File I/0 and the AsspDataObj
Let’s get started by locating some example material distributed with the package.
## Lade nötiges Paket: tibble# get the path to the data that comes with the package
wavPath = system.file('extdata', package='wrassp')
# now list the .wav files so we have some audio files to play with
wavFiles = list.files(wavPath, pattern=glob2rx('*.wav'), full.names=TRUE)One of the aims of wrassp is to provide mechanisms to
handle speech-related files such as sound files and parametric data
files. wrassp therefore comes with a class called
AsspDataObj which does just that.
# load an audio file, e.g. the first one in the list above
au = read.AsspDataObj(wavFiles[1])
# show class
class(au)## [1] "AsspDataObj"## Assp Data Object of file /tmp/Rtmp3QfY0F/Rinst186cc6eed5e45/wrassp/extdata/lbo001.wav.
## Format: WAVE (binary)
## 19983 records at 16000 Hz
## Duration: 1.248938 s
## Number of tracks: 1
## audio (1 fields)au is an object of the class AsspDataObj
and, using print, we can get some information about the
object, such as its sampling rate, its duration and what kind of data
are stored in what form. Since the file we loaded is audio only, the
object contains exactly one track. And since it’s a mono file, this
track only has one field. We will later encounter different types of
data with more than one track and more fields per track.
Here are some more ways of extracting attributes from the object, such as duration, sampling rate and the number of records:
## [1] 1.248938## [1] 16000## [1] 19983## $names
## [1] "audio"
##
## $trackFormats
## [1] "INT16"
##
## $sampleRate
## [1] 16000
##
## $filePath
## [1] "/tmp/Rtmp3QfY0F/Rinst186cc6eed5e45/wrassp/extdata/lbo001.wav"
##
## $origFreq
## [1] 0
##
## $startTime
## [1] 0
##
## $startRecord
## [1] 1
##
## $endRecord
## [1] 19983
##
## $class
## [1] "AsspDataObj"
##
## $fileInfo
## [1] 21 2An important property of AsspDataObj is of course that
it contains data tracks, or at least one data track. As mentioned above,
the currently loaded object contains a single mono audio track.
Accessing the data is easy: AsspDataObj stores data in
simple matrices, one matrix for each track. Broadly speaking,
AsspDataObj is nothing but a list of at least one matrix.
All of them have the same number of rows (number of records) but each
can have a different number of columns (number of fields). Each track
has a name and we can access the track using that name.
## [1] "audio"## [1] "audio"## [,1]
## [1,] 5
## [2,] -2
## [3,] 17
## [4,] -5
## [5,] -5
## [6,] -2# and we can of course also plot these samples
# (only plot every 10th element to accelerate plotting)
plot(seq(0,numRecs.AsspDataObj(au) - 1, 10) / rate.AsspDataObj(au),
au$audio[c(TRUE, rep(FALSE,9))],
type='l',
xlab='time (s)',
ylab='Audio samples')
Now, purely to give us something unequal to the original
au object to write to disc, let’s manipulate the audio data
by simply multiplying all the sample values by a factor of
0.5. The resulting AsspDataObj will then be
saved to a temporary directory provided by R.
