Parse the ID3v2.4 TIPL frame

scanner/metadata/taglib/taglib.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"os"
 	"strconv"
+	"strings"
 
 	"github.com/navidrome/navidrome/log"
 	"github.com/navidrome/navidrome/scanner/metadata"
@@ -46,10 +47,58 @@ func (e *Extractor) extractMetadata(filePath string) (metadata.ParsedTags, error
 			tags["duration"] = []string{strconv.FormatFloat(duration, 'f', 2, 32)}
 		}
 	}
+	// Adjust some ID3 tags
+	parseTIPL(tags)
+	delete(tags, "tmcl") // TMCL is already parsed by TagLib
 
 	return tags, nil
 }
 
+// These are the only roles we support, based on Picard's tag map:
+// https://picard-docs.musicbrainz.org/downloads/MusicBrainz_Picard_Tag_Map.html
+var tiplMapping = map[string]string{
+	"arranger": "arranger",
+	"engineer": "engineer",
+	"producer": "producer",
+	"mix":      "mixer",
+	"dj-mix":   "djmixer",
+}
+
+// parseTIPL parses the ID3v2.4 TIPL frame string, which is received from TagLib in the format
+//
+//	"arranger Andrew Powell engineer Chris Blair engineer Pat Stapley producer Eric Woolfson".
+//
+// and breaks it down into a map of roles and names, e.g.:
+//
+//	{"arranger": ["Andrew Powell"], "engineer": ["Chris Blair", "Pat Stapley"], "producer": ["Eric Woolfson"]}.
+func parseTIPL(tags metadata.ParsedTags) {
+	tipl := tags["tipl"]
+	if len(tipl) == 0 {
+		return
+	}
+
+	addRole := func(tags metadata.ParsedTags, currentRole string, currentValue []string) {
+		if currentRole != "" {
+			role := tiplMapping[currentRole]
+			tags[role] = append(tags[currentRole], strings.Join(currentValue, " "))
+		}
+	}
+
+	var currentRole string
+	var currentValue []string
+	for _, part := range strings.Split(tipl[0], " ") {
+		if _, ok := tiplMapping[part]; ok {
+			addRole(tags, currentRole, currentValue)
+			currentRole = part
+			currentValue = nil
+			continue
+		}
+		currentValue = append(currentValue, part)
+	}
+	addRole(tags, currentRole, currentValue)
+	delete(tags, "tipl")
+}
+
 func init() {
 	metadata.RegisterExtractor(ExtractorID, &Extractor{})
 }

scanner/metadata/taglib/taglib_test.go

@@ -4,6 +4,7 @@ import (
 	"io/fs"
 	"os"
 
+	"github.com/navidrome/navidrome/scanner/metadata"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 )
@@ -195,4 +196,46 @@ var _ = Describe("Extractor", func() {
 		})
 	})
 
+	Describe("parseTIPL", func() {
+		var tags metadata.ParsedTags
+
+		BeforeEach(func() {
+			tags = metadata.ParsedTags{}
+		})
+
+		Context("when the TIPL string is populated", func() {
+			It("correctly parses roles and names", func() {
+				tags["tipl"] = []string{"arranger Andrew Powell dj-mix François Kevorkian engineer Chris Blair"}
+				parseTIPL(tags)
+				Expect(tags["arranger"]).To(Equal([]string{"Andrew Powell"}))
+				Expect(tags["engineer"]).To(Equal([]string{"Chris Blair"}))
+				Expect(tags["djmixer"]).To(Equal([]string{"François Kevorkian"}))
+			})
+
+			It("handles multiple names for a single role", func() {
+				tags["tipl"] = []string{"engineer Pat Stapley producer Eric Woolfson engineer Chris Blair"}
+				parseTIPL(tags)
+				Expect(tags["producer"]).To(Equal([]string{"Eric Woolfson"}))
+				Expect(tags["engineer"]).To(ConsistOf("Pat Stapley", "Chris Blair"))
+			})
+		})
+
+		Context("when the TIPL string is empty", func() {
+			It("does nothing", func() {
+				tags["tipl"] = []string{""}
+				parseTIPL(tags)
+				Expect(tags).To(BeEmpty())
+			})
+		})
+
+		Context("when the TIPL is not present", func() {
+			It("does nothing", func() {
+				parseTIPL(tags)
+				Expect(tags).To(BeEmpty())
+			})
+		})
+
+		// Add any additional edge cases if necessary
+	})
+
 })

scanner/metadata/taglib/taglib_wrapper.go

@@ -69,7 +69,7 @@ func Read(filename string) (tags map[string][]string, err error) {
 }
 
 var lock sync.RWMutex
-var maps = make(map[uint32]map[string][]string)
+var allMaps = make(map[uint32]map[string][]string)
 var mapsNextID uint32
 
 func newMap() (id uint32, m map[string][]string) {
@@ -78,14 +78,14 @@ func newMap() (id uint32, m map[string][]string) {
 	id = mapsNextID
 	mapsNextID++
 	m = make(map[string][]string)
-	maps[id] = m
+	allMaps[id] = m
 	return
 }
 
 func deleteMap(id uint32) {
 	lock.Lock()
 	defer lock.Unlock()
-	delete(maps, id)
+	delete(allMaps, id)
 }
 
 //export go_map_put_m4a_str
@@ -116,7 +116,7 @@ func do_put_map(id C.ulong, key string, val *C.char) {
 
 	lock.RLock()
 	defer lock.RUnlock()
-	m := maps[uint32(id)]
+	m := allMaps[uint32(id)]
 	v := strings.TrimSpace(C.GoString(val))
 	m[key] = append(m[key], v)
 }
@@ -151,7 +151,7 @@ func go_map_put_lyric_line(id C.ulong, lang *C.char, text *C.char, time C.int) {
 
 	key := "lyrics-" + language
 
-	m := maps[uint32(id)]
+	m := allMaps[uint32(id)]
 	existing, ok := m[key]
 	if ok {
 		existing[0] += formatted_line