Exported videos too heavy

Hello everybody, I’m new here !
Let me explain : I sometimes need Kdenlive simply to take a movie extract and fiddle with it a bit, like include a fade in/out or edit it marginally (I’m a teacher, I use video in my classes). The problem is : the original video is, say, 100Mo ; the exported video after editing (same format (mp4), same video quality, same length or sometimes shorter) jumps up to more than 500Mo.
My question is simple : is there a preset I’m overlooking that allows me to export a video of roughly the same weight as the original ?
Your help would be greatly appreciated,

You can use the “Custom Quality” setting on the Render page to drop the quality and therefore the file size. You could also rescale if you don’t need your clip in high resolution.

I hear you.
Does that mean I’m going to obtain a lesser quality file compared to the original, for the same size ?

You’re always going to get ‘lesser quality’ for any lossy to lossy transcode, even if you infinitely increase the bitrate and ‘quality’ settings of the reencode.

The only important measure is whether or not your result has Acceptable quality.

If your original source files use things like variable frame rate to efficiently improve compression, you’re going to lose that when reencoding with kdenlive as it currently doesn’t support that kind of thing. mlt currently has a fixed frame rate assumption that lots of things are pinned to.

So the only way to try and win some of that ‘efficiency’ back is to dial back the bitrate as far as you can before you can actually see the artifacts lossy encoding tries to perceptually hide - or use an inherently more efficient codec, like AV1, which will give you much better quality than H.264 or H.265 for far fewer bits.

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