I have seen several videos on youtube and my conclusion is that this is a good setting to compress 4k videos to 1080p:
Format: MKV
Codec: H.265(x265)
Compression speed: SLOW
Average Bitrate(kbps): 5000
Audio: AAC autopass-thru
Can compression be further improved without losing quality?
This compression setting can be improved?
Re: This compression setting can be improved?
If you want MKV, use the H.264 MKV 1080p30 preset. Adjust as slow as you'd like.