CW-Opus 1.6.1.0
Cole Williams Opus Encoder for Windows
Cole Williams Software Limited

OVERVIEW
========

CW-Opus is a Windows command-line Opus encoder and decoder based on Opus 1.6.1.

It writes standard Ogg Opus files, supports WAV input directly, and supports
FLAC input when libFLAC.dll is present beside cw-opus.exe.

QUICK START
===========

Default VBR:

  cw-opus.exe input.wav -o output.opus
  cw-opus.exe input.flac -o output.opus

Requested bitrate:

  cw-opus.exe -b 192000 input.flac -o output.opus

CW protective cVBR:

  cw-opus.exe -cvbr -b 192000 input.flac -o output.opus

Standard constrained VBR:

  cw-opus.exe -cvbr input.flac -o output.opus

Constant bitrate:

  cw-opus.exe -cbr -b 192000 input.flac -o output.opus

Decode to 48 kHz PCM16 WAV:

  cw-opus.exe -d input.opus -o output.wav

INPUT SUPPORT
=============

Built-in WAV formats:

  - PCM16
  - PCM24
  - PCM32
  - Float32

Supported channels:

  - Mono
  - Stereo

Supported frontend sample rates:

  8000, 12000, 16000, 24000, 44100 and 48000 Hz

44.1 kHz input is automatically resampled to 48 kHz using the CW-Opus 64-tap
Blackman-windowed sinc frontend. Native Opus API rates bypass this resampler.

FLAC INPUT
==========

FLAC input is optional at runtime.

Place a matching libFLAC.dll beside cw-opus.exe to enable it.

WAV input remains available without libFLAC.dll.

ENCODING OPTIONS
================

Bitrate:

  -b <bits/s>
  --bitrate <bits/s>

Default:

  128000 bits/s

VBR is the normal Opus mode when neither -cvbr nor -cbr is specified.

CW protective cVBR:

  -cvbr -b <bits/s>

With -cvbr and an explicit -b value, the requested bitrate acts as a minimum
for eligible CELT frames while retaining VBR behaviour above that floor.

Standard constrained VBR:

  -cvbr

Constant bitrate:

  -cbr -b <bits/s>

Complexity:

  -complexity <0..10>
  --complexity <0..10>

Default complexity is 10.

Frame duration:

  -framesize <2.5|5|10|20|40|60>
  --framesize <2.5|5|10|20|40|60>

Default frame duration is 20 ms.

METADATA
========

CW-Opus writes Opus/Vorbis-comment metadata directly.

Supported convenience switches include title, artist, album artist, album,
genre, date, track/disc numbering, comment, composer, performer, ISRC,
description, organization, licence, version tag and copyright.

Arbitrary tags can be added with:

  --tag NAME=VALUE

EXACT AUDIO COPY
================

CW-Opus can be used as a User Defined Encoder in Exact Audio Copy.

The current EAC preset uses CW protective cVBR at 256000 bits/s with complexity
10.

See EAC.txt for the full field-by-field configuration and alternative modes.

COMMAND REFERENCE
=================

  cw-opus.exe --help
  cw-opus.exe --features
  cw-opus.exe --version

PROJECT
=======

Product: CW-Opus
Version: 1.6.1.0
Company: Cole Williams Software Limited
Copyright: Copyright (c) 2026 Cole Williams. All rights reserved.
