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Apply a digital filter to audio signals

trk_affilter.Rd

Filters audio waveforms using FIR or Butterworth IIR designs implemented in the libassp C library (Scheffers 2012) . Supports high-pass, low-pass, and band-pass configurations. At least one of highPass or lowPass must be specified.

Usage

trk_affilter(listOfFiles, highPass = NULL, lowPass = NULL, stopBand = 96, transition = 250, useIIR = FALSE, numIIRsections = 4L, beginTime = 0, endTime = 0, toFile = TRUE, explicitExt = "flt", outputDirectory = NULL, assertLossless = NULL, logToFile = FALSE, keepConverted = FALSE, convertOverwrites = FALSE, verbose = TRUE)

Arguments

listOfFiles

Character vector of audio file paths. Any format supported by av is accepted; non-native inputs are transcoded automatically.

highPass

Numeric. High-pass cutoff frequency in Hz. NULL disables high-pass filtering. Default NULL.

lowPass

Numeric. Low-pass cutoff frequency in Hz. NULL disables low-pass filtering. Default NULL.

stopBand

Numeric. FIR stop-band attenuation in dB (Kaiser window design). Default 96.0.

transition

Numeric. FIR transition band width in Hz. Default 250.0.

useIIR

Logical. Use Butterworth IIR filter instead of FIR. Default FALSE.

numIIRsections

Integer. Number of 2nd-order IIR sections (filter order). Default 4L.

beginTime

Numeric. Start of analysis window in seconds. Default 0 (file start).

endTime

Numeric. End of analysis window in seconds. Default 0 (file end).

toFile

Logical. If TRUE, write SSFF output files and return the count written (invisibly). If FALSE, return an AsspDataObj. Default TRUE.

explicitExt

Character. Output file extension. Default "flt".

outputDirectory

Character. Directory for output files. NULL (default) writes alongside the input file.

assertLossless

Character vector of additional file extensions to treat as losslessly encoded.

logToFile

Logical. Write processing log to a file in outputDirectory rather than the console. Default FALSE.

keepConverted

Logical. Retain intermediate transcoded files. Default FALSE.

convertOverwrites

Logical. Allow transcoding to overwrite existing files. Default FALSE.

verbose

Logical. Print per-file progress. Default TRUE.

Value

If toFile = FALSE: an AsspDataObj with track name preserved from libassp output (the filtered waveform, same label as the input channel), containing INT16 or REAL32 sample values. If toFile = TRUE: integer count of files written, returned invisibly.

Details

Filter mode is determined by highPass/lowPass: supply only highPass for a high-pass filter, only lowPass for a low-pass filter, or both for a band-pass filter. stopBand and transition govern the FIR Kaiser-window design; set useIIR = TRUE to switch to a Butterworth IIR design instead.

References

Scheffers M (2012). “Advanced Speech Signal Processor.” https://sourceforge.net/projects/libassp/files/libassp/.

Author

Fredrik Nylén

Examples

path2wav <- list.files(system.file("samples", "sustained", package = "superassp"),
                       pattern = glob2rx("a1.wav"), full.names = TRUE)
# High-pass filter above 100 Hz
res <- trk_affilter(path2wav, highPass = 100, toFile = FALSE)
#> Applying `method(trk_affilter, class_character)()` to 1 recording