Whether it's a downloaded video or a rip from a disc I use the same bitrate depending on what the file is when I compress it. For DVD's I use 1500-2000 kbps. For Blu-Ray (1080) I use 5100 kbps, although an even 5000 would work just as well and be easier to remember. For UHD (4K) I use 20,600 kbps, although an even 20,000 would work just fine here too and be easier to remember. These numbers will greatly reduce the file size and give a great picture without artifacting or blurring. These are all compressing using x265 and I personally use mkv not mp4 but that shouldn't matter as far as this goes. Some downloaded videos already have a bitrate smaller than that which I would normally use for conversion. In those instances I simply keep the downloaded video as is and don't attempt to convert it as it is already smaller than I would convert it to. Fab 13 and Unifab is not working very well though so I'm still using v12. Hope that helped. If you have any other questions just let me know.
