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KaraokeSyllable is the atomic unit of karaoke-style lyrics. Each KaraokeLine holds an ordered list of syllables, and each syllable knows exactly when it starts and ends on the playback timeline. This makes it possible to animate word-by-word highlighting at millisecond granularity. Construction enforces end >= start; an IllegalArgumentException is thrown if that constraint is violated.

​
Constructor

data class KaraokeSyllable(
    val content: String,
    val start: Int,
    val end: Int,
    val phonetic: String? = null,
)
​
content
String
required
The display text of this syllable (e.g. "hel", "lo").
​
start
Int
required
Start time in milliseconds. Must be less than or equal to end.
​
end
Int
required
End time in milliseconds. Must be greater than or equal to start; otherwise construction throws IllegalArgumentException.
​
phonetic
String?
default:"null"
Optional phonetic (romanized) annotation for this syllable. When present, it is used by phoneticToString() to build a full phonetic string for the line.

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Properties

​
content
String
The display text of the syllable.
​
start
Int
Start time in milliseconds.
​
end
Int
End time in milliseconds.
​
phonetic
String?
Optional phonetic annotation; null when not provided.
​
duration
Int
Computed as end - start. Always non-negative due to the init constraint.

​
Methods

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progress(current: Int): Float

fun progress(current: Int): Float
Returns normalized playback progress for this syllable clamped to [0.0, 1.0].
ConditionReturn value
current < start0.0
current in start..end(current - start).toFloat() / duration
current > end1.0
​
current
Int
Current playback position in milliseconds.
Use this value directly to drive animation — for example, as the sweep fraction of a clip mask or the interpolation factor of a color transition. 
val progress: Float = syllable.progress(player.currentPosition.toInt())
// 0.0f = not yet reached, 1.0f = fully sung

​
Extension functions on Collection<KaraokeSyllable>

These extension functions are defined in the com.mocharealm.accompanist.lyrics.core.model.karaoke.mapper package and operate on any Collection<KaraokeSyllable>.

​
contentToString()

fun Collection<KaraokeSyllable>.contentToString(): String
Joins the content of every syllable in the collection with an empty separator, reconstructing the full plain-text line. 
val syllables = listOf(
    KaraokeSyllable("Hel", 0, 300),
    KaraokeSyllable("lo ", 300, 600),
    KaraokeSyllable("world", 600, 1200),
)
println(syllables.contentToString()) // "Hello world"

​
phoneticToString()

fun Collection<KaraokeSyllable>.phoneticToString(): String
Joins the phonetic value of every syllable with a single space separator. Syllables that have phonetic == null contribute an empty string to the join, which may produce consecutive spaces if phonetic annotations are sparse. 
val syllables = listOf(
    KaraokeSyllable("你", 0, 400, phonetic = "nǐ"),
    KaraokeSyllable("好", 400, 900, phonetic = "hǎo"),
)
println(syllables.phoneticToString()) // "nǐ hǎo"

​
Usage examples

​
Animating individual syllables

val positionMs = player.currentPosition.toInt()

line.syllables.forEach { syllable ->
    val progress = syllable.progress(positionMs)
    // Drive a horizontal clip: reveal `progress * width` pixels of the highlighted layer
    Canvas(modifier = Modifier.width(textWidth)) {
        drawText(syllable.content, color = Color.Gray)
        clipRect(right = size.width * progress) {
            drawText(syllable.content, color = Color.White)
        }
    }
}

​
Rebuilding line text from syllables

val line: KaraokeLine = lyrics.lines.filterIsInstance<KaraokeLine>().first()
val fullText: String = line.syllables.contentToString()
val phonetics: String = line.syllables.phoneticToString()

println(fullText)   // e.g. "Hello world"
println(phonetics)  // e.g. "hēllō wörld"

​
Iterating syllables with timing info

line.syllables.forEachIndexed { index, syllable ->
    println(
        "[$index] '${syllable.content}' " +
        "${syllable.start}ms – ${syllable.end}ms " +
        "(${syllable.duration}ms)" +
        if (syllable.phonetic != null) " [${syllable.phonetic}]" else ""
    )
}

​
Finding the active syllable

val positionMs = player.currentPosition.toInt()
val activeSyllable: KaraokeSyllable? = line.syllables
    .firstOrNull { positionMs in it.start..it.end }

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