csound-xtract : Csound feature extraction using libXtract

Overview

csound-xtract is a set of plugin opcodes which use libXtract to perform feature extraction and associated tasks from within Csound.

Development is still ongoing and subject to various research matters, thus is provided in an experimental/alpha state and may contain bugs. Parts of the code are due overhauls and refactoring, but the intention is for the opcodes and general operation to remain the same as presented here.

Requirements

Cmake >= 2.8.12
Csound with development headers >= 6.14.0
LibXtract

Tested on Linux and Windows 7 with MSYS as of March 2021.

Installation

Create a build directory at the top of the source tree, execute cmake .., make and optionally make install as root. If the latter is not used/possible then the resulting libcsxtract library can be used with the --opcode-lib flag in Csound. eg:

mkdir build && cd build
cmake ..
make && sudo make install

Cmake should find Csound and libXtract using the modules in the cmake/Modules directory and installation should be as simple as above.

Examples

Some examples are provided in the examples directory.

Opcode reference

iprofile xtprofile [ibuffersize=4096, iblocksize=512, imfccs=1, icentroid=1, izerocrossings=1, irms=1, iflatness=1, iirregularity=1, ipower=1, isharpness=1, ismoothness=1]

Declare a feature extraction profile for use in extraction opcodes. The exact techniques for extraction of individual features can be found by examining the libXtract documentation and source code.

iprofile : the profile handle
ibuffersize : buffer size used in extraction
iblocksize : block size for extraction
imfccs : use MFCCs
icentroid : use spectral centroid
izerocrossings : use zero crossings
irms : use RMS
iflatness : use spectral flatness
iirregularity : use spectral irregularity
ipower : use spectral power
isharpness : use spectral sharpnesss

icorpus xtcorpus iprofile, ifn

Analyse sound contained in a f-table and store in a handle, for later use in comparison/matching opcodes. Done during init time.

icorpus : the corpus handle
iprofile : profile handle as created by xtprofile
ifn : f-table containing the sound to be analysed, typically GEN1

ixtract, kdone xtractor iprofile, ain

Analyse a live sound.

ixtract : the extraction handle
iprofile : profile handle as created by xtprofile
ain : sound to analyse

kdistance xtdistance ixtract1, ixtract2, ktrigger, [idistancefunc=0]

Compare two extraction streams using a basic distance function between each frame of the analyses. The profiles used for the streams must be the same.

kdistance : the calculated distance, 0 should represent no difference between the analyses.
ixtract1 : analysis stream as created by xtractor
ixtract2 : analysis stream as created by xtractor
ktrigger : comparison is conducted when 1
idistancefunc : 0 for Euclidean distance, 1 for Manhattan distance

kanalysis[] xtdump ixtract

Obtain the analysis data from an xtractor handle. The array length will depend on the number of features specified in the profile used (MFCC uses 13 indexes, all others use 1). The indexes are presented in the same order as declared in xtprofile. For example, a profile using MFCC and centroid would mean indexes 0 to 12 would be MFCCs, and 13 would be centroid. Similarly a profile using only centroid and flatness would imply index 0 would be centroid, and 1 would be flatness.

kanalysis[] : the analysed features
ixtract : analysis stream as created by xtractor

kdone, kanalysis[] xtaccdump ixtract, ktrigger

Obtain the analysis data from an xtractor handle as with xtdump, but accumulate the analyses and output the mean when ktrigger is 1.

kdone : outputs 1 when new data is provided, 0 at all other times
kanalysis[] : the analysed features as with xtdump.
ixtract : analysis stream as created by xtractor
ktrigger : triggers the output of data when 1

kposition xtcorpusmatch icorpus, ixtract, ktrigger, [idistancefunc=0]

Obtain the nearest match in a corpus created with xtcorpus by comparing a live input stream created by xtractor.

kposition : position of nearest corpus region, in sample points
icorpus : corpus handle as created by xtcorpus
ixtract : analysis stream as created by xtractor
ktrigger : perform the comparison when 1
idistancefunc : 0 for Euclidean distance, 1 for Manhattan distance