MLT - Documentation

Plugin Information
Notes
Bugs
Parameters
- resource
- preroll
- keyer
- keyer_level
- devices
- device.*
- sliced_swab
- terminate_on_pause

Plugin Information

title: Blackmagic Design DeckLink Output
media types: Audio Video
description: Output audio and video using Blackmagic Design DeckLink SDI or Intensity HDMI cards.
version: 3
creator: Dan Dennedy
copyright: Copyright (C) 2010-2025 Meltytech, LLC
license: LGPL

Notes

Please ensure that you use a MLT profile that is compatible with a broadcast standard which the card you are using supports.

Bugs

Only internal keying is supported at this time.
Only 8-bit Y’CbCr or RGBA (key) is supported at this time.

Parameters

resource

title: Card
type: integer
readonly: no
required: no
minimum: 0
default: 0
widget: spinner

preroll

title: Pre-roll Count
description: This controls the amount of buffering in the DeckLink driver/library. Increase this if you get video tearing or choppy audio. However, as you increase the amount, you increase the risk of audio and video becoming out of synchronization.
type: integer
readonly: no
required: no
minimum: 2
default: 3
unit: frames
widget: spinner

keyer

title: Enable Keyer
description: Keying is the process of compositing MLT output over a live SDI input. The alpha channel of the MLT video controls the transparent areas, and the keyer supports alpha-blending. You can not control the compositing rectangle. Rather, the entire MLT output overlays the entire video input. Therefore, you must use MLT's compositing services to control the size and position. The value 1 enables the internal keyer, the value 2 enables the external keyer, and the value 0 disables it.
type: integer
readonly: no
required: no
minimum: 0
maximum: 2
default: 0

keyer_level

title: Key Opacity
description: This controls the level of blending between the key and the input video. 1 is fully opaque and something near 0 is transparent. However, absolute 0 is considered as "not supplied" and also fully opaque. 0.5 is an evenly balanced blending of the key and input video.
type: float
readonly: no
required: no
minimum: 0
maximum: 1
default: 1
widget: slider

devices

title: Number of devices
type: integer
readonly: yes
required: no
minimum: 0

device.*

title: Device model
description: The model name of each device that provides output.
type: string
readonly: yes
required: no

sliced_swab

title: Use sliced swab operation
description: This option enables multithreaded parallel swab frame data operation
type: boolean
readonly: no
required: no
minimum: 0
maximum: 1
default: 0
widget: checkbox

terminate_on_pause

title: Stop automatically
description: Whether to stop playback at the end of the producer or when playback is paused.
type: boolean
readonly: no
required: no
default: 0
widget: checkbox

Consumer: decklink