Handbrake encoding slower with external monitor on macbook?

[iOrbit]

what effects handbrake encoding times? or CPU power/usage in MacBook pros?


today i began encoding a movie, i tried 3 different movies - and they all had the same experience - handbrake was quoting up to 6 and a half hours - even stayed this way after %25 of the encode was done. i knew something wasnt right. in my mind it couldn't be because the macbook was in clamshell mode in my 'bookarc' with the external monitor plugged in.

but it seems it was! when i unplugged it and used it how i usually do - handbrake has not quoted the same encode as before as 3:32 for time.

this is the same movie that it quoted me for 6 hours on. the avg FPS in clamshell was between 4-6.

now in my usual use of the laptop its back up to 12FPS. what is going on?

 

[dynaflash]

Likely in "clamshell" mode (presuming you mean closed) the mbp is getting hotter and thermal throttling when using HB. HB will typically peg your cpu (s). You want all of the cooling you can get.

Now, that said to really have evidence you would want to complete the same exact movie with exactly the same preset in both setups and use the activity log to verify the actual encoding fps which is reported there which will look like this :

[14:06:42] work: average encoding speed for job is 23.503603 fps

 

[iOrbit]

Likely in "clamshell" mode (presuming you mean closed) the mbp is getting hotter and thermal throttling when using HB. HB will typically peg your cpu (s). You want all of the cooling you can get.

Now, that said to really have evidence you would want to complete the same exact movie with exactly the same preset in both setups and use the activity log to verify the actual encoding fps which is reported there which will look like this :

[14:06:42] work: average encoding speed for job is 23.503603 fps

well, i'll do this on the next encode after the current job. i think you must be right because i keep an eye on my Temps with istat -

i notice generally my macbook pro uses its fans more in clamshell but that CPU temp hovers around 78 during handbrake, not as high as 89 as seen in non clamshell mode.

thanks a lot for replying and helping