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

Input file name: AFileI:
The environment variable AUDIOPATH specifies a list of directories to be searched for the input audio file. Output file name: AFileO:
This name specifies the optional output file containing the linear prediction residual. Specifying "-" as the output file indicates that output is to be written to standard output. -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
Audio file information string for the output file. -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)

By default, the output file contains a standard audio file information string.



  Standard Audio File Information:


     date: 1994-01-25 19:19:39 UTC    date


     program: LPanal                  program name


     parameters: <parameters>         list of analysis 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.



  Record delimiter: Newline character or the two character escape


      sequence "\" + "n".


  Line delimiter: Within records, lines are delimiteded by a carriage


      control character, the two character escape sequence "\" + "r",


      or the two character sequence "\" + newline.

If the information string starts with a record delimiter, the header information string is appended to the standard header information. If not, the user supplied header information string appears alone.

Environment variables

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 Windows).

Author / version