athola/media-composition

Table of Contents

• Overview
• Prerequisites
• Required TodoWrite Items
• Manifest Format
• Manifest Schema
• Step-by-Step Process
• FFmpeg Composition Commands
• Layout Options
• Example Compositions
• Exit Criteria

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