Using the portal I uploaded a video to an input-asset and encoded it into an output-asset. On the output-asset I uploaded a .vtt file via "Upload captions" button. I can reproduce the video with the captions/subtitles in https://ampdemo.azureedge.net/, using the manifest URL and an extra URL for the .vtt file in the "Tracks" options. However other video players don't seem to support captions/subtitles via an extra URL (for example in Android or here). Is there a way to somehow include the captions/subtitles in the manifest? I see manifests from other sources including subtitles. For example, https://d3rlna7iyyu8wu.cloudfront.net/skip_armstrong/skip_armstrong_stereo_subs.m3u8 (can be played here).