Why the absurdly long export times for H265?

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
I have a late 2015 Imac with an I5 3.3 & Radeon 395 & 24 gigs RAM. Export times on FCP X using H264 are generally done in real time or a bit less. However exporting HDR/HLG H265 clips via Compressor take in the ballpark of 16-18x real time! I don't understand why this is such an apparent drag on the system.

I had tried the new MM with an I7 with 16gigs RAM and the export times were very similar and just a tad quicker with H265 & Compressor. Yesterday I went over to an Apple store and did the best I could to approximate what it would be on an Imac Pro. Unfortunately I was unable to use the same clips I did for these other tests since they have it locked out for either an external drive or even an SD card. But using their own project, I exported a 1 minute clip to H265 and got a similar, very long export time of about 18x real time. That surprised me too given the muscle of the Imac Pro.

Interestingly, I also use Edius Professional on a PC with an HP All-In-One and for whatever reason, H265 export times with the same project are only 2x real time, a hugely faster export experience. Yet the export times for H264 on the HP are considerably slower than they are via FCP.

Does anyone have any ideas on this or how export for H265 can be improved on FCP X/Compressor?
 

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
8 bit Sony A7iii HLG clips to HEVC output on FCP/Compressor. This preserves the HDR on either YouTube or an HLG enabled display. 10 bit HLG clips from a GH5 run 23x real time. Ouch!
 
  • Like
Reactions: jerwin

chrfr

macrumors G3
Jul 11, 2009
8,178
2,509
8 bit Sony A7iii HLG clips to HEVC output on FCP/Compressor. This preserves the HDR on either YouTube or an HLG enabled display. 10 bit HLG clips from a GH5 run 23x real time. Ouch!
H.265 is done completely in software on a computer that old, while H.264 is (or at least can be) hardware accelerated so it should be expected that there's going to be a huge difference in processing speed. I'd suspect that you'd need to determine specific settings to do it, but should be able to get much better performance on the newer computers.
This may be useful reading: https://larryjordan.com/articles/first-look-hevc-vs-h-264-in-apple-compressor-4-4/
 
Last edited:
  • Like
Reactions: Gorms

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
H.265 is done completely in software on a computer that old, while H.264 is (or at least can be) hardware accelerated so it should be expected that there's going to be a huge difference in processing speed. I'd suspect that you'd need to determine specific settings to do it, but should be able to get much better performance on the newer computers.
This may be useful reading: https://larryjordan.com/articles/first-look-hevc-vs-h-264-in-apple-compressor-4-4/
Thanks, but I got similar times on both the new I7 MM and the new IMac Pro. In fact that’s why I initially bought the new MM.

So I’m really seeing little difference between my IMac, the new MM and the IMac Pro. It seems the limitation is Compressor. But Compressor is needed if you’re doing H265 from FCP
 

EugW

macrumors 604
Jun 18, 2017
7,297
4,683
upload_2018-11-20_20-56-13.jpeg


Apple does hardware 8-bit HEVC encode on Skylake 6th generation or later. Assuming you have the i5-6600 then it will be supported, since that is a Skylake CPU.

However, for 10-bit HDR HEVC encode, Apple strictly uses software encode. It’s moot for you though since Skylake doesn’t support this in hardware anyway. Kaby Lake does but for some reason (quality?) Apple doesn’t support this in their software regardless of the hardware support. That’s too bad since the hardware support is already built into 2017 Kaby Lake Macs.
 
Last edited:

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
View attachment 805569

Apple does hardware 8-bit HEVC encode on Skylake 6th generation or later. Assuming you have the i5-6600 then it will be supported, since that is a Skylake CPU.

However, for 10-bit HDR HEVC encode, Apple strictly uses software encode. It’s moot for you though since Skylake doesn’t support this in hardware anyway. Kaby Lake does but for some reason (quality?) Apple doesn’t support this in their software regardless of the hardware support. That’s too bad since the hardware support is already built into 2017 Kaby Lake Macs.
Thanks, that probably does explain what I’m seeing with some exports in Compressor. I’m not sure I tested 8bit HLG Sony HEVC clips as an 8bit export. I need to keep HLG as a 10bit export or its not recognized as HLG by either an HLG capable display or YouTube. I’m curious though to try an 8bit HEVC export to see if speeds are relatively fast.

It’s odd that Edius Professional is so fast with 10bit HEVC exports (2x real time) on my PC. Certainly my HP All-In-One is not a souped up machine, but Edius does have a reputation of being very fast on the software end.

I might just have to resort to Edius for HLG/HDR work and use FCP for SDR projects.
 

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
Is it based on a more recent chip?

Apparently, Skylake isn't that flexible when it comes to encoding HEVC

https://www.anandtech.com/show/10610/intel-announces-7th-gen-kaby-lake-14nm-plus-six-notebook-skus-desktop-coming-in-january/3
The HP has an I7 7700T, 2.9-3.8 turbo. Not a powerhouse. The graphics card is an Nvidia GTX950M. The new MM I had (and since returned) had a more powerful and newer I7, yet far slower H265 export times.

I’m wondering if the H265 high speed export in the HP computer is due more to the Edius software than the computer itself?
 

EugW

macrumors 604
Jun 18, 2017
7,297
4,683
The HP has an I7 7700T, 2.9-3.8 turbo. Not a powerhouse. The graphics card is an Nvidia GTX950M. The new MM I had (and since returned) had a more powerful and newer I7, yet far slower H265 export times.

I’m wondering if the H265 high speed export in the HP computer is due more to the Edius software than the computer itself?
i7 7700T has full hardware 10-bit HEVC encode, if the software supports it.

Mac mini hardware supports it but macOS and Compressor do not.
 

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
i7 7700T has full hardware 10-bit HEVC encode, if the software supports it.

Mac mini hardware supports it but macOS and Compressor do not.
AH! Bingo. Thanks, this finally makes sense. It’s pretty obvious to me, based on H265 export times, Edius Professional does support the hardware on the software side.

I guess we can hope that Apple will soon offer OS/Compressor support for this. I like Edius, but prefer FCP.
 

EugW

macrumors 604
Jun 18, 2017
7,297
4,683
AH! Bingo. Thanks, this finally makes sense. It’s pretty obvious to me, based on H265 export times, Edius Professional does support the hardware on the software side.
It does according to its website.

upload_2018-11-21_8-17-14.png


i7-7700T is 7th generation.

Note though that the late 2015 iMacs are 6th generation.

I guess we can hope that Apple will soon offer OS/Compressor support for this. I like Edius, but prefer FCP.
We have been hoping since the Sierra days. We are now on Mojave, two OSes later with no change.
 

vidguy7

macrumors member
Original poster
Nov 12, 2018
35
21
New York
In light of that, my best approach would be to use Edius for HDR and FCP for everything else. I’ve used Edius for years and they always were able to max out your hardware on their software side. That’s always been their claim to fame.

I’ll upgrade my IMac when & if Apple makes these changes. BTW, it also explains why even the IMac Pro I tested, was virtually as slow. As I said, thanks, it all makes sense now.