Kirika/audio/filter/resample_filter_nocgo.go

//go:build !cgo

package filter

import (
	"git.gammaspectra.live/S.O.N.G/Kirika/audio"
	"git.gammaspectra.live/S.O.N.G/Kirika/audio/filter/internal/resampler"
	"log"
)

const (
	QualityBest    ResampleQuality = 10
	QualityGood    ResampleQuality = 8
	QualityFast    ResampleQuality = 5
	QualityFastest ResampleQuality = 0
)

func (f ResampleFilter) Process(source audio.Source) audio.Source {
	if source.GetSampleRate() == f.sampleRate { //no change
		return source
	}

	outSource := audio.NewSource[float32](source.GetBitDepth(), f.sampleRate, source.GetChannels())

	go func() {
		defer outSource.Close()

		samplerateConverter := resampler.New(source.GetChannels(), source.GetSampleRate(), f.sampleRate, int(f.quality))

		for block := range source.ToFloat32().GetBlocks() {
			output := make([][]float32, source.GetChannels())
			input := make([][]float32, source.GetChannels())

			outputBufferLength := 0
			for i := 0; i < source.GetChannels(); i++ {
				input[i] = make([]float32, len(block)/source.GetChannels())

				ix := 0
				for j := i; j < len(block); j += source.GetChannels() {
					input[i][ix] = block[j]
					ix++
				}

				output[i] = make([]float32, int(float64(len(block)/source.GetChannels())*(float64(f.sampleRate)/float64(source.GetSampleRate()))*1.1)) //resize to match expected output, with a fuzz factor of 10%

				read, written := samplerateConverter.ProcessFloat32(i, input[i], output[i])
				if read != len(input[i]) {
					log.Panicf("could not read whole input: %d vs %d", len(input[i]), read)
				}
				output[i] = output[i][:written]

				outputBufferLength += written
			}

			buffer := make([]float32, outputBufferLength)
			for i, b := range output {
				for j := range b {
					buffer[i+j*len(output)] = b[j]
				}
			}

			outSource.IngestFloat32(buffer)
		}

	}()

	return outSource
}