Converting with R

    In this section we will discuss some options for working with different audio formats in R, and converting between those formats. When using R to work with audio files, we typically use the tuneR package to import audio, which stores the data as a Wave class object. The packages and functions discussed below will cover importing a range of audio formats (WAVE, MP3, FLAC, WAC) as a Wave object. Once you have a Wave object, you can export the audio as a WAVE file if you desire. It is also possible to convert between WAVE and FLAC within R, which will be discussed.

    Throughout this guide, we will provide examples of how to call the various R functions, based on the example R project working directory shown below. Three audio files are provided to use in the examples, and you can download those files here.

    .
├── my-project.Rmd
├── data
│   ├── CC1_20171010_125500.wav
│   ├── CC1_20171011_053000.mp3
│   └── 20220421T100000+1000_SEQP-Samford-Wet-B_644370_0000_5857.flac
├── output
└── my-project.Rproj

    Importing WAVE files #

    If you already have WAVE files, then no conversion is necessary. You can read your files directly into R with the tuneR function readWave:

    library(tuneR)
# Import WAVE file
CC1_20171010_125500_Wave <- readWave(filename = "data/CC1_20171010_125500.wav")

    Reading sound files with tuneR stores the data in a Wave class object:

    CC1_20171010_125500_Wave
## Wave Object
##	Number of Samples:      1323008
##	Duration (seconds):     60
##	Samplingrate (Hertz):   22050
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16

    Importing and converting MP3 #

    If you have MP3 files, you can read those directly into R using the tuneR package, with the function readMP3:

    library(tuneR)
# Import MP3 file
CC1_20171011_053000_Wave <- readMP3(filename = "data/CC1_20171011_053000.mp3")

    CC1_20171011_053000_Wave
## Wave Object
##	Number of Samples:      1324224
##	Duration (seconds):     60.06
##	Samplingrate (Hertz):   22050
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16

    A Wave object can be exported as a WAVE audio file at any point using the writeWave function. See this example of exporting the audio which was imported above with the readMP3 function as a WAVE file.

    # Export the wave object as a .wav sound file
writeWave(CC1_20171011_053000_Wave, filename = "output/CC1_20171011_053000.wav")

    Converting a directory from MP3 to WAVE #

    If you wish to convert all MP3 files within a directory to WAVE prior to analysis, you can do so with the mp32wav function in the warbleR package.

    library(warbleR)
mp32wav(path = "data/", dest.path = "output/")
    Warning:
    The mp32wav function relies on the tuneR package. Sometimes, this function does not work, and RStudio may abort. Although this bug should be fixed in future versions of tuneR, if this happens to you, alternative conversion methods are available (see our ffmpeg or Audacity (todo) help pages).

    Importing and converting WAC files #

    The utility to read the Wildlife Acoustics proprietary Compressed format (WAC, file extension: .wac) is provided by the bioacoustics package, with their read_wac function. See the example below on using the read_wac function directly using the bioacoustics package. This function also the useful option of converting your WAC files into WAVE using the write_wav setting. The example code below is provided by the bioacoustics package, which reads in a practice WAC file that is included with the bioacoustics package.

    library(bioacoustics)
filepath <- system.file("extdata", "recording_20170716_230503.wac", package = "bioacoustics")
read_wac(file = filepath)

    sound_wac
## Wave Object
##	Number of Samples:      230144
##	Duration (seconds):     0.6
##	Samplingrate (Hertz):   384000
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16

    Importing and converting FLAC #

    tuneR does not read FLAC files, but there are R packages which can help you to work with FLAC, and perform conversions between FLAC and WAVE.

    Warning:
    Sometimes, these R functions for reading or converting FLAC files may not work for very large or long duration files (such as files greater than 1 hour in duration). If you find this issue, we have guides for other converting methods available. See the help pages in Converting audio files.

    seewave #

    The seewave package provides an integration with a software called FLAC that converts FLAC files into WAVE, by using the function wav2flac. The function actually converts both ways (FLAC to WAVE, WAVE to FLAC). Before seewave can convert FLAC, you will need to install the FLAC software. See our FLAC help page for more information. Further details on the wav2flac function can be found here.

    library(seewave)
# reverse = TRUE covnerts a flac to a wav file
wav2flac(
        file = "data/20220421T100000+1000_SEQP-Samford-Wet-B_644370_0000_5857.flac",
        reverse = TRUE,
        overwrite = FALSE)

# reverse = FALSE converts a wav to a flac file
wav2flac(
        file = "data/CC1_20171010_125500.wav",
        reverse = FALSE,
        overwrite = FALSE)

    warbleR #

    The wableR package can read FLAC files directly, using the function read_sound_file. However, they point out in the documentation that to read FLAC files the function is actually creating a temporary copy of your sound file in WAVE format and this can take a long time to process, especially for long files. If the goal is opening and processing many long duration files, this might be slow. Like the seewave function described previously, this function also requires the FLAC software to be installed on your system.

    Besides reading FLAC files, the read_sound_file function in the warbleR package is also useful because it can read sound files in WAVE, FLAC, MP3 and WAC format, and return a Wave class object. See the examples below that demonstrate importing different audio formats using the read_sound_files function:

    library(warbleR)
CC1_20171010_125500_Wave <- read_sound_file("data/CC1_20171010_125500.wav")

    CC1_20171010_125500_Wave
## Wave Object
##	Number of Samples:      1323008
##	Duration (seconds):     60
##	Samplingrate (Hertz):   22050
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16 

    library(warbleR)
Samford_Wet_B_644370_0000_5857_Wave <- read_sound_file("data/20220421T100000+1000_SEQP-Samford-Wet-B_644370_0000_5857.flac")

    Samford_Wet_B_644370_0000_5857_Wave
## Wave Object
##	Number of Samples:      77985651
##	Duration (seconds):     3536.76
##	Samplingrate (Hertz):   22050
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16 

    library(warbleR)
CC1_20171011_053000_Wave <- read_sound_file("data/CC1_20171011_053000.mp3")

    CC1_20171011_053000_Wave
## Wave Object
##	Number of Samples:      1324224
##	Duration (seconds):     60.06
##	Samplingrate (Hertz):   22050
##	Channels (Mono/Stereo): Mono
##	PCM (integer format):   TRUE
##	Bit (8/16/24/32/64):    16 

    library(warbleR)
filepath <- system.file("extdata", "recording_20170716_230503.wac", package = "bioacoustics")
recording_20170716_230503_Wave <- read_sound_file(filepath)

    recording_20170716_230503_Wave
## Wave Object
##  Number of Samples:      230144
##  Duration (seconds):     0.6
##  Samplingrate (Hertz):   384000
##  Channels (Mono/Stereo): Mono
##  PCM (integer format):   TRUE
##  Bit (8/16/24/32/64):    16
    Note:
    The warbleR package uses functions from various packages internally, including seewave, monitoR, tuneR and dtw, to simplify the process of acoustic analysis in R. These packages should also be given credit when using warbleR, by including citations in publications as appropriate (e.g. citation("seewave")).

    Help! I’m using a different audio format #

    If you have a different audio format that was not discussed above, you may need to convert your files using a different software. See our FFmpeg help page for more information.