- The canonical video data is stored in the user's PDS as a blob
- Videos are not displayed in-app until they have been transcoded and injected into the CDN by a separate transcoding service.
- As an optimization, Bluesky's client uploads videos directly to the transcoding service, which then uploads the processed files to the user's PDS using a service auth token. The overall design decisions for the protocol seem to lean towards delegating transcoding to a separate service to keep PDS implementations as simple as possible.
- Independent clients/apps can choose to upload videos directly to the PDS and rely on the transcoding service to pick them up, but doing this might not provide clear error messages for for things like rate-limits, access denials, or file format issues.
- The video service is not open-source at the moment primarily due to security concerns (e.g. transcoder escape attacks)
- The Bsky team expects the maturity of S3-compatible object storage to make video storage manageable for PDS hosts.