* 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>
* sfu/buffer: parse the dependency descriptor without allocating
Every VP9 and AV1 SVC packet allocated six objects in the dependency
descriptor parse: the descriptor, a clone of the frame template with
its three slices, a resolution copy, and a frame entity that took the
address of a parameter.
The pooled ExtDependencyDescriptor now owns the storage for the
descriptor, the template and the resolution, with fixed arrays for the
template's slices. The reader copies the matching template into that
storage.
Delta frame parse: 6 allocs, 176 B, 174 ns -> 0 allocs, 0 B, 122 ns.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
* sfu/dd: never copy a parsed frame into a structure template
A caller can hand Unmarshal a descriptor whose FrameDependencies points
at one of the structure's templates. Copying the packet's custom fields
into it would change the template for every later packet, so the reader
allocates a fresh template in that case.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>
* Use sync.Pool for objects in packet path.
Seeing cases of forwarding latency spikes that aling with GC.
This might be a bit overkill, but using sync.Pool for small +
short-lived objects in packet path.
Before this, all these were increasing in alloc_space heap profile
samples over time. With these, there is no increase (actually the lines
corresponding to geting from pool does not even show up in heap
accounting when doing `list` in `pprof`)
* merge
* Paul feedback
* Add debugging from DD frame number wrap around.
On a DD parser restart, the extended highest sequence number oes not
seem to be updated. Adding some debug to understand it better.
* more logs
* log incoming sequence number and frame number
If the first packet of keyframe has template structure is lost then
subsequent packets rely on it will report invalid tempalte error which
is expected.
* Add support for "abs-capture-time" extension.
Currently, it is just passed through from publisher -> subscriber side.
TODO: Need to store in sequencer and restore for retransmission.
* abs-capture-time in retransmissions
* clean up
* fix test
* more test fixes
* more test fixes
* more test fixes
* log only when size is non-zero
* log on both sides for debugging
* add marshal/unmarshal
* normalize abs capture time to SFU clock
* comment out adding abs-capture-time from registered extensions
When starting from scratch (like mute -> unmute), it is possible
that the check sync does not detect a broken chain. That results
in PLIs not being sent and the video frozen till a gratuitous key
frame arrives.
Unclear why there are not PLIs from client side. That is something else to
dig into.
* Don't update dependency info if unordered packet received
* Trace all active svc chains for downtrack
* Try to keep lower decode target decodable
* remove comments
* Test case
* clean code
* solve comments
* Decode chains
* clean up
* clean up
* decode targets only on publisher side
* comment out supported codecs
* fix test compile
* fix another test compile
* Adding TODO notes
* chainID -> chainIdx
* do not need to check for switch up point when using chains, as long as chain integrity is good, can switch
* more comments
* address comments
