LPanal

Routine

LPanal [options] -p PFile -c LPFile AFileI [AFileO]

Purpose

LPC analysis on a speech file

Description

This program does linear prediction analysis on an audio file. The output file is a file of linear prediction coefficients and the residual file.

The steps involved in forming the linear prediction coefficients are as follows.

1: Preemphasize the input signal (first difference filter)
2: Window the data
3: Calculate the autocorrelation coefficients for the windowed data
4: Calculate the LPC coefficients
5: Bandwidth expand the LPC coefficients

The steps involved in forming the residual signal are as follows.

1: Preemphasize the input signal (first difference filter)
2: Use the LPC coefficients to form the prediction error residual signal.

Options

The command line specifies options and file names. The last file name specifies the output file of the linear prediction residual. Options specify the level of information printed during processing.

-p PFile, --parameter_file=PFile: Parameter file.
-c LPFile, --lpc_file=LPFile: LPC predictor coefficient file.
-s, --statistics: Print frame-by-frame statistics.
-I INFO, --info=INFO: Header information string.
-h, --help: Print a list of options and exit.
-v, --version: Print the version number and exit.

The analysis parameters are read from the parameter file.

  preemphasis_factor = float  ! preemphasis factor (0 to 1, default 0)
  window_length = int         ! analysis window length
  window_offset = int         ! initial offset of the center of the analysis
                              ! window from the center of the frame (negative
                              ! values mean that the analysis window precedes
                              ! frame, default  0)
  window_type = char          ! window type (Hamming or rectangular, default
                              ! Hamming)
  frame_length = int          ! frame size
  LPC_number = int            ! number of LPC coefficients
  LPC_BW_expansion = float    ! bandwidth expansion factor (1 gives no
                              ! bandwidth expansion, default 1)

For AFsp output files, the audio file header contains an information string.

  Standard Header Information:
    date:1994/01/25 19:19:39 UTC    date
    user:kabal@aldebaran            user
    program:LPanal                  program name
    parameters:<parameters>         list of parameters

This information can be changed with the header information string which is specified as one of the command line options. Structured information records should adhere to the above format with a named field terminated by a colon, followed by numeric data or text. Comments can follow as unstructured information. For the purpose of this program, records are terminated by newline characters. However in the header itself, the newline characters are replaced by nulls. To place a newline character into the header, escape the newline character by preceding it with a '\' character. If the first character of the user supplied header information string is a newline character, the header information string is appended to the standard header information. If not, the user supplied header information string replaces the standard header information.

Environment variables

RAWAUDIOFILE:

This environment variable defines the data format for headerless or non-standard input audio files. The string consists of a list of parameters separated by commas. The form of the list is

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

Format: File data format

The lowercase versions of these format specifiers cause a headerless file to be accepted only after checking for standard file headers; the uppercase versions cause a headerless file to be accepted without checking the file header.

 "undefined"                - Headerless files will be rejected
 "mu-law8" or "MU-LAW8"     - 8-bit mu-law data
 "A-law8" or "A-LAW8"       - 8-bit A-law data
 "unsigned8" or "UNSIGNED8" - offset-binary 8-bit integer data
 "integer8" or "INTEGER8"   - two's-complement 8-bit integer data
 "integer16" or "INTEGER16" - two's-complement 16-bit integer data
 "float32" or "FLOAT32"     - 32-bit floating-point data
 "text" or "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
 "big-endian" - file data is in big-endian byte order
 "swap" - swap the data bytes as the data is read

Nchan: number of channels

The data consists of interleaved samples from Nchan channels

ScaleF: Scale factor

Scale factor 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, 1.0"

AUDIOPATH:

This environment variable specifies a list of directories to be searched when opening the input audio files. Directories in the list are separated by colons (semicolons for MS-DOS).

Author / version

P. Kabal / v1r5 1996/08/13