Raja SubramanianandClaude Opus 5.5 099e03fdf8 sfu: forward the dependency descriptor for VP8 simulcast (#4987) ...

* sfu: forward the dependency descriptor for VP8 simulcast

libwebrtc sends VP8 with a one byte payload descriptor when it sends the
dependency descriptor, so a VP8 subscriber gets neither picture IDs nor the
descriptor and finds frame references by sequence number alone. Under loss
with temporal filtering it stalls until a key frame.

DDForwarder rewrites the publisher's descriptor for each forwarded packet:
frame numbers continue across simulcast layer switches and stream restarts,
the structure goes out with the current layer's key frame, and the active
decode targets follow the forwarded temporal layer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* sfu: keep VP8 descriptor frame numbers from going back

Rebase frame numbers only when a new stream would go back past the last
number sent: on a layer switch, a stream restart (also when it starts with a
delta frame) and a new forwarder on the same downtrack, which now carries
over the last number sent.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* sfu: set VP8 descriptor decode targets from the packet's layer

The active decode targets use the temporal layer the packet is forwarded at,
not the selector's next layer on the last packet before a down switch. They
also go out on key frames, combined with the publisher's own mask.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* sfu: carry the current active decode targets on every DD packet

The parser puts the stream's current mask on every packet, so a mask change
on a dropped packet still reaches the VP8 descriptor forwarder, which no
longer tracks the publisher's mask itself.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* sfu: take the first DD active decode targets mask at any sequence number

A publisher whose first packet has RTP sequence number 0 never had its key
frame's mask applied, so every packet reported no active decode targets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

2026-10-12 12:08:49 +05:30

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sfu: forward the dependency descriptor for VP8 simulcast (#4987)

2026-10-12 12:08:49 +05:30