GoKawiilStreaming Learning Center tests show x264 tuning cuts H.264 bitrate 33%
A study using x264 and FFmpeg on 1080p clips found that tuning encoder settings—switching to the veryslow preset, extending GOP length to ten seconds, using two-pass encoding, adding reference frames, and applying a per-title encoding ladder—raised VMAF quality by 0.66 points while cutting bitrate from 4.9 Mbps to 3.27 Mbps. The tradeoff is that encoding time more than tripled compared to default settings.