiple settings ........ with and without chapter markers, do nothing or open in QT player etc.

Every setting, whether used with the display asleep or awake took 60 seconds, as you would expect.

Going back to my original 63 minute project and re-testing it to see how much encoding it could do in 6 minutes, the results were as follows:-

Display Asleep = 1%

Display Awake = 3%

So for some weird reason, with this particular project, sleeping the display reduces the encoding speed to around 30%

Admittedly I was only encoding the first part of the video but earlier when I had been encoding the whole lot, I put it to sleep at various points throughout the video with the same dramatic slowdown.

One problem I have solved is why the Master File sometimes completes at 50% and at others 100%.

If you choose to "Do Nothing" on completion, the scale stops at 100% but if you elect to "Open in QT Player" at completion, the scale stops at 50%. (Regardless of whether it stops at 50% or 100% the encoding takes the same time).

Strange but understandable and consistent.

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Answer 4

Jun 21, 2013 5:45 AM in response to Ian R. Brown

One problem I have solved is why the Master File sometimes completes at 50% and at others 100%.

If you choose to "Do Nothing" on completion, the scale stops at 100% but if you elect to "Open in QT Player" at completion, the scale stops at 50%. (Regardless of whether it stops at 50% or 100% the encoding takes the same time).

Strange but understandable and consistent.

Good catch!

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Answer 5

Jun 21, 2013 5:48 AM in response to Ian R. Brown

Ian R. Brown wrote:

I am getting even more baffled.

I created a 20 second project and exported it to a Master File using multiple settings ........ with and without chapter markers, do nothing or open in QT player etc.

Every setting, whether used with the display asleep or awake took 60 seconds, as you would expect.

Going back to my original 63 minute project and re-testing it to see how much encoding it could do in 6 minutes, the results were as follows:-

Display Asleep = 1%

Display Awake = 3%

So for some weird reason, with this particular project, sleeping the display reduces the encoding speed to around 30%

Perhaps the question is: how is this particular project different? Color correction, or the use some particular effects, that could affect how it is rendered or exported?

I tried a similar experiment with a short project and also did not find any speed difference.

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Answer 6

Ian R. Brown Author

Level 7

24,503 points

Jun 21, 2013 5:57 AM in response to Luis Sequeira1

This project has no difference whatsoever that I can see, Luis, apart from adding chapter markers for the first time.

It is just 63 minutes of clips straight from the camera, not edited in any way other than having a cross dissolve between each one.

I have done the same sort of thing many times before.

No way can I replicate this behaviour in other tests.

In the good old days I could start sharing an hour long project, put the display to sleep and know that it would take around 3 hours.

If I tried it with this one I would be looking at 9 or more hours!

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Answer 7

Ian R. Brown Author

Level 7

24,503 points

Jun 21, 2013 12:18 PM in response to Ian R. Brown

I think this is destined to be one more of those unexplained mysteries which plague me.

I tested an almost identical 66 minute project (minus chapter marks) and could not get it to slow down. (I had made 3 virtually identical projects yesterday using over 3 hours of clips strung together).

I've also done a few more short test projects with and without chapter marks with no trouble but the moment I return to the original project and put the display to sleep, the encoding slows to a crawl.

I'm just pleased that it appears to be a one-off, but it's still irritating not to know why.

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