HTK tools can read speech waveform files with alien formats provided that their overall structure is that of a header followed by data. This is done by setting the format to ALIEN and setting the environment variable HEADERSIZE to the number of bytes in the header. HTK will then attempt to infer the rest of the information it needs. However, if input is from a pipe, then the number of samples expected must be set using the environment variable NSAMPLES . The sample rate of the source file is defined by the configuration parameter SOURCERATE as described in section 5.2. If the file has no header then the format NOHEAD may be specified instead of ALIEN in which case HEADERSIZE is assumed to be zero.