fix(core): send mixer transform properties (opacity, fill, clip, etc.) via OSC by dedicatedbroadcastsolutions · Pull Request #1804 · CasparCG/server

dedicatedbroadcastsolutions · 2026-09-21T13:31:57Z

Problem

Mixer/transform properties applied via the MIXER family of AMCP commands (MIXER OPACITY, MIXER FILL, MIXER CLIP, MIXER CONTRAST/BRIGHTNESS/SATURATION, MIXER ANCHOR, MIXER ROTATION, MIXER VOLUME, etc.) are never sent over OSC - only layer::state() producer info (foreground/background/paused/frames_left) is pushed per tick. The current value is only reachable synchronously via an AMCP query (stage::get_current_transform()), not pushed to OSC subscribers.

This is issue #37, originally reported in 2013 against CasparCG 2.1 and still valid today - core::monitor::state (the OSC state system) was built out extensively since then for producer/consumer/audio-level state, but transform/mixer properties were never wired into it.

Fix

In stage::impl's per-tick state assembly (core/producer/stage.cpp), alongside the existing layer::state() call, fetch each layer's current frame_transform (already tracked per-layer in tweens_ for MIXER command playback) and expose it as new, purely additive OSC addresses:

/channel/N/stage/layer/L/transform/opacity
/channel/N/stage/layer/L/transform/contrast
/channel/N/stage/layer/L/transform/brightness
/channel/N/stage/layer/L/transform/saturation
/channel/N/stage/layer/L/transform/anchor
/channel/N/stage/layer/L/transform/fill_translation
/channel/N/stage/layer/L/transform/fill_scale
/channel/N/stage/layer/L/transform/clip_translation
/channel/N/stage/layer/L/transform/clip_scale
/channel/N/stage/layer/L/transform/angle
/channel/N/stage/layer/L/transform/volume

No existing OSC address is renamed, removed, or changes shape, so this doesn't break existing OSC listener implementations - it's strictly new, additional addresses.

To avoid spamming subscribers with unchanged mixer telemetry every tick, each layer's transform is only added to the outgoing state when it differs from the last transform actually sent for that layer (tracked in a new last_sent_transforms_ map, using the existing frame_transform::operator!=). A static/idle layer sends its transform once and then goes quiet; an actively-tweened MIXER animation continues updating every tick until it settles, matching the pattern already used elsewhere for OSC (e.g. audio levels).

Testing

Verified the change compiles with no diagnostics. Not yet tested against a live OSC subscriber on hardware.

Summary by CodeRabbit

New Features
- OSC state updates now include mixer and transform properties, including image adjustments, positioning, rotation, and audio volume.
- Layer transform updates are sent when properties change and resent when a new subscriber connects.
Bug Fixes
- Transform changes to color saturation or geometry modifiers are now detected correctly.
- Multiple pending OSC updates are combined, and bundles use timestamps derived from the system clock.

…) via OSC Only when they change since the last tick, to avoid spamming subscribers with unchanged mixer telemetry every frame. Fixes CasparCG#37

…rors)

Issue linkage belongs in the PR description/commit trailer, not repeated across code comments.

…_ entries C++20's std::map overload of std::erase_if replaces the manual find-and-erase-while-iterating loop with a single expression - same behavior, less ceremony.

coderabbitai · 2026-10-15T12:02:39Z

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Reviewing files that changed from the base of the PR and between 0eee3a9 and c5c9cc2.

📒 Files selected for processing: 3

src/core/monitor/monitor.h
src/core/producer/stage.cpp
src/protocol/osc/client.cpp

🚧 Files skipped from review as they are similar to previous changes: 2

src/core/monitor/monitor.h
src/core/producer/stage.cpp

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📝 Walkthrough

The stage adds serialized transform properties and audio volume to monitor state when a per-layer change gate permits sending. The monitor tracks subscription epochs. The OSC client merges pending state, timestamps bundles with NTP-format tags, and signals new subscriptions.

Changes: Monitor transform state

Layer / File(s)	Summary
Track monitor subscription changes `src/core/monitor/monitor.h`	The monitor adds a subscription epoch and a change gate. The gate sends values when they differ from the last recorded value or the subscription epoch changes.
Track subscriptions and merge pending OSC state `src/protocol/osc/client.cpp`	The OSC client increments the epoch when an endpoint gains its first subscription reference. It merges incoming state entries into a pending bundle, assigns an NTP timestamp when the bundle becomes pending, and clears the pending flag after the sender takes the state.
Serialize and track layer transforms `src/core/frame/frame_transform.cpp`, `src/core/producer/stage.cpp`	The stage serializes image transform properties and audio volume, adds transform state when the per-layer gate allows sending, and removes tracking entries for absent layers. Image transform equality now requires both compared fields to match.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to c5c9c

The change adds subscription-aware transform updates to OSC monitoring, and pending messages retain current values. No demonstrated behavior requires delaying merge.

### Architecture Summary

Architecture risk: 🔵 Low · up to c5c9c

The change affects 1 system.

Changed systems: src

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

observed — src (service) was modified; 4 changed files map to changed impact.

Before / after behavior

observed — Modified behavior in src/core/frame/frame_transform.cpp: operator== now combines the cdl_saturation and enable_geometry_modifiers checks with && instead of ||, requiring both fields to match.
observed — Modified behavior in src/core/monitor/monitor.h: Adds the <atomic> and <optional> includes; <cstdint> remains included.
observed — Modified behavior in src/core/monitor/monitor.h: Adds a shared atomic subscription epoch, initialized to 1, with relaxed-load and increment operations. change_gate<T>::should_send returns true if no value has been recorded, the input differs from the last recorded value, or the epoch differs from the last recorded epoch; on true, it updates both recorded values.
observed — Modified behavior in src/core/producer/stage.cpp: Adds transform_state, which maps image opacity, contrast, brightness, saturation, anchor, fill and clip transforms, angle, and audio volume into monitor state.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: sending per-layer mixer transform properties through OSC.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 2

🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/core/producer/stage.cpp:
- Line 253: Update the `last_sent` cache comparison so it compares the
serialized transform properties rather than relying on
`image_transform::operator==`; ensure image-property changes such as opacity
changes are treated as updates even when geometry-modifier flags remain
unchanged.
- Line 255: Update the transform handling around last_sent_transforms_ so
updating stage state does not mark a transform as delivered; retain the latest
transform in outgoing state or update the delivery cache only when OSC
transmission succeeds and a subscriber is available.

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src/core/producer/stage.cpp

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…are OSC change gate image_transform::operator== ORed the entire property comparison chain with just the enable_geometry_modifiers check, due to && binding tighter than ||. Since enable_geometry_modifiers is never set on the frame_transform objects stored in tweens_, this made operator== always return true, so the per-layer OSC transform cache added for CasparCG#37 never detected a change after the first tick. Generalize the fix instead of patching stage.cpp's cache in place: added core::monitor::change_gate<T>, a small reusable primitive that gates a value on both change and on a new core::monitor::subscription_epoch(), which protocol::osc::client now bumps whenever a genuinely new endpoint subscribes (not on every additional token for an already-subscribed endpoint). This means a layer's transform is resent once a new OSC subscriber connects even if nothing changed, so late-joining subscribers aren't stuck without a value until the next MIXER command. Future OSC additions that want change-based suppression can reuse the same gate and get the same subscriber catch-up for free. Verified src/CMakeLists.txt builds clean end-to-end (ENABLE_HTML=OFF, no CEF SDK available here) including core, protocol and the final casparcg binary link. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Actionable comments posted: 1

🪄 Fix comments: Fix CodeRabbit comments on this PR

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
minimal, and validate.

Inline comments:
Review comments at @src/core/monitor/monitor.h:
- Around line 165-166: Update impl::send and the sender’s bundle-consumption
condition so a pending first bundle is delivered even when its timestamp is
zero, or assign that first bundle a positive timestamp; preserve the
change_gate::should_send behavior that caches unchanged transforms.

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Reviewing files that changed from the base of the PR and between 1dc3c0c and c5f3b85.

📒 Files selected for processing: 4

src/core/frame/frame_transform.cpp
src/core/monitor/monitor.h
src/core/producer/stage.cpp
src/protocol/osc/client.cpp

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… OSC Port the generic subscription-aware change-gating mechanism from fix-osc-mixer-transform-state (CasparCG#1804) onto this branch ahead of time, so the upcoming diagnostics-over-OSC work can use it without waiting on that PR to merge or rebasing mid-feature. - core::monitor::subscription_epoch()/bump_subscription_epoch(): a counter any subscription transport can bump when a new subscriber connects. - core::monitor::change_gate<T>: gates a value so it's only pushed into monitor::state when it changed since the last should_send() call, or when the subscription epoch moved on since then (so late-joining subscribers get caught up instead of waiting for the next real change). - protocol::osc::client::get_subscription_token bumps the epoch on a genuine new endpoint (ref count 0->1), not on every additional token for an already-subscribed endpoint. Deliberately leaves out the frame_transform.cpp equality-operator fix and stage.cpp usage from CasparCG#1804 - those are specific to that PR's mixer-transform feature and will arrive with it; this is just the shared primitive. To use for a new diagnostic value: keep a core::monitor::change_gate<T> member alongside wherever the value is tracked, and only write it into monitor::state when gate.should_send(value) returns true. Verified core and protocol build clean (ENABLE_HTML=OFF, no CEF SDK available here). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

CodeRabbit correctly flagged that client::impl::send() replaced the pending bundle_ wholesale on every call, and the sender thread only woke on bundle_time_ > 0 - so the very first bundle ever sent (timestamp 0) was never picked up, and any bundle not yet drained by the sender thread before the next send() call was silently discarded in favor of the newer one. This defeats core::monitor::change_gate: a key written into state because it just changed (or because the subscription epoch moved on) only survives if that exact send() call's bundle happens to be the one the sender thread consumes. If another tick's send() lands first, the gated key is gone, and since the gate already considers it sent, nothing resends it until the next real change or subscription event. Fix in the client rather than the gate: merge incoming state into bundle_ by key instead of replacing it, and track a pending bundle with an explicit flag instead of inferring it from the timestamp. A merged-in key survives across replace, so it reaches the sender whenever it next drains, and bundle_ is cleared after each drain so keys that stop appearing in the per-tick state (e.g. a removed layer) don't linger. Verified full project builds clean (ENABLE_HTML=OFF, no CEF SDK available here), including the final casparcg binary. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Replace the 'time_++ is a hack' OSC bundle timestamp with a proper NTP-format time tag (seconds since 1900 + fractional seconds, per the OSC spec), and drop the now-unused time_ counter. - Trim the comments added for the equality fix, change_gate, and bundle-merge fix down to one line of functional explanation each. Left two pre-existing TODOs in client.cpp alone - neither is touched by or required for this PR's changes: - "< 2048 is a hack. Properly calculate if messages will fit." (message packing into a bundle) - unrelated to bundle delivery/merging. - "(refactor) This is weird..." on get_subscription_token - a stylistic note about the shared_ptr<void>-as-RAII-token idiom, not a correctness issue; changing it would mean a public API change (client.h, 3 call sites) outside this PR's scope. Verified full project builds clean (ENABLE_HTML=OFF, no CEF SDK available here), including the final casparcg binary. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

"< 2048 is a hack. Properly calculate if messages will fit.": the message loop decided whether to add the next message based on the bundle's size as of the end of the previous one, so a bundle could overshoot the 2048-byte soft limit by up to one message's worth, and there was no real calculation of whether a given message would fit at all. Replaced it with an actual calculation: each candidate message is first written into a scratch probe stream to measure its real encoded size (using the same write_osc_message() helper used for the live stream, so the estimate can't drift from the real encoding), then only added to the bundle if it fits. The first message of a bundle is always added regardless of size, so a single oversized message gets its own bundle instead of stalling the loop forever. Verified standalone against the real oscpack encoder: many small messages split into multiple <=2048-byte bundles, an oversized single message gets its own (over-limit) bundle without blocking the next one, and an empty state produces no bundles. "(refactor) This is weird...": get_subscription_token's shared_ptr<void> with a null pointee and a cleanup deleter is the same lifetime-binding shape protocol_strategy::add_lifecycle_bound_object(shared_ptr<void>) requires for every per-connection resource (see lock_container.cpp for the identical pattern) - it's intentional, not a mistake. Replaced the TODO with a comment documenting why, since a "fix" here would mean changing a public API (client.h) used by 3 call sites outside this PR just to relocate the same shared_ptr<void> requirement to the caller, not remove it. Verified full project builds clean (ENABLE_HTML=OFF, no CEF SDK available here), including the final casparcg binary. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dedicatedbroadcastsolutions · 2026-10-16T02:42:33Z

Coderabbit stopped providing reviews because I made too many pushes close together. I'll continue with a manual review and testing later, but I think this is getting close.

dedicatedbroadcastsolutions · 2026-10-16T12:08:58Z

Not sure how to unpause coderabbit

fix(core): send mixer transform properties (opacity, fill, clip, etc.…

a39fe36

…) via OSC Only when they change since the last tick, to avoid spamming subscribers with unchanged mixer telemetry every frame. Fixes CasparCG#37

dedicatedbroadcastsolutions marked this pull request as draft September 21, 2026 13:32

chore: retrigger CI (Launchpad PPA was returning transient 500/503 er…

e49282b

…rors)

dedicatedbroadcastsolutions marked this pull request as ready for review September 21, 2026 14:03

dedicatedbroadcastsolutions added 4 commits September 21, 2026 14:04

refactor: trim inline comments to functional explanation only

e34b8ad

Issue linkage belongs in the PR description/commit trailer, not repeated across code comments.

refactor(core): use std::erase_if to prune stale last_sent_transforms…

f58289f

…_ entries C++20's std::map overload of std::erase_if replaces the manual find-and-erase-while-iterating loop with a single expression - same behavior, less ceremony.

Merge branch 'CasparCG:master' into fix-osc-mixer-transform-state

88e59bd

Merge branch 'CasparCG:master' into fix-osc-mixer-transform-state

82d36ff

coderabbitai Bot reviewed Oct 15, 2026

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Comment thread src/core/producer/stage.cpp Outdated

Comment thread src/core/producer/stage.cpp Outdated

dedicatedbroadcastsolutions and others added 2 commits October 15, 2026 17:49

Merge branch 'CasparCG:master' into fix-osc-mixer-transform-state

1dc3c0c

coderabbitai Bot reviewed Oct 16, 2026

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Comment thread src/core/monitor/monitor.h

dedicatedbroadcastsolutions and others added 3 commits October 16, 2026 01:48

dedicatedbroadcastsolutions marked this pull request as draft October 16, 2026 02:33

dedicatedbroadcastsolutions marked this pull request as ready for review October 16, 2026 02:40

dedicatedbroadcastsolutions marked this pull request as draft October 16, 2026 02:41

dedicatedbroadcastsolutions marked this pull request as ready for review October 16, 2026 02:51

fix(protocol): account for OSC bundle element size

9cd46c5

dedicatedbroadcastsolutions marked this pull request as draft October 16, 2026 03:18

dedicatedbroadcastsolutions marked this pull request as ready for review October 16, 2026 03:26

dedicatedbroadcastsolutions marked this pull request as draft October 16, 2026 03:26

dedicatedbroadcastsolutions marked this pull request as ready for review October 16, 2026 12:07

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fix(core): send mixer transform properties (opacity, fill, clip, etc.) via OSC - #1804

fix(core): send mixer transform properties (opacity, fill, clip, etc.) via OSC#1804
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