# LAME 3.101 (beta 3, May 2026) q4 patched (MinGW build)

This is a modified MinGW build of the LAME MP3 encoder.

Original LAME Project:
https://lame.sourceforge.io/

Fork:
Constrained VBR (cVBR) by Cole Williams
https://www.lamemp3.co.uk/

## DESCRIPTION

This build extends the standard LAME encoder with:

* Constrained Variable Bitrate (cVBR) mode
* q4-related bug patch from this fork
* Portable Windows MinGW builds
* mpg123-based MP3 decoding support

These MinGW builds do not use OpenMP.

## FEATURES

### Constrained VBR (cVBR)

A modified VBR mode that enforces a strict minimum and optional maximum bitrate.
Useful for compatibility, streaming constraints, or bitrate floors.

### Difference from standard LAME -F option

The standard -F option in LAME does NOT enforce a minimum bitrate.

-F only biases the encoder toward higher bitrates during VBR encoding,
but the encoder is still free to select lower bitrate frames when it
determines they are sufficient. As a result, frames may still be encoded
below the bitrate specified with -b.

The --vbr-min-strict option enforces a hard minimum bitrate.

When enabled, any frame that would be encoded below the bitrate specified
with -b is clamped to that minimum. No frames will be encoded below the
configured bitrate.

In short:

-F                  -> suggestion (soft constraint)
--vbr-min-strict    -> rule (hard constraint)

### q4 Bug Patch

This build includes a q4-related bug fix from this fork.

The patch is intended to correct behavior in the affected VBR path and should
not be treated as a separate preset, quality mode, or compatibility option.

### MP3 Decoding Support

These builds include MP3 decoding support through mpg123.

The MinGW executables are dynamically linked against libmpg123-0.dll. The
matching libmpg123-0.dll must be shipped beside the executable for --decode
support to work.

Advanced users may replace libmpg123-0.dll with a newer ABI-compatible build,
provided it is the same architecture as the executable:

* 32-bit lame.exe requires a 32-bit libmpg123-0.dll
* 64-bit lame.exe requires a 64-bit libmpg123-0.dll

The replacement DLL must keep the same exported mpg123 API used by LAME and
must include or be able to find any of its own required dependencies.

### SIMD / CPU Notes

These MinGW builds do not require SSE.

They do not include the AVX2 or AVX-512 runtime SIMD paths used by some other
builds of this fork. The MinGW builds are intended as portable Windows builds
rather than maximum-SIMD builds.

These MinGW builds do not use OpenMP.

## USAGE

Standard LAME options are supported.

Additional cVBR options:

--vbr-min-strict
Enables constrained VBR mode with a strict minimum bitrate.
The minimum bitrate is set with -b.

--vbr-max <bitrate>
Sets the maximum allowed bitrate for constrained VBR mode.

Example:

lame -V0 -b 192 --vbr-min-strict --vbr-max 320 input.wav output.mp3

In this example, VBR encoding is constrained between 192 kbps and 320 kbps.

Decode example:

lame --decode input.mp3 output.wav

## BUILD INFORMATION

### Windows MinGW

Two MinGW builds may be provided:

* x86 / 32-bit
* x64 / 64-bit

These builds are portable Windows builds and do not require SSE, AVX2, AVX-512,
or OpenMP.

Required runtime files:

* libmpg123-0.dll
* libiconv-2.dll

Use the matching architecture for each DLL:

* 32-bit executable -> 32-bit DLLs
* 64-bit executable -> 64-bit DLLs

The mpg123 DLL is required for MP3 decoding support. If libmpg123-0.dll is
missing, --decode will not be usable.

libiconv-2.dll is shipped as a runtime dependency of the MinGW build.

### Dependency Notes

To check runtime DLL dependencies, use:

objdump -p lame.exe | grep "DLL Name"

or, with Visual Studio tools:

dumpbin /dependents lame.exe

## LICENSE

LAME is distributed under the GNU Lesser General Public License (LGPL).

mpg123 is distributed under the GNU Lesser General Public License (LGPL).

See COPYING and the relevant dependency licenses for details.

## DISCLAIMER

This is an unofficial build of LAME with additional features.
It is not affiliated with or endorsed by the original LAME project.

---

Cole Williams
https://www.lamemp3.co.uk/
