For reading waveform data files, HTK can support a variety of different formats and these are all briefly described in this section. The default speech file format is HTK. If a different format is to be used, it can be specified by setting the configuration parameter SOURCEFORMAT. However, since file formats need to be changed often, they can also be set individually via the -F command-line option. This over-rides any setting of the SOURCEFORMAT configuration parameter.
Similarly for the output of waveforms, the format can be set using either the configuration parameter TARGETFORMAT or the -O command-line option. However, for output only native HTK format (HTK), Esignal format (ESIG) and headerless (NOHEAD) waveform files are supported.
The following sub-sections give a brief description of each of the waveform file formats supported by HTK.