Exporting 10-bit video in FCPX

[Gary Huff]

You can export a 10-bit H.265 (HEVC) from Compressor, but not H.264 (AVC). If your LG TV has HEVC support, then I would export using that.

[Jeff Kirkland]

Apart from some limited use encoders that were more experimental than anything, there is no 10-bit version of h264. Certainly, as far as I’m aware, there are no hardware 10-bit decoders. As Gary mentioned, you need to move to H265 to export and play 10-bit.

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Jeff Kirkland | Video Producer & Cinematographer
Hobart, Tasmania | Twitter: @jeffkirkland

[Cees Timmer]

@Gary and Jeff:
Thanks for your response. My LG TV supports HEVC. As you indicated there is no hardware 10-bit encoding for HEVC like Quick Sync for 8-bit H264. Therefore, HEVC export takes much more calculation time than H264. I read on the internet that from an image quality point of view, there’s no real difference between H.264 and HEVC.

Nevertheless it is good to hear that it is possible and I will certainly give it a try.

[Joe Marler]

[Jeff Kirkland] “there is no 10-bit version of h264. Certainly, as far as I’m aware, there are no hardware 10-bit decoders. As Gary mentioned, you need to move to H265 to export and play 10-bit.”

There are 10-bit Long GOP H264 codecs, but as you say, this is not that common and you may frequently encounter various issues.

The Sony FS5 can do 10-bit 4:2:2 H264 using XAVC-L, and the Panasonic GH5 can do Long GOP 10-bit 4:2:2.

You then get into issues on both editing and playback. Does the NLE and version of Quick Sync (or AMD’s UVD/VCE on the iMac Pro) support 4k 10-bit 4:2:2 H264? Even if you could export 10-bit H264, would the playback device handle that? TVs probably have an ASIC for H264 decoding but I tend to doubt it’s designed for the less common 10-bit format.

Exporting 10-bit HEVC is possible but I don’t think FCPX/Compressor on any current Mac supports hardware acceleration for 10-bit HEVC. It is incredibly slow. Macs using the “Kaby Lake” CPU or later (e.g, the 2017 iMac) have hardware support for 10-bit HEVC encoding. Unfortunately FCPX/Compressor do not use this.

In December 2018 I tested this on a 2017 i7 iMac 27 using FCPX 10.4.3 and Mojave 10.14.1.

A 4k XAVC-S 63-second test file had these export times:

4k H264 “Fast Encode”: 40 sec
4k HEVC 8-bit: 1 min 23 sec
4k HEVC 10-bit: 40 min 15 sec

I just re-tested this using FCPX 10.4.6 and Mojave 10.14.4, and it’s not greatly different. They may have optimized HEVC software encoding but it’s still extremely slow. On prior versions, 10-bit HEVC encoding was 29x slower than 8-bit. Now it’s only 15x slower.

FCPX still does not use the available hardware acceleration in the Kaby Lake CPU for 10-bit HEVC encoding.

Re image quality of H264 vs HEVC, in theory HEVC produces about the same image quality at 1/2 the bit rate, or better image quality at the same bit rate. However — this is *highly* variable and codec dependent. The DJI X5S camera on our Inspire 2 drone produces much *worse* image quality using 8-bit HEVC than 8-bit H264 at the same bit rate. For that reason we only shoot ProRes.

[Cees Timmer]

I found out that QuickTime Player can export H265. A ProRes 4K 10-bit 4:2:2 clip (489 Mbps) will be exported as 4K 10-bit H265 (15 Mbps) by QuickTime Player. However, the chroma subsampling went down to 4:2:0. No problem playing this clip on my LG TV.

What about the chroma subsampling when encoding 4K 10-bit HEVC with Compressor?