APPLE FINAL CUT PRO: Apple Final Cut Pro X FCPX Debates FCP Legacy FCP Tutorials

How much computing power and read and write speeds do I need for 4k playback?

COW Forums : Apple Final Cut Pro X

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Terry Flaxton
How much computing power and read and write speeds do I need for 4k playback?
on Mar 29, 2019 at 11:04:32 am

I now use FCP X for 4k files - often running 4 layers and my machine is stuttering on playback

My question is what of the following should I change to eliminate stutter on playback - is it just where the library is situated in this case?

I have a mac tower 5.1
Running High Sierra 10.13.6
Processor: 2 x 2.66 Ghz 6-Core Intel Xeon
Memory: 40 GB 1333 Mhz DDR3
Startup: SSD fast 1 terrabyte
Graphics: NVIDIA Quadro K2000 2047 MB
My library is on a La cie 4tb currently writes 160 mb reads 125 mb (average)

I have a raid I can lodge the library on that can read at 260 mb and write at 560 - would this be better and how many layers of 4k could I run and how many layers of HD?

Would a pro imac do better - should I want for the next mac pro - or will this do for a while if I kit it out better

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index

Oliver Peters
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 29, 2019 at 12:37:15 pm

5K iMac, iMac Pro, 15" MBP would all do better than the tower. Although your combo should be just fine for a single layer of 4K (depending on the codec). Faster storage would also help. I would recommend a fast TB RAID on a newer machine. If you don't want to spring for a new machine yet, you could look into swapping out your GPU for a fast Radeon, increase the RAM, and build an internal RAID-0 set-up with several installation internal drives.

- Oliver

Oliver Peters - oliverpeters.com


Return to posts index

Terry Flaxton
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 29, 2019 at 12:50:26 pm

Thanks Oliver - I tried changing my question after I'd moved the library over to an internal ssd at 650 read and write (ish) no stutter: 4 layers of 4k using effects distortion grading etc.

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index


Joe Marler
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 29, 2019 at 1:23:47 pm

[Terry Flaxton] "I now use FCP X for 4k files - often running 4 layers and my machine is stuttering on playback

My question is what of the following should I change to eliminate stutter on playback - is it just where the library is situated in this case?

I have a mac tower 5.1
Running High Sierra 10.13.6
Processor: 2 x 2.66 Ghz 6-Core Intel Xeon...library is on a La cie 4tb currently writes 160 mb reads 125 mb (average)...
I have a raid I can lodge the library on that can read at 260 mb and write at 560 - would this be better and how many layers of 4k could I run and how many layers of HD?

Would a pro imac do better - should I want for the next mac pro - or will this do for a while if I kit it out better"


It depends on what codec you are editing. If it is 4k H264 (inc'l variants such as XAVC-S, XAVC-L, etc), it is almost impossible to get perfectly smooth scrubbing or skimmer performance. Mac Pros -- whether the trash can or older towers -- are especially poor at this since Xeon does not have Quick Sync. Smooth 1x playback is more achievable but few editors restrict themselves to 1x speed. For HD I don't know as my doc team has shot only 4k for several years.

The I/O load for 4k H264 is not that high -- typically about 12.5 megabytes/sec per stream. It is predominately a CPU-intensive task and cannot be meaningfully accelerated by normal GPU methods. If your timeline contains effects that can be GPU-accelerated, this helps -- but only so much. Many so-called GPU-accelerated effects also entail significant CPU load.

If your editing codec is all-intraframe, that can be a more I/O-bound task. In those case improving I/O bandwidth can help.

Especially for 4k H264, the quickest step is use proxies. These are ProRes 422 at 1/2 the linear and 1/4 the pixel resolution of 4k. Proxies have certain complications such as no alpha channel, hard-coded dependence on the original volume name and inability to relink, but in general they work very well.

If you are doing acquisition in 4k H264, it might be possible to move toward doing acquisition in ProRes, ProRes RAW or other all-intraframe codec. There are various recorders like the Atomos Ninja V which work well on several cameras. That can eliminate need for proxies, at the cost of about 4x or 6x the storage and I/O bandwidth.

That said, 125 MB/sec is not very fast -- even for 4k H264, esp for four 4k layers. 4k 8-bit 4:2:0 H264 will be over 50 MB/sec, plus FCPX does additional small random I/Os for the SQLite database which can disrupt the sequential I/O stream. If your library and cache are on a separate drive (vs the media files) this might help.

The new 8-core i9 iMac 27 is about as fast as an 8-core iMac Pro and uses a 9th-generation Intel CPU with the latest version of Quick Sync. The Intel code name for that chip is "Coffee Lake Refresh". It has some hardware mitigations for the Spectre and Meltdown vulnerabilities. On older CPUs, firmware and OS patches are used. The older the CPU the greater the performance cost of those firmware/OS patches, although this varies based on workload.

A 2019 8-core i9 iMac 27 would be vastly faster on 4k H264 than your current machine. Whether you could edit four layers of 4k H264 without proxies, I don't know. You definitely cannot on a 10-core Vega 64 iMac Pro. The iMac Pro will be quieter under high load but early tests indicate the 2019 i9 iMac is quieter than the 2017 model. The iMac Pro also does not have Quick Sync but FCPX uses the similar UVD/VCE hardware acceleration on the AMD Vega GPU. It is not as fast as Quick Sync but it's much better than previous Xeon-powered Macs. The iMac Pro has multiple Thunderbolt channels and 10-gig ethernet, whereas the 2019 i9 iMac has a single Thunderbolt controller and 1-gig ethernet, but this is adequate for many tasks.

Nobody has any details on the upcoming modular Mac Pro. It will likely be Xeon powered and might use some kind of upgradable stackable modules with a proprietary high-bandwidth connector, vaguely like a RED camera.


Return to posts index

Terry Flaxton
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 29, 2019 at 4:54:34 pm

Hi and thanks for that explanation - so I input pro res 422 - so the thought of these being transcoded to H264 is a horror story straight off the bat. Fine if they're reference fils to take instructions back to the original media - but having only in the last could pf years embraced FCPX I haven't understood wht the under the bonnet stuff is and how it works.

Take a for instance: if I output a 4k pro res 4444 file and re-input it for use as a layer - does this really mean it's been then taken to H264 for manipulation by FCPX - if that's the case that's killer because I have to screen at minimum 20 foot and up...

I realise I probably don;t understand this and am looking for simple structural understanding of FCPX - is there anything out there? To be frank it should just be a one pager because anything else would be the addendum to the fundamentals (i.e in case a such and such, in case b, such and such.

Thanks in advance...

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index

Joe Marler
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 30, 2019 at 11:47:57 am

[Terry Flaxton] "so I input pro res 422 - so the thought of these being transcoded to H264 is a horror story straight off the bat. Fine if they're reference fils to take instructions back to the original media - but having only in the last could pf years embraced FCPX I haven't understood wht the under the bonnet stuff is and how it works."

If your camera records in 4k H264, then if you import that to FCPX and do not create proxies or optimized media, you are editing 4k H264. That is your editing codec. However -- internally FCPX edits in ProRes, even for H264 media -- IOW the render scratch files are ProRes. But these render files are somewhat short lived and often invalidated by editing steps, which can result in frequent re-rendering. The dotted line above the timeline means it's not rendered.

Normally FCPX is fast enough to edit a non-rendered timeline, so you don't need background rendering enabled in FCPX preferences. You usually don't need to manually render the timeline with CTRL+R -- at least on a contemporary machine. However 4k H264 is a difficult case (esp. for multiple layers or multi-cam), and in that case it's often better to use proxies or optimized media.

Either during import or after import you can optionally create optimized media or proxies. Optimized media is full-res 4k ProRes 422, proxies (for 4k originals) are 1080p ProRes 422. Optimized media is typically about 4x to 5x the size of H264. Proxies are about 60% the size of the originals. To use proxies you must set the viewer to View>Proxies. For optimized media it will automatically use that. Optimized media and proxies are all intraframe and much faster to decode/encode, so editing is smoother. However due to the larger size, I/O bandwidth is more often an issue.

[Terry Flaxton] "...Take a for instance: if I output a 4k pro res 4444 file and re-input it for use as a layer - does this really mean it's been then taken to H264 for manipulation by FCPX - if that's the case that's killer because I have to screen at minimum 20 foot and up...

If your editing codec is H264 you can output that as 4k ProRes 422, 4444, etc. then re-import that. However it's normally easier to just create optimized media within FCPX. One benefit to output then re-import is to "bake in" a computationally-intensive effect like Neat Video noise reduction, but normally you'd just wait and apply that as the last editing step.

If your original content is 4k H264 8-bit 4:2:0, then transcoding that to ProRes 4444 will not create any more useful resolution, luma or chroma data. The final quality won't be any better.

It does not improve image quality to transcode ingested content from H264 to optimized media. This is only a performance enhancement. FCPX does not internally re-write H264 edits. The list of edit steps are stored in a SQL database, then during render the H264 media is read, those edit steps are applied and the result is an internal render file or (for export) a rendered timeline encoded in the desired codec.

You don't want to export H264 then re-import that, which would entail "generation loss" due to re-compressing an interframe codec. Any round-trip should ideally be in ProRes or similar codec.

[Terry Flaxton] "...I realise I probably don;t understand this and am looking for simple structural understanding of FCPX - is there anything out there?"

There are numerous tutorials available. See MacBreak Studio: https://www.youtube.com/playlist?list=PLj5Nh9NxSxdlDLI_z-GBII8_vTXD7J5AL

For a detailed FCPX media management tutorial, Ripple Training has a good one:
https://www.rippletraining.com/products/final-cut-pro/media-management-in-f...


Return to posts index


Terry Flaxton
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 30, 2019 at 12:23:31 pm

Well thank you so far for answers - It may all be in my head but the proposal about using 264 is against everything I've ever done for this reason: H264 is a very compressed codec - a GoP structure which inherently means at best a display codec (and that was what it as originally designed for). Group of pictures leave out various frames and 'Long Gops' are the worst for colour and movement. 422 Pro Res is better - but it is still lossy (which is why you get choices). Yes they're all based upon wavelet transforms as opposed to DCT's but that can only do so much.

So casually going in and out of 264 is a problem because you're trashing your quality each time you go in and out of it.

So: If I want to stay at least in Pro Res - how do I make FCPX stay true to the input codec? Is this about NOT optimising media?

Thanks in advance

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index

Joe Marler
Re: How much computing power and read and write speeds do I need for 4k playback?
on Mar 30, 2019 at 2:13:08 pm

[Terry Flaxton] "It may all be in my head but the proposal about using 264 is against everything I've ever done for this reason: H264 is a very compressed codec...422 Pro Res is better...So casually going in and out of 264 is a problem because you're trashing your quality each time you go in and out of it.

So: If I want to stay at least in Pro Res - how do I make FCPX stay true to the input codec? Is this about NOT optimising media?"


During ingest of H264 material to FCPX you can create optimized ProRes media or you can do this after ingest by selecting the clips in the Event Browser, right-click, transcode and pick "Optimized Media". It will create full-res ProRes 422 versions of the media and use that for all edit or color correction operations but from a quality standpoint it won't be any different than just editing the H264 material.

FCPX never re-compresses or re-encodes when editing an H264 timeline. You can make 1,000 edits or color correction steps to the same clip and it will be no different quality than if that clip was transcoded from H264 to ProRes and those same 1,000 edit steps done to the ProRes version.

If your camera media was H264 at a certain resolution, bit depth and chroma sampling, the quality was fixed for all time during acquisition. Transcoding that to ProRes will not help quality -- but it can help editing performance.

*Acquiring* in ProRes is generally better from a quality standpoint (vs H264), but only because it often captures more sensor data. E.g, our Panasonic DVX200 can only internally record 4k 8-bit 4:2:0, but externally to an Atomos Ninja V it can record 10-bit 4:2:2 ProRes. Commonly, H264 is 8-bit 4:2:0 but there are exceptions.

The Panasonic GH5 can record inter-frame H264 4k 10-bit 4:2:2 internally, and if compared to HDMI ProRes 422 capture of that same stream, there's not much difference. The ProRes is easier to edit but the image quality, dynamic range, chroma sampling are similar. In FCPX the H264 version will not degrade with subsequent editing because FCPX is not like Photoshop -- it's not re-editing and re-writing the same compressed data. In FCPX the edits are stored as metadata in a SQL database.

Re export and playback for large screen formats, it's important to consider the playback chain. You hypothetically might want to export 4k ProRes 422 or higher, but some playback devices can't handle the data rate. The output signal chain might not handle the resolution or fail during the EDID/HDMI handshake. If time permits, export a 720p, 1080p and 4k H264 version, plus a 1080p and 4k ProRes version, then test them all at the venue ahead of time. If it can't be tested, then having a 720p or 1080p H264 version might enable playback if the venue's equipment is antiquated. During playback testing, especially scrutinize gamma since there is often lack of standardization on how this is handled. E.g, VLC playback of an FCPX Quicktime file shows different gamma than playback with Quicktime 10 player. Obviously the venue audio should also be tested for sync and quality.

If the venue requires a Digital Cinema Package, here is a discussion on that: https://forums.creativecow.net/docs/forums/post.php?forumid=335&postid=1010...

Many projectors are not 4k and even if 4k, the THX-recommended viewing distance is less than one screen width. Further away and the viewer cannot perceive 4k: https://www.engineeringcalculator.net/home-theater-calculator.html


Return to posts index

Doug Metz
Re: How much computing power and read and write speeds do I need for 4k playback?
on Apr 1, 2019 at 4:29:11 pm

Hey Terry,

I think Joe is assuming you are ingesting H264 from the get-go. I'm getting the impression you ingest ProRes. Could you share your acquisition workflow steps to clarify?

Doug Metz

Dalton+Anode


Return to posts index


Terry Flaxton
Re: How much computing power and read and write speeds do I need for 4k playback?
on Apr 1, 2019 at 5:13:53 pm

Doug - spot on. I tried to say that I wouldn’t use H264 as it was designed as a display codec (if I had a choice that is).. So I start with 1920 x 1080 Pro Res 422 or 3749 x 2160 Pro Res 422. Then edit and manipulate - sometimes output a file at 4K 422 or even 4444 if I want an alpha channel then reimport and manipulate again. Eventually I want a 4K pro res 422 HQ. So if I’m fact any of this is dipping down to 264 - that’s be worrying. Thanks in advance - Terry

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index

Doug Metz
Re: How much computing power and read and write speeds do I need for 4k playback?
on Apr 1, 2019 at 6:48:26 pm
Last Edited By Doug Metz on Apr 1, 2019 at 7:50:21 pm

If your source material is all ProRes, then H264 doesn't enter the equation.

Given the ProRes source, it may be that you just don't have a big enough pipe from the LaCie to your Mac. Are you using eSATA for that?

As always, Joe's got lots of great info above. Make note of the delivery conditionals, gamma gotchas, and data rates.
Doug Metz

Dalton+Anode


Return to posts index

Terry Flaxton
Re: How much computing power and read and write speeds do I need for 4k playback?
on Apr 1, 2019 at 8:33:09 pm

Doug you've made me a happy man. If I can ingest pro res and get it out - all is well.

I moved everything to an SSD and things are now working fine - I got 8 x 4k layers flowing without a stutter.

Thanks for your help (and everyone else) often it's asking the Right question to cut it all down.

Thanks again.

Made my first video in 1976, A long term programme maker, DP, editing etc - changing with AR/VR/MR media -


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2020 CreativeCOW.net All Rights Reserved
[TOP]