highascg

Mixer API — MIXER AMCP over HTTP

CasparCG layer and channel mixer commands: opacity, fill, crop, color, audio volume, deferred tweens, and inspector effects.

Caspar: required (503 if AMCP is down).

Implementation: src/api/routes-mixer.js · AMCP: src/caspar/amcp-mixer.js

AMCP table: docs/reference/amcp-mapping.md

CG, scene take, and PiP are separate: mixer-cg-scene.md.

Endpoints

POST /api/mixer/{command}
GET  /api/mixer/{command}?channel=1&layer=10
{command} Layer required Query (GET) Set (POST)
opacity yes current opacity opacity, optional tween
fill yes FILL tuple position/scale + optional stretch
clip yes CLIP tuple x, y, xScale, yScale
anchor yes anchor x, y
crop yes crop left, top, right, bottom
rotation yes rotation degrees
blend yes blend mode mode (e.g. normal, add)
keyer yes keyer on/off keyer 0 | 1
chroma yes chroma Caspar chroma fields (see below)
invert yes invert invert bool
brightness yes brightness value
saturation yes saturation value
contrast yes contrast value
levels yes levels minInput, maxInput, gamma, minOutput, maxOutput
volume yes volume volume
mastervolume channel only master volume
straight_alpha channel only straight alpha enable bool
grid channel only grid resolution
commit channel only — applies deferred mixer
clear optional layer — clear mixer state
effect yes — inspector effectType + params

Not a top-level path: perspective — use POST /api/mixer/effect with effectType: "perspective".

Common POST fields

Field Type Default Description
channel number 1 Caspar channel
layer number — Caspar layer (channel-layer)
duration number — Tween length in frames
tween string — Easing (linear, easeInOutCubic, …)
defer boolean — Append DEFER — apply on commit

Deferred multi-change (looks / batches)

  1. Send several mixer POSTs with "defer": true.
  2. POST /api/mixer/commit with { "channel": 1 }.

Do not wrap MIXER … COMMIT inside /api/amcp/batch BEGIN/COMMIT — send commit as its own line (playback-and-amcp.md).

UI selection integration

When the operator has a look layer selected (POST /api/selection with context: "scene_layer"), opacity and fill can omit channel / layer:

Relative nudges: pass "+0.01" or "-0.05" for opacity or fill x / y / scaleX / scaleY — server applies delta from current project/UI state.

Aspect lock: when the look layer has aspectLocked, changing scaleX or scaleY adjusts the other axis to preserve aspect.

Commands (detail)

POST /api/mixer/opacity

{
  "channel": 1,
  "layer": 10,
  "opacity": 0.5,
  "duration": 25,
  "tween": "linear",
  "defer": false
}

AMCP: MIXER 1-10 OPACITY 0.5 25 linear

POST /api/mixer/fill

Normalized position and scale (0–1 style, Caspar FILL semantics):

{
  "channel": 1,
  "layer": 10,
  "x": 0,
  "y": 0,
  "xScale": 1,
  "yScale": 1,
  "duration": 0
}

Content-aware stretch (queries layer INFO for width/height):

stretch Behaviour
none Native scale; clip if larger than layer box
fit Letterbox inside layer rect
fill-h Full width, height by aspect
fill-v Full height, width by aspect
stretch Fill layer rect; resets clip to full frame

Optional geometry hints: channelW, channelH, layerW, layerH, layerX, layerY.

POST /api/mixer/clip

Mask rectangle (same tuple shape as FILL in AMCP):

{
  "channel": 1,
  "layer": 10,
  "x": 0,
  "y": 0,
  "xScale": 0.5,
  "yScale": 0.5
}

Inspector clip_mask effect maps params.left/top/width/height → x, y, xScale, yScale.

POST /api/mixer/crop

{
  "channel": 1,
  "layer": 10,
  "left": 0,
  "top": 0,
  "right": 0,
  "bottom": 0
}

POST /api/mixer/levels

{
  "channel": 1,
  "layer": 10,
  "minInput": 0,
  "maxInput": 1,
  "gamma": 1,
  "minOutput": 0,
  "maxOutput": 1,
  "duration": 0,
  "defer": true
}

Inspector effect uses minIn / maxIn / minOut / maxOut aliases inside effect → mapped to minInput etc.

POST /api/mixer/chroma

Pass Caspar chroma options on the body (forwarded to AMCP):

{
  "channel": 1,
  "layer": 10,
  "enable": true,
  "targetHue": 120,
  "hueWidth": 0.1,
  "minSaturation": 0.3,
  "minBrightness": 0.2,
  "softness": 0.1,
  "spillSuppress": 0.5
}

POST /api/mixer/blend

{ "channel": 1, "layer": 10, "mode": "normal" }

POST /api/mixer/keyer

Layer straight-alpha keyer (not DeckLink hardware key):

{ "channel": 1, "layer": 10, "keyer": 1 }

POST /api/mixer/volume · POST /api/mixer/mastervolume

{ "channel": 1, "layer": 10, "volume": 1, "duration": 0 }

{ "channel": 1, "volume": 0.8 }

POST /api/mixer/straight_alpha

Channel output straight alpha:

{ "channel": 1, "enable": true }

POST /api/mixer/grid

Safe-area / grid overlay on channel:

{ "channel": 1, "resolution": 1 }

POST /api/mixer/commit

{ "channel": 1 }

POST /api/mixer/clear

Per layer or whole channel:

{ "channel": 1, "layer": 10 }

{ "channel": 1 }

POST /api/mixer/effect

Single inspector effect (same types as the client effect registry):

{
  "channel": 1,
  "layer": 10,
  "effectType": "brightness",
  "params": { "value": 1.2 },
  "duration": 25,
  "tween": "linear",
  "defer": true
}
effectType params (typical) AMCP routed to
blend_mode mode blend
brightness value brightness
contrast value contrast
saturation value saturation
levels minIn, maxIn, gamma, minOut, maxOut levels
chroma_key key, threshold, softness, spill, blur chroma
crop left, top, right, bottom crop
clip_mask left, top, width, height clip
perspective ulX, ulY, urX, urY, lrX, lrY, llX, llY perspective
grid resolution grid
keyer enabled keyer
rotation degrees rotation
anchor x, y anchor

Alias: type instead of effectType.

400 from handler: { "error": "Unknown inspector effectType: …" }
502 / 503 from handleMixerSafe on AMCP/connection errors.

GET — query current value

Omit value fields in POST; GET runs the AMCP query form (no arguments → read current state).

curl -s 'http://127.0.0.1:4200/api/mixer/opacity?channel=1&layer=10'

Typical response:

{
  "ok": true,
  "data": "1"
}

data is the raw AMCP payload (often a string or string array).

Examples

Fade layer in over 1 second @ 50 fps

curl -s -X POST http://127.0.0.1:4200/api/mixer/opacity \
  -H 'Content-Type: application/json' \
  -d '{"channel":1,"layer":10,"opacity":1,"duration":50,"tween":"easeInOutCubic"}'

Deferred look tweak + commit

curl -s -X POST http://127.0.0.1:4200/api/mixer/fill \
  -H 'Content-Type: application/json' \
  -d '{"channel":1,"layer":10,"x":0.1,"y":0,"xScale":0.8,"yScale":0.8,"defer":true}'

curl -s -X POST http://127.0.0.1:4200/api/mixer/opacity \
  -H 'Content-Type: application/json' \
  -d '{"channel":1,"layer":10,"opacity":1,"duration":25,"tween":"linear","defer":true}'

curl -s -X POST http://127.0.0.1:4200/api/mixer/commit \
  -H 'Content-Type: application/json' \
  -d '{"channel":1}'

JavaScript

await fetch(`${apiBase}/api/mixer/fill`, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    channel: 1,
    layer: 10,
    x: 0,
    y: 0,
    xScale: 1,
    yScale: 1,
    stretch: 'fit',
    channelW: 1920,
    channelH: 1080,
  }),
})

Responses and errors

Status Meaning
200 AMCP success — body is passthrough Caspar JSON (ok, data, …)
400 Unknown {command}
502 Caspar/command failure
503 Not connected / socket errors
Doc Topic
playback.md PLAY / LOAD / layer transport
scene-take.md Look take applies mixer + LOADBG/PLAY
timelines.md Keyframed mixer during timeline tick
playback-and-amcp.md Batch AMCP + COMMIT rules

OpenAPI

openapi.yaml — MixerCommand path param, MixerCommonFields, per-command request notes, examples for opacity, fill, commit, effect.

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