Choppy and laggy in 4K

edited November 2016 in Pro Support

Hey all, I know there has been a lot of discussion about this before, but since I am totally new to editing and I could not understand anything from the suggestions - I could really use a close guidance here.
Basically - Hitfilm was all good until i started shooting videos in 4K, and it became choppy and laggy while editing the footage. The proxy thing does not work either, I thought I could get over it but obviously I got a headache real quick.
my pc specifications SHOULD handle the 4k.

The format that my camera is using is mp4, XAVCS 4K that's all I know to say.. any help?


  • edited November 2016

    Really only a complete top of the line PC is capable of doing 4k and even then maybe not real time all the time.

    Things you can do are to transcode to a lower overhead codec to make decode easier. XAVC-S is not typically encoded as low overhead. AVC can be lower overhead but it takes special settings. Most commonly people transcode to DNxHD or Prores as a lower overhead codec compared to most AVC camera encodes. For 4k that means DNxHR and not DNxHD.  Either way it needs to be in Quicktime format. Same for Prores.

    I have some 700Mbps Prores 4k 24p files from a BMPCC camera and they are harsh to work with. They take up half my CPU and that means when you have more than one file like in compositing and transitions things can possibly get touch and go. My CPU is a 4Ghz 4-core with hyperthread.

    I have some GH4 4k files that can decode reasonable well on my machine and more so in a lower overhead AVC.

    For any grading effects and such you will want a pretty stout GPU. My Nvidia GTX 980 does not break a sweat doing such on 4k. The bottleneck is the media decode.

    There was once a thread where I posted some sime test numbers to this effect. Maybe I can find it and insert a link here after typing this post.

    The Hitfilm "proxy" feature is not intended to proxy media files for faster edit. An unfortunate choice of words given use more common use of the word Proxy. Hitfilm proxies are intended to pre-render complex composite effects shots, aka slow (seconds per frame), so that those can be used on the edit on a timeline and possibly playback reasonably. Hitfilm proxies are full resolution, full quality, lossless renders (aka BIG files).

    Ideally, Really you are probably best off using HD proxies to cut/edit the video and only the 4k files for final renders and pixel critical effects during edit/grade. Unfortunately Hitfilm is not(?)  capable of this since it does not auto conform source frame size to project size and, I think, does not use relative coordinates. An HD "proxy" would need to be scaled for a 4k project and that scale needs to be removed on the 4k version. So you proxy will want to stay at the same frame size as the source. Also, run your viewer at "half" (effectively HD) to increase playback performance.


  • Thank you NormanPCN for taking the time to respond :)
    I must stress this out - i'm REALLY new to editing, so most of what you wrote is Chinese to me... if you can just guide me step by step as to what can i do - should i download any software? & how can i use that HD proxies you mentioned? as i said i'm pretty much clueless about these topics 

  • If you're that new, it might be easier to convert your files to 1080p and edit those instead, because the time and effort involved in getting it to deal with 4k is rarely worth it unless you have a specific need for a 4k output. At least until you get more familiar with editing.

    You'd then be potentially able to change the project type to 4k, replace the 1080p clips with 4k versions, add a new 'Scaler Point' to each Composite, parent everything to that, then scale it up (or it is down?) to the new frame size, then render it out when you're all done.

  • Sounds good. how can I convert without damaging the quality of the image, can you recommend any software?
    Thank you all

  • Lots of free programs around and they all have their merits, but you have one right in front of you: Hitfilm.

    Drag your 4k clips into a 1080p project, Right Click>Transform>Fit To Frame and export it back out again with a slightly different name.

    Or there is Handbrake and instructions on how to use that are covered here: how-to-work-with-edit-video-game-footage-in-hitfilm

    After that your next step might be converting to DnxHD or ProRes format for smoother editing speed, and you'll find into on that on the forum if you search too, but.. .baby steps. :)

  • Stargazer54Stargazer54 Moderator
    edited March 2017

    @NormanPCN Hey Norman, what package are you using to convert to DNxHR (if at all)?  I'm guessing Cliptools V3?

  • edited November 2016

    @Stargazer54 I'm anti-4k. Don't believe in it or want to touch it. If one is targeting the theater or Blu-ray 4k then sure. I am just a nothing schmuck who does things for personal/friend entertainment. Most all video delivery mechanisms have such low bitrates in common use, HD and 4k is it exists, that the real fine detail one probably is looking for from 4k is largely lost. My standard def DVD movies actually surpass my FIOS TV signal in "resolution" these days which is sad. A quality HD signal is awesome but outside of Blu-ray it does not exist, IMO.

    I've only done tests with 4k and that only prompted from reading online posts.

    Now that I got that off my chest! Whew. Opened up a can of worms eh!

    The ffmpeg (open source) world does not currently support DNxHR for encode. Only decode right now. So that means Convert V3 cannot encode DNxHR.

    The only DNxHR 4k tests I have generated were via Sony Vegas through Quicktime via the Avid codec install. Any utility that uses Quicktime for export should be able to do DNxHR. This assuming no silliness like max resolution clamping which can happen in older stuff. Tools like MPEG streamclip are dead and have not been updated in like 5 years so who knows. Not me.

    Absent that Prores maybe.

    From the tests I have done I would want my app to have native Cineform decode for 4k work. Why? Because Cineform uses a wavelet type compression. What does that wavelet technobabble mean? It means that it can decode directly to lower resolutions. So put your viewer at "Half" and edit your 4k footage. The performance is very close to "Full" HD performance. Have your cake and eat it too! Without the wavelet, you decode to full res (CPU) and then interpolate down ( hopefully GPU). That is an overall slower function. 4k is so much work you need to squeeze blood out of a turnip to keep the performance up.

  • @NormanPCN ; Wow.  Didn't mean to make you go off on rant.  Agreed, 4K is overkill in a 1080p world.   But you threw DNxHR out there and I was curious.

    I've been trying to come up with the best workflow for editing  footage from my GH4.   Downconverting to DNxHd  or ProRes at 1080p before the edit works pretty well.   My use case for staying 4K might be to stay there for tracking a shot with the idea that there would be more pixel information to work with and thus a more accurate track. 

    But yeah, a full on edit in 4K all the way through is problematic.    But good info on wavelet compression.  We live in interesting times.

  • @Stargazer54 Sorry for the rant.

    With the GH4, or any DSLR with AVC MOV output, If you do not convert to DNxHD/HR or Prores then you should rename your .MOV files to .MP4. I have a few 4k GH4 clips and the performance difference is significant. The Quicktime AVC decoder performance seems to suck.

    If you have/use Vegas then Cineform is something to look into since Vegas takes advantage of Cineform decode capabilities.

  • edited December 2016

    idk why everyone keeps saying you need a super powered p.c. to edit4k video lol. I have a yoga 910 and it's able to playback 4k in adobe premier oh though a bit choppy it still plays it back and exports it even though a simple video takes about 10 minutes for 2 minute video. on my msi 1060,6gb 16gb ram it handles the same video with no choppy play back or while editing and exports it in about the video length. I think the new hitfilm 2017 can handle smooth 4k video, since they advertise 8k editing lol I'm assuming 4k should edit twice as fast. waiting on hitfilm to confirm this though!

  • Perhaps the best option for you is compressing 4K to 1080p.

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