# HG changeset patch
# User Chris Cannam
# Date 1553875711 0
#      Fri Mar 29 16:08:31 2019 +0000
# Branch non-power-of-two
# Node ID 0c26728f91f06336dd1ef062ee50c73513c92d01
# Parent  1bbc32e21f8009ac0343ce46311ea3b50b9c22ea
Doc notes

diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -4,7 +4,16 @@
 
 A small library wrapping various FFT implementations for some common
 audio processing use cases. Note this is not a general FFT interface,
-as it handles only power-of-two FFT sizes and real inputs.
+as it handles only real inputs.
+
+Transforms of any length are supported, but if you request a length
+not supported by any of the library implementations provided here, or
+by any of the libraries compiled in, a simple slow DFT will be used
+instead. Of the most commonly used libraries, Accelerate and IPP
+support power-of-two lengths only, KissFFT supports any multiple of
+two (because we only use the real-input interface), and FFTW supports
+any length. You can compile in more than one library, so as to use
+e.g. VDSP for powers of two and KissFFT for other even lengths.
 
 Requires the bqvec library.
 
@@ -18,9 +27,10 @@
  * To compile on Linux: Edit Makefile to select implementation, then make test.
    Do read the notes in the Makefile, and don't attempt to use the default
    implementation, which is very slow
+   
  * To compile on macOS: make -f build/Makefile.osx test
 
 [![Build Status](https://travis-ci.org/breakfastquay/bqfft.svg?branch=master)](https://travis-ci.org/breakfastquay/bqfft)
 
-Copyright 2007-2017 Particular Programs Ltd. See the file COPYING for
+Copyright 2007-2019 Particular Programs Ltd. See the file COPYING for
 (BSD/MIT-style) licence terms.