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//
// dolmetschctl
//
//
// Copyright (C) 2019 Christian Pointner <equinox@spreadspace.org>
//
// This file is part of dolmetschctl.
//
// dolmetschctl is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// dolmetschctl is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with dolmetschctl. If not, see <http://www.gnu.org/licenses/>.
//
package mixer
import (
"container/list"
"errors"
"fmt"
"strings"
"github.com/scgolang/midi"
)
type Channel uint8
type FaderLevel uint8
type EventType int
const (
EventFaderChange = iota
EventMute
)
func (et EventType) String() string {
switch et {
case EventFaderChange:
return "fader-change"
case EventMute:
return "mute"
default:
return "unknown"
}
}
type Event struct {
Channel Channel
Type EventType
Value uint8
}
func (e Event) String() string {
return fmt.Sprintf("Event(%s) for channel 0x%02X, value=%d", e.Type, e.Channel, e.Value)
}
type Mixer struct {
DevIn *midi.Device
DevOut *midi.Device
subscribers map[Channel]*list.List
}
// TODO: make this configurable
const (
CC_MUTE = byte(0xB1)
CC_FADER = byte(0xB0)
FaderLevelMax = FaderLevel(0x7F)
FaderLevel0db = FaderLevel(0x60)
FaderLevelOff = FaderLevel(0x00)
)
func openDevice(devices []*midi.Device, prefix string) (d *midi.Device, err error) {
for _, device := range devices {
if strings.HasPrefix(device.Name, prefix) {
d = device
}
}
if d == nil {
return nil, errors.New("could not find device with prefix " + prefix)
}
return d, d.Open()
}
func NewMixer(c Config) (*Mixer, error) {
devices, err := midi.Devices()
if err != nil {
return nil, err
}
// TODO: add support for DevIn == DevOut
m := &Mixer{}
if m.DevIn, err = openDevice(devices, c.DevIn); err != nil {
return nil, err
}
m.DevIn.QueueSize = 100
if m.DevOut, err = openDevice(devices, c.DevOut); err != nil {
return nil, err
}
m.subscribers = make(map[Channel]*list.List)
return m, nil
}
func (m *Mixer) sendEvent(ev Event) {
subs, exists := m.subscribers[ev.Channel]
if exists && subs != nil {
var next *list.Element
for sub := subs.Front(); sub != nil; sub = next {
next = sub.Next()
ch, ok := (sub.Value).(chan<- Event)
if !ok {
panic(fmt.Sprintf("mixer: subscriber list element value has wrong type: %T", sub.Value))
}
select {
case ch <- ev:
default:
// subscriber is not respoding...
subs.Remove(sub)
}
}
}
}
func (m *Mixer) handleMidiPacket(p midi.Packet) {
ev := Event{}
ev.Channel = Channel(p.Data[1])
switch p.Data[0] {
case CC_FADER:
ev.Type = EventFaderChange
ev.Value = p.Data[2]
case CC_MUTE:
ev.Type = EventMute
if p.Data[2] > 0 {
ev.Value = 1
}
default:
return
}
m.sendEvent(ev)
}
func (m *Mixer) Init() error {
ch, err := m.DevIn.Packets()
if err != nil {
return err
}
go func() {
for {
m.handleMidiPacket(<-ch)
}
}()
return nil
}
func (m *Mixer) Shutdown() error {
if m.DevIn != nil {
m.DevIn.Close()
}
if m.DevOut != nil {
m.DevOut.Close()
}
return nil
}
func (m *Mixer) sendMute(channel byte, value byte) error {
n, err := m.DevOut.Write([]byte{CC_MUTE, channel, value})
if err != nil {
return err
}
if n != 3 {
return errors.New("sending mute command failed.")
}
return nil
}
func (m *Mixer) Mute(ch Channel) error {
return m.sendMute(byte(ch), 0x7F)
}
func (m *Mixer) UnMute(ch Channel) error {
return m.sendMute(byte(ch), 0x00)
}
func (m *Mixer) SetLevel(ch Channel, level FaderLevel) error {
if level > FaderLevelMax {
level = FaderLevelMax
}
n, err := m.DevOut.Write([]byte{CC_FADER, byte(ch), byte(level)})
if err != nil {
return err
}
if n != 3 {
return errors.New("setting fader level failed.")
}
return nil
}
func (m *Mixer) Subscribe(ch Channel, out chan<- Event) {
subs, exists := m.subscribers[ch]
if !exists {
subs = list.New()
m.subscribers[ch] = subs
}
subs.PushBack(out)
}
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