1.3 KiB
1.3 KiB
ECP-0042: Multi-Variant Publishing and Automatic Selection
Why
Different networks and devices need different bitrates/resolutions. A single stream quality forces either wasted bandwidth or playback stalls. We also need a consistent representation of variants so multiple peers can publish/verify the same logical channel.
Decisions
- A "channel" may have multiple variants (e.g.
1080p,720p,480p) produced from the same timing grid. - Manifests include per-variant metadata (resolution/bitrate) and per-variant chunk hashes for the same chunk index.
- Viewers implement automatic selection:
- Prefer the highest variant that keeps steady playback.
- Step down quickly on sustained stalls; step up conservatively.
- Where available, the desktop app may present variants via a master playlist so the platform player can do ABR; protocol objects remain per-variant CMAF.
- Initial implementation may subscribe to all variants concurrently and let the player switch locally. More efficient "switch by resubscribe" can come later.
Non-Goals (for this ECP)
- Global policy/quotas/anti-junk (separate proposal).
- Hardware encode determinism guarantees (separate proposal).
Reversibility
High. Variant publishing and selection policies can evolve without breaking base single-variant streams.