Unexpectedly large exported file

I have a trail camera that shoots nightime video of 20" duration max. To create a decent sequence I have used Shotcut 21.05.01 to combine clips. Typically these 20" black and white clips are 60MB MP4 files. As a test I exported 3 such clips imported ‘raw’ with no transitions or effects then exported the combined files expecting the result to be somewhat less that the aggregated 180MB - especially as the audio was removed. Yet the best I have achieved is 222MB using H.264 High Profile with these settings;
Video: 1920 x 1080 aspect 16:9 Frames 25p.s.
Codec: Quality 75% [‘Defaults’ were Codec: libx264 Rate: Qual-based VBR GOP: 300 B frames: 3 Codec threads: 0. I freely confess that I understand none of these apart from the altered quality which I assume = compression.]
Audio: disabled
All other settings were unchanged.

What am I getting wrong? Many thanks for any advice. [Sorry if wrong place, off topic etc. I’m new here.]

What is the worst result you have got? Do you know what bitrate of your video is set while exporting?

And if size is increasing, I do not think it is a bug or problem, as I have five 80mb files which has size larger than a GB after export, And after exporting the same video even on another video editor (i.e. Vegas 15) It gives me the same size.

Size doesn’t matter too much, If the video comes out with some problems, like unwanted movements, effects, blur, etc., Than it could be a problem. But you have only stated the size is bigger and not reported any problem in exported video, that mean there is no problem in your video.

And if you could provide the size of the worst result and the bitrate set in export settings and the real bitrate of your video, Than I could help you to reduce size.

The reason is your codec Quality=75%, which is equivalent to a constant rate factor (CRF) of about 13. To produce “visually lossless” HD video (i.e a video were you cannot discern any loss but still have compression) you shouldn’t need to go lower than CRF=17 (i.e. Quality=67%).

Thanks for your posts Ar_D and Elusien. The exported video has no visual problems but the size concerns me a] because the broadband speed locally is absolutely pathetic so the bigger the file the longer to upload and b] because the above test used a mere 3 clips whereas I have one sequence of videos containing 32 clips. Uploading that would take decades!
BITRATE of the 3 original vids = 25190 kbps; the frame rate = 60 fps. The bitrate of the exported video is 30556 kbps [as is the total bitrate] and frames 25 fps. [B.t.w. I don’t see anywhere in the ‘advanced’ export settings to set or adjust the bitrate.]
CRF is a new one to me! but having had another look at the ‘advanced’ export settings I see where it is and have exported an otherwise identical file with CRF=17 as suggested. The result, to my mind, is a massive reduction if file size to 133 MB with no discernible loss in quality so thanks for that tip.

This is often the case. People look at the Quality setting default (55%) and think that they need to increase that. However, in many cases that value is fine. If however you find it is not quite good enough you should increase it a bit and check out the new export. Eventually you reach a point (definitely below 67%) where it is good enough. The higher the value the larger file-sizes you will get. Also, if you are doing Hardware Encoding, this will in general produce much bigger files of poorer quality video than software encoding.

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