2.8.1 Too heavy to use

[zarigan]

I recently started using 2.8.1 and it is too heavy to use.
Therefore, I am using 2.7.5 reluctantly.
Avidemux was useful because of its light processing, but it is very disappointing.
When DXVA etc. was enabled, it became extra heavy and worsened.
I feel Qt the lightest.
Could you tell me why the version upgrade made the processing so heavy?

[eumagga0x2a]

I feel Qt the lightest.

Please update to the latest available 2.8.2 nightly (2.8.1 is very old actually), launch Avidemux, load a video, close it and attach admlog.txt from %localappdata%\avidemux\ to your reply. "Qt" is an unaccelerated path, normally orders of magnitude slower than anything else, but the opposite can be the case with a very powerful CPU and a very bad graphics card or driver.

A special case are HDR videos: older Avidemux versions were unable to convert HDR sources to SDR (called HDR tone mapping). This conversion, even the fastest one, is extremely demanding and is done entirely on the CPU (albeit multi-threaded). Unless you re-encode HDR sources, you should probably disable HDR tone mapping when editing HDR sources in copy mode (ordinary SDR sources are not affected and turning tone mapping off won't change anything for such videos).

If you mean by "too heavy to use" the GUI being less responsive, e.g. during zoom changes, you might try to disable OpenGL in Avidemux Preferences. OpenGL performance indeed regressed in recent Qt5 versions and OpenGL is currently entirely broken at least on Linux with Qt6.