Moonstriker

A pair of Bash scripts to divide up a video into chunks—one per caption—and then post them to Mastodon, e.g. as a bot. This is designed to post MP4s, but with some tweaks it can post any asset (e.g. images, audio). It was created for excerpts of Moonstruck, hence the name.

The video processor iterates through each caption in an SRT file and, for each one, saves that clip from the associated video. The Mastodon bot gets a file listing from an S3 bucket, randomly selects one of the files, and posts it to Mastodon.

Setup

Video processor

• Prerequisite: a video file that contains captions and an SRT file of those captions
• Ensure that ffmpeg is installed
• If running this on macOS 13.1 or older, the version of date that ships with it doesn't support sub-second accuracy. Install GNU date via brew install coreutils and change the date reference in processor.sh to gdate.
• Configure processor.sh to use the correct filenames for the two files (or name them video.m4v and captions.srt)

Mastodon bot

• Ensure that ffmpeg, cURL, and AWS CLI are installed, and that the account is configured to have permission to retrieve files from S3
• Create a new application in your Mastodon account’s settings, giving it write:statuses and write:media permissions (no other permissions are required), and note the application’s access token
• Put your video clips into a dedicated S3 bucket (or a dedicated directory within an S3 bucket)
• Configure the three variables in the header of mastobot.sh: MASTODON_SERVER, MASTODON_TOKEN, and S3_BUCKET
• Create a new cron task to run mastobot.sh periodically

Use

• Run processor.sh and clips/ will be filled up with incrementally numbered files, which must be uploaded to an S3 bucket to be accessible to the bot
• Run mastobot.sh and it will post a single video clip to Mastodon