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+---- Thread: Multi-threaded software decode ? (/showthread.php?tid=205259)
Multi-threaded software decode ? - DBMandrake - 2014-09-27
Hi All,
Could one of the devs comment on whether XBMC supports multi-threaded software video decoding on Mac OS, or indeed any platform ?
I was always under the impression that multi-threaded decode was supported but my testing today shows that software decoding an H.264 MKV on Mac OS is most definitely single threaded, leaving some 40% of the total combined CPU time idle when trying to play a 30Mbps file which is dropping frames because vcpu is pegged to 100%...
This is both 13.2 and a recent Helix Alpha.
Thanks.
RE: Multi-threaded software decode ? - Ned Scott - 2014-09-27
Yes, but it has to be specifically enabled due to stability reasons. Make sure the settings level is set to advanced and go to: XBMC/Kodi -> Settings -> Videos -> Acceleration
That should allow you to turn on multithreading, which also disables hardware video decoding.
RE: Multi-threaded software decode ? - DBMandrake - 2014-09-27
Cool, I'll give that a try.
I'm assuming it's not present in Gotham then ?
RE: Multi-threaded software decode ? - Ned Scott - 2014-09-27
It is present in v13 Gotham.
RE: Multi-threaded software decode ? - DBMandrake - 2014-09-27
Well I'm stunned.
I've been an XBMC user for close on two years and even participated in development/debugging, but I never realised that having hardware decoding turned on (even if it was falling back to software decoding because hardware decoding wasn't supported) would disable multi-threaded decoding...
If so there is a bug in the UI in Helix - not only does it show "allow multi-threaded software decoding" as on when hardware accelerated is enabled, it even lets you toggle it on and off. There is no indication that the multi-threaded decoding option does nothing unless software rendering is also selected.
That's not the case on Gotham though, where selecting hardware decoding both toggles multi-threaded off and greys it out...
The difference in performance on Gotham is amazing - it gives the old Mac a whole new lease on life!
Without multi-threaded decoding it can software decode up to about 25Mbps without dropping frames but with multithreading enabled it's managing 45Mbps (tested with the jellyfish clips) without dropping a single frame and almost managing 50Mbps - that's on a 1.83Ghz Core 2 Duo... It might even be fast enough for full bitrate blu-ray rips. (I don't have any to test though)
On the latest Helix build performance isn't as good though - with multi-threading enabled it can now just manage 40Mbps but no way can it manage 50Mbps...
RE: Multi-threaded software decode ? - Memphiz - 2014-09-28
yes its a bug in the ui / settings dependencies - there is a pr for this already which will fix it (allowing multithreaded sw decode even if hw decoder is enabled.