SCTE-35 Ad Markers to existing HLS Encoded package

Hi
First, MediaConvert doesn't support HLS input at this moment https://docs.aws.amazon.com/mediaconvert/latest/ug/reference-codecs-containers-input.html. So, you can only re-encode the source to HLS by MediaConvert, then use either passthrough or ESAM XML to add the SCTE-35 message to output. Detail could be found here https://docs.aws.amazon.com/mediaconvert/latest/ug/including-scte-35-markers.html .

Thanks. I want to make sure I am not "missing something" as the workflow for publishers doing AVOD VOD models (tubi for example) seems very, very limited in terms of Mediatailor.

My understanding if a Publisher wanted to do BOTH pre-roll and Mid-roll based on https://docs.aws.amazon.com/mediatailor/latest/ug/ad-behavior-vod.html is that SCTE-35 markers either need to be embedded from the original encode or the ADS needs to send a VMAP to Mediatailer.

My experience is that most of the large header bidding based ADS do not use VMAP much. For some reason they avoid VMAP.

So what to do? A publisher could embed the SCTE-35 from the encode but then they are "stuck" with the ad markers called out in the original encode. What if you want to change the frequency of the ad slots? based on what I see you will need to re-encode your entire library (could be thousands of longform). Embedding the SCTE-35 into an HLS package meant for VOD without any easy means to modify seems very inefficient to me...

Does anyone know of any third party utility or AWS method that would allow us to place or modify SCTE-35 markers into an existing HLS package?

Thanks,
RG