Track short-term zero-crossing rate

Computes the average of the short-term positive and negative zero-crossing rates of audio signals using the libassp C library (Scheffers 2012) . ZCR is a simple, fast measure correlated with spectral centroid and useful for voicing detection and fricative classification.

Usage

trk_zcr(
  listOfFiles,
  beginTime = 0,
  centerTime = FALSE,
  endTime = 0,
  windowShift = 5,
  windowSize = 25,
  toFile = FALSE,
  explicitExt = "zcr",
  outputDirectory = NULL,
  assertLossless = NULL,
  logToFile = FALSE,
  convertOverwrites = FALSE,
  keepConverted = FALSE,
  verbose = TRUE
)

Arguments

listOfFiles: Character vector of audio file paths. Any format supported by av is accepted; non-native inputs are transcoded automatically.
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.
centerTime: Numeric or logical. Single-frame analysis time point in seconds; overrides beginTime, endTime, and windowShift. Default FALSE.
endTime: The end time of the section of the sound files that should be analysed (in seconds). Use 0 for end of file.
windowShift: Numeric. Frame shift in milliseconds; sets output frame rate (1000 / windowShift Hz). Default 5.0 ms (200 Hz). Must be strictly less than 32 ms (the 512-sample analysis window at 16 kHz). Values other than the training default (5 ms) may slightly reduce accuracy.
windowSize: Numeric. Analysis window size in milliseconds. Default 25 ms.
toFile: Logical. If TRUE, write SSFF output files and return the count written. If FALSE, return an AsspDataObj (single file only). Default FALSE.
explicitExt: By default, a character "d" will be prepended to the file name suffix when writing the output to file. The user can also specify an explicit extension which will be used instead.
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.
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.
convertOverwrites: Logical. Allow transcoding to overwrite existing files. Default FALSE.
keepConverted: Logical. Retain intermediate transcoded files. Default FALSE.
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 track:

ZCR[Hz]: REAL32, Hz, n_frames x 1 column. Average zero-crossing rate (positive and negative crossings combined) per frame, expressed as a rate in Hz.

Frame rate: 1000 / windowShift Hz (default 200 Hz). If toFile = TRUE: integer count of files written, returned invisibly.

Details

The ZCR is reported in Hz (crossings per second), averaged over the positive and negative zero-crossing rates within each analysis window.

Author

Raphael Winkelmann

Lasse Bombien

Fredrik Nylén

Examples

# get path to audio file
path2wav <- list.files(
   system.file("samples", "sustained", package = "superassp"),
   pattern = glob2rx("a1.wav"), full.names = TRUE)

# calculate zcr values
res <- trk_zcr(path2wav, toFile=FALSE)
#> Applying `method(trk_zcr, class_character)()` to 1 recording

# plot zcr values
plot(seq(0, n_records(res) - 1) / sample_rate(res) +
      attr(res, 'startTime'),
    res[["ZCR[Hz]"]],
    type='l',
    xlab='time (s)',
    ylab='Zero Crossing Rates (Hz)')