go-mix/routing.go

package main

import (
	"fmt"

	"github.com/xthexder/go-jack"
)

type PortState struct {
	Mute    bool    `json:"mute"`
	Volume  float32 `json:"volume"`
	Balance float32 `json:"balance"`
}

type PortProperties struct {
	Backend  string `json:"backend"`
	Channels uint8  `json:"channels"`
}

type PortRoute struct {
	ToUUID  string  `json:"toUUID"`
	Mute    bool    `json:"mute"`
	Volume  float32 `json:"volume"`
	Balance float32 `json:"balance"`
}

type Port struct {
	UUID       string         `json:"UUID"`
	Name       string         `json:"name"`
	Properties PortProperties `json:"properties"`
	State      PortState      `json:"state"`
	Route      []PortRoute    `json:"route"`
	object     []*jack.Port
}

var portConfig struct {
	Input  []Port `json:"inputs"`
	Output []Port `json:"outputs"`
}

var portsInited bool = false

// Find index and pointer of port
func findPort(findUUID string) (*Port, int, string) {
	var port *Port
	var portIndex int = -1
	var portType string
	for i, p := range portConfig.Input {
		if p.UUID == findUUID {
			port = &portConfig.Input[i]
			portIndex = i
			portType = "input"
		}
	}
	for i, p := range portConfig.Output {
		if p.UUID == findUUID {
			port = &portConfig.Output[i]
			portIndex = i
			portType = "output"
		}
	}

	return port, portIndex, portType
}

func registerPort(port *Port, portType string) {
	switch backend := port.Properties.Backend; backend {
	case "jack":
		if !config.Jack.Enabled {
			return
		}
		var jackFlag int
		if portType == "input" {
			jackFlag = jack.PortIsInput
		} else if portType == "output" {
			jackFlag = jack.PortIsOutput
		} else {
			fmt.Printf("WARN! Trying to register port with invalid type `%s`\n", portType)
			return
		}
		port.object = registerJackPort(port.Name, port.Properties.Channels, uint64(jackFlag))
	default:
		fmt.Printf("WARN! Error loading port %s: Backend %s is not implemented!\n", port.UUID, backend)
	}
}

func unregisterPort(port *Port) {
	switch backend := port.Properties.Backend; backend {
	case "jack":
		if !config.Jack.Enabled {
			return
		}
		unregisterJackPort(port.object)
		port.object = nil
	default:
		fmt.Printf("WARN! Error unloading port %s: Backend %s is not implemented!\n", port.UUID, backend)
	}
}

func startRouting() {
	// Load port configuration from config file
	loadConfig("ports", &portConfig)

	// Register ports
	for i := range portConfig.Input {
		registerPort(&portConfig.Input[i], "input")
	}
	for i := range portConfig.Output {
		registerPort(&portConfig.Output[i], "output")
	}

	portsInited = true
}

type JackOutputBuffers struct {
	Output  *Port
	Buffers [][]jack.AudioSample
}

func addToBuffer(src *[]jack.AudioSample, dst *[]jack.AudioSample, volume float32) {
	for i, sample := range *src {
		(*dst)[i] += sample * jack.AudioSample(volume)
	}
}

func multiplyBuffer(dst *[]jack.AudioSample, factor float32) {
	for i := range *dst {
		(*dst)[i] *= jack.AudioSample(factor)
	}
}

func calcBalanceFactor(ch uint8, balance float32) float32 {
	if ch == 0 {
		return max(0, min(1, 1-balance))
	} else {
		return max(0, min(1, 1+balance))
	}
}

func processJackCb(nframes uint32) int {
	if !portsInited {
		return 0
	}

	// Get memory addresses to write to for all outputs
	var outputBuffers []JackOutputBuffers = []JackOutputBuffers{}
	for i, out := range portConfig.Output {
		outputBuffer := JackOutputBuffers{&portConfig.Output[i], [][]jack.AudioSample{}}
		for _, port := range out.object {
			buffer := port.GetBuffer(nframes)
			for i := range buffer {
				buffer[i] = 0
			}
			outputBuffer.Buffers = append(outputBuffer.Buffers, buffer)
		}
		outputBuffers = append(outputBuffers, outputBuffer)
	}

	// Write audio data from every input to all outputs it routes to
	for _, in := range portConfig.Input {
		if in.State.Mute {
			// Input is muted
			continue
		}

		// For every channel
		for ch := uint8(0); ch < in.Properties.Channels; ch++ {
			if in.object == nil || uint8(len(in.object)) <= ch {
				// Input is not initialized
				continue
			}
			chSamples := in.object[ch].GetBuffer(nframes)

			// For every route that exists for the input
			for _, route := range in.Route {
				if route.Mute {
					// Route is muted
					continue
				}

				for _, out := range outputBuffers {
					if out.Output.UUID != route.ToUUID {
						continue
					}

					if out.Buffers == nil || uint8(len(out.Buffers)) <= ch {
						// Output is not initialized
						continue
					}

					if out.Output.State.Mute {
						// Output is muted
						continue
					}

					routeVolume := in.State.Volume * route.Volume * calcBalanceFactor(ch, in.State.Balance)

					if in.Properties.Channels < uint8(len(out.Buffers)) {
						// If input is mono and output is stereo, write to both output channels at once
						for i, buf := range out.Buffers {
							finalVolume := routeVolume * calcBalanceFactor(uint8(i), route.Balance)
							addToBuffer(&chSamples, &buf, finalVolume)
						}
					} else {
						// Else only write to current channel (or channel 0 if output is mono)
						finalVolume := routeVolume * calcBalanceFactor(ch, route.Balance)
						index := min(uint8(len(out.Buffers)-1), ch)
						addToBuffer(&chSamples, &out.Buffers[index], finalVolume)
					}
				}
			}
		}

		// Apply output volume and balance
		// (mute state is already checked above)
		for _, out := range outputBuffers {
			for ch, buf := range out.Buffers {
				multiplyBuffer(&buf, out.Output.State.Volume*calcBalanceFactor(uint8(ch), out.Output.State.Balance))
			}
		}
	}
	return 0
}