Bad preview of 4k video

[Evert Vorster]

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
Tel: +264 (0) 811477690


On Sun, 28 Jun 2020 at 17:45, Mehdi Haghgoo <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> 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
> Tel: +264 (0) 811477690
>
>
> On Sun, 28 Jun 2020 at 14:24, Camille Moulin <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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