AV1 encoding time is extremely slow compared to HEVC in FFmpeg, what could be causing this?

I am trying to compare the AV1 and HEVC codecs using tractor_1080p25.y4m, this being done by compressing the video at different bitrates and then putting PSNR into the Bjontegaard metric for each codec (I am keeping framerate and resolution the same). These are the commands I am using for FFmpeg to compress the video:

AV1: ffmpeg -i tractor_1080p25.y4m -c:v libaom-av1 -minrate 9500k -b:v 10000k -maxrate 10500k av1_test.mkv

HEVC: ffmpeg -i tractor_1080p25.y4m -c:v libx265 -minrate 9500k -b:v 10000k -maxrate 10500k hevc_test.mkv

For some reason, the process for HEVC takes around 30 seconds while the process for AV1 can take up to 5 hours. From my understanding they should be fairly similar in terms of speed, so could someone tell me what I'm doing wrong?

https://stackoverflow.com/questions/66947498/av1-encoding-time-is-extremely-slow-compared-to-hevc-in-ffmpeg-what-could-be-ca April 05, 2021 at 10:05AM