Anyone else encode video? I started using h265, and for a while one hour of video took about an hour and a half to encode. Now, an hour of video is taking a little over three hours to encode. This is with the same settings, and even pulling the original un-compressed video and using it for real results. Nothing has changed, if anything I have more space available and less programs running then before. This is of old VHS footage which was archived and I am just re-compressing it for so save space. In HandBrake, I am using h.265 at quality reference 19. If other settings are needed, I can provide them.
CPU usage before encoding is between 1 and 5%, when encoding it jumps to 98-100% all cores maxed out. My CPU doesn't have Hyper Threading. I went as far as to disconnect from the net, and close every other program on my PC and that made no difference. I noticed when telling handbrake to make a 5 second preview file, it usually speeds through to about 50%, and then slows down. If I do a 10 second preview, it's quick to about 25%, then slower to about 50%, and then it starts crawling. If the encodes times were always this long, I wouldn't have thought anything of it. Also, if I have encodes queued, about four hours of video will take almost 20 hours to encode. The longer it runs, the slower it gets.
Without encoding, RAM usage is either around 40 or 50%. When encoding, RAM usage goers up at most 5%, usually only by only a couple hundred meg. Source file is on an internal drive, and destination is on a different physical internal drive. I tried placing the source on an external drive, and it made no difference. Originally, the source would be from either an external drive, or on the destination drive. And as I was writing this, I tried something and it seemed to have fixed it... I made a custom preset in HandBrake, and making a new one and using it seems to have corrected it. I have no idea why or how that would matter, especially as the settings are the exact same as the previous one. However switching between the two presets I made validated it. The old preset ran slow, and the new one ran properly.
How about your OS drive? Try de-fraging it or use a SSD. HandBrake would be using your OS drive temp folder for caching/processing although your destination is some other drive.