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Track formants and bandwidths using the Snack/ESPS LPC tracker

trk_formant_snack.Rd

Extracts formant frequencies and bandwidths using the Snack Sound Toolkit dynamic-programming LPC formant tracker (Talkin / AT&T / KTH, jkFormant.c). This tracker applies normalized cross-correlation for voicing detection and a DP smoother for temporal continuity. It is a strong general-purpose alternative to Burg-method trackers, particularly for lower sample-rate or telephone-bandwidth speech.

Usage

trk_formant_snack(listOfFiles, beginTime = 0, endTime = 0, numFormants = 4, lpcOrder = 12, windowLength = 0.049, windowShift = 10, preEmphasis = 0.7, dsFreq = 10000, nomF1 = -10, lpcType = 0, windowType = 2, toFile = TRUE, explicitExt = "snackfmt", outputDirectory = NULL, verbose = TRUE)

Arguments

listOfFiles

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

beginTime

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

endTime

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

numFormants

Integer. Number of formants to track (1–7). Default 4.

lpcOrder

Integer. LPC order; must satisfy lpcOrder >= numFormants * 2 + 4. Default 12.

windowLength

Numeric. Analysis window duration in seconds. Default 0.049 s.

windowShift

Numeric. Frame shift in milliseconds; sets output frame rate (1000 / windowShift Hz). Default 10.0 ms.

preEmphasis

Numeric. Pre-emphasis filter coefficient (0–1). Default 0.7.

dsFreq

Numeric. Target downsample frequency in Hz; limits formant search to 0–dsFreq/2 Hz. Default 10000 Hz.

nomF1

Numeric. Nominal F1 for DP cost function. -10 (default) uses built-in defaults derived from dsFreq.

lpcType

Integer. LPC method: 0 = autocorrelation, 1 = stabilized covariance, 2 = covariance. Default 0.

windowType

Integer. Window type: 0 = rectangular, 1 = Hamming, 2 = cos^4, 3 = Hanning. Default 2.

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 "snackfmt".

outputDirectory

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

verbose

Logical. Print per-file progress. Default TRUE.

Value

If toFile = FALSE: an AsspDataObj with tracks:

fm

REAL32, formant frequencies in Hz, n_frames × numFormants. Columns correspond to F1, F2, …, F{numFormants}.

bw

REAL32, formant bandwidths in Hz, n_frames × numFormants.

Frame rate: 1000 / windowShift Hz (default 100 Hz). If toFile = TRUE: integer count of files written, returned invisibly.

Examples

if (FALSE) { # \dontrun{
# 4-formant tracking
res <- trk_formant_snack("recording.wav", toFile = FALSE)
names(res)  # "fm" "bw"

# Custom LPC order and formant count
trk_formant_snack("speech.mp3", numFormants = 5, lpcOrder = 14)
} # }