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TOPIC: 4K HEVC 8-bit?

4K HEVC 8-bit? 17 Dec 2017 18:23 #92410

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What in tarnation is this ruckus all about? 4K HEVC 8-bit? Really?

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Last edit: by FCPX.guru.

4K HEVC 8-bit? 17 Dec 2017 18:49 #92414

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OK, so from the Compressor 4.4 manual;
"8-Bit Color: Provides a good balance between picture quality and file size. (This option is available only on recent Mac computers that support hardware encoding of HEVC.)"

Now, is a 2013 Mac Pro not recent enough? What is recent enough? Mine can encode 10-bit but not 8-bit HEVC? That's nuts...

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4K HEVC 8-bit? 17 Dec 2017 21:46 #92418

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Only Skylake or Kaby Lake CPUs have 8-bit HEVC encode hardware, and only Kaby Lake has it for 10-bit. The only exception is the new iMac Pro which may use special encoding hardware on the AMD Vega64 for this, but nobody is sure.

I agree the wording of the Compressor documentation is confusing. You can obviously encode anything using software, so disabling the HEVC 8-bit preset doesn't make sense. For whatever reason the code must be implemented in one way -- only hardware-accelerated encoding for 8-bit HEVC (also called HEVC Main).

HEVC encode/decode is much slower on machines without hardware support -- much more than the software/hardware difference in H264 was. However it lets you select the HEVC 10-bit preset which is obviously software-only on a 2013 nMP, so I don't know why not 8-bit.

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Last edit: by joema.

4K HEVC 8-bit? 26 Apr 2018 02:35 #95311

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This makes no sense. On my MBP13 Early 2015, HEVC-10 bit is available but not HEVC-8 bit. Not logical.
It has a 3.1 GHz Intel Core i7 with 16 GB 1867 MHz DDR3 and Intel Iris Graphics 6100 1536 MB (top available model)

joema wrote: Only Skylake or Kaby Lake CPUs have 8-bit HEVC encode hardware, and only Kaby Lake has it for 10-bit. The only exception is the new iMac Pro which may use special encoding hardware on the AMD Vega64 for this, but nobody is sure.

I agree the wording of the Compressor documentation is confusing. You can obviously encode anything using software, so disabling the HEVC 8-bit preset doesn't make sense. For whatever reason the code must be implemented in one way -- only hardware-accelerated encoding for 8-bit HEVC (also called HEVC Main).

HEVC encode/decode is much slower on machines without hardware support -- much more than the software/hardware difference in H264 was. However it lets you select the HEVC 10-bit preset which is obviously software-only on a 2013 nMP, so I don't know why not 8-bit.

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4K HEVC 8-bit? 31 Jul 2018 15:40 #96614

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paul.atreides wrote: This makes no sense. On my MBP13 Early 2015, HEVC-10 bit is available but not HEVC-8 bit. Not logical.
It has a 3.1 GHz Intel Core i7 with 16 GB 1867 MHz DDR3 and Intel Iris Graphics 6100 1536 MB (top available model)..


This is probably because the "Broadwell" CPU in your MBP does not have HEVC hardware support, so it can't do 8-bit hardware-assisted encoding. As you can see on below chart, under HEVC Main Encode, for Broadwell it says "No": www.anandtech.com/show/10610/intel-annou...-coming-in-january/3

Any computer can do software encoding. Starting with High Sierra and FCPX 10.4, that code was already there for software-only 10-bit, so Apple just used that for your case. They could have added an additional software decision tree to check the CPU type and provide 8-bit software HEVC encoding but this would not satisfy most people. HEVC software encoding is incredibly slow. See below numbers.

The question is NOT why 10-bit and not 8-bit HEVC encoding shows up on your machine. By all rights your machine would not show either 10-bit or 8-bit options since it has no hardware for 8-bit and software encoding for either 8-bit or 10-bit is incredibly slow. I don't know why Apple enabled 10-bit HEVC encoding on any machine, since their current implementation is software only. For unknown reasons Apple does not currently use hardware acceleration for 10-bit HEVC encoding -- even on Kaby Lake and later CPUs. Maybe at the time High Sierra and FCPX 10.4 were planned, the projected user base of Kaby Lake-powered Macs which would also be doing video encoding of HEVC material was quite low.

It seems likely that in future versions of macOS and FCPX the hardware support for 10-bit HEVC on Kaby Lake and later would be used. However since your 2015 MBP doesn't have this hardware support, that will never appear.

The iMac Pro uses Xeon which does not have Quick Sync acceleration for H264 or HEVC, so it uses AMD's UVD/VCE hardware. This works fairly well for H264, although for the 4k case it's a little slower than Quick Sync on the 2017 iMac. Whether this supports 10-bit HEVC encoding, I don't know.

HEVC Encoding Results, Top-Spec 2017 iMac 27 (60 -sec UHD 4k/29.97 H264 8-bit 4:2:0 clip)
macOS 10.13.6 and FCPX 10.4.3.

4k H264 Fast Encoding: 40.1 sec
4k 8-bit HEVC: 1 min 29 sec
4k 10-bit HEVC: 54 minutes

HEVC Encoding Results, 2017 10-core Vega 64 iMac Pro (same test clip):

4k H264 Fast Encoding: 45.0 sec (typical for iMP to be a little slower than 2017 iMac at this one case)
4k 8-bit HEVC: 44.8 sec
4k 10-bit HEVC: 33 minutes

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Last edit: by joema.

4K HEVC 8-bit? 31 Jul 2018 23:20 #96617

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Contrary to my original post, an update since gave me both options. Just FYI.

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