I have converted a video of mine with ffmpeg into H265 codec. Great: Much smaller at the same quality. But then I noticed the video is blocky. I thought there was an error during re-coding. But no: I noticed that it gets blocky if I run other programs than VLC. I looked at how much of the CPU is required: 16% with the old codec, 60% with H265. So: Is H265 too demanding for me, since my computer (from 2013) is too weak?