Bad preview of 4k video

[Massimo Stella]

Hi Mehdi,
I remind you that you can render the timeline preview for the zones you 
need to get a perfect smooth playback before to export  (as you have to 
do if you use application like Avid, Premiere and FCP.)
If you check you'll find that this feature is available on Lightworks 
too but only for the premium version.
Cheers.
Hi there, Mehdi.

MLT does use some GPU accel, and I have some scripts for the encoding of 
x264 and x265 video in kdenlive. 


The thing about GPU acceleration is that someone has to write the module 
in the low level language that a GPU understands. As there are a lot of 
people re-encoding video, it made sense for the big houses like Google 
to pay the people that are smart enough to develop a library for 
encoding video. 


For the mathematics involved in merging various effects per frame in 
video, you need different libraries. There was an attempt to use some of 
the accelerations  available on a GPU with the movit project. 
Unfortunately it is so unstable in Kdenlive that it crashes out on my 
system in minutes. I'll enable it from time to time to see the progress 
on the project, but for any serious editing it's turned off on my 
system.


This might break your heart, applying effects is not even properly 
multi-threaded. You can set the number of threads higher for the 
effects, but there are some concurrency issues and if your effect stack 
depends on the effects being applied in a certain order you will see 
some weird visual effects. 


You might think about just dropping the preview resolution until you can 
apply the effects smoothly, do your edits and let the system render the 
high resolution stuff at some later time when you can be doing something 
else.







Evert Vorster
Awesome Chapters Tours
http://www.awesomechapters.com <http://www.awesomechapters.com>
Tel: +264 (0) 811477690









On Sun, 28 Jun 2020 at 17:45, Mehdi Haghgoo <powergame_coder2 at yahoo.com 
<mailto:powergame_coder2 at yahoo.com> > wrote:
Thanks Evert, 
I have not used proxies, but as I understand from your comment, it would 
not do much good for me here. 


One more thing Camille, do you mean MLT does make zero use of GPU for 
video processing? If so, this seems quite a drawback, but then adding 
GPU might be extra work on different platforms like mobile, Desktop, 
etc. because of different GPU architectures.  
Any thoughts? 


- mehdi



On Sun, Jun 28, 2020 at 19:18, Evert Vorster
<evorster at gmail.com <mailto:evorster at gmail.com> > wrote:




Hi there, Mehdi.

To second Camille's suggestion, the first thing to try would be to lower 
the preview resolution. This setting does not affect the rendered video, 
but does provide a much smoother editing experience on older hardware. 
When editing 4K footage on my machine, I use a resolution of 540p for my 
monitor. This is near VHS quality, if you are old enough to remember 
that format.


Proxies are lower resolution copies of your original footage that 
Kdenlive can create automatically, and represents another level of 
smoothing of the editing process on older hardware. Unfortunately 
proxies create all sorts of problems in Kdenlive. Drawbacks include 
extra disk space used as well as the time it takes to generate. For your 
own sanity, please avoid using proxies if you can. 


Kind regards,






Evert Vorster
Awesome Chapters Tours
http://www.awesomechapters.com <http://www.awesomechapters.com>
Tel: +264 (0) 811477690









On Sun, 28 Jun 2020 at 14:24, Camille Moulin <camille.moulin at free.fr 
<mailto:camille.moulin at free.fr> > wrote:


Hi Mehdi,




Thanks for the  kind words about       kdenlive :-).

About your performance problem, on       short term you can try to lower 
down the preview resolution (in       the lower left corner of the 
monitor, see picture attached.)or you       can enable proxies.

On the medium/long term, the goal is to       be able to use GPU, but 
this is quite a large task and needs also       to be implemented at 
MLT's level.

Cheers,

Camille







On 28/06/2020 13:05, Mehdi Haghgoo       wrote:

                    [...]
I have a small         problem though, Kdenlive is bad at previewing 
in-edit tracks         especially for high-res videos like 4k and when 
layering         multiple tracks. It just plays with a lot of hiccups. I 
have low         end laptop: core i5 6200u dual core with Intel 520 
graphics.

Is there a way         to improve the performance in future versions or 
are there any         plans? 

I have not         tried kdenlive with a discrete graphics. Maybe, these 
issues are         not present on powerful systems. 








Again thank you         for your great work. I would love this message 
to be seen as a         query and suggestion at its best. 



Looking forward         to hearing your thoughts. 





Best regards

- mehdi









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