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Extract Mel-Frequency Cepstral Coefficients (MFCCs) via SPTK

trk_mfcc.Rd

Computes HTK-style MFCCs using the SPTK C++ library. MFCCs are the standard frame-level feature for speech recognition, speaker identification, and general audio classification. Covers the full filterbank-DCT pipeline with optional cepstral liftering.

Usage

trk_mfcc(listOfFiles, beginTime = 0, endTime = 0, windowShift = 10, windowSize = 25, n_mfcc = 13, n_mels = 40, fmin = 0, fmax = NULL, lifter = 22, floor = 1, toFile = TRUE, explicitExt = "mfcc", 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.

windowShift

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

windowSize

Numeric. Analysis window length in milliseconds. Default 25.0 ms.

n_mfcc

Integer. Number of MFCC coefficients to extract (must be < n_mels). Default 13.

n_mels

Integer. Number of Mel filterbank channels. Default 40.

fmin

Numeric. Lowest filterbank center frequency in Hz. Default 0.0 Hz.

fmax

Numeric. Highest filterbank center frequency in Hz. NULL (default) uses the Nyquist frequency.

lifter

Integer. Cepstral liftering exponent (HTK default is 22). Set to 0 to disable liftering. Default 22.

floor

Numeric. Minimum energy floor for Mel filterbank outputs (prevents log(0)). Default 1.0.

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 "mfcc".

beginTime

Start time for the extracted portion in seconds. Default: NULL (beginning of signal). Note: uses beginTime/endTime (seconds) matching DSP function conventions, unlike read_audio() which uses begin/end.

endTime

The end time of the section of the sound files that should be analysed (in seconds). Use 0 for end of file.

outputDirectory

The directory where the slice file should be stored. If not defiled (NULL), the sparse slice file will placed in the same folder as the media file.

verbose

Logical. Show a progress bar (sequential path) or a progress-aware parallel apply (pbapply/pbmcapply, if installed).

Value

If toFile = FALSE: an AsspDataObj with tracks:

mfcc_0 … mfcc_{n_mfcc-1}

REAL32, cepstral coefficients c0 through c{n_mfcc-1}, n_frames × 1 each. Dimensionless.

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

Examples

if (FALSE) { # \dontrun{
# Extract 13 MFCCs (default)
trk_mfcc("recording.wav")

# Extract 20 MFCCs with custom parameters
trk_mfcc("speech.mp3", n_mfcc = 20, n_mels = 80)

# Return data without writing file
mfcc_data <- trk_mfcc("audio.wav", toFile = FALSE)

# Process with specific frequency range
trk_mfcc("recording.wav", fmin = 80, fmax = 8000)

# Process video file (extracts audio)
trk_mfcc("interview.mp4")
} # }