Audio conversion, read/write

[noamross]

R has wav files readers in the audio and tuneR packages, (simple as wav files are just raw audio samples), and the tuneR package can read mp3 files. However, there is now way to write mp3 or other compressed formats.

ffmpeg allows conversion between audio formats. It would be great if one could convert wav tomp3 using av. As ffmpeg allows conversion of raw audio, one could in theory use it to write audio directly to mp3 from a numeric vector and vice versa.

[muschellij2]

It may be possible to hack it (you need to pass in something "video" related):

library(av)
library(tuneR)
library(gapminder)
library(ggplot2)
wav = noise()
input = tempfile(fileext = ".wav")
writeWave(wav, input)
makeplot <- function(){
  datalist <- split(gapminder, gapminder$year)
  lapply(datalist, function(data){
    p <- ggplot(data, aes(gdpPercap, lifeExp, size = pop, color = continent)) +
      scale_size("population", limits = range(gapminder$pop)) + geom_point() + ylim(20, 90) +
      scale_x_log10(limits = range(gapminder$gdpPercap)) + ggtitle(data$year) + theme_classic()
    print(p)
  })
}
res = av_capture_graphics(makeplot(), output = tempfile(fileext = ".mp3"),
                          audio = input)

tuneR::readMP3(res)
#> 
#> Wave Object
#>  Number of Samples:      46080
#>  Duration (seconds):     1.04
#>  Samplingrate (Hertz):   44100
#>  Channels (Mono/Stereo): Mono
#>  PCM (integer format):   TRUE
#>  Bit (8/16/24/32/64):    16

^{Created on 2019-08-11 by the reprex package (v0.3.0)}

Session info

devtools::session_info()
#> ─ Session info ──────────────────────────────────────────────────────────
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[jeroen]

The dev version now has av_encode_audio() which allows you to convert audio from a video/audio file into another audio format.

[muschellij2]

FYI, the command is now av_audio_convert.