cVBRb bitrate boost
cVBRb is a branch idea built on constrained VBR. It adds an optional bitrate-boost control that nudges allocation toward higher MP3 frame bitrates.
What it is
cVBRb starts with the cVBR idea: keep variable bitrate encoding, but enforce a stricter lower floor. It then adds --bitrate-boost as an extra allocation bias.
The aim is not to replace LAME quality settings such as -V0 or -V2. Instead, it gives advanced users a way to make the encode more conservative when they want additional bitrate margin.
Boost levels
| Option | Plain-English effect |
|---|---|
--bitrate-boost=1 | Light boost. |
--bitrate-boost=2 | Medium boost. |
--bitrate-boost=3 | Aggressive boost. |
What it changes
In the published cVBRb comparison, boost levels progressively shifted more frames toward 256 kbps and 320 kbps buckets. The average bitrate increased from 263.1 kbps for the baseline VBR/cVBR run to 268.0, 273.5, and 280.2 kbps for light, medium, and aggressive boost levels.
That is a useful result because it shows actual encoder behaviour. It is also modest enough to avoid overclaiming: the boost is a controlled allocation change, not a new audio format.
ABR boost
The branch also exposes bitrate boost in ABR mode at level 1. ABR and cVBR do not mean the same thing: ABR aims for a chosen average bitrate, while cVBR keeps a stricter lower VBR floor.
Careful interpretation
Frame distribution and average bitrate tables are not listening tests. They show how the encoder allocated bits. They do not prove that every listener will hear a difference.
For audible quality claims, use blind testing with your own music and compare against ordinary LAME VBR at sensible settings.