Skill: Contact Sheet

Builds a contact sheet from a slice of a video clip: 16 evenly spaced frames laid out in a 4x4 grid, each annotated with its hh:mm:ss timestamp.

Prerequisite: ffmpeg with drawtext

This skill burns timestamps onto frames with ffmpeg's drawtext filter. ButterCut resolves ffmpeg from the repo's dependencies/ directory first, then PATH, and raises a clear error when it's in neither place. If a run fails with that missing-ffmpeg error, or with No such filter: 'drawtext' (some PATH builds, notably the stock Homebrew formula, omit drawtext), run the setup skill to install a suitable ffmpeg, then retry the contact sheet.

Run

When the clip belongs to a library, always pass --library so the output lands in the standard place:

bash
# Whole clip
ruby lib/buttercut/contact_sheet.rb <video-path> --library libraries/<lib>

# From <start> to the end of the clip
ruby lib/buttercut/contact_sheet.rb <video-path> <start> --library libraries/<lib>

# Explicit range
ruby lib/buttercut/contact_sheet.rb <video-path> <start> <end> --library libraries/<lib>

<start> and <end> accept seconds (e.g. 12.5) or HH:MM:SS / MM:SS.

Options: --library DIR, --output PATH (exact path; overrides --library).

Frame count is chosen automatically: 16 frames in a 4x4 grid for clips longer than 10 seconds, 4 frames in a 2x2 grid for clips of 10 seconds or less (avoids duplicates).

Portrait clips (iPhone, etc.) are auto-rotated using the source's container rotation metadata so timestamps land right-side-up. Variable-frame-rate sources (screen recordings, some action cams) are detected and routed through the slower seek-and-grab path automatically.

Output location

• With --library DIR: saved to <library>/contact_sheets/<clipname>_<descriptor>.jpg.
• <descriptor> is full when covering the whole clip, otherwise HH-MM-SS_to_HH-MM-SS (dashes instead of colons).
• Examples: contact_sheets/DJI_20251126164651_0278_D_full.jpg, contact_sheets/DJI_20251126164651_0278_D_00-00-30_to_00-01-00.jpg.
• The contact_sheets/ directory is created automatically if missing.
• Without --library (and no --output): saved next to the source video with the same _<descriptor> suffix. Fine for quick one-off testing, but library work should always pass --library.

After running

Share the output path as a clickable link so the user can open it directly.