Hello community,

I'm new to this board and also fairly new to video editing. I record video lessons for my pupils and use Kdenlive to cut them.

The only tools I use is cutting (cutting out mistakes) and changing speed (to 500%) for some pieces of the video, and also removing the audio track for those pieces.

My problem is now that the original video has a size of 25MB and a length of 17 minutes, while the video rendered by Kdenlive has a size of 90MB and a length of 11 minutes. Intuitively, I would expect the rendered video to be smaller than 25MB since it contains only parts of the original video. What can I do to reduce the file size of the rendered video? When rendering I chose the default X264/AAC setting (MP4 container).

Please let me know what information you need to further analize the problem!

Thanks in advance for any input,
Photon

P.S.: Using Kdenlive version 20.12.1 on Arch Linux.

Photon wrote: Intuitively, I would expect the rendered video to be smaller than 25MB since it contains only parts of the original video. What can I do to reduce the file size of the rendered video? When rendering I chose the default X264/AAC setting (MP4 container).

"Intuitively" not... because you can do this kind of "comparison" only using UNCOMPRESSED RAW FOOTAGES (loseless) when there is a compression involved (always) the output of a rendering can change on size based on rendering codec.. quality... sound... framerate....

if you have a 50mb clip compressed to a quality of 70% (you can't know what is the compression level looking at the output file) .. and you make a rendering with the same (or different) codec without changing quality (maybe maximum quality) you have the same clip in a larger file and the differences are visible only on edges of squares created by compression algorithms.

for example i'm using Kdenlive to create videos for youtube.. my original footages (taken by a smarthpne at 1920x1080 30fps) are maybe 400 megabytes... and the output of rendering (same resolution same frame rate) using the default MP4 dominating format (best quality to prevent issues with borders of added titles) can be 2 Gbytes ..

if you want a smaller output is possible using other profiles (for example you can download some using the download button on rendering dialog) i made one of these that reduce about 50% of the clip (mp4 dominating format)

Thanks. I got the hint to try HandBrake and it reduced the file size from 90MB to 18.5MB without visible quality loss. So I will just let HandBrake run over it after cutting, I guess.

handbrake is just a GUI for FFMPEG... take ffmpeg settings from handbrake and use it on Kdenlive

Thanks for the hint! I tried to extract the FFMPEG options from Handbrake but the best I could get was an approximately 100 line json file. I guess, I cannot import such a file in Kdenlive, right?

I just realized this is basically the same issue that I have: viewtopic.php?f=272&t=169718

So this seems to be a common problem, and I haven't seen a solution yet. I tried creating my own rendering profiles for kdenlive, but there are many parameters that I do not understand, and the options in the kdenlive dialogue don't seem to correspond directly to parameters in ffmpeg, the file sizes were always much larger compared to re-rendering with ffmpeg. So I am also looking forward to an answer here.

I finally found a solution that works for me: Using version 12.20.1 of kdenlive, I found it much easier to create new rendering profiles and play around with the parameters.
What I observed is that a very high g-parameter makes my files very small.
So I chose the standard MP4-export profile and changed the g-value to 450, and the file size dropped by over 70%. This could be related to my type of content, which are screencasts with few changes in the picture from frame to frame. If I understand correctly, the g-value is the number of frames between key frames, which can be larger if the picture is mostly static.

Specifically, I use the following parameters:

Code: Select all

f=mp4 movflags=+faststart vcodec=libx264 progressive=1 g=450 crf=25 acodec=aac ab=128k

can i publish as an optional download these settings?