LPsyn

Routine

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

Purpose

LPC synthesis from a residual file

Description

This program does linear prediction synthesis given a file of residual samples and a file of linear prediction coefficients. The output is an audio file containing the reconstructed signal.

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

1: Use the all-pole LPC filter to filter the residual signal
2: Deemphasize the reconstructed 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:LPsyn                   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

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 / v1r3 1995/09/12