SYNOPSIS

ch_wave [-h ] [-itype file type ] [-n channels ] [-f sample rate ] [-ibo byte order ] [-iswap ] [-istype sample type ] [-c channel ] [-start seconds ] [-end seconds ] [-from sample ] [-to sample ] [-o output file ] [-otype file type ] [-F sample rate ] [-obo byte order ] [-oswap ] [-ostype sample type ] [-scale factor ] [-scaleN factor ] [-lpfilter frequency ] [-hpfilter freqency ] [-forder order ] [-fafter ] [-info ] [-add ] [-pc LONGEST | FIRST ] [-key keylab file ] [-divide ] [-ext file extension ] [-extract file ] input files ...

DESCRIPTION

ch_wave performs various operations on an input waveform file and writes it out to another file. Among other things, it can extract subsections or individual channels, resample, rescale, mix down channels, and perform simple filtering operations.

The following option flags are recognized:

-h

Options help

-itype file type

Input file type (optional). If set to raw, this indicates that the input file does not have a header. While this can be used to specify file types other than raw, this is rarely used for other purposes as the file type of all the existing supported types can be determined automatically from the file's header. If the input file is unheadered, files are assumed to be shorts (16bit). Supported types are nist, est, esps, snd, riff, aiff, audlab, raw, ascii

-n channels Number of channels in an unheadered input file

-f sample rate

Sample rate in Hertz for an unheadered input file

-ibo byte order

Input byte order in an unheadered input file: possibliities are: MSB , LSB, native or nonnative. Suns, HP, SGI Mips, M68000 are MSB (big endian) Intel, Alpha, DEC Mips, Vax are LSB (little endian)

-iswap

Swap bytes. (For use on an unheadered input file)

-istype sample type

Sample type in an unheadered input file: short, alaw, mulaw, byte, ascii

-c channel

Select a single channel (starts from 0). Waveforms can have multiple channels. This option extracts a single channel for progcessing and discards the rest.

-start seconds

Extract sub-wave starting at this time, specified in seconds

-end seconds

Extract sub-wave ending at this time, specified in seconds

-from sample

Extract sub-wave starting at this sample point

-to sample

Extract sub-wave ending at this sample point

-o output file

Output filename. If not specified output is to stdout.

-otype file type

Output file type, (optional). If no type is Specified the type of the input file is assumed. Supported types are: nist, est, esps, snd, riff, aiff, audlab, raw, ascii

-F sample rate

Output sample rate in Hz. If this is different from the input sample rate, resampling will occur

-obo byte order

Output byte order: MSB, LSB, native, or nonnative. Suns, HP, SGI Mips, M68000 are MSB (big endian), Intel, Alpha, DEC Mips, Vax are LSB (little endian)

-oswap

Swap bytes when saving to output

-ostype sample type

Output sample type: short, alaw, mulaw, byte or ascii

-scale factor

Scaling factor. Increase or descrease the amplitude of the whole waveform by the factor given (relative to 1.0)

-scaleN factor Scaling factor with normalization. The waveform is

scaled to its maximum level, after which it is scaled by the factor given (relative to 1.0)

-lpfilter frequency

Low pass filter, with cutoff frequency in Hz Filtering is performed by a FIR filter which is built at run time. The order of the filter can be given by -forder. The default value is 199

-hpfilter freqency

High pass filter, with cutoff frequency in Hz Filtering is performed by a FIR filter which is built at run time. The order of the filter can be given by -forder. The default value is 199.

-forder order

Order of FIR filter used for lpfilter and hpfilter. This must be ODD. Sensible values range from 19 (quick but with a shallow rolloff) to 199 (slow but with a steep rolloff). The default is 199.

-fafter

Do filtering after other operations such as resampling (default : filter before other operations)

-info

Print information about file and header. This option gives useful information such as file length, sampling rate, number of channels etc No output is produced

-add

A new single channel waveform is created by adding the corresponding sample points of each input waveform

-pc LONGEST | FIRST

Combine input waveforms to form a single multichannel waveform. The argument to this option controls how long the new waveform should be. If the option is LONGEST, the output wave if the length of the longest input wave and shorter waves are padded with zeros at the end. If the option is FIRST, the length of the new waveform is the length of the first file on the command line, and subsequent waves are padded or cut to this length

-key keylab file

Label file designating subsections, for use with -divide. The KEYLAB file is a label file which specifies where chunks (such as individual sentences) in a waveform begin and end. See section on wave extraction.

-divide

Divide a single input waveform into multiple output waveforms. Each output waveform is extracted from the input waveform by using the KEYLAB file, which specifies the start and stop times for each chunk. The output files are named according to the filename in the KEYLAB file, with extension given by -ext. See section on wave extraction

-ext file extension

File extension for divided waveforms

-extract file

Used in conjunction with -key to extract a single section of waveform from the input waveform. The argument is the name of a file given in the file column of the KEYLAB file.

EXAMPLES