Untested beep aac integration

beep_aac.go

package beepaac

import (
	"fmt"
	"io"

	"github.com/gopxl/beep/v2"

	"github.com/pkg/errors"
	fdkaac "github.com/qrtc/fdk-aac-go"
)

func Decode(rc io.ReadCloser) (s beep.StreamSeekCloser, format beep.Format, err error) {
	defer func() {
		if err != nil {
			err = errors.Wrap(err, "aac")
		}
	}()

	d, err := fdkaac.CreateAccDecoder(&fdkaac.AacDecoderConfig{
		TransportFmt: fdkaac.TtMp4Adts,
	})
	if err != nil {
		return
	}

	info, err := d.GetStreamInfo()
	if err != nil {
		return
	}

	format = beep.Format{
		SampleRate:  beep.SampleRate(info.AacSampleRate),
		NumChannels: info.AacNumChannels,
		Precision:   info.AacNumChannels * info.AacSamplesPerFrame,
	}

	return &decoder{rc, d, format, 0, nil, info}, format, nil
}

type decoder struct {
	closer io.Closer
	d      *fdkaac.AacDecoder
	f      beep.Format
	pos    int
	err    error
	info   *fdkaac.CStreamInfo
}

func (d *decoder) Stream(samples [][2]float64) (n int, ok bool) {
	if d.err != nil {
		return 0, false
	}

	return n, d.err == nil
}

func (d *decoder) Err() error {
	return d.err
}

func (d *decoder) Len() int {
	totalFrames := int(d.info.NumTotalBytes) / d.info.FrameSize
	return totalFrames
}

func (d *decoder) Position() int {
	return d.pos / d.info.AacSamplesPerFrame
}

func (d *decoder) Seek(p int) error {
	if p < 0 || d.Len() < p {
		return fmt.Errorf("aac: seek position %v out of range [%v, %v]", p, 0, d.Len())
	}

	// Calculate the byte position based on the sample rate and the number of channels
	bytePosition := int64(p) * int64(d.f.SampleRate) * int64(d.f.NumChannels) * 2

	_, err := d.closer.(io.Seeker).Seek(bytePosition, io.SeekStart)
	if err != nil {
		return errors.Wrap(err, "aac")
	}

	d.pos = p
	return nil
}

func (d *decoder) Close() error {
	err := d.closer.Close()
	if err != nil {
		return errors.Wrap(err, "aac")
	}
	return nil
}