LAME cVBR: how do -V and -b work together?
cVBR keeps a VBR quality target while enforcing a strict minimum bitrate. The table shows the actual average output and file size from the current encoder.
LAME cVBR quality
LAME cVBR: how do
cVBR: combining -V quality with a strict -b minimum
In cVBR, -V keeps the VBR quality target while -b supplies the minimum bitrate used with --vbr-min-strict.
Frequency context: the conventional human audible range is about 20 Hz–20 kHz, and CD audio is normally considered to cover that full audible range. A result close to 20 kHz therefore reaches the top of the usual audible-band reference. Frequency reach is only one part of MP3 quality; extra bitrate can also improve how accurately the retained audio is represented.
| LAME command | Average bitrate | Approx. file size | High-frequency reach |
|---|---|---|---|
-V0 -b 192 --vbr-min-strict | 248.1 kbps | 1.78 MiB/min | No default low-pass |
-V2 -b 160 --vbr-min-strict | 186.3 kbps | 1.33 MiB/min | about 19.2 kHz |
-V4 -b 128 --vbr-min-strict | 147.0 kbps | 1.05 MiB/min | about 17.8 kHz |
Example:
-V2 -b 160 --vbr-min-strict averaged about 186.3 kbps across the three samples, very close to ordinary V2 while maintaining the requested minimum frame bitrate.What does the minimum bitrate change?
The floor mainly prevents the encoder from dropping into lower bitrate frames where ordinary VBR would choose to do so. It does not turn VBR into CBR, and the final average can still vary substantially with the source.
How these figures were measured
Each setting was encoded with the current LAME 4.0 build against the same three stereo WAV sources. Average bitrate is the mean of the three encoder results. File size is normalized to MiB per minute so clips of different lengths can be compared fairly. The high-frequency figure is the approximate point where the default encoder response has effectively tailed off.
The three source WAV files are CC0 material from Freesound: Erokia 524947, Usilaya 546205, and astro_denticle 846944.
Listen to these settings
Hear the same source at different cVBR settings and switch between them without restarting playback.
The listening test opens with this mode already selected.
Open the cVBR listening testCommon questions
What does -b mean in cVBR?
With the cVBR command shown here, -b supplies the minimum bitrate while -V still selects the VBR quality target.
Does cVBR make every frame the minimum bitrate?
No. The minimum is a floor, not a fixed output rate. Harder passages can still use higher bitrate frames.
How different is cVBR V2 from normal V2?
In these tests ordinary V2 averaged about 184.6 kbps, while V2 with a strict 160 kbps minimum averaged about 186.3 kbps.