[x-post from reddit] Unbearably long rendering times with Kdenlive x265 [email protected] with i7-6700k

Quick note: if you’re active in the r/kdenlive subreddit you may notice this same post there. I’m x-posting here to hopefully get some more opinions and different solutions.

Today I just edited my first [email protected] video with Kdenlive (latest flatpak from Flathub on Arch), but It’s been 3 hours and the rendering is not even at 50% yet (13 minute long video).

I’m not writing this post to whine, but rather to understand if this is expected of Kdenlive for 4k videos. My PC is rather beefy and I would expect shorter rendering times even for a 4k video.

Here are my specs:

  • i7-6700k @ 4.4 GHz (can’t overclock further due to summer temps)

  • 16 GB dual channel DDR4 RAM @ 2400 MHz

  • GTX 960 4GB (GPU acceleration/movit is turned off in Kdenlive settings since it inevitably causes random crashes)

  • 2x Samsung 850 evo 500GB SSD (not RAID, one hosts the OS and home folder, the other one all of the project files and the final rendered file location)

I have used the following rendering options:

  • Format: “MP4-H265 (HEVC)”

  • Quality: Video 15; Audio 192

  • Encoder speed slider set in the second position counting from the leftmost being 1

  • Threads: 7

If you can give me a hand getting some more acceptable rendering times, I’d highly appreciate it.

Thank you.

You are probably running without hardware acceleration. Which isn’t a bad thing in terms of quality but does result in very long rendering times. HEVC at 4k is no joke.

Sure, hardware acceleration would be a great thing, if it worked. Unfortunately it’s not the case for Kdenlive, in fact as I said in the OP it causes crashes. Maybe using another codec other than HEVC could result in faster rendering times (even if that means bigger file size)?

H264 should render a lot faster and won’t look much different if you give it a beefy bitrate.

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I would recommend just exporting it in a lossless codec and transcoding it with something like handbrake. should be higher quality with more control and possibly even faster render times

These both sound like great suggestions. Will try as soon as possible and report back with the results. Thanks a lot!

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For Info

I recently converted a 4k Movie (2h 30 mins approx) from H264 to H265 on my [email protected] and it took about 13 hours or so without using h/w accel

This was with Handbrake on Win 2012r2 but i doubt the OS makes much difference

If i did it on my 6700k i would expect i might get it down to say 10hrs if i was lucky

3hrs for 13 min video sound like you might have gone a bit OTT on the settings

Ive never done 4K in Kdenlive, so I cannot compare directly.

My suggestion would be to play with your settings, and the use of other codecs. Depending upon what you are using the footage for, it may be worth while.

Ive rendered out of Kdenlive lossless and handbraked, as well as tweaked my settings in Kdenlive to get acceptable results. Overall I think a lossless render and using handbrake yields the best results in the end. However, it is much slower. Lately, ive spent the time to tweak my settings and get a render straight from Kdenlive. File size is bigger than with handbrake, but still acceptable.

Another thing to consider is the size of the raw video. If you can cut your bitrate here and get the quality you want, this should save time in the final render, though I have yet to test this method.

KDenLive is still getting there with 4K as I remember. Why they don’t just fix the hardware encoding issues they’ve had since 2012 is beyond me.