A quality target used by the x264 and x265 video encoders that holds a consistent visual standard while letting file size vary. Rather than dictating how many bits to spend each second, an RF value tells the encoder how good the picture must look, and the encoder spends whatever the footage requires to get there. The scale runs from 0 to 51, and it is inverted: lower numbers mean higher quality and larger files. It is also logarithmic, so small moves matter. Raising the value by roughly six points cuts the resulting bitrate in half.
Choosing a Value
Useful settings cluster into a few well-worn ranges, and the right one depends on whether the file is a master or a delivery copy.
- RF Range: 0 to 17
- Result: Visually lossless
- Typical Use: Archival masters and footage headed back into an editor
- RF Range: 18 to 22
- Result: Excellent
- Typical Use: High-quality 1080p publishing
- RF Range: 23 to 28
- Result: Good
- Typical Use: Web and social delivery, background video
- RF Range: 29 and up
- Result: Visibly degraded
- Typical Use: Bandwidth-starved situations only
Resolution shifts the sweet spot slightly; higher resolutions hide compression better, so they tolerate slightly higher values.
Rate Factor Versus Average Bitrate
The two encoding philosophies answer different questions. A rate factor target guarantees how the video will look but not how large it will be, which suits publishing a content library at consistent quality. An average bitrate target guarantees size but not appearance, which suits hard ceilings such as platform upload caps, and encoders compensate for its rigidity with multi-pass analysis that spends the fixed budget where motion demands it. Neither is better; they simply promise different things.
Why Marketers Should Care
Teams that publish video continuously need repeatable quality more than they need any single perfect file. Standardizing on a rate factor keeps every product demo and social cut looking the same without anyone budgeting bits per clip, and it prevents the silent waste of encoding calm footage at bitrates only action scenes need. One number, chosen once, becomes the house standard for how good the brand looks in motion.
Additional Acronyms for RF
- RF - Royalty-Free
