Trigger audio files using a slider in R Shiny

Hi I'm trying to develop a Shiny app where a moveable slider triggers the audio samples, whereby each point in a slider (say ranging from 0 to 100) is mapped to a specific audio. So moving the slider will alter the sound according to the slider position. Ideally, I would want the transition between slider positions to smooth sounding and highly interactive.

I'm guessing I would need to use the code below to map each slider value to a specific audio file.

tags$audio(src = "sound.mp3", type = "audio/mp3", autoplay = NA, controls = NA)

Anyone know of the best approach for getting such task done or give me some pointers?

Solution

You can change the src argument via JS and trigger the change with the slider. Please check the following:

library(shiny)
library(htmltools)
library(tuneR)
library(shinyjs)

xseq <- round(seq(from = 440, to = 880, length.out = 100), digits = 0)

if(!dir.exists("audio")){
  dir.create("audio")
}

# create some audio files
filenames = paste0("audio/", xseq, ".wav")
for (i in seq_along(xseq)) {
  Wobj <- sine(xseq[i])
  writeWave(Wobj, filename = filenames[i])
}

# Add directory of static resources to Shiny's web server
addResourcePath(prefix = "audioResources", directoryPath = "audio")

myAudioResources <- paste0("audioResources/", xseq, ".wav")

ui <- fluidPage(
  useShinyjs(),
  tags$audio(id = "myaudio", controls = NA, autoplay = NA, src = ""),
  sliderInput(inputId = "selectTrack", "Select track", min = 1,
              max = length(xseq),
              value = 1)
)

server <- function(input, output, session) {
  observeEvent(input$selectTrack, {
    runjs(sprintf("document.getElementById('myaudio').src = '%s';", myAudioResources[input$selectTrack])) # dynamically change src
  })
}

shinyApp(ui, server)

This is based on my earlier answer here.