HOW TO: Trigger SCTE-35 / SCTE-104

What are SCTE signals?

SCTE signals are used to trigger markers downstream of the SCTE broadcasting source. These markers are used to signal an inline insertion opportunity for devices downstream such as commercial breaks or alternative programming. A daily example of this would be watching major television network's primetime programming. When a local commercial opportunity is available during network programming, a SCTE message is sent to the local broadcaster with identifiers and data like event id and duration. Then the local broadcaster's commercials will playout and return back to the main program. 

Difference between SCTE 35 and SCTE 104?

• SCTE 104 applies only to SDI baseband video (in the VANC)
• SCTE 35 applies to transport streams (compressed video)

Requirements

To trigger SCTE (35 or 104), you will need:

• either the free DEMO version of OnTheAir Video 4, or if you use a valid license of OnTheAir Video 4, (OnTheAir Video Express is not supported), you will need the CC option, 
• a video device that supports to output VANCs (all recent cards that we support and that have a SDI output should work fine, but older models of Blackmagic devices may not support it). Note that for AJA cards, you need to enable VANCs in AJA Control Panel.

Note that we write the SCTE info in the VANC of an SDI output, so this will only work with an SDI output. When using the direct link (for example to send video from one of our playout application to another), the SCTE info is preserved.

There are two ways to trigger SCTE:

• with the SCTE trigger embedded in an MXF file
• with an Action on OnTheAir Video

SCTE embedded in an MXF file

You can embed the SCTE info in a MXF file containing special VANCs of DID 0x41 and SDID 0x07. Those triggers will be passed on to the SDI output signal.

The advantage of this solution is that the SCTE trigger will always follow the video file. There will be nothing to do, but it may be complex to generate.

What about reacting to a SCTE trigger

This article explains how to output SCTE triggers, but OnTheAir Video can also read as an ad server and you can perform actions based on SCTE triggers received in the VANCs of a SDI signal. Check the this article.

How to Trigger SCTE using Actions

Depending on the version of OnTheAir Video that you are using, you will have different options. 

With OnTheAir Video 4.2 or later

In OnTheAir Video 4.2 or later, actions can be more than just an AppleScript. You can still use the AppleScript that you were using in OnTheAir Video 4.1 or earlier, but additionally you can create "Direct" actions which do not go through AppleScripts. 

Just select the "Send SCTE Trigger" type in the "Inspector > Timeline > Actions" section:

Then click on "Parameters..." to edit it.

See above for the different variables that you can edit.

Splice Types

You can choose the type of event for the SCTE trigger, among which:

• Cancel (splice_cancel)
• Start Normal (splicestart_normal)
• End Normal (spliceend_normal)
• Start Immediate (splicestart_immediate)
• End Immediate (spliceend_immediate)

Please see SCTE documentation for the various splice commands.

Event ID

You can set the event ID. Each splice event is uniquely identified with a splice_event_id. If it is not specified, it will be automatically incremented, starting at zero when the application starts.

Program ID

This value should provide a unique identification for a viewing event within the service.

Duration

You can also send the duration of the event, simply by adding a duration, expressed in deciseconds (so if you indicate 10 it is 1 second).

Auto-return

The break duration provides for an optional auto_return flag that, when set to 1, indicates
that the splicer is to return to the network at the end of the Break .

After delay (ms)

This is not part of the SCTE implementation itself, it's a delay you can apply to all action types in OnTheAir Video. You can set a delay in milliseconds (ms) before the SCTE is actually triggered. This will compensate for potential delays in your output chain.

With OnTheAir Video 4.1 or earlier

In OnTheAir Video 4.1 or earlier, an Action in OnTheAir Video is a "Secondary Event". An Action is in fact an AppleScript that can be triggered at any moment of a video file using the inspector of OnTheAir Video. Read more about actions in OnTheAir Video...

Splice Types

Here is an example of an Action that will do a SCTE trigger:

on Action(parameter)
     tell application "OnTheAir Video"
        send SCTE trigger splice_insert_type "spliceStart_normal" splice_event_id 32 unique_program_id 48
    end tell
end Action

Interestingly enough, the action is sent to OnTheAir Video itself (so the application is sending an AppleScript to itself). 

Depending on the command to be sent, the "splice_insert_type" property can have a value of:

• splicestart_normal
• splicestart_immediate
• spliceend_normal
• spliceend_immediate
• splice_cancel

Setting the duration

You can also set a duration for the event (the duration is expressed in deciseconds, so 600 will be a duration of 60 seconds):

on Action(parameter)
     tell application "OnTheAir Video"
        send SCTE trigger splice_insert_type "spliceStart_normal" unique_program_id 1 duration 600
    end tell
end Action

Using Parameters to change some values later on

You can also use the "parameter" in the AppleScript. For example, if we use the following AppleScript:

on Action(parameter)
     tell application "OnTheAir Video"
        send SCTE trigger splice_insert_type parameter splice_event_id 32 unique_program_id 48 duration 3600
    end tell
end Action

The splice_insert_type will be defined in the OnTheAir Video inspector:

The advantage of using a parameter in your AppleScript is that you can write one AppleScript, and simply change that value of the parameter depending on the clip.

Watch

YouTube: How to Trigger & View SCTE