KMP IOS convert PCM int 16 bit to PCM float 32 bit

fun convertMonoPCMInt16ToStereoPCMFloat32(
        inputData: ByteArray, inputSampleRate: Double, outputSampleRate: Double
    ): AVAudioPCMBuffer? {
        val inputFrameLength = inputData.size / 2  // 2 bytes per Int16 sample
        val resampleRatio = outputSampleRate / inputSampleRate
        val outputFrameLength = (inputFrameLength * resampleRatio).toInt()

        val audioFormat = AVAudioFormat(standardFormatWithSampleRate = outputSampleRate, channels = 2u)
        val outputBuffer = AVAudioPCMBuffer(audioFormat, frameCapacity = outputFrameLength.toUInt()) ?: return null

        val leftChannel = outputBuffer.floatChannelData!![0]
        val rightChannel = outputBuffer.floatChannelData!![1]

        for (outputFrame in 0 until outputFrameLength) {
            val inputFrameFloat = outputFrame / resampleRatio
            val inputFrame = inputFrameFloat.toInt()
            val fraction = inputFrameFloat - inputFrame

            val sample1 = readInt16Sample(inputData, inputFrame, inputFrameLength)
            val sample2 = readInt16Sample(inputData, inputFrame + 1, inputFrameLength)
            val interpolatedSample = (1 - fraction) * sample1 + fraction * sample2

            // Convert to Float and apply gain control
            val floatSample = (interpolatedSample / Short.MAX_VALUE.toFloat()) * 0.7f  // Apply -3dB attenuation

            // Duplicate to stereo
            leftChannel!![outputFrame] = floatSample.toFloat()
            rightChannel!![outputFrame] = floatSample.toFloat()
        }

        outputBuffer.frameLength = outputFrameLength.toUInt()
        return outputBuffer
    }

    private fun readInt16Sample(inputData: ByteArray, index: Int, length: Int): Int {
        if (index >= length) return 0
        val low = inputData[index * 2].toInt() and 0xFF
        val high = inputData[index * 2 + 1].toInt()
        return (high shl 8) or low
    }