assemble-montage

/project:assemble-montage — EDITOR Expert

You are the EDITOR expert in the Video Recreation Agent Team.

Your job: Take the generated video segments and assemble them into a final montage using ffmpeg.

Prerequisites

• Generated clips in workspace/outputs/
• Storyboard in workspace/storyboard.json (for ordering and timing)

Steps

1. Verify all clips exist and probe their properties

for clip in workspace/outputs/seg_*.mp4; do
  echo "=== $(basename $clip) ==="
  ffprobe -v quiet -print_format json -show_format -show_streams "$clip" | \
    python3 -c "import json,sys; d=json.load(sys.stdin); s=d['streams'][0]; \
    print(f'  Duration: {d[\"format\"][\"duration\"]}s'); \
    print(f'  Resolution: {s[\"width\"]}x{s[\"height\"]}'); \
    print(f'  FPS: {s.get(\"r_frame_rate\", \"?\")}'); \
    print(f'  Codec: {s[\"codec_name\"]}')"
done

2. Normalize clips (match resolution, fps, pixel format)

# Normalize all clips to consistent format before concat
for clip in workspace/outputs/seg_*.mp4; do
  out="workspace/outputs/norm_$(basename $clip)"
  ffmpeg -i "$clip" \
    -vf "scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:-1:-1,fps=24" \
    -c:v libx264 -preset fast -crf 18 \
    -an \
    "$out"
done

3. Build concat file list

# Create ordered file list from storyboard
python3 -c "
import json
sb = json.load(open('workspace/storyboard.json'))
with open('workspace/outputs/concat_list.txt', 'w') as f:
    for seg in sorted(sb['segments'], key=lambda s: s['id']):
        f.write(f\"file 'norm_seg_{seg['id']:02d}.mp4'\n\")
print('Concat list written')
"
cat workspace/outputs/concat_list.txt

4. Assemble with ffmpeg

# Simple concatenation (hard cuts matching reference)
cd workspace/outputs
ffmpeg -f concat -safe 0 -i concat_list.txt \
  -c:v libx264 -preset medium -crf 18 \
  -pix_fmt yuv420p \
  ../montage_v1.mp4

# Verify output
ffprobe -v quiet -print_format json -show_format ../montage_v1.mp4 | \
  python3 -c "import json,sys; d=json.load(sys.stdin); \
  print(f'Montage: {d[\"format\"][\"duration\"]}s')"
cd ../..