For me Kdenlive seems to be a very good alternative to openS***... but both are still very hard to use on my computer... somebody can tell me what is wrong with my configuration :

Gigabyte GA-H77N-WIFI (LGA1155 socket)
Intel Processeur Core i3-3220 / 3.30 GHz 2 coeurs Socket LGA1155 3 Mo
SSD OCZ Vertex 4, 128 Go, SATA III
Kit Dual Channel DDR3 Corsair Vengeance Low Profile, 2 x 4 Go, PC3-12800, CAS 9

I work with the raw video that I do with my sony action cam (1080p 60 fps).

Must I add graphic card ? which one ?
Change everything ?
Just adjust software configuration ?

what version of kdenlive do you use? what is your linux flavor?

and what graphics chip do you have?

I recommend making proxy files to improve playback performance

I use the last version of Kdenlive (16.12.2) on Kubuntu 16.04

The graphic chip is on the motherboard... Here is what "sudo lshw -C display" returns :
*-display
description: VGA compatible controller
produit: Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller
fabriquant: Intel Corporation
identifiant matériel: 2
information bus: pci@0000:00:02.0
version: 09
bits: 64 bits
horloge: 33MHz
fonctionnalités: msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
ressources: irq:28 mémoire:f7800000-f7bfffff mémoire:e0000000-efffffff portE/S:f000(taille=64)

What is proxy file ?

So, checking the processor, you have a HD2500 graphics chip in use. For preview the HD2500 may (don't know) support MPEG4 hardware decoding, but I am not sure, if your raw material with 60fps fits into that.

So, you will get best preview results, with proxy clips. Find details to proxy clipshere:
https://userbase.kde.org/Kdenlive/Manua ... roxy_clips

Raw format at 60fps must give huge bitrate, if they are on external media you might be limited by the USB channel?
Raw pixel format is probably not YUV, so color conversion has a high computing cost?
Using proxies in the target color space, with a small compression (eg DNxHD or MJPEG) and maybe at lower resolution will probably help to get a smooth workflow.

GPU usage with Kdenlive/MLT is still buggy, and the performance improvement is effective only under several restrictions (should use only GPU effects/transitions, if you mix with CPU operations then it is actually much slower and crashy!), so I wouldn't advice a GFX card upgrade only for Kdenlive, you would be disappointed!
Having a faster CPU is always nice, but not especially many more cores: multithreading does not give much improvement while editing. The bonus comes only at encoding time, and beyond 3 or 4 threads the speed change is minimal!

More RAM is nice with large projects: with 100's of clips preloaded, audio/video thumbnails etc, I've already touched the 8Gb limit...

Conclusion: don't by a GPU but use proxies!

Bonne chance...

Vincent