Questions about AviDemux

[HugoNabais]

So, I've been using Avidemux recently to edit, cut, and reencode 8k videos to 4k (I have some TVs that don't play well 8k videos)
I've been using Mpeg4 AVC x264 to encode in a mp4 file with the resize filter.
I have two Pcs, one main 5950X with 32 threads, and a i5-12400F with 12 threads.

My questions are:
 1º Why is Avidemux limited to 4 threads? In the codec x264 settings I can only set 1,2 or 4 threads, it takes many hours to encode those 8k to 4k files, but CPU usage in my 5950x is only at around 12% (4-5 threads working only).

 2º Since my workflow that I've explained only uses a max of 4 threads they take almost the same time in both my PCs, but it always is faster on the intel! Which is very strange, the AMD is around 30-40% slower! But every other software I use or bench is faster on the AMD. I'm using version 2.8.2, running from same network folder, all settings are equal on both. Does Avidemux run better on intel systems?


Other than these small things I would like to understand, the results are very good, and the edit GUI is very intuitive!

[szlldm]

You should use Auto-detect, then all cores will be used

[HugoNabais]

You should use Auto-detect, then all cores will be used

It's always on auto!
It only uses 4 threads!!

[szlldm]

Then i guess the botleneck is the decoding.

[HugoNabais]

I have the latest version of LAV video decoder that supports many threads... it's strange.
Is there another decoder I can try?