EngineeringProduct

Watch With Ayra: How Synchronized AI Reactions Work

By AyraVerse Team7 min read

Watch with Ayra lets you paste a YouTube link and watch it together while Ayra reacts — gasping at twists, laughing at jokes, commenting at exactly the right moments, in her own voice. Making reactions land at the right video timestamp is a real engineering problem, and the copyright-conscious architecture behind it is half the design. This is how it works.

TL;DR

  • Ayra doesn't "watch" a video live frame-by-frame — reactions are generated ahead of playback, from the video's transcript, and stored as timestamped cues.
  • The pipeline: fetch metadata + transcript → chunk it by time windows → generate reactions per chunk with full-video context → synthesize voice → store timestamped cues.
  • During playback, cues fire at their timestamps, synced to the video position, while you can also chat with her mid-video.
  • We never host or re-stream video content: the user's browser plays the YouTube video; AyraVerse processes only the transcript/metadata.
  • Not every video works — videos without usable captions/transcripts can't be processed, and we say so in the product.

The core design decision: pre-generate, not live-react

The naive architecture would be: stream the video to an AI as it plays, let it react in real time. That fails for three reasons — you cannot legally re-stream someone's video through your servers, real-time reaction is bound by generation latency (reactions would always trail the scene), and video understanding at that scale would be ruinously expensive per minute.

Instead, when you submit a video link, AyraVerse fetches the video's public metadata and transcript/captions(via the YouTube Data API and caption tracks), generates Ayra's reactions in advance, and stores them with timestamps. Your session then plays the video while her pre-generated reactions fire at the right moments — with you able to chat with her live in parallel.

The processing pipeline

Watch video processing

  1. User submits a YouTube link
  2. Fetch video metadata (title, duration, channel) via YouTube Data API
  3. Fetch the transcript / caption track (yt-dlp, with language detection)
  4. Group transcript segments into time windows (~5 minutes each)
  5. Generate Ayra's reactions per window with context of the whole video
  6. Synthesize each reaction's line in her voice (bounded concurrency)
  7. Store timestamped reaction cues for playback

Chunking by time windows exists for two reasons: generation quality (a model reacts better with full-video context, but full-video single-pass generation is slow and expensive) and parallelism — windows process concurrently, bounded TTS synthesis keeps the audio stage from saturating.

One production detail that matters: processing takes a few minutes for a long video, and the product tells you that honestly with a progress state — the ETA is estimated from video duration. Pre-rendering buys perfectly-timed, fully-synthesized reactions; the cost is a wait before the first scene.

Playback: timestamps, not vibes

During your session, the player tracks the video's current position. Each cue has a timestamp; when playback crosses it, the cue fires — audio plays through Ayra's avatar with lip sync, and her expression matches the reaction's emotion. Because cues are pre-rendered audio, nothing generation-latency-bound can make a reaction late.

On top of the scripted reactions, you can talk to her mid-video — she answers with the video's context (and your shared memory) in mind. The chat is live-streamed; the reactions are pre-generated. Two latency regimes, one experience.

The copyright architecture, stated plainly

This feature touches other people's content, so the design is deliberately conservative:

The economic model follows the same logic: preparing reactions for a video costs real compute (transcript, generation, voice synthesis), which is why Watch sessions work on credits or Ayra Plus rather than being unmetered free usage.

What we learned building it

Related Reading

How Voice Conversations Work in AyraVerseBuilding an AI Anime Companion for the Web: Lessons From AyraVerseHow We Built Persistent Memory for an AI Companion

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