Will this iMac be good enough for 4K video editing?

[Mat Mayer]

Finally settling down for a while so jumping on the chance to get another iMac. I have seen this one almost half the price of the top spec one and it looks good enough to me on paper. Anyone have any real world experience with the same or similar specced iMac? Is it enough for 4K editing; pretty basic timelines exporting as HD H.264 at 9 bitrate, 4K at 25 bitrate, and 4K H.265 at 13 bitrate: on MP4. Will be just using footage in UHD from G7 and GH4 recorded at 100Mbps (but likely to get the GH5 next year). I currently have a standard 1TB hard drive, i7 2.7GHZ, 2GB 960M graphics card, 16GB RAM (Windows 10), so I appreciate rendering will be slow- just wondering if any specific tweaks will make a big difference like either better GPU or SSD or i7 for example?

• 3.2GHz quad-core Intel Core i5 processor
• Turbo Boost up to 3.6GHz
• 8GB (two 4GB) memory, configurable up to 32GB (I will add an extra 16GB myself)
• 1TB Fusion Drive1
• AMD Radeon R9 M390 with 2GB video memory
• Retina 5K 5120x2880 P3 display

Thanks. So excited to get back on the iMac train with a 5K 27" screen 

[fuzzynormal]

Directly editing h.264 just stinks.  Even on a zippy machine.  It'll work --and I do it all the time for short TRT projects, but I still like to edit with transcoded files.  Or, better yet, edit with proxies.  Once you start doing that, a modern machine will slice and scroll through stuff without much effort.  It's pretty cool.

Lagging video when trying to set heads/tails or just previewing a clip is the worst.

Premiere CC 2015.3 has been very effective for me with proxies.  My assistant editor even does work on our 7 year old Mac with LUMIX UHD footage.  Works great.  With proxies you can use cheap slow drives for editing, so it's a great way to stretch a budget and still be productive.

FCPX is also well regarded in this area too.

Resolve also does "proxies" by creating "Optimized" media, but I had a hell of a time making that work.  Too buggy.  Moved onto Premiere.  Not my fav editing platform, but it's robust enough to handle my documentary workload.  Decent media management tools too, I think.

[Mat Mayer]

Naaaa, I like the simplicity of sticking with camera files, but it's nice to know the option is there for proxies. I just export single 20 minute scenes, so a single frame preview is all that is needed. Plus I want that new 5K screen after using a cheap monitor for 2 years and an average laptop.

Strangely noticed on my Windows machine using 8-10 settings in Lumertri on PP CC made the preview render take quite a while last night, whereas the built in LUTs were near instant. Can't use the usual preview window at moment (video only visible at export stage), maybe because subscription expired. So getting some LUT packs might be a big help? I have been going for less flat in-camera settings recently too, so new stuff may just need contrast and saturation tweaking.

Just been to look and torn between the one in 1st post (£1600) and upgrading to i7 and the next step up graphics card (M395 with 2GB) for £500 extra.

 

[joema]

5 hours ago, Mat Mayer said:

Naaaa, I like the simplicity of sticking with camera files, but it's nice to know the option is there for proxies...Plus I want that new 5K screen after using a cheap monitor for 2 years and an average laptop....Just been to look and torn between the one in 1st post (£1600) and upgrading to i7 and the next step up graphics card (M395 with 2GB) for £500 extra.

The problem is H264 4k is four times the data of 1080p. It is an incredible load on any editing machine. Even FCPX can struggle with this on a top-spec 2015 iMac 27, and it uses hardware accelerated Quick Sync on Sandy Bridge and later Intel CPUs (excluding Xeon). 

GPUs by themselves cannot meaningfully accelerate H264 encode/decode, so import, export and scrubbing the timeline is mostly a CPU-oriented task if no effects are used. Effects can often (but not always) be GPU-accelerated, but this does not remove the CPU load from H264 encode/decode -- it just adds another burden.

The bottom line is if you want fluid, responsive H264 4k editing you generally need to use proxy files -- whether on Premiere CC or FCPX. A higher-end Mac Pro or powerful Windows workstation might be able to avoid that but not an iMac. I edit lots of 4k every day on my 2015 top-spec iMac 27 using both FCPX and Premiere CC. It does fine on 1080p, but for my taste it's just not fast enough on 4k without using proxy files, except in limited situations for small single-camera clips. Other people might tolerate some sluggishness but it gets irritating pretty quickly.

Since the iMac is about to be refreshed I'd recommend waiting to see what that includes. For the first time in several years, new 14/16nm GPU technology is available which may provide a significant increase on the GPU side. Although the GPU is mostly only usable for effects, this is still an issue so the more GPU horsepower the better.

E.g, if just editing seems slow on 4k, try applying a computationally-intensive effect like Neat Video noise reduction. This and similar effects are incredibly slow to run on 4k, whether using GPU or CPU rendering. For effects using GPU rendering, at least there is an option of using a faster GPU on machines where this is available.

[Justin Bacle]

Editing FullHD 1080p H264 AVCHD with a Color Correction LUT and a Grading LUT (on premiere CC) on my i7 4790k with 16Gigs of ram is not pleasant.
So I'm pretty sure it'll lag quite a bit more if you don't transcode it :s

[Mattias Burling]

Final cut would handle it lag free on an old mba without a dedicated gpu. Thats one of the reasons I switched from Premire to a FCPX/Resolve combo at home after 6 years of Premiere.

[Mat Mayer]

I didnt realise they are about to bring out new ones, thought that was just Macbook Pros.

Maybe I will give Final Cut another try then on my old MBA. I remember it having inflexible export settings when i last had an iMac a few years ago, but I will have another look. Edit: Jesus, just learned this doesn't even export H.265 yet. And I need to be able to choose the export bitrate. This jamoke software lets you choose things like "Best" instead of a specific value. Looks like you have to use a separate software just for that (Compressor). Sticking with the devil I know PP: drag and drop, edit color, then export. Slow but it works. Looks like 28th October is when new iMacs might be announced.

Thanks guys, might of just saved me £2049 plus whatever the extra 16GB RAM would of cost. After doing lots of Youtubing and Googling I decided it was essential to get the 4.2 Ghz i7 option with 2TB Fusion drive (has 128gb SSD, 1TB only has 24GB SSD) and M395 2GB GPU.

[joema]

3 hours ago, Mat Mayer said:

....just learned this doesn't even export H.265 yet. And I need to be able to choose the export bitrate. This jamoke software lets you choose things like "Best" instead of a specific value. Looks like you have to use a separate software just for that (Compressor). Sticking with the devil I know PP: drag and drop, edit color, then export. Slow but it works. Looks like 28th October is when new iMacs might be announced....

FCPX exports to H264 at about 3.5x to 4x the performance of Premiere on Macs with Sandy Bridge or later CPUs (excepting Xeon on the Mac Pro). It is a huge performance difference. The CPU load during editing is much lower on FCPX, maybe because Apple uses Quick Sync which Premiere does not, at least on Mac.

That said you're right FCPX does not yet support H265/HEVC and Premiere does but H265 is new and has limited support everywhere. To my knowledge the only camera which used that was the Samsung NX1 which was cancelled. If you give an H265 file to somebody they might not be able to play it without specific help, and if their computer doesn't have specialized H265 hardware acceleration it won't play smoothly. I've tested numerous 4k H265/HEVC files on my 2015 top-spec iMac 27 and several of them play sluggishly in any available player. 

The computational load of H265 CPU can be up to 10x that of H264, which is why hardware support for H265 encode/decode will be important -- whenever H265 becomes widely adopted.

Re Compressor, this costs $49 (one time purchase) which is the same as Adobe's monthly rental fee for their suite including Premiere CC.

If I had to edit a lot of H264 4k using Premiere CC, I would personally build a powerful Windows PC for that, not use a Mac.

Premiere's recently-added proxy feature makes a huge improvement when editing H264 4k files.

[Mat Mayer]

Thanks for the proxy info, I will look into that. But I MUST export H.265 files and H.264 files in an MP4 wrapper at SPECIFIC bitrates. So FCPX is not a possibility. I have exported plenty of H.265 already. I have very simple timelines (just one clip to grade) and am not using PP more than once a week, so slow performance is cool. I have PP templates to use too, so want to stay with that. Hopefully the new Macs at the end of this month will be a nice step up in speed. My mediocre Windows laptop is good enough for editing, so I just want the best bang for my buck with an iMac screen as they are so much nicer to use.

My experiece is that more new 4K SMART TVs play H.265 than H.264 (they generally play both but some manufacturers like Vizio seem to of skipped H.264). I dont know why computers can't play them, but they generally have trouble with H.264 in 4k too in my experience. The H.265 files are far smaller which is why I assume the TVs want to play them- in readiness for streaming smaller files. I think H.265 will be the norm next year and am hoping that cameras start filming in it too, starting with the GH5.

[joema]

1 hour ago, Mat Mayer said:

...I MUST export H.265 files and H.264 files in an MP4 wrapper at SPECIFIC bitrates...I have very simple timelines (just one clip to grade) and am not using PP more than once a week, so slow performance is cool. I have PP templates to use too, so want to stay with that. Hopefully the new Macs at the end of this month will be a nice step up in speed. My mediocre Windows laptop is good enough for editing, so I just want the best bang for my buck with an iMac screen as they are so much nicer to use.

My experiece is that more new 4K SMART TVs play H.265 than H.264...I dont know why computers can't play them, but they generally have trouble with H.264 in 4k too in my experience... The H.265 files are far smaller which is why I assume the TVs want to play them- in readiness for streaming smaller files. I think H.265 will be the norm next year and am hoping that cameras start filming in it too, starting with the GH5.

Well, you know your own needs and if you're experienced with PP just stay with that. The problem is H.265/HEVC is extremely compute-intensive. A new 4k TV can handle this since they can add hardware support for H.265 decoding. Digital TV broadcasts currently use H.264, as does Blu-Ray but to squeeze 4k into over-the-air channel bandwidth will require H.265. Testing is ongoing and years in the future the upgraded ATSC 3.0 TV standard will support that. This will also probably be used for satellite and cable providers but that is years away. UHD Blu-Ray will apparently use H.265/HEVC but the decoding for that is currently only available in stand-alone hardware players. I don't think any PC or Mac can play a 4k UHD Blu-Ray disc.

The Quick Sync in Intel's Skylake (used in the 2015 iMac 27) supports H.265 hardware acceleration for 8-bits per color channel, so if playback and editing software supports that it will be vastly faster. The upcoming Kaby Lake on-chip will support H.265 at 10-bits per color channel, but that will not be used for broadcast FCPX has used Quick Sync for years but unfortunately Adobe has not put this in PP for the Mac yet. They made some ambiguous statements at the last PP update which might imply they began using Quick Sync on PP in Windows.

nVidia has hardware support for H.264 and H.265 in certain graphics cards, via the NVENC API. Likewise AMD has this in certain cards, accessed via the VCE API. However software developers must write to those APIs, and there are various versions and many different cards out there. Note this fixed-function logic for video acceleration is separate from the GPU, although it is bundled on the GPU card in a different chip. The software API fragmentation between NVENC and VCE plus the multiple versions of those discourages developers from using them. By contrast most computers with an Intel CPU Sandy Bridge and later has Quick Sync (excepting Xeon) so it's a broader platform to target.

The problem with Macs is you can't change the GPU card to obtain better performance or to harness new software which has recently added support for NVENC or VCE. So (hypothetically speaking) if Adobe chose to support nVidia's NVENC over Quick Sync, there would be nothing the typical Mac owner could do, since recent Macs use AMD GPUs.

[fuzzynormal]

15 hours ago, Mat Mayer said:

I like the simplicity of sticking with camera files.

Simple is better, until it isn't.  I'd suggest trying the proxy work flow a few times and compare.  Those 2 or 3 second delays when dealing with h.264 footage tend to add up over the course of a longer edit.

7 minutes ago, joema said:

nVidia has hardware support for H.264 and H.265 in certain graphics cards, via the NVENC API.

It does, and I do utilize that feature, which is nice.   Still, when things hum with along proxy footage it then becomes rather difficult to go back to a slower workflow; even if it's not a lot slower.

6 hours ago, Mat Mayer said:

this doesn't even export H.265 yet.

Why exactly are you wanting to export h.265?

[Mat Mayer]

13 hours ago, fuzzynormal said:

Simple is better, until it isn't.  I'd suggest trying the proxy work flow a few times and compare.  Those 2 or 3 second delays when dealing with h.264 footage tend to add up over the course of a longer edit.

Why exactly are you wanting to export h.265?

I don't have longer edits so those 2-3 second delays dont matter. I make different videos to you- they are simple videos not films. I use H.265 because more TVs can play it, the files are less than half the size to download (saves lots of money) and it will be a big deal for streaming. My home wifi couldnt stream an 8GB movie so I had to plug in a hard drive to the TV, it can stream smaller files. 

[fuzzynormal]

Fair enough. Good luck. 

[Xavier Plagaro Mussard]

If you use FCP X you won't have any problem. I use it with a Macbook and it cuts through those 100mbps 4K files!

[BenEricson]

On October 10, 2016 at 7:33 AM, Justin Bacle said:

Editing FullHD 1080p H264 AVCHD with a Color Correction LUT and a Grading LUT (on premiere CC) on my i7 4790k with 16Gigs of ram is not pleasant.
So I'm pretty sure it'll lag quite a bit more if you don't transcode it :s

You editing with a spinning drive? I have a 2012 matte screen. I can cut 4k Pro Res/With Looks at 1/4 or 1/2 quality no problem. 1080 is nothing...

[Mat Mayer]

My Premiere Pro on Windows laptop has started working again. Works fine with GH4 UHD files. Instant updates when using Lumetri for grading. Export times are fast enough, even for H265 export. Could be faster but it is acceptable. Might not risk going back to Mac as they seem to handle things differently. Might just get a good monitor instead.

[Justin Bacle]

1 hour ago, BenEricson said:

You editing with a spinning drive? I have a 2012 matte screen. I can cut 4k Pro Res/With Looks at 1/4 or 1/2 quality no problem. 1080 is nothing...

Videos are stored on a RAID 1 (two disks) and scratch disk is an SSD. Grading 1080p videos in full res. As soon as I have a couple of LUTs it is quite laggy when scrubbing through the timeline (PC is an 4790k w/ 16 gigs of ram)