WIP: Sample rate conversion
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package com.rhubarb_lip_sync.audio
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import java.io.InputStream
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import java.nio.ByteBuffer
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import java.nio.ByteOrder
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import kotlin.math.max
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import kotlin.math.min
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import kotlin.math.round
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import kotlin.math.roundToInt
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typealias CoeffArray = FloatArray
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const val SRC_MAX_RATIO = 256
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inline class FixedPoint constructor(private val value: Int) {
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companion object {
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private const val SHIFT_BITS = 12
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private const val FP_ONE = (1 shl SHIFT_BITS).toDouble()
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private const val INV_FP_ONE = 1.0 / FP_ONE
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fun fromDouble(doubleValue: Double) = FixedPoint((doubleValue * FP_ONE).roundToInt())
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fun fromInt(intValue: Int) = FixedPoint(intValue shl SHIFT_BITS)
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val ZERO = fromInt(0)
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}
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fun toInt() = value shr SHIFT_BITS
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fun toDouble() = getFractionPart() * INV_FP_ONE
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private fun getFractionPart() = value and ((1 shl SHIFT_BITS) - 1)
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operator fun plus(other: FixedPoint) = FixedPoint(value + other.value)
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operator fun minus(other: FixedPoint) = FixedPoint(value - other.value)
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operator fun div(other: FixedPoint) = value / other.value
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operator fun times(other: Int) = FixedPoint(value * other)
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operator fun compareTo(other: FixedPoint) = value.compareTo(other.value)
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}
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fun InputStream.readLittleEndianInt32() = read() or (read() shl 8) or (read() shl 16) or (read() shl 24)
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class SincFilter(val inputSampleRate: Int, val outputSampleRate: Int) {
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val ratio = outputSampleRate.toDouble() / inputSampleRate
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init {
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if (ratio < (1.0 / SRC_MAX_RATIO) || ratio > (1.0 * SRC_MAX_RATIO)) {
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throw Error("SRC ratio outside [1/$SRC_MAX_RATIO, $SRC_MAX_RATIO] range.")
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}
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}
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var last_position: Double = 0.0
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var in_count: Int = 0
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var in_used: Int = 0
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var out_count: Int = 0
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var out_gen: Int = 0
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companion object {
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// Load coefficients from resource
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val index_inc: Int
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val coeffs: CoeffArray
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val coeff_half_len: Int
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init {
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// Load coefficient data from stream
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val stream = ::SincFilter.javaClass.getResourceAsStream("coeffs.bin")
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check(stream != null) { "Error loading coefficients." }
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index_inc = stream.readLittleEndianInt32()
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val floatBuffer = ByteBuffer.wrap(stream.readBytes())
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.also { it.order(ByteOrder.LITTLE_ENDIAN) }
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.asFloatBuffer()
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stream.close()
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val coeffCount = floatBuffer.limit()
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coeffs = CoeffArray(coeffCount).also { floatBuffer.get(it) }
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coeff_half_len = coeffCount - 2
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}
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}
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var b_current: Int = 0
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var b_end: Int = 0
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var b_real_end: Int = -1
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val b_len: Int = run {
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var length = 3 * ((coeff_half_len + 2.0) / index_inc * SRC_MAX_RATIO + 1).roundToInt()
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length = max(length, 4096)
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// There is a <= check against samples_in_hand requiring a buffer bigger than the calculation above
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length += 1
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return@run length
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}
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val buffer: SampleArray = SampleArray(b_len + 1 /* 1 channel */)
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fun process(data: Data) {
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in_count = data.data_in.size
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out_count = data.data_out.size
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in_used = 0
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out_gen = 0
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// Check the sample rate ratio wrt the buffer len.
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var count: Double = (coeff_half_len + 2.0) / index_inc
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if (ratio < 1.0) count /= ratio
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/* Maximum coefficientson either side of center point. */
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val half_filter_chan_len: Int = count.roundToInt() + 1
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var input_index: Double = last_position
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var rem: Double = fmod_one (input_index)
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b_current = (b_current + (input_index - rem).roundToInt()) % b_len
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input_index = rem
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val terminate: Double = 1.0 / ratio + 1e-20
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/* Main processing loop. */
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while (out_gen < out_count) {
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/* Need to reload buffer? */
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var samples_in_hand: Int = (b_end - b_current + b_len) % b_len
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if (samples_in_hand <= half_filter_chan_len) {
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prepare_data(data, half_filter_chan_len)
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samples_in_hand = (b_end - b_current + b_len) % b_len
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if (samples_in_hand <= half_filter_chan_len) break
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}
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/* This is the termination condition. */
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if (b_real_end >= 0) {
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if (b_current + input_index + terminate > b_real_end) break
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}
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val float_increment: Double = index_inc * (if (ratio < 1.0) ratio else 1.0)
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val increment: FixedPoint = FixedPoint.fromDouble(float_increment)
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val start_filter_index: FixedPoint = FixedPoint.fromDouble(input_index * float_increment)
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data.data_out[out_gen] = ((float_increment / index_inc) * calc_output_single (increment, start_filter_index)).toFloat()
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out_gen++
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/* Figure out the next index. */
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input_index += 1.0 / ratio
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rem = fmod_one(input_index)
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b_current = (b_current + (input_index - rem).roundToInt()) % b_len
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input_index = rem
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}
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last_position = input_index
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data.input_frames_used = in_used
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data.output_frames_gen = out_gen
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}
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private fun prepare_data (data: Data, half_filter_chan_len: Int) {
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if (b_real_end >= 0) return
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var len: Int = 0
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if (b_current == 0) {
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// Initial state.
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// Set up zeros at the start of the buffer and then load new data after that.
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len = b_len - 2 * half_filter_chan_len
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b_current = half_filter_chan_len
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b_end = half_filter_chan_len
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} else if (b_end + half_filter_chan_len + 1 /* 1 channel */ < b_len) {
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/* Load data at current end position. */
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len = max(b_len - b_current - half_filter_chan_len, 0)
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} else {
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/* Move data at end of buffer back to the start of the buffer. */
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len = b_end - b_current
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System.arraycopy(buffer, b_current - half_filter_chan_len, buffer, 0, half_filter_chan_len + len)
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b_current = half_filter_chan_len
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b_end = b_current + len
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/* Now load data at current end of buffer. */
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len = max(b_len - b_current - half_filter_chan_len, 0)
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}
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len = min(in_count - in_used, len)
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check(len >= 0 && b_end + len <= b_len) { "Internal error: Bad length in prepare_data()." }
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System.arraycopy(data.data_in, in_used, buffer, b_end, len)
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b_end += len
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in_used += len
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if (in_used == in_count && b_end - b_current < 2 * half_filter_chan_len && data.end_of_input) {
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// Handle the case where all data in the current buffer has been consumed and this is
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// the last buffer.
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if (b_len - b_end < half_filter_chan_len + 5) {
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/* If necessary, move data down to the start of the buffer. */
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len = b_end - b_current
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System.arraycopy(buffer, b_current - half_filter_chan_len, buffer, 0, half_filter_chan_len + len)
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b_current = half_filter_chan_len
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b_end = b_current + len
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}
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b_real_end = b_end
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len = half_filter_chan_len + 5
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if (len < 0 || b_end + len > b_len) {
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len = b_len - b_end
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}
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buffer.fill(0.0f, b_end, len)
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b_end += len
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}
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}
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private fun calc_output_single(increment: FixedPoint, start_filter_index: FixedPoint): Double {
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var fraction: Double
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var icoeff: Double
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var data_index: Int
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var coeff_count: Int
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var indx: Int
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/* Convert input parameters into fixed point. */
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val max_filter_index = FixedPoint.fromInt(coeff_half_len)
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/* First apply the left half of the filter. */
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var filter_index: FixedPoint = start_filter_index
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coeff_count = (max_filter_index - filter_index) / increment
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filter_index += increment * coeff_count
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data_index = b_current - coeff_count
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var left = 0.0
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do {
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if (data_index >= 0) {
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/* Avoid underflow access to buffer. */
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fraction = filter_index.toDouble()
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indx = filter_index.toInt()
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icoeff = coeffs [indx] + fraction * (coeffs[indx + 1] - coeffs[indx])
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left += icoeff * buffer[data_index]
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}
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filter_index -= increment
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data_index += 1
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} while (filter_index >= FixedPoint.ZERO)
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/* Now apply the right half of the filter. */
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filter_index = increment - start_filter_index
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coeff_count = (max_filter_index - filter_index) / increment
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filter_index += increment * coeff_count
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data_index = b_current + 1 + coeff_count
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var right = 0.0
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do {
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fraction = filter_index.toDouble()
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indx = filter_index.toInt()
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icoeff = coeffs[indx] + fraction * (coeffs[indx + 1] - coeffs[indx])
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right += icoeff * buffer[data_index]
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filter_index -= increment
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data_index -= 1
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} while (filter_index > FixedPoint.ZERO)
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return left + right
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}
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}
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class Data(val data_in: SampleArray, val data_out: SampleArray, val end_of_input: Boolean) {
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var input_frames_used: Int = 0
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var output_frames_gen: Int = 0
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}
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fun fmod_one (x: Double): Double {
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val res = x - round(x)
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return if (res < 0.0) res + 1.0 else res
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}
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"""Generates coeffs.bin file from one of the three coefficient files that come with libsamplerate."""
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from re import search, findall
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import struct
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from array import array
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# 'fastest_coeffs.h', 'mid_qual_coeffs.h', or 'high_qual_coeffs.h'
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input_file_name = 'mid_qual_coeffs.h'
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coeffs = None
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with open(input_file_name, 'r') as input_file:
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content = input_file.read()
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# Read increment
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increment = int(search(r"=\s*\{\s*(\d+)", content).group(1))
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# Read coefficients
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coeffs = [float(coeffString) for coeffString in findall(r"-?\d+\.\d+e[-+]\d+", content)]
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# ...add a final zero coefficient
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coeffs.append(0.0)
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with open('coeffs.bin', 'wb') as output_file:
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output_file.write(struct.pack('i', increment))
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array('f', coeffs).tofile(output_file)
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