Rendering Engine components

This page describes the parameters and commands that is used for controlling the video mixer, audio mixer, HTML renderers and media players in the Ateliere Live Rendering Engine. This topic is closely related to this page on how to configure the rendering engine at startup.

Control command protocol

All commands to the Ateliere Live Rendering Engine are sent as human readable JSON objects and are listed below.

Each subsystem of the rendering engine has their own set of parameters and commands, and can be reached using:

• /video for the video mixer
• /audio for the audio mixer (if using the built-in mixer)
• /ndi_audio for the NDI audio mixer
• /html for the html renderer instances
• /media for the media playback instances

Video mixer resources

Background

The video mixer is built as a tree graph of processing nodes, please see this page for further information on the video mixer node graph. The names of the nodes defined in the node graph are used as part of the resources: /video/nodes/{node_name} and they all have the parameter type which describes which type of video node it is.

There are 10 different node types.

• The Transition node is used to pick which input slots to use for the program and preview output. The node also supports making transitions between the program and preview.
• The Select node simply forwards one of the available sources to its output.
• The Alpha combine node is used to pick two input slots (or the same input slot) to copy the color from one input and combine it with some information from the other input to form the alpha. The color will just be copied from the color input frame, but there are several modes that can be used to produce the alpha channel in the output frame in different ways. This is known as “key & fill” in broadcasting.
• The Alpha over node is used to perform an “Alpha Over” operation, that is to put the overlay video stream on top of the background video stream, and let the background be seen through the overlay depending on the alpha of the overlay. The node also features fading the graphics in and out by multiplying the alpha channel by a constant factor.
• The Transform node takes one input stream and transforms it (scaling and translating) to one output stream.
• The Chroma Key node takes one input stream, and by setting appropriate parameters for the keying, it will remove areas with the key color from the incoming video stream both affecting the alpha and color channels
• The Fade to black node takes one input stream, which it can fade to or from black gradually, and then outputs that stream.
• The Output node has one input stream and will output that stream out from the video mixer, back to the Rendering Engine. It has no control commands
• The Crop node takes one input stream and can crop a video stream to a new size
• The Video delay node takes one input stream and will hold the frames for a configured amount of time before forwarding the frames, causing a delay of the video output

To reset the runtime configuration of all video nodes to their default state use the reset command of the /video resource.

Transition

The transition node picks a program and a preview video source from the input slots and forward these to other nodes. The node also features auto transitions between the program and the preview sources. Some transition commands last over a duration of time, for example wipes. These can be performed either automatically or manually. The automatic mode works by the operator first selecting the type of transition, for instance a fade, setting the preview to the input slot to fade to and then trigger the transition at the right time with a auto command with the duration for the transition. In manual mode the exact position of the transition is set by the control panel by setting the factor parameter. This is used for implementing T-bars, where the T-bar repeatedly sends the current position of the bar. In the manual mode, the transition type is set before the transition begins, just as in the automatic mode. Note that an automatic transition will be overridden in case the transition position/factor is manually set, by interrupting the automatic transition and jumping to the manually set position.

resource: /video/nodes/{node name} type: transition

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "factor": 0.0,
        "mode": "fade",
        "preview": 0,
        "program": 0
    }
}

Commands

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "auto",
       "parameters": {
           "duration_ms": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "cut"
   }
}

Select

A node to select a video source from the input slots and send it on to the next node.

resource: /video/nodes/{node name} type: select

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "input": 0
    }
}

Alpha combine

A node to combine the color channels of one video stream with the alpha from another. This node is useful for video sources where the alpha channel is provided as a separate black and white video source that must be combined with the color source. The node supports multiple modes of obtaining the alpha, either by copying a specific color or alpha channel of some input slot, or by taking the average of the R, G and B channels of the video from some input slot.

resource: /video/nodes/{node name} type: alpha_combine

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "alpha": 0,
        "color": 0,
        "mode": "average-rgb"
    }
}

Alpha over

A node to combine two video streams using alpha over compositing, overlaying the foreground stream on the background stream. The node will keep the transparency of both layers. The overlay stream can be faded in and out of the background stream.

resource: /video/nodes/{node name} type: alpha_over

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "factor": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "fade_from",
       "parameters": {
           "duration_ms": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "fade_to",
       "parameters": {
           "duration_ms": <uint32>
       }
   }
}

Transform

A node to transform an incoming video stream, by scaling and transposing it. The canvas size of the input will be kept and all surrounding area in case the source video is shrunk, is filled with transparent black.

resource: /video/nodes/{node name} type: transform

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "scale": 1.0,
        "x": 0.0,
        "y": 0.0
    }
}

Chroma key

A node to perform chroma keying on an incoming video stream. The output video stream will have the alpha and possibly the color channels modified, according to the parameter values in this node. To remove a color from the incoming video stream, first enable the node and then select the key color to remove. The key color can be selected in two ways, either by manually setting the color with the R, G and B channel values, or by using the color picker. When using the color picker, the color picker command will define the position and size of the color picker square to sample the incoming video stream. The R, G and B color parameters will be updated according to the average color of the area when the command was received by the Rendering Engine. The currently selected color can be shown in the upper left hand corner in the output video stream of the node by setting the parameter show_key_color to true. Also, the latest sampled color picker area can be drawn in the node’s output by setting show_color_picker to true. When a suitable color has been chosen, adjust the distance and falloffparameters to get a clear mask. To aid the tweaking of the parameters, set the show_alpha parameter to true. This will make the node output the black and white mask instead of the keyed result, which makes it easier to see which parts are masked away and not. Remember to turn this off before going on air. As a last step, any remaining fringes of the key color around the subject can be desaturated with the color_spill parameter. But remember this will desaturate colors close to the key color even in parts of the frame fully visible.

resource: /video/nodes/{node name} type: chroma_key

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "color_spill": 0.1,
        "distance": 0.1,
        "enabled": false,
        "falloff": 0.08,
        "show_alpha": false,
        "show_color_picker": false,
        "show_key_color": false
    }
}

Commands

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "pick_color",
       "parameters": {
           "size": <uint32>,
           "x": <float>,
           "y": <float>
       }
   }
}

Chroma key / Key color

The key color

resource: /video/nodes/{node name}/key_color type: chroma_key

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}/key_color",
    "body": {
        "b": 0.0,
        "g": 0.0,
        "r": 0.0
    }
}

Fade to black

A node to fade the incoming video stream to and from black.

resource: /video/nodes/{node name} type: fade_to_black

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "factor": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "fade_from",
       "parameters": {
           "duration_ms": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/video/nodes/{node name}",
   "body": {
       "command": "fade_to",
       "parameters": {
           "duration_ms": <uint32>
       }
   }
}

Crop

A node to crop the incoming video stream. The node can crop the left, right, top and bottom edge of the incoming video stream. The areas outside of the cropped area will be transparent in the output.

resource: /video/nodes/{node name} type: crop

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "bottom": 1.0,
        "left": 0.0,
        "right": 1.0,
        "top": 0.0
    }
}

Video delay

A node to delay the video stream a given number of frames.

resource: /video/nodes/{node name} type: video_delay

Parameters

{
    "type": "set",
    "resource": "/video/nodes/{node name}",
    "body": {
        "delay": 0
    }
}

Audio mixer resources

Overview

The audio mixer has the following data path:

The three main elements of the audio mixer are the Input strips, the Mixes, and the Outputs.

Input strips

Audio enters the audio mixer through the input strips. When a strip has been created, the audio for the strip is selected among the available channels in the Rendering Engine’s input slots.

In the example picture above, three sources are connected to the input slots. The slots have four, two, and six channels respectively. In the illustration we can see that the first strip uses a single channel from the first slot, the second strip uses channel three and four from the second slot and so on. Several input strips may select the same input slot channels.

Each input strip has two stereo output connection points (), one before the volume fader (pre fader) and one after the volume fader (post fader). When a mix or an output is connected to the output of a strip, which of these two locations to take the audio from can be selected using the origin parameter.

Mixes

Mixes are used to combine the output from input strips, or other mixes, and also allows for further filtering of the audio signal. When a mix has been created, the input strips and other mixes contributing to the mix can be controlled in the /inputs/strips and /inputs/mixes sections of the mix.

Just like an input strip a mix has two stereo output connection points () that can be used when connecting the output of the mix to another mix or an output.

Outputs

Each output corresponds to an audio output in the Rendering Engine configuration. An output takes audio from a single location, either directly from an input strip or from a mix. In both cases it can be specified whether to take the audio pre_fader or post_fader.

Note: The audio mixer is completely separate from the video mixer, so switching image in the video mixer will not change the audio mixer in any way.

Audio mixer root

The internal audio mixer consists of input strips (/strips), mixes (/mixes) and output buses (/outputs). The strips are the inputs of the audio mixer, taking audio from the inputs of the Rendering Engine. The mixes mix audio from strips and other mixes. Finally the output buses are the outputs of the audio mixer, taking audio from a single strip or a mix.

resource: /audio

Commands

{
   "type": "command",
   "resource": "/audio",
   "body": {
       "command": "reset"
   }
}

To reset the audio mixer to the default state, including removal of all configured input strips, use the reset command of the /audio resource.

Input strips

An input strip in the audio mixer, which takes audio from the input slots of the Rendering Engine (/input). Audio is either taken as a mono channel or as a stereo pair. The audio is sent through a filter chain (/filters). After the filter chain the output loudness of the strip is controlled by a main fader. There are peak meters placed before (/pre_fader_meter) and after (/post_fader_meter) the fader, as well as before the filter chain, measuring the raw audio input (/input_meter).

resource: /audio/strips/{strip index}

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}",
    "body": {
        "label": ""
    }
}

Input strip input configuration

Input settings for a strip.

resource: /audio/strips/{strip index}/input

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/input",
    "body": {
        "first_channel": 0,
        "input_slot": 0,
        "is_stereo": false,
        "second_channel": 1
    }
}

Input loudness meter

Peak loudness meter for incoming audio, measured before the filters of this input strip. This meter will either have one streaming parameter called ‘peak’ in case the strip is in mono mode, else two streaming parameters ‘peak_left’ and ‘peak_right’ will replace the ‘peak’ parameter when in stereo mode.

resource: /audio/strips/{strip index}/input_meter

Streaming parameters

Mid side stereo

Filter for controlling the mid and side amount of an audio signal. The input can either be Mid-Side (MS) or Left-Right (LR) stereo. Mono input will be passed through unaltered. If the input is LR, it is converted to MS with the mid channel being the average of the input channels and the side channel being half the difference of the channels. With the signal in MS format the mid and the side amount can be controlled using the mid_amount, side_amount, and invert_polarity parameters.

resource: /audio/strips/{strip index}/filters/mid_side

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/filters/mid_side",
    "body": {
        "enabled": false,
        "input_format": "lr_stereo",
        "invert_polarity": true,
        "mid_amount": 1.0,
        "side_amount": 1.0
    }
}

Pre-gain

Gain filter

resource: /audio/strips/{strip index}/filters/gain

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/filters/gain",
    "body": {
        "value": 0.0
    }
}

Parametric equalizer

Equalizer filter

resource: /audio/strips/{strip index}/filters/eq

Commands

{
   "type": "command",
   "resource": "/audio/strips/{strip index}/filters/eq",
   "body": {
       "command": "reset"
   }
}

Parametric equalizer bands

A filter/band in the equalizer

resource: /audio/strips/{strip index}/filters/eq/bands/{band index}

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/filters/eq/bands/{band index}",
    "body": {
        "freq": 1000.0,
        "gain": 0.0,
        "q": 0.707,
        "type": "none"
    }
}

Dynamic range compressor

Dynamic range compressor

resource: /audio/strips/{strip index}/filters/compressor

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/filters/compressor",
    "body": {
        "attack": 50.0,
        "gain": 0.0,
        "knee": 0.0,
        "ratio": 1.0,
        "release": 200.0,
        "threshold": 0.0
    }
}

Panning

Panning filter

resource: /audio/strips/{strip index}/filters/pan

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/filters/pan",
    "body": {
        "value": 0.0
    }
}

Pre-fader loudness meter

Peak loudness meter for filtered audio, measured after the filters of this input strip, but before the fader. This meter will always have two streaming parameters called ‘peak_left’ and ‘peak_right’, since the output of the strip is stereo.

resource: /audio/strips/{strip index}/pre_fader_meter

Streaming parameters

Input strip fader

Volume fader controlling the output loudness of this strip

resource: /audio/strips/{strip index}/fader

Parameters

{
    "type": "set",
    "resource": "/audio/strips/{strip index}/fader",
    "body": {
        "muted": false,
        "volume": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/audio/strips/{strip index}/fader",
   "body": {
       "command": "fade",
       "parameters": {
           "volume": <float>,
           "duration_ms": <uint32>
       }
   }
}

Post-fader loudness meter

Peak loudness meter for filtered audio, measured after the fader and after the filters of this input strip. This meter will always have two streaming parameters called ‘peak_left’ and ‘peak_right’, since the output of the strip is stereo.

resource: /audio/strips/{strip index}/post_fader_meter

Streaming parameters

Mixes

A mix in the audio mixer, which takes audio from selected input strips and possibly other mixes to mix to a single stereo pair. After mixing the inputs (/inputs) of the mix, the audio is sent through a filter chain (/filters), similar to that of an input strip. After the filter chain the output loudness of the mix is controlled by a main fader. The inputs of a mix can either be taken pre- or post-fader from the strips and other mixes included in the mix. There are peak meters placed before (/pre_fader_meter) and after (/post_fader_meter) the fader, as well as before the filter chain, after the inputs has been mixed down to a single stereo pair (/input_meter).

resource: /audio/mixes/{mix index}

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}",
    "body": {
        "label": ""
    }
}

Mixes inputs

The inputs to this mix.

resource: /audio/mixes/{mix index}/inputs

Mixes inputs from input strips

Volume fader for controlling the contribution of the result of the other mix to this mix

resource: /audio/mixes/{mix index}/inputs/strips/{strip index}

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/inputs/strips/{strip index}",
    "body": {
        "muted": false,
        "origin": "post_fader",
        "volume": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/audio/mixes/{mix index}/inputs/strips/{strip index}",
   "body": {
       "command": "fade",
       "parameters": {
           "volume": <float>,
           "duration_ms": <uint32>
       }
   }
}

Mixes inputs from other mixes

Volume fader for controlling the contribution of the result of the other mix to this mix

resource: /audio/mixes/{mix index}/inputs/mixes/{mix index}

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/inputs/mixes/{mix index}",
    "body": {
        "muted": false,
        "origin": "post_fader",
        "volume": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/audio/mixes/{mix index}/inputs/mixes/{mix index}",
   "body": {
       "command": "fade",
       "parameters": {
           "volume": <float>,
           "duration_ms": <uint32>
       }
   }
}

Input loudness meter

Peak loudness meter for incoming audio, measured before the filters of this mix. This meter will always have two streaming parameters ‘peak_left’ and ‘peak_right’, since the input to the mix is always stereo.

resource: /audio/mixes/{mix index}/input_meter

Streaming parameters

Pre-gain

Gain filter

resource: /audio/mixes/{mix index}/filters/gain

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/filters/gain",
    "body": {
        "value": 0.0
    }
}

Parametric equalizer

Equalizer filter

resource: /audio/mixes/{mix index}/filters/eq

Commands

{
   "type": "command",
   "resource": "/audio/mixes/{mix index}/filters/eq",
   "body": {
       "command": "reset"
   }
}

Parametric equalizer bands

A filter/band in the equalizer

resource: /audio/mixes/{mix index}/filters/eq/bands/{band index}

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/filters/eq/bands/{band index}",
    "body": {
        "freq": 1000.0,
        "gain": 0.0,
        "q": 0.707,
        "type": "none"
    }
}

Dynamic range compressor

Dynamic range compressor

resource: /audio/mixes/{mix index}/filters/compressor

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/filters/compressor",
    "body": {
        "attack": 50.0,
        "gain": 0.0,
        "knee": 0.0,
        "ratio": 1.0,
        "release": 200.0,
        "threshold": 0.0
    }
}

Panning

Panning filter

resource: /audio/mixes/{mix index}/filters/pan

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/filters/pan",
    "body": {
        "value": 0.0
    }
}

Pre-fader loudness meter

Peak loudness meter for filtered audio, measured after the filters of this mix, but before the fader. This meter will always have two streaming parameters called ‘peak_left’ and ‘peak_right’, since the output of the mix is stereo.

resource: /audio/mixes/{mix index}/pre_fader_meter

Streaming parameters

Mix output fader

Volume fader controlling the output loudness of this mix

resource: /audio/mixes/{mix index}/fader

Parameters

{
    "type": "set",
    "resource": "/audio/mixes/{mix index}/fader",
    "body": {
        "muted": false,
        "volume": 0.0
    }
}

Commands

{
   "type": "command",
   "resource": "/audio/mixes/{mix index}/fader",
   "body": {
       "command": "fade",
       "parameters": {
           "volume": <float>,
           "duration_ms": <uint32>
       }
   }
}

Post-fader loudness meter

Peak loudness meter for filtered audio, measured after the fader and after the filters of this mix. This meter will always have two streaming parameters called ‘peak_left’ and ‘peak_right’, since the output of the strip is stereo.

resource: /audio/mixes/{mix index}/post_fader_meter

Streaming parameters

Output bus

Audio mixer output bus to select which input strip or mix should be sent to the output of the audio mixer. The outputs are populated from the Rendering Engine config. Audio from a strip or a mix can be selected for the output. The selected source of this output can either be taken pre- or post-fader from the referenced strip or mix.This makes it possible for outputs meant for pre-listening to listen to a mix or strip without touching its fader. Such outputs can also jump freely between mixes to listen to what is being output from the mixer or strips to listen to the incoming components to tweak the audio filters. The selected audio is fed through a loudness meter.

resource: /audio/outputs/{output name}

Parameters

{
    "type": "set",
    "resource": "/audio/outputs/{output name}",
    "body": {
        "label": ""
    }
}

Output bus input

The source of an output bus.

resource: /audio/outputs/{output name}/input

Parameters

{
    "type": "set",
    "resource": "/audio/outputs/{output name}/input",
    "body": {
        "index": 0,
        "origin": "post_fader",
        "source": "mix"
    }
}

Output bus loudness meter

Loudness meters for the output bus. Used to monitor the loudness of the outgoing audio from the mixer.This meter will always have two streaming parameters called ‘peak_left’ and ‘peak_right’. When the parameter ’enable_ebu_meters’ is set to true, three additional streaming parameters will be available, called ’ebu_m’, ’ebu_s’ and ’ebu_i’, which measure loudness according to the EBU R 128 standard.

resource: /audio/outputs/{output name}/meters

Parameters

{
    "type": "set",
    "resource": "/audio/outputs/{output name}/meters",
    "body": {
        "enable_ebu_meters": false
    }
}

Streaming parameters

Commands

{
   "type": "command",
   "resource": "/audio/outputs/{output name}/meters",
   "body": {
       "command": "reset"
   }
}

External audio mixing via NDI

The internal audio mixer can be replaced with an external audio mixer, where NDI is used for communicating with the external mixer. To enable the external NDI audio mixer the Rendering Engine application should be started with the environment variable ACL_AUDIO_MIXER set to external_ndi.

The external NDI audio mixer bridge

resource: /ndi_audio

Sending audio to external mixer

All streams to send to the external audio mixer

resource: /ndi_audio/send_streams

Commands

{
   "type": "command",
   "resource": "/ndi_audio/send_streams",
   "body": {
       "command": "add_stream",
       "parameters": {
           "name": <string>
       }
   }
}

{
   "type": "command",
   "resource": "/ndi_audio/send_streams",
   "body": {
       "command": "remove_stream",
       "parameters": {
           "name": <string>
       }
   }
}

A stream to send to the external audio mixer

resource: /ndi_audio/send_streams/{send stream index}

Parameters

Commands

{
   "type": "command",
   "resource": "/ndi_audio/send_streams/{send stream index}",
   "body": {
       "command": "disable_channel",
       "parameters": {
           "index": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/ndi_audio/send_streams/{send stream index}",
   "body": {
       "command": "enable_channel",
       "parameters": {
           "index": <uint32>,
           "input_slot": uint32,
           "channel": uint32
       }
   }
}

List of audio channels to send

resource: /ndi_audio/send_streams/{send stream index}/channels

A channel to send to the external audio mixer

resource: /ndi_audio/send_streams/{send stream index}/channels/{channel index}

Parameters

{
    "type": "set",
    "resource": "/ndi_audio/send_streams/{send stream index}/channels/{channel index}",
    "body": {
        "channel": 0,
        "input_slot": 0
    }
}

Receiving audio in return from the external mixer

All streams that returns audio from the external audio mixer

resource: /ndi_audio/return_streams

Commands

{
   "type": "command",
   "resource": "/ndi_audio/return_streams",
   "body": {
       "command": "add_stream",
       "parameters": {
           "name": <string>
       }
   }
}

{
   "type": "command",
   "resource": "/ndi_audio/return_streams",
   "body": {
       "command": "remove_stream",
       "parameters": {
           "name": <string>
       }
   }
}

A stream which returns audio from the external audio mixer

resource: /ndi_audio/return_streams/{return stream index}

Parameters

Mapping received audio to outputs

All audio outputs from this component

resource: /ndi_audio/outputs

An output from this component consisting of audio from one or more NDI return streams

resource: /ndi_audio/outputs/{output bus}

Parameters

The list of channels for one output

resource: /ndi_audio/outputs/{output bus}/channels

An output channel

resource: /ndi_audio/outputs/{output bus}/channels/1

Parameters

{
    "type": "set",
    "resource": "/ndi_audio/outputs/{output bus}/channels/1",
    "body": {
        "return_channel": 0,
        "return_stream": 0
    }
}

HTML rendering

The Rendering Engine features a built-in HTML renderer which uses the Chromium web browser engine to render HTML pages. This resource can create and close HTML renderers.

resource: /html

Commands

{
   "type": "command",
   "resource": "/html",
   "body": {
       "command": "close",
       "parameters": {
           "input_slot": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/html",
   "body": {
       "command": "create",
       "parameters": {
           "input_slot": <uint32>,
           "width": <uint32>,
           "height": <uint32>,
           "url": string
       }
   }
}

{
   "type": "command",
   "resource": "/html",
   "body": {
       "command": "reset"
   }
}

HTML renderer

This resource controls an HTML renderer instance and allows loading of new URLs and executing JavaScript snippets.

resource: /html/{input slot}

Parameters

Commands

{
   "type": "command",
   "resource": "/html/{input slot}",
   "body": {
       "command": "execute",
       "parameters": {
           "javascript": <string>
       }
   }
}

{
   "type": "command",
   "resource": "/html/{input slot}",
   "body": {
       "command": "load",
       "parameters": {
           "url": <string>
       }
   }
}

Media players

The Rendering Engine can create media player instances to play video and audio files from the hard drive of the machine running the Rendering Engine. It is up to the user of the API to ensure the files are uploaded to the machines running the Rendering Engine(s) before trying to run them. The media players use the FFmpeg library to demux and decode the media files, so most files supported by FFmpeg should work. This resource can create and close media players.

resource: /media

Commands

{
   "type": "command",
   "resource": "/media",
   "body": {
       "command": "close",
       "parameters": {
           "input_slot": <uint32>
       }
   }
}

{
   "type": "command",
   "resource": "/media",
   "body": {
       "command": "create",
       "parameters": {
           "input_slot": <uint32>,
           "path": string
       }
   }
}

{
   "type": "command",
   "resource": "/media",
   "body": {
       "command": "reset"
   }
}

Media player

This resource controls a media player instance. The media players have three parameters that can be set to control if only a portion of the file should be played, and if the playback should loop once it reaches the end. See the section_start_ms, section_duration_ms and loop parameters below.

resource: /media/{input slot}

Parameters

{
    "type": "set",
    "resource": "/media/{input slot}",
    "body": {
        "loop": false,
        "section_duration_ms": 4294967295,
        "section_start_ms": 0
    }
}

Streaming parameters

Commands

{
   "type": "command",
   "resource": "/media/{input slot}",
   "body": {
       "command": "load",
       "parameters": {
           "path": <string>
       }
   }
}

{
   "type": "command",
   "resource": "/media/{input slot}",
   "body": {
       "command": "pause"
   }
}

{
   "type": "command",
   "resource": "/media/{input slot}",
   "body": {
       "command": "play"
   }
}

{
   "type": "command",
   "resource": "/media/{input slot}",
   "body": {
       "command": "seek",
       "parameters": {
           "time_ms": <int32>
       }
   }
}