Passing VAST tag parameter values for MediaTailor Channel Assembly FAST Channel Programs



I would like help with setting up the right VAST parameter values for targeting MediaTailor Channel Assembly FAST Channel Programs.

Suppose, I've setup a Channel Assembly FAST Channel with 2 Programs (A and B). Program A has 2 mid-roll ad breaks. Program B has 1 mid-roll ad break. Channel is configured to play these 2 programs after each other in a loop. That is,

**Program A -> Program B -> Program A -> Program B ... and so on in loop **

I see that there are these 3 parameters ("splice_insert.avail_num", "splice_insert.splice_event_id", "splice_insert.unique_program_id") available when setting up an ad break in a Program.

Which of these should be used for distinguishing between Program A and B? And, which of these should be used for identifying a specific mid roll ad break (say, 1 or 2) within that program?

Also, could these be values be passed as parameters in VAST tag to Ad Server? For example, I want to use these parameters passed in the VAST tag to target the 2nd mid-roll ad break in Program A.


asked 2 years ago431 views
1 Answer


The values that are used for the splice_insert parameters in Channel Assembly are sent through to the server side ad insertion (SSAI) in the form of the session variables. For example, in Channel Assembly, splice_insert.avail_num becomes [scte.avail_num] in SSAI. Based on what you are trying to do, we would recommend one of the following:

Channel Assembly's splice_insert.splice_event_id > SSAI's [scte.event_id] or Channel Assembly's splice_insert.unique_program_id > SSAI's [scte.unique_program_id]

For more information on the SSAI session variables, please review

Please let us know if you have further queries or concerns on this. Thank you!

answered 2 years ago
  • Hi,

    As per the example in my question, can you please clarify which of these 3 (splice_insert.splice_event_id or splice_insert.unique_program_id or splice_insert.avail_num) should I be using to

    1. differentiate between Program A and B? 2) differentiate between the mid-roll ad breaks (1 or 2) in Program A?

    And, is it possible to pass the AssetID values for these FAST Channel Programs to VAST tag? Anything similar to the asset.CAID macro?


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