Java audio won't init TargetDataLine with correct arguments

Question

I have a mic that uses exactly 48000 sample rate, 24 bits, and 1 channel. So I feed this data into AudioSystem.isLineSupported() and get a false.

I try feeding in 8 bits instead of 24, and it works. But there's a weird background hiss in the audio, so I'm guessing that's not my thing.

Question: how can I debug what's going on? I know for a fact that the settings I'm feeding are correct, so what can it be?

Code I'm using (yes, it's Kotlin):

fun main(args : Array<String>) {
    var line: TargetDataLine? = null
    val thread = Thread(Runnable
    {
        val format = AudioFormat(48000f, 24, 1,
                false, false)
        val info = DataLine.Info(TargetDataLine::class.java, format)
        if (!AudioSystem.isLineSupported(info)) {
            System.out.println("Failed")
        } else {
            line = AudioSystem.getLine(info) as TargetDataLine
            line?.open(format)
            line?.start()
            val ais = AudioInputStream(line)
            AudioSystem.write(ais, AudioFileFormat.Type.WAVE, File("c:/temp/temp.wav"))
        }
    })
    if (line != null) {
        thread.start()
        readLine()
        line?.stop()
        line?.close()
    }
}

Answer 1

I am not completely confident what is really goes on under the hood in your code. But since you feeding in 8 bits it might be just an audio aliasing. So this hiss is expected.

8 bits depth is a very poor audio resolution. It gives your only 256 possible values per sample. Actually the bit depth has an impact to signal-to-noise ratio. And this ratio for 8 bit depth is equal to 48.16 dB which is quite noticeable as a hiss.

Using 24-bits for a resulting format do not improve your 8-bit source automatically. Try to feeding at least in 16-bits and hiss should be gone.