How to Reduce Preview Lag?

I have a file that I’ve been working with .MP4 files in. I converted all my raw clips to MP4, becuase using the .MTS files directly was too resource intensive and would cause preview lag.

Everything seemed fine, until today, when I began noticing preview stutter/lag when performing cross fades. Why is this happening again?

What would cause a cross-fade that I have already had saved in the file many times to start lagging when it did not before? Is my file simply getting too large with too many clips? Should I render what I have as a chunk, and then import it back into the project file to save on clip number/file size, or is something I am unaware of going on here?

Thanks in advance!

Smooth playback from the timeline simply comes down to how powerful your machine is and how much editing you’ve done.
Converting from MTS to MP4 isn’t of great help, try first transcoding to ProRes instead. This always helps me especially with 4K files.

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OK, that makes sense. So converting raw files to ProRes and then breaking the project file into chunks should help. That’s a shame because my video is only about 4 minutes long, but requires a HUGE amount of clips, transitions, and editing (it’s a music video). Are all Video Editors like this, or is there one that is able to pre-render certain areas of the track while you work?

And this is why you need a powerful machine.

You can try Da Vinci Resolve (if you’re looking for free software) though the learning curve is much higher than ShotCut. It can optimise your media for editing (plenty of YouTube tutorials).
But again, smooth playback from the timeline is always hardware dependent.

Hmmm… So Ive tried those methods, but I am still getting preview lag during crossfade transitions, even with smaller files. It almost seems the more times I play back the section i am having a problem with, the more it gets worse. It literally seems to play back slower the more times I try to play it… =P Happens very randomly, I’m pretty sure nothing else is using up my computer’s resources. Sometimes when I start the program it is just slow… sometimes it plays back fine but there is a drastic difference in performance/playback quality between when it is fine, or lagging and I can’t tell why sometimes it will play the entire project smoothly, and sometimes it will not.

Also, I can’t find the “ProRes” format in my export settings… is there a codec pack I need to install first? I’ve been using the H.264 profiles to transcode into .mp4s.

You’re going to have to change your workflow to suit your computer’s hardware/performance.
Something to try is to create all of your crossfades, then export the entire video to a lossless format, then import and work on that.

Video editing is not a breeze nor is it as smooth as working on photographs. You’re asking your PC to render effects on 24/30/50/60 stills per second in real time. You can imagine this needs real power, right?

What are your PC or Laptop specs?

It’s a gaming PC, 64 bit system with an overclocked i7 processor, 16GB ram, and an Nvidia/MSi GTX970 2GB graphics card… I feel like the program is not able to fully use the hardware I have, but I guess video codecs are different than graphics in a game…

Also, can I get a link to this ProRes format? Or any suggested transcoding options from .MTS/HD-AVC? Busting the project files into chunks and rendering the clips together and then importing them as a single file seems to help reduce perfomance issues, but I can’t help but feel its a waste of time, and that I am somehow losing a little bit of quality every time I render/import, if there is any truth to that

The ProRes is included as all FFMEG codecs are inside. In Intermediate/ProRes

It’s not a waste of time if it helps you complete your project. Also you can use a lossless/H.264 format [see export list] for each of your edited ‘chunks’…

Maybe that could help to batch the re encoding :

If full HD quality is something you don’t need while you are editing you can try to use the “proxy” edition method:

In Hitfilm there’s an option to reduce the preview window to half or quarter quality and this improves performance. Is there a similar feature in Shotcut? I think that would reduce preview lag.

You can manually resize the preview window, but this isn’t the issue because it’s the same source. You need to play around with some of the ‘proxy file’ work-arounds posted on this forum. But bear in mind, even using these methods you will experience preview lag when there are many filters applied. As mentioned earlier, smooth playback in and editor is still very muchdependent on hardware.

GPU and CPU and graphics memory controller utilisation are all below 25% during playback and the only filter applied is a crop. VLC media player plays back the videos perfectly smoothly so I think there is something suboptimal about Shotcut.

I don’t think the proxy methods apply to what I’m trying to do and would make the process take much longer.

25% of a low end CPU/GPU isn’t the same as 25% of a high end CPU and GPU.
It will depend on what CPU and which GPU you have and to a degree how much RAM.

Shotcut is not playing back exported rendered footage, it’s trying to playback footage AND apply the crop filter to EACH FRAME ‘on the fly’.
You expect too much I think :slight_smile:

What are you trying to do??

I made a new thread since I doubt my situation applies to people who can use proxies.

It can apply.
What he just point, is using “compressed” and lighter versions of your clips to edit and just switch at the moment you want to import.

or that :slight_smile:Proxy files - different approach from my workflow with GoPro footage

But there are about 12 moments I want to export so I’d have to switch them back and forth 24 times. It’s not practical.

i’m running two gtx980ti’s in sli mode…i managed to alleviate some lag, and tearing for that matter in other programs such as mspaint which would tear vertically when scrolling horizontally…which made really no sense as i was only dealing with static images…but that’s another story entirely…
anyway, right click your desktop, (if your are using nvidia cards), and click nvidia control panel…and go to 3d settings…in the upper left of the dialog box there is a space to adjust for how your video handles shotcut. scroll down that list until you find shotcut.exe and, (because i have no idea what you have for a rig), play with the settings until you achieve satisfactory results.
nice thing about the nvidia control panel is that if you went and played a little too far on the ragged edge of disaster, you have a button that will restore your programs default settings so you can start over…worked for me.
hope this helps.

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If you are not happy with Shotcut, try Da Vinci Resolve (DVR) - especially as you say you’re only cropping.
In DVR you can import your media then chose to ‘optimise media’. It does all the work in the background and makes editing even easier.
I find DVR much less laggy than Shotcut for larger projects.