Media Composition Skill

Combine multiple media assets (GIFs, videos, images) into composite outputs for detailed tutorials and documentation.

When To Use

• Combining multiple media outputs into compositions
• Creating composite demos from terminal and browser recordings

When NOT To Use

• Single-format output that does not need composition
• Simple terminal recordings - use scry:vhs-recording directly

Overview

This skill orchestrates the combination of separately generated media assets into unified outputs. It reads manifest files that define components and their composition rules, validates all inputs exist, and executes FFmpeg commands to produce the final composite media.

Prerequisites

The following tools must be available on PATH before using this skill:

• ffmpeg: media composition and encoding
• yq: YAML manifest parsing

Run ffmpeg -version and yq --version to verify availability.

Required TodoWrite Items

- Parse composition manifest file
- Validate all component outputs exist
- Determine composition layout and parameters
- Execute FFmpeg composition command
- Verify combined output file created
- Report composition metrics (file size, dimensions)

Manifest Format

Manifests define the components to combine and how to arrange them:

# Example manifest: tutorials/mcp.manifest.yaml
name: mcp
title: "MCP Server Integration"
components:
  - type: tape
    source: mcp.tape
    output: assets/gifs/mcp-terminal.gif
  - type: playwright
    source: browser/mcp-browser.spec.ts
    output: assets/gifs/mcp-browser.gif
    requires:
      - "skrills serve"
combine:
  output: assets/gifs/mcp-combined.gif
  layout: vertical
  options:
    padding: 10
    background: "#1a1a2e"

Manifest Schema

Field	Type	Required	Description
name	string	Yes	Identifier for the composition
title	string	No	Human-readable title
components	array	Yes	List of media components to combine
components[].type	string	Yes	Source type: tape, playwright, static
components[].source	string	Yes	Path to source file
components[].output	string	Yes	Path to generated output
components[].requires	array	No	Commands to run before generation
combine.output	string	Yes	Path for combined output
combine.layout	string	Yes	Layout mode (see table below)
combine.options	object	No	Layout-specific options

Step-by-Step Process

1. Parse Manifest File

# Read and validate manifest structure
yq eval '.' manifest.yaml

# Extract component outputs
yq eval '.components[].output' manifest.yaml

2. Validate Component Outputs

# Check all required files exist
for output in $(yq eval '.components[].output' manifest.yaml); do
  if [[ ! -f "$output" ]]; then
    echo "ERROR: Missing component: $output"
    exit 1
  fi
done

3. Execute FFmpeg Composition

Based on the layout specified in the manifest, execute the appropriate FFmpeg command.

4. Verify Combined Output

# Verify output exists and has content
if [[ -f "$output" && -s "$output" ]]; then
  echo "Composition successful: $output"
  ls -lh "$output"
else
  echo "ERROR: Composition failed"
  exit 1
fi

FFmpeg Composition Commands

Vertical Stacking

Stack GIFs/videos top to bottom:

ffmpeg -i top.gif -i bottom.gif \
  -filter_complex "[0:v][1:v]vstack=inputs=2" \
  -y output.gif

With padding between:

ffmpeg -i top.gif -i bottom.gif \
  -filter_complex "[0:v]pad=iw:ih+10:0:0:color=black[top];[top][1:v]vstack=inputs=2" \
  -y output.gif

Horizontal Stacking

Stack GIFs/videos side by side:

ffmpeg -i left.gif -i right.gif \
  -filter_complex "[0:v][1:v]hstack=inputs=2" \
  -y output.gif

Sequential Concatenation

Play GIFs/videos one after another:

# Create concat list file
cat > concat_list.txt << EOF
file 'first.gif'
file 'second.gif'
file 'third.gif'
EOF

# Concatenate
ffmpeg -f concat -safe 0 -i concat_list.txt \
  -y output.gif

Grid Layout (2x2)

ffmpeg -i tl.gif -i tr.gif -i bl.gif -i br.gif \
  -filter_complex "[0:v][1:v]hstack=inputs=2[top];[2:v][3:v]hstack=inputs=2[bottom];[top][bottom]vstack=inputs=2" \
  -y output.gif

With Background Color

ffmpeg -i top.gif -i bottom.gif \
  -filter_complex "color=c=#1a1a2e:s=800x600[bg];[bg][0:v]overlay=0:0[tmp];[tmp][1:v]overlay=0:300" \
  -y output.gif

Layout Options

Layout	Description	Options
vertical	Stack top to bottom	padding, background, align
horizontal	Stack left to right	padding, background, align
sequential	Play in order	transition, duration
grid	N x M grid arrangement	rows, cols, padding
overlay	Layer on top of each other	position, opacity
pip	Picture-in-picture	corner, scale, margin

Layout Option Details

Option	Type	Default	Description
padding	int	0	Pixels between components
background	string	"black"	Background color (hex or name)
align	string	"center"	Alignment: left, center, right
transition	string	"none"	Transition type: fade, wipe, none
scale	float	0.25	Scale factor for PiP
corner	string	"br"	PiP corner: tl, tr, bl, br

Example Compositions

Terminal and Browser Tutorial

name: plugin-demo
components:
  - type: tape
    source: demo.tape
    output: terminal.gif
  - type: playwright
    source: browser.spec.ts
    output: browser.gif
combine:
  output: demo-combined.gif
  layout: vertical
  options:
    padding: 5
    background: "#0d1117"

Side-by-Side Comparison

name: before-after
components:
  - type: static
    source: before.gif
    output: before.gif
  - type: static
    source: after.gif
    output: after.gif
combine:
  output: comparison.gif
  layout: horizontal
  options:
    padding: 10

Picture-in-Picture

name: pip-demo
components:
  - type: tape
    source: main.tape
    output: main.gif
  - type: playwright
    source: overlay.spec.ts
    output: overlay.gif
combine:
  output: pip-demo.gif
  layout: pip
  options:
    corner: br
    scale: 0.3
    margin: 20

Exit Criteria

• Manifest file parsed successfully
• All component outputs validated as existing
• FFmpeg composition command executed without errors
• Combined output file exists and has non-zero size
• Output dimensions and duration logged
• Temporary files cleaned up