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Technology Stack: Tag Editing

Project: YellowJacket v1.2 Tag Editing Researched: 2026-03-16

Recommended Stack

MP3 Tag Writing — bogem/id3v2/v2

Technology Version Purpose Why
github.com/bogem/id3v2/v2 v2.1.4 ID3v2.3/v2.4 read + write for MP3 Only mature pure-Go ID3v2 writing library. 359 stars, 57 importers, 579 commits. Supports SetTitle/SetArtist/SetAlbum/SetGenre/SetYear, AddAttachedPicture (cover art embedding), AddTextFrame (track/disc numbers, composer via TRCK/TPOS/TCOM), and tag.Save().

Key capabilities verified (HIGH confidence — pkg.go.dev docs):

  • tag.SetArtist(), tag.SetTitle(), tag.SetAlbum(), tag.SetGenre(), tag.SetYear() — direct setters
  • tag.AddTextFrame("TRCK", id3v2.EncodingUTF8, "5/12") — track number
  • tag.AddTextFrame("TPOS", id3v2.EncodingUTF8, "1/2") — disc number
  • tag.AddTextFrame("TCOM", id3v2.EncodingUTF8, "Bach") — composer
  • tag.AddAttachedPicture(PictureFrame{...}) — cover art embedding with MIME type, picture type (front cover), and raw image bytes
  • tag.Save() — writes modified tag back to file
  • tag.DeleteFrames(id) — remove specific frame types (needed for replacing cover art)
  • ID3v2.3 and v2.4 version support with tag.SetVersion()
  • UTF-8 encoding default for v2.4, ISO-8859-1 for v2.3
  • id3v2.Open(path, Options{Parse: true}) — open existing file, parse all frames, then modify and save

Integration with existing dhowden/tag:

  • dhowden/tag stays for READ operations (already integrated in backend/metadata/tags.go)
  • bogem/id3v2 used ONLY for WRITE operations
  • No conflict: dhowden/tag reads from io.ReadSeeker, bogem/id3v2 reads from file path and writes back
  • Read flow unchanged: dhowden/tag.ReadFrom() → TrackMetadata struct
  • Write flow new: id3v2.Open() → modify → tag.Save() → close

Dependency footprint: Only dependency is golang.org/x/text (already in go.mod). Pure Go, no CGo.

FLAC Tag Writing — go-flac/go-flac + go-flac/flacvorbis + go-flac/flacpicture

Technology Version Purpose Why
github.com/go-flac/go-flac/v2 v2.x FLAC metadata block manipulation (parse + save) Purpose-built for FLAC metadata manipulation. Parses metadata blocks separately from audio frames. f.Save() writes back metadata blocks + raw audio frames without re-encoding. 44 stars, clean API.
github.com/go-flac/flacvorbis/v2 v2.x Vorbis Comment read/write for FLAC metadata blocks Companion to go-flac. Provides ParseFromMetaDataBlock(), Add(), Marshal() for Vorbis Comment manipulation. Has field constants (FIELD_TITLE, FIELD_ARTIST, etc.).
github.com/go-flac/flacpicture latest PICTURE metadata block manipulation for FLAC Companion to go-flac. NewFromImageData() creates PICTURE blocks, Marshal() serializes for embedding.

Why go-flac over mewkiz/flac for WRITING:

  • mewkiz/flac is primarily a FLAC codec (encoder/decoder). Its Encode() API re-encodes audio data, which is unacceptably slow and potentially lossy for metadata-only edits.
  • go-flac/go-flac is specifically designed for metadata manipulation. It stores audio frames as raw bytes and copies them verbatim on save — no re-encoding.
  • mewkiz/flac stays as an indirect dependency (via beep) for FLAC decoding during playback and duration extraction. No conflict.

Key capabilities verified (HIGH confidence — GitHub README + examples):

  • flac.ParseFile(fileName) — returns File with Meta (metadata blocks) and Frames (raw audio data)
  • flacvorbis.ParseFromMetaDataBlock(*meta) — parse existing Vorbis Comment block
  • cmts.Add(flacvorbis.FIELD_TITLE, "New Title") — add/modify comment fields
  • cmts.Marshal() — serialize back to MetaDataBlock
  • f.Meta[idx] = &cmtsmeta — replace metadata block in-place
  • f.Save(fileName) — write modified file (metadata blocks + raw audio frames, no re-encoding)
  • flacpicture.NewFromImageData(PictureTypeFrontCover, "Front cover", imgData, "image/jpeg") — create picture block
  • picture.Marshal() → append to f.Meta — embed cover art

FLAC tag writing approach — metadata block replacement:

  1. flac.ParseFile(path) — parses metadata blocks + stores audio frames as raw bytes
  2. Find existing VorbisComment block in f.Meta slice, or create new via flacvorbis.New()
  3. Modify/add comment fields via cmts.Add() (handles field replacement)
  4. Marshal back: f.Meta[idx] = &cmts.Marshal()
  5. For cover art: create via flacpicture.NewFromImageData(), append to f.Meta
  6. f.Save(tmpPath) — writes "fLaC" + metadata blocks + raw audio frames to temp file
  7. Atomic rename temp file over original

Critical detail: go-flac/go-flac's Save() copies audio frames as raw bytes — no re-encoding. A metadata-only edit of a 50MB FLAC file takes ~50ms, not minutes.

OGG Vorbis Tag Writing — Custom Implementation Required

Technology Version Purpose Why
Custom OGG page rewriter n/a OGG Vorbis Comment + Picture writing No pure-Go OGG tag writing library exists. jfreymuth/oggvorbis is decode-only. OGG tag writing requires parsing OGG pages, modifying the Vorbis Comment header packet, and rewriting pages.

Why custom OGG writing is necessary:

  • jfreymuth/oggvorbis (existing indirect dep) is a decoder only — no write API
  • No other pure-Go OGG Vorbis tag writer exists in the ecosystem
  • OGG Vorbis comments are stored in the second header packet (comment header), which is an OGG page
  • Modifying comments changes page sizes, requiring page-level rewriting

OGG tag writing approach:

  1. Parse OGG pages to find the three Vorbis header packets (identification, comment, setup)
  2. Decode existing Vorbis Comment from the comment header packet
  3. Modify comment fields (same key=value format as FLAC Vorbis Comments)
  4. Re-encode comment packet into new OGG pages
  5. Copy identification and setup headers unchanged
  6. Copy all audio data pages unchanged
  7. Write to temp file, atomic rename

Complexity assessment: MEDIUM-HIGH. OGG page framing is well-documented but requires careful implementation. The Vorbis Comment format itself is simple (same as FLAC). The OGG page CRC and segment tables are the tricky parts.

Cover art in OGG: Stored as METADATA_BLOCK_PICTURE Vorbis Comment tag (base64-encoded FLAC Picture block). Same encoding as FLAC Picture but base64-wrapped in a comment field.

Recommendation: Implement OGG writing LAST. Start with MP3 and FLAC (libraries exist). OGG uses the same Vorbis Comment format as FLAC, so the comment serialization code is shared — only the OGG page framing is new work.

Atomic File Writing — No New Dependency

Technology Version Purpose Why
os.CreateTemp + os.Rename (stdlib) Go 1.25 Write-to-temp-then-rename pattern The stdlib approach is simpler and sufficient. natefinch/atomic is already an indirect dep but provides WriteFile(filename, io.Reader) which doesn't match our use case (we need to write to temp first, THEN rename). The stdlib pattern gives more control over temp file location (same directory as target for same-filesystem rename).

Pattern:

// Create temp file in same directory as target (ensures same filesystem for atomic rename)
dir := filepath.Dir(targetPath)
tmp, err := os.CreateTemp(dir, ".yj-tag-*.tmp")
// ... write tag data to tmp ...
tmp.Close()
// Atomic rename (POSIX guarantees atomicity for same-filesystem rename)
os.Rename(tmp.Name(), targetPath)

Why NOT natefinch/atomic: It's designed for io.Reader → file workflows. Our workflow is: read original → write modified to temp → rename. The stdlib os.CreateTemp + os.Rename is the right primitive. natefinch/atomic also uses os.Rename internally on Unix anyway.

Why same-directory temp file matters: os.Rename is only atomic when source and destination are on the same filesystem. Music files could be on any mount point. Creating the temp file in the same directory guarantees this.

Alternatives Considered

Category Recommended Alternative Why Not
MP3 write bogem/id3v2/v2 dhowden/tag dhowden/tag is read-only. No write API. Would require forking.
MP3 write bogem/id3v2/v2 go-id3 (mikkyang) Dead project, archived, no v2 module support, last commit 2015
FLAC write go-flac/go-flac + flacvorbis mewkiz/flac mewkiz/flac is a codec (encoder/decoder); its Encode() re-encodes audio. go-flac is purpose-built for metadata manipulation — copies audio frames as raw bytes.
FLAC write go-flac/go-flac + flacvorbis Custom FLAC writer go-flac handles the format correctly with proven Save(); reinventing would be fragile
OGG write Custom CGo (libvorbis) Violates no-CGo constraint
OGG write Custom dhowden/tag fork dhowden/tag OGG parsing is minimal, not designed for writing
Atomic write stdlib os.CreateTemp+Rename natefinch/atomic Doesn't match our write pattern; stdlib is sufficient
Atomic write stdlib os.CreateTemp+Rename renameio Unnecessary dep for a 5-line pattern

What NOT To Add

Library Why Avoid
Any CGo-based tag library (taglib-go, etc.) Violates pure-Go constraint from PROJECT.md
go-id3 (mikkyang/id3-go) Archived, unmaintained since 2015, no module support
Any "universal tag writer" that wraps TagLib via CGo Violates pure-Go constraint
natefinch/atomic as direct dep Already indirect; stdlib pattern is more appropriate for this use case
goflac (CGo wrapper around libFLAC) Violates pure-Go constraint

Existing Dependencies Leveraged (No Version Changes)

Library Current Use New Use in Tag Editing
dhowden/tag v0.0.0-20240417 Tag reading during library scan Unchanged — still used for all READ operations
mewkiz/flac v1.0.12 (indirect via beep) FLAC audio decoding during playback + duration extraction Unchanged — remains indirect for decoding only
golang.org/x/image v0.12.0 Cover art thumbnail generation Image validation before embedding (ensure valid JPEG/PNG)
natefinch/atomic v1.0.1 (indirect) Not directly used Remains indirect; not needed for our pattern

Installation

# New direct dependencies
go get github.com/bogem/id3v2/v2@v2.1.4
go get github.com/go-flac/go-flac/v2
go get github.com/go-flac/flacvorbis/v2
go get github.com/go-flac/flacpicture

Format Coverage Matrix

Format Text Tags Cover Art Embed Library Confidence
MP3 (ID3v2) ✓ Full ✓ APIC frame bogem/id3v2/v2 HIGH
FLAC ✓ Full ✓ Picture block go-flac/go-flac + flacvorbis + flacpicture HIGH
OGG Vorbis ✓ Full ✓ METADATA_BLOCK_PICTURE Custom (built on Vorbis Comment format) MEDIUM
WAV ✗ Not supported ✗ Not supported n/a — WAV has no standard tag format n/a

WAV exclusion rationale: WAV files have no widely-adopted metadata standard. Some players use INFO chunks, some use ID3v2 headers prepended to WAV. The project already supports WAV playback but doesn't extract meaningful tags from WAV during scanning. Tag editing for WAV is out of scope.

Vorbis Comment Field Mapping

Both FLAC and OGG use Vorbis Comments. Field names are standardized:

YellowJacket Field Vorbis Comment Key ID3v2 Frame ID
Title TITLE TIT2
Artist ARTIST TPE1
Album ALBUM TALB
Album Artist ALBUMARTIST TPE2
Genre GENRE TCON
Year DATE TDRC (v2.4) / TYER (v2.3)
Track Number TRACKNUMBER TRCK
Total Tracks TRACKTOTAL TRCK (as "N/Total")
Disc Number DISCNUMBER TPOS
Total Discs DISCTOTAL TPOS (as "N/Total")
Composer COMPOSER TCOM
Comment COMMENT COMM
Lyrics LYRICS USLT

Sources

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