Support for WebVTT in captions output for apple HLS not working

Question

I am trying to convert an .mp4 file into an HLS output with captions/subtitles using AWS Mediaconvert. My end goal is to have multiple language selectors in the HLS video (ex. German and French) however I can only "Burn in" one set of captions. According to the AWS docs, if I am using .SRT file as input and HLS as my output container I should be able to also use WebVTT as a output caption format but when I go to create a template for that it gives me this error:

```
/outputGroups/0/outputs/0/captionDescriptions/0/destinationSettings/destinationType: Should be equal to one of the allowed values in ["BURN_IN","DVB_SUB","EMBEDDED","EMBEDDED_PLUS_SCTE20","SCTE20_PLUS_EMBEDDED","TELETEXT"]

```

According to another blog (https://www.vidbeo.com/blog/hls-subtitles-captions-webvtt/) it seems doable to insert subtitles into the .m3u8 manifest file like this:

```
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",DEFAULT=NO,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",CHARACTERISTICS="public.accessibility.transcribes-spoken-dialog",URI="subtitles_en.m3u8"
```

It doesn't seem like I can do this via mediaconvert without choosing the burn in option which wont meet my requirement. Any assistance is much appreciated!

Answer

Thank you for contacting AWS Re:post,

To answer your question, when selecting **IMSC, TTML, or WebVTT** as output captions, you need to NOTE that these are only supported as **sidecar captions**.

What that means is, for these 3 output caption formats, under your output group (say HLS in your case) you need to create separate **caption-only** outputs for as many caption languages as you need in your output. This is also known as DE-MUXING in media technical terms. To do this, you have to remove the `Video` and `Audio` from each caption output under your output-group.

Therefore, your output group should look like this:
```
Output-Group : HLS
     • Output-1 : Video (mp4) + Audio (xyz format)
     • Output-2 : Caption Eng (WebVTT)
     • Output-3 : Caption Ger (WebVTT)
        ...
```

Please check this public document that explains the above -> https://docs.aws.amazon.com/mediaconvert/latest/ug/ttml-and-webvtt-output-captions.html

Answer

I have also run into this issue and the answer is not clear. Can you show us how this group is supposed to look using the media convert console? Enter image description here

We are trying to use an SRT file with our weather videos and are not trying to do burn-in. But we are currently burning in from the source.

Help would be greatly appreciated

We are trying to use an SRT file with our weather videos and are not trying to do burn-in. But we are currently burning in from the source.

Help would be greatly appreciated

Support for WebVTT in captions output for apple HLS not working

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