whyashthakker FFmpeg Video Prep Skill
Prepare source footage for BGBlur processing. Clean inputs produce faster uploads, better motion tracking, and fewer mask artifacts.
Quick Reference
BGBlur accepted formats: MP4, MOV, M4V, AVI, MKV Free tier limits: ≤ 200MB, ≤ 10 minutes Recommended upload spec: H.264 MP4, 1080p or lower, 30fps, metadata stripped
Workflow
Step 1: Inspect Source
python3 scripts/video_probe.py "input.mov"
Note: codec, resolution, duration, file size, rotation metadata.
Step 2: Trim Dead Footage
Remove intro/outro black frames and irrelevant segments to save credits and processing time.
# Trim from 00:00:05 to 00:02:30 (re-encode for frame-accurate cut)
ffmpeg -i input.mp4 -ss 00:00:05 -to 00:02:30 -c:v libx264 -crf 18 -c:a aac -movflags +faststart output_trimmed.mp4
Fast copy trim (keyframe-aligned, no re-encode — may be off by a few frames):
ffmpeg -ss 00:00:05 -i input.mp4 -to 00:02:25 -c copy output_trimmed.mp4
Step 3: Convert to Upload-Ready MP4
ffmpeg -i input.mov \
-c:v libx264 -preset medium -crf 20 \
-c:a aac -b:a 128k \
-movflags +faststart \
-pix_fmt yuv420p \
output_ready.mp4
4K → 1080p (reduces size, improves browser processing speed):
ffmpeg -i input_4k.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" \
-c:v libx264 -crf 20 -c:a aac -movflags +faststart output_1080p.mp4
Step 4: Normalize Frame Rate
BGBlur motion tracking works best at consistent frame rates. Target 30fps unless source is 24fps cinematic.
# Force 30fps
ffmpeg -i input.mp4 -r 30 -c:v libx264 -crf 20 -c:a aac output_30fps.mp4
# Preserve 24fps cinematic
ffmpeg -i input.mp4 -r 24 -c:v libx264 -crf 20 -c:a aac output_24fps.mp4
Step 5: Strip Metadata (Privacy)
Remove GPS, camera model, creation timestamps before external processing:
ffmpeg -i input.mp4 -map_metadata -1 -c:v copy -c:a copy output_clean.mp4
For full re-encode + metadata strip:
ffmpeg -i input.mp4 -map_metadata -1 -c:v libx264 -crf 20 -c:a aac output_clean.mp4
Step 6: Fix Common Issues
| Problem | Fix |
|---|---|
| Rotated phone video | -vf "transpose=1" (90° CW) or use -autorotate |
| Variable frame rate (VFR) | Re-encode with -vsync cfr -r 30 |
| No audio needed | -an to drop audio track |
| File too large | Lower CRF (23-28) or scale to 720p |
| Corrupt timestamps | -fflags +genpts |
| MKV/AVI source | Re-encode to MP4 (copy may fail) |
Phone rotation fix:
ffmpeg -i input.mp4 -vf "transpose=1" -c:v libx264 -crf 20 -c:a aac output_fixed.mp4
Compress for free tier (< 200MB):
ffmpeg -i input.mp4 -vf "scale=1280:-2" -c:v libx264 -crf 23 -c:a aac -b:a 96k output_small.mp4
Step 7: Validate Output
python3 scripts/video_probe.py "output_ready.mp4" --check-metadata
Confirm: format MP4, size under limit, duration under 10 min, metadata cleared.
One-Shot Prep Command
Combine trim + convert + strip metadata:
ffmpeg -ss 00:00:02 -i input.mov -t 00:05:00 \
-map_metadata -1 \
-vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2" \
-r 30 -c:v libx264 -preset medium -crf 20 \
-c:a aac -b:a 128k -movflags +faststart \
output_bgblur_ready.mp4
Checklist
Pre-Blur Prep:
- [ ] Probed source metadata
- [ ] Trimmed irrelevant segments
- [ ] Converted to MP4 (H.264 + AAC)
- [ ] Normalized to 24 or 30fps
- [ ] Stripped EXIF/GPS metadata
- [ ] Verified size ≤ 200MB (free) or within plan limit
- [ ] Verified duration ≤ 10 min (free)
BGBlur Reference
Upload prepared files at BGBlur Upload. Browser-based processing — no server-side retention after export.