Routine

int AFsetNHpar (const char String[])

Purpose

Set defaults for input headerless audio files from a string specification

Description

This routine sets the default audio file data parameters. These parameters are used for reading audio files with unrecognized (non-standard) headers or files with no headers (raw audio files). This routine must be called before opening the file with AFopnRead. The parameters for AFsetNHpar are determined from an input string which consists of a list of parameters separated by commas and/or white space. The form of the list is

  "Format, Start, Sfreq, Swapb, Nchan, ScaleF"

Format: File data format

 "undefined" - Headerless files will be rejected


 "mu-law8"   - 8-bit mu-law data


 "A-law8"    - 8-bit A-law data


 "unsigned8" - offset-binary 8-bit integer data


 "integer8"  - two's-complement 8-bit integer data


 "integer16" - two's-complement 16-bit integer data


 "integer24" - two's-complement 24-bit integer data


 "integer32" - two's-complement 32-bit integer data


 "float32"   - 32-bit floating-point data


 "float64"   - 64-bit floating-point data


 "text"      - text data

Start: byte offset to the start of data (integer value) Sfreq: sampling frequency in Hz (floating-point number) Swapb: Data byte swap parameter

 "native" - no byte swapping


 "little-endian" - file data is in little-endian byte order and


    will be swapped if the current host uses big-endian byte order


 "big-endian" - data is in big-endian byte order and will be


    swapped swapped if the current host uses little-endian byte


    order


 "swap" - swap the data bytes

Nchan: number of channels
The data consists of interleaved samples from Nchan channels ScaleF: Scale factor

 "default" - Scale factor chosen appropriate to the type of data. The


    scaling factors shown below are applied to the data in the file.


    8-bit mu-law:    1


    8-bit A-law:     1


    8-bit integer:   128


    16-bit integer:  1


    24-bit integer:  1/256


    32-bit integer:  1/65536


    float data:      32768


 "<number or ratio>" - Specify the scale factor to be applied to


    the data from the file.

The default values for the audio file parameters correspond to the following string.

  "undefined, 0, 8000., native, 1, default"

Leading and trailing white-space (as defined by isspace) is removed from each item. Any of the parameters may be omitted, in which case whatever value has been previously set remains in effect for that parameter. The string ",512, 10000." would set the Start and Sfreq parameters and leave the other parameters undisturbed.

If the input string contains has a leading '$', the string is assumed to specify the name of an environment variable after the '$'. This routine uses the value of this environment variable to determine the parameters. If this routine is called as AFsetNHpar("$AF_NOHEADER"), this routine would look for the parameter string in environment variable AF_NOHEADER.

Parameters

<- int AFsetNHpar
Error flag, zero for no error
-> const char String[]
String containing the list of parameters for headerless files or the name of an environment variable (with a leading $)

Author / revision

P. Kabal / Revision 1.53 2003/05/09

See Also

AFopnRead