Merge pull request #103 from dweymouth/feature/replay-gain

Add ReplayGain support

backend/app.go

@@ -9,6 +9,7 @@ import (
 	"path"
 	"supersonic/backend/util"
 	"supersonic/player"
+	"supersonic/sharedutil"
 
 	"github.com/20after4/configdir"
 	"github.com/zalando/go-keyring"
@@ -51,6 +52,16 @@ func StartupApp() (*App, error) {
 	a.Config.LocalPlayback.Volume = clamp(a.Config.LocalPlayback.Volume, 0, 100)
 	a.Player.SetVolume(a.Config.LocalPlayback.Volume)
 
+	rgainOpts := []string{ReplayGainNone, ReplayGainAlbum, ReplayGainTrack}
+	if !sharedutil.StringSliceContains(rgainOpts, a.Config.ReplayGain.Mode) {
+		a.Config.ReplayGain.Mode = ReplayGainNone
+	}
+	a.Player.SetReplayGainOptions(player.ReplayGainOptions{
+		Mode:            player.ReplayGainMode(a.Config.ReplayGain.Mode),
+		PreventClipping: a.Config.ReplayGain.PreventClipping,
+		PreampGain:      a.Config.ReplayGain.PreampGainDB,
+	})
+
 	a.ServerManager = NewServerManager()
 	a.PlaybackManager = NewPlaybackManager(a.bgrndCtx, a.ServerManager, a.Player, &a.Config.Scrobbling)
 	a.LibraryManager = NewLibraryManager(a.ServerManager)

backend/config.go

@@ -59,6 +59,12 @@ type ScrobbleConfig struct {
 	ThresholdPercent     int
 }
 
+type ReplayGainConfig struct {
+	Mode            string
+	PreampGainDB    float64
+	PreventClipping bool
+}
+
 type Config struct {
 	Application    AppConfig
 	Servers        []*ServerConfig
@@ -70,6 +76,7 @@ type Config struct {
 	PlaylistPage   PlaylistPageConfig
 	LocalPlayback  LocalPlaybackConfig
 	Scrobbling     ScrobbleConfig
+	ReplayGain     ReplayGainConfig
 }
 
 func DefaultConfig() *Config {
@@ -108,6 +115,11 @@ func DefaultConfig() *Config {
 			ThresholdTimeSeconds: 240,
 			ThresholdPercent:     50,
 		},
+		ReplayGain: ReplayGainConfig{
+			Mode:            ReplayGainNone,
+			PreampGainDB:    0.0,
+			PreventClipping: true,
+		},
 	}
 }
 

backend/playbackmanager.go

@@ -12,6 +12,12 @@ import (
 	"github.com/dweymouth/go-subsonic/subsonic"
 )
 
+const (
+	ReplayGainNone  = string(player.ReplayGainNone)
+	ReplayGainAlbum = string(player.ReplayGainAlbum)
+	ReplayGainTrack = string(player.ReplayGainTrack)
+)
+
 type PlaybackManager struct {
 	ctx           context.Context
 	cancelPollPos context.CancelFunc

player/libmpv.go

@@ -104,6 +104,14 @@ func (m libmpv) SetProperty(name string, format MPVFormat, value any) error {
 	return toMPVError(C.mpv_set_property(m.handle, cname, C.mpv_format(format), p))
 }
 
+func (m libmpv) SetPropertyString(name, value string) error {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	cvalue := C.CString(value)
+	defer C.free(unsafe.Pointer(cvalue))
+	return toMPVError(C.mpv_set_property_string(m.handle, cname, cvalue))
+}
+
 func (m libmpv) GetProperty(name string, format MPVFormat) (any, error) {
 	cname := C.CString(name)
 	defer C.free(unsafe.Pointer(cname))

player/player.go

@@ -38,12 +38,31 @@ const (
 	SeekRelativePercent
 )
 
+// One of "no", "track", or "album"
+type ReplayGainMode string
+
+const (
+	ReplayGainNone  ReplayGainMode = "no"
+	ReplayGainTrack ReplayGainMode = "track"
+	ReplayGainAlbum ReplayGainMode = "album"
+)
+
+// Replay Gain options (argument to SetReplayGainOptions).
+type ReplayGainOptions struct {
+	Mode            ReplayGainMode
+	PreampGain      float64
+	PreventClipping bool
+	// Fallback gain intentionally omitted
+}
+
 // Player encapsulates the mpv instance and provides functions
 // to control it and to check its status.
 type Player struct {
 	mpv            libmpv
 	initialized    bool
 	vol            int
+	replayGainOpts ReplayGainOptions
+	haveRGainOpts  bool
 	status         Status
 	seeking        bool
 	curPlaylistPos int64
@@ -102,6 +121,9 @@ func (p *Player) Init(audioExclusive bool, maxCacheMB int) error {
 		if audioExclusive {
 			m.SetOptionString("audio-exclusive", "yes")
 		}
+		if p.haveRGainOpts {
+			p.SetReplayGainOptions(p.replayGainOpts)
+		}
 
 		if p.clientName != "" {
 			m.SetOptionString("audio-client-name", p.clientName)
@@ -235,6 +257,30 @@ func (p *Player) SetVolume(vol int) error {
 	return nil
 }
 
+// Sets the ReplayGain options of the player.
+// Unlike most Player functions, SetReplayGainOptions can be called
+// before Init, to set the initial volume of the player on startup.
+func (p *Player) SetReplayGainOptions(options ReplayGainOptions) error {
+	p.replayGainOpts = options
+	p.haveRGainOpts = true
+	if p.initialized {
+		if err := p.mpv.SetPropertyString("replaygain", string(options.Mode)); err != nil {
+			return err
+		}
+		if err := p.mpv.SetProperty("replaygain-preamp", MPVFormatDouble, options.PreampGain); err != nil {
+			return err
+		}
+		clip := "no"
+		if options.PreventClipping {
+			clip = "yes"
+		}
+		if err := p.mpv.SetPropertyString("replaygain-clip", clip); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // Gets the current volume of the player.
 func (p *Player) GetVolume() int {
 	return p.vol