pion/webrtc · error

%w: invalid comment %d

Error message

%w: invalid comment %d

What it means

Returned by parseSingleUserComment when a comment string, though fully present in the payload, contains no '=' separator. Per the Opus spec, every user comment must be a 'NAME=value' pair, so a comment without '=' is structurally invalid.

Source

Thrown at pkg/media/oggreader/oggreader.go:482

func parseSingleUserComment(payload []byte, pos, u32Size, index int) (UserComment, int, error) {
	if pos+u32Size > len(payload) {
		return UserComment{}, 0, fmt.Errorf("%w: payload too short for comment len %d", errBadOpusTagsSignature, index)
	}

	commentLen32 := binary.LittleEndian.Uint32(payload[pos : pos+u32Size])
	pos += u32Size

	commentLen := int(commentLen32)
	if commentLen < 0 || pos+commentLen > len(payload) {
		return UserComment{}, 0, fmt.Errorf("%w: payload too short for comment %d", errBadOpusTagsSignature, index)
	}

	comment := string(payload[pos : pos+commentLen])
	pos += commentLen

	parts := strings.SplitN(comment, "=", 2)
	if len(parts) != 2 {
		return UserComment{}, 0, fmt.Errorf("%w: invalid comment %d", errBadOpusTagsSignature, index)
	}

	return UserComment{
		Comment: parts[0],
		Value:   parts[1],
	}, pos, nil
}

View on GitHub (pinned to 8c25dc09fa)

Solutions

1. Fix the metadata with a conforming tag editor (e.g. opustags, ffmpeg -metadata) ensuring every comment is NAME=value.
2. Inspect the raw comments in the file to find the offending entry and correct or remove it.
3. Use errors.Is(err, errBadOpusTagsSignature) to detect this and either reject the file or strip invalid comments.
4. If you generate OpusTags yourself, always validate each comment contains '=' before serializing.

Example fix

// before: writing a bare comment
comments := []string{"TITLE Song"}
// after: ensure KEY=value form
comments := []string{"TITLE=Song"}
for _, c := range comments { if !strings.Contains(c, "=") { return errors.New("invalid comment") } }

func allCommentsAreKeyValue(rawComments []string) bool {
    for _, c := range rawComments {
        if !strings.Contains(c, "=") { return false }
    }
    return true
}

tags, err := ParseOpusTags(payload)
if err != nil {
    if errors.Is(err, errBadOpusTagsSignature) && strings.Contains(err.Error(), "invalid comment") {
        return nil, fmt.Errorf("non-conforming metadata (comment missing '='): %w", err)
    }
    return nil, err
}

When it happens

Trigger: Parsing an OpusTags payload where comment N is a non-empty string lacking an '=' character (e.g. 'TITLE' instead of 'TITLE=Song'), so strings.SplitN(comment, "=", 2) yields only one part.

Common situations: Metadata written by broken or non-conforming taggers, hand-edited OpusTags blocks, tools that append bare strings as comments, or comments that were truncated exactly at (or before) the '=' sign by a prior corruption.

Related errors

• %w: user comment is too long
• %w: %s is too long
• bad opus tags signature
• %w: ambisonics family type 3 is not supported
• %w: payload too short

AI-assisted analysis of pion/webrtc@8c25dc09fa (2026-09-03). Data as JSON: /api/errors/71b5a60121d51b45. Report an issue: GitHub.