On Publish Graphics Scripting

Blackbird supports the ability to manipulate and automate sequences. The “source cladder” feature enables an overlay such as a bug to be added to a sequence and also provides the ability to append fixed content such as an end board sting to the end of a sequence upon publish. Both features can be combined to automate branding associated with each individual publishing button.

Upload of individual images

Elements required for the overlay or stings must be present in the Blackbird platform, either by ingesting from an Edge server watch folder or from web upload. For low volume operations such as static images or occasional branding changes – the web upload is a fast way to upload into Blackbird. Image pixel sizes should be an even numeric height and width (e.g. 1920x1080 rather than 1333x1000).

The upload button can be seen on the Blackbird Control Centre upon login or within the Blackbird editor if your account has permission enabled

Within the web uploader, select the files (e.g. logos) to be uploaded and select the frame rate applicable to the output sequences to use these files. Typical Blackbird resolutions vary by account but for digital delivery/render workflows typically the related 360P with the frame rate as desired where needed unless you are advised otherwise.

Uploaded media from the web uploader will be sent to the root folder for your account.

Building Source Sequences

Overlays are repeated for the duration of the original sequence created by a user. This means that the sequence to be used as an overlay must either be a loop of content or that for more complex overlays, that the overlay sequence should be set to the duration of the expected publishes that will be overlaid upon.

Stings / end board are more straightforward since they do not increase the number of effective channels of video on a sequence. A sting is essentially appended after the users selected sequence/edit meaning that transparencies and mixes are not supported on the start of this element.

Note that both the overlay and append sequences must be sequences (shown by the icon in the editor with a scissor logo in the top left of the icon. Source clips must be made into sequences. A source clip is shown by a film strip in the upper left of the item icon.

Files can be locked by right clicking and selecting the “locked” property for individual items to avoid risk of accidental deletion.

Build a new sequence in Blackbird from either single or multiple layers. Note that the layer count will be added to the number of layers on the published sequence so typical total Blackbird concurrent video tracks will apply for the total of both the sequence and the overlay sequence.

A simple overlay sequence for a static graphic bug can be created by dragging and dropping a still from the “files” window onto the timeline. This will position the element centrally with default properties.

Rescaling and moving the element can be performed by expanding the pan/zoom pane and manipulating the position and size within an output video frame.

To enter the pan/zoom controls, right click the video track to be manipulated

Then right click the pan/zoom control

The pan/zoom then opens and can be used to drag the scale slider up/down for increase/decrease of size and the active video window acts as a drag / drop positioning tool.

Tip: if your workflow includes a full frame graphic with pixel precision size and location and you have a uniform output resolution such as 1920x1080p then creating an overlay sequence from an original full frame image with transparency is an easy way to achieve accuracy.

Positioning within the Blackbird editor is relative and will be determined by output rules including any cropping such as square 1080x1080p.

The sequence can be saved by using the save icon on the timeline and providing a name. If you save or move the sequence to a specific folder, make a note of this for setting up the publishing configurations since this requires both the name and the location of the sequence.

Configuration of publishing buttons

On initial creation of a publishing button, if the option is enabled for your account(s) then you will be presented with an additional dialog to enable the overlay/sting manipulation with the option “Choose sources for publishing, with the ability to modify edits” which must be selected at this point to enable the feature.

On the button that is created, on the Source tab – a “Source Cladder Recipe” is enabled where specific syntax can be used to enable and map overlay, prepend and append (preroll and end sting), overlaystart and overlayend (on top of existing content as overlay with transparency typically) to an output publish automatically.

The syntax to be entered is:

  • “overlay “ + path to sequence for overlay

  • “append “ + path to sequence for end sting

  • “prepend “ + path to sequence for preroll

  • “overlaystart ” + path to sequence for preroll

  • “overlayend” + path to sequence for preroll

Order of operation

The source cladder recipe is processed in the order of the commands being used and in accordance with the associated Z ordering based on the chain of manipulation being performed, this example below will add an overlay to the user defined edit/selection, then add overlay start and overlay end sections for alpha channel wipe, then add the preroll and postroll.

overlay AutoGFX/Full_edit_overlay_30 fps

overlaystart AutoGFX/5_sec_overlaystart_sag_30 fps

overlayend AutoGFX/6_sec_overlayend_sag_30 fps

prepend AutoGFX/Prepend_sag_30 fps

append AutoGFX/Append_7_sec_sag_30 fps

Other examples might be to add an append (postroll), then the overlay meaning that the overlay (e.g. logo) would apply to the complete clip including the postroll


From an operational perspective, a user only needs to know which button to be using for publishing and that they should consider positioning of any additional elements to ensure that the output does not have too many overlaid graphics.

Note that frame rate of source sequence and all graphic sequences must match.

Any source cladder using the overlaystart and overlayend operations will be front or back timed against the original user selection so long wipes are not recommended and users should avoid putting video cuts within the region of the overlaystart/end region of video to avoid too much visual change.

An existing clip being used for a wipe out (preroll) or wipe in (postroll) should be split into 2 sequences if being used within an overlaystart and overlayend since they can then be used to avoid any full frame content being used on top of edit/clip selections