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fix(nests): T13 reset Opus decoder on publisher boundary in NestPlayer

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The reissuing-subscribe wrapper splices fresh-publisher frames into the
same `SharedFlow` that NestPlayer consumes, so across a JWT-refresh
hot-swap (speaker side) or a cliff-detector recycle (listener side)
the decoder receives a discontinuous frame stream while keeping its
Opus predictor state. Result: an audible warble at every publisher
cycle. Single-stream tests don't catch it because they never present
two distinct publishers.

Detect the boundary via `MoqObject.trackAlias` — the underlying
`MoqLiteSession.subscribe` assigns a fresh subscribeId per SUBSCRIBE,
which the listener wrapper surfaces verbatim as `trackAlias` on every
emitted object. A change between consecutive objects = new publisher.

Add an optional `decoderFactory: (() -> OpusDecoder)?` to NestPlayer.
When non-null, NestPlayer tracks `lastTrackAlias` and on a change
releases the current decoder and rebuilds via the factory. The
default `null` preserves the legacy single-decoder behaviour so
existing tests / callers that don't care about boundaries stand
unchanged.

NestViewModel.openSubscription wires the factory: a closure capturing
the catalog-derived `channelCount` so a rebuild reuses the SAME
channel layout — without that capture, a rebuild after a stereo-
publisher cycle would default to mono and silently downmix.

Two new NestPlayerTest cases pin the behaviour:
  - `publisher_boundary_rebuilds_decoder_when_factory_provided`:
    factory invoked twice (initial + boundary), first decoder
    released on boundary, second released on stop.
  - `publisher_boundary_no_op_when_factory_is_null`: legacy path
    holds onto the same decoder across trackAlias changes (unchanged
    semantics).

NestPlayer's first constructor parameter is now `initialDecoder`
(was `decoder`); positional-arg call sites are unchanged but the
named-arg call sites in the test suite are updated accordingly.

https://claude.ai/code/session_014JfZJHSTvyYYWJbC9VbB47
This commit is contained in:
Claude
2026-05-06 18:00:52 +00:00
parent be4e0b9f98
commit 4714e3c723
3 changed files with 175 additions and 8 deletions
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nestsClient/src/commonMain/kotlin/com/vitorpamplona/nestsclient/audio/NestPlayer.kt
+61 -1
View File
@@ -42,7 +42,7 @@ import kotlinx.coroutines.launch
* decoder. Idempotent.
*/
class NestPlayer(
private val decoder: OpusDecoder,
initialDecoder: OpusDecoder,
private val player: AudioPlayer,
private val scope: CoroutineScope,
/**
@@ -61,11 +61,44 @@ class NestPlayer(
* Default is `0` so existing tests stand without modification.
*/
private val prerollFrames: Int = 0,
/**
* Optional factory called on every detected publisher boundary
* (track-alias change in the inbound [MoqObject] stream) to mint a
* fresh [OpusDecoder]. Used by the listener wrapper's re-issuing
* subscription pump
* ([com.vitorpamplona.nestsclient.ReconnectingNestsListener.reissuingSubscribe]):
* each new SUBSCRIBE through the relay produces objects with a
* different `trackAlias`, but they're spliced into the same
* `SharedFlow` — without a decoder reset on the boundary, Opus's
* predictor state from the prior publisher's last frame is fed
* into the new publisher's first frame, producing an audible
* warble at every JWT-refresh hot-swap on the speaker side OR
* cliff-detector recycle on the listener side.
*
* Default `null` keeps the legacy behaviour (no boundary
* detection, decoder lives for the player's whole lifetime) so
* existing tests / callers that don't care about boundaries
* stand unchanged. Production callers in
* [com.vitorpamplona.amethyst.commons.viewmodels.NestViewModel.openSubscription]
* pass a closure that captures the per-subscription channel-count
* and rebuilds via `decoderFactory(channelCount)`.
*/
private val decoderFactory: (() -> OpusDecoder)? = null,
) {
init {
require(prerollFrames >= 0) { "prerollFrames must be >= 0, got $prerollFrames" }
}
/**
* Active decoder. Replaced on detected publisher boundary when
* [decoderFactory] is non-null. `var` so the boundary path can
* release + rebuild without changing the rest of the loop's
* decoder reference; the `private` confines mutation to this
* class, and the decode loop runs single-coroutine so no cross-
* thread visibility hazards.
*/
private var decoder: OpusDecoder = initialDecoder
private var job: Job? = null
private var stopped = false
@@ -157,6 +190,13 @@ class NestPlayer(
com.vitorpamplona.quartz.utils.Log
.d("NestPlay") { "NestPlayer beginPlayback returned" }
}
// Track-alias of the most recently observed object.
// A change signals a publisher boundary (re-issuing
// subscription wrapper spliced in a new SUBSCRIBE).
// Only consulted when [decoderFactory] is non-null;
// legacy callers without a factory keep the prior
// single-decoder behaviour.
var lastTrackAlias: Long? = null
try {
objects.collect { obj ->
receivedObjects += 1
@@ -165,6 +205,26 @@ class NestPlayer(
"NestPlayer received obj #$receivedObjects (decoded=$decodedFrames empty=$emptyDecodes enqueued=$enqueued playbackBegun=$playbackBegun)"
}
}
// Publisher-boundary detection: if the trackAlias
// changed since the last object AND we have a
// factory to mint a fresh decoder, release the
// current decoder + build a new one. Without
// this, Opus's predictor state from the prior
// publisher's last frame is fed into the new
// publisher's first frame, producing audible
// warble at every JWT-refresh hot-swap (speaker
// side) or cliff-detector recycle (listener side).
// The prior-trackAlias guard avoids a spurious
// rebuild on the very first frame.
val factory = decoderFactory
if (factory != null && lastTrackAlias != null && obj.trackAlias != lastTrackAlias) {
com.vitorpamplona.quartz.utils.Log.d("NestPlay") {
"NestPlayer publisher boundary: trackAlias $lastTrackAlias → ${obj.trackAlias}; rebuilding decoder"
}
runCatching { decoder.release() }
decoder = factory()
}
lastTrackAlias = obj.trackAlias
val pcm =
try {
decoder.decode(obj.payload)