Clarify buffer handling on stream/start messages during an active stream - #283
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…at change `stream/start` on an active stream let the client clear buffers "unless its implementation requires it", leaving the transition timeline ambiguous when the player format changes. The player role already assumes the timeline continues, so state it explicitly and drop the escape hatch. - messaging.md: an in-place `stream/start` updates the configuration without ending the stream. Each role defines how previously received data is handled, since artwork discards its pending image while the player keeps its chunks. - roles/player/v1.md: the format changes at a chunk boundary. Servers MUST continue the timeline without resending audio. Clients MUST decode each buffered chunk in the format in effect when it arrived. A player that cannot switch formats gaplessly SHOULD list a single `sample_rate` and `channels` and let the server resample. Fixes #276
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Perfect, this is a good clarification. |
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This was referenced Oct 1, 2026
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# What does this implement/fix? <!-- Quick description and explanation of changes. --> A mid-stream player format change restarted the stream near the playhead, resending up to a buffer's worth of audio the player already had. That only works for players that clear their buffer on `stream/start`, but most keep it (`sendspin-js`, `sendspin-cpp`, `sendspin-cli` and the `aiosendspin` client). Now the new format starts where the last chunk in the old format ended, as the spec requires. Old-format audio still queued on the connection is sent first instead of dropped, and an in-place `stream/start` for any role now queues behind that role's queued messages. When a player switches to a format another group member already uses, the shared encoder's chunks don't line up with the old end, so it resumes at the next chunk boundary. That leaves a gap of less than one chunk. > [!NOTE] > This can break clients that don't follow the spec and clear their buffer on an in-place `stream/start`, like SendSpinDroid. They get a gap at a format change until playback reaches the new audio. > Switching formats on a live stream is rare enough that we accept this in that edge case, since playback recovers on its own. **Related issue or spec PR (if applicable):** - Sendspin/spec#283 - Sendspin/spec#294 ## Types of changes <!-- Tick exactly one box. CI (.github/workflows/pr-labels.yaml) applies the matching label, and the release notes use it to sort this change. --> - [x] Bugfix (non-breaking change which fixes an issue): `bugfix` - [ ] New feature (non-breaking change which adds functionality): `new-feature` - [ ] Enhancement to an existing feature: `enhancement` - [ ] Breaking change (changes the public API or the protocol in a way that is not backwards compatible): `breaking-change` - [ ] Refactor (no behavior change): `refactor` - [ ] Documentation only: `documentation` - [ ] Maintenance / chore: `maintenance` - [ ] CI / workflow change: `ci` - [ ] Dependencies bump: `dependencies`
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stream/starton an active stream let the client clear buffers "unless itsimplementation requires it", leaving the transition timeline ambiguous when
the player format changes. The player role already assumes the timeline
continues, so state that explicitly.
stream/startupdates the configuration withoutending the stream. Each role defines how previously received data is
handled, since artwork discards its pending image while the player keeps
its chunks.
continue the timeline without resending audio. Clients MUST decode each
buffered chunk in the format in effect when it arrived. A player that
cannot switch formats gaplessly SHOULD list a single
sample_rateandchannelsand let the server resample.Fixes #276
Breaking changes
stream/start. Must continue the timeline instead.sendspin-js, SendspinKit, and sendspin-cpp already conform. The conformance suite needs a scenario for a format change with chunks in flight.