demo

Agent Demo Video Production

Transforms raw screen recordings into polished, shareable demo clips. Applies a spotlight focus effect (sharp focal region, blurred and dimmed background), adds optional lower-third captions, and merges multiple segments into one mp4. Audio is always stripped — screen recordings of dev sessions may contain sensitive audio.

Privacy and Integrity Rules

Before producing a demo from any recording:

• Strip audio always. The tool does this automatically (-an). Never re-add audio from a recording session.
• Frame-scan for secrets. Review captured frames with spectra_capture mode=auto or a frame-by-frame read before sharing. Look for API keys, tokens, passwords, hostnames, and internal URLs in terminal output or browser developer tools.
• Real footage only. The on-camera work must be a real run, never a replayed or scripted sequence presented as live. Staging is fine for setup; what runs on camera is real.
• Keep artifacts local. Outputs go into .spectra/ or a user-specified path. Never move demo artifacts into artifacts/ (the library) or any public-facing directory without an explicit review step.

Workflow

Step 1 — Scan for active stretches

spectra_demo action=scan input=/path/to/recording.mp4

Returns:

• perMinute — scene-change count per minute (identify the busiest 2-3 minutes)
• activeRanges — contiguous stretches of activity (gap-merged with 5s tolerance)

Use the returned ranges to identify which segments are worth including. Prefer segments where the agent is visibly doing work — not idle pauses, loading screens, or terminal waiting states.

Step 2 — Read key frames to pick segments

For each candidate active range, use spectra_capture or a frame read to see what's actually on screen at that point. Make a judgment call:

• Is the content comprehensible to an outside viewer?
• Does it show a distinct beat (action → result, not mid-action blur)?
• Is anything sensitive visible (key material, internal hostnames, passwords)?

Write one caption per beat — present-tense, outcome-focused. "Claude Code routes the task to codex" not "Task routing occurring".

Step 3 — Polish and merge

spectra_demo action=polish spec={
  canvas: { w: 1920, h: 1080 },
  segments: [
    {
      input: "/path/to/recording.mp4",
      startSec: 45,
      durationSec: 12,
      focal: { x: 200, y: 100, w: 1520, h: 800 },
      caption: "Build-loop hands triage to codex via Rally Point"
    },
    {
      input: "/path/to/recording.mp4",
      startSec: 120,
      durationSec: 8,
      focal: { x: 200, y: 100, w: 1520, h: 800 },
      caption: "codex responds with a targeted fix in 4 seconds"
    }
  ],
  speed: 1.2
} out=/path/to/demo-output.mp4

Returns: { out, segmentCount, warnings }. Check warnings for caption fallbacks or skipped captions.

Focal Region Selection

The focal rect (x, y, w, h) should frame the most important content on screen — the terminal output, the specific UI element, the rally message — not the full display. Tight framing creates sharper contrast between the spotlight and the blurred background.

For a typical 1920x1080 display:

• Full terminal pane (left half): { x: 0, y: 0, w: 960, h: 1080 }
• Browser pane (right half): { x: 960, y: 0, w: 960, h: 1080 }
• Terminal output region (centered): { x: 80, y: 200, w: 1760, h: 600 }

For a side-by-side composite recording (from spectra_capture composite mode), each pane is typically 960px wide.

Caption Strategy

drawtext captions appear as a dimmed lower-third bar with centered white text. If drawtext is not available in the installed ffmpeg build, supply a captionPngPath as a pre-rendered PNG overlay.

Caption rules:

• Present tense, agent as subject: "Build-loop plans the migration" not "Planning the migration"
• Outcome, not action: "codex lands the fix" not "codex is writing code"
• Keep under ~60 characters — longer text overflows the bar at 36px
• One caption per segment — captions that change mid-segment are not supported; split the segment instead

Speed

speed: 1.5 makes all segments play at 1.5x. Useful for idle stretches that couldn't be trimmed. Avoid > 2x on content with visible typing or mouse movement — it looks unnatural. Typical values: 1.0–1.5 for active work, 1.5–2.5 for connecting/loading transitions.

Limitations

• Audio is unconditionally stripped.
• Segment re-encode uses the spotlight filtergraph; for very long segments this may take time.
• Concat merge uses -c copy — all segments must have the same codec, resolution, and frame rate. If segments differ, the merge step will fail with a codec error.
• captionPngPath PNG overlay loops via -loop 1 -shortest. Static PNGs of any size work; animated GIFs do not.
• The drawtext font path /System/Library/Fonts/Helvetica.ttc exists on macOS 11+. On other platforms, supply captionPngPath instead.