Video Social
Prepare video for social media platforms: correct aspect ratios, resolutions, bitrates, and container settings.
Platform Presets
| Platform | Aspect | Max Resolution | Max Duration | Video Bitrate | Audio |
|---|---|---|---|---|---|
| Instagram Feed | 4:5 portrait or 1:1 | 1080×1350 / 1080×1080 | 60s | 3.5 Mbps | AAC 128k |
| Instagram Reels | 9:16 | 1080×1920 | 90s | 8 Mbps | AAC 192k |
| TikTok | 9:16 | 1080×1920 | 10min | 8 Mbps | AAC 192k |
| YouTube Shorts | 9:16 | 1080×1920 | 60s | 8 Mbps | AAC 192k |
| YouTube Standard | 16:9 | 1920×1080 | unlimited | 8 Mbps (1080p) | AAC 192k |
| Twitter / X | 16:9 or 1:1 | 1920×1200 | 140s | 25 Mbps cap | AAC 128k |
| 16:9 or 9:16 | 1920×1080 | 240min | 4 Mbps | AAC 128k | |
| 16:9 | 1920×1080 | 10min | 5 Mbps | AAC 128k |
Process
1. Identify platform
If the request is ambiguous (e.g., "make it vertical"), ask which platform — bitrate and audio requirements differ.
2. Probe source
bashffprobe -v quiet -print_format json -show_streams -show_format "$INPUT"
Extract: width, height, duration, existing bitrate, audio codec.
3. Determine required transforms
Compare probe output against the platform row in the presets table. Apply only the transforms that are actually needed:
- Aspect ratio mismatch → crop or pad (see Key Decisions for the choice rule)
- Resolution too large → scale down (never upscale; social platforms reject oversized files at upload)
- Duration exceeds platform limit → trim; confirm cut point with user first
- Bitrate over limit → re-encode with target bitrate (platforms reject or silently degrade over-bitrate uploads)
Exit condition: when all four properties (aspect ratio, resolution, duration, bitrate) are within platform bounds and -movflags +faststart will be set, proceed to Step 4. If source already matches all properties, skip to Step 5 with a simple re-encode plan.
4. Construct command
Crop to fit (preferred when subject is centered):
bash# 16:9 source → 9:16 (1080×1920), center crop: ffmpeg -i "$INPUT" \ -vf "crop=ih*9/16:ih,scale=1080:1920" \ -c:v libx264 -b:v 8000k \ -c:a aac -b:a 192k \ -movflags +faststart "$OUTPUT"
Pad to fit (preserves full frame, adds letterbox/pillarbox):
bash# 16:9 source → 9:16 with black bars: ffmpeg -i "$INPUT" \ -vf "scale=1080:-2,pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black" \ -c:v libx264 -b:v 8000k \ -c:a aac -b:a 192k \ -movflags +faststart "$OUTPUT"
Square (1:1) from 16:9 — center crop:
bashffmpeg -i "$INPUT" \ -vf "crop=ih:ih,scale=1080:1080" \ -c:v libx264 -b:v 3500k \ -c:a aac -b:a 128k \ -movflags +faststart "$OUTPUT"
5. Confirm
State: crop vs. pad choice, any trim, output resolution and bitrate, output path. Wait for approval.
6. Run and verify
After encoding, verify bitrate: ffprobe -v quiet -show_format "$OUTPUT" | grep bit_rate
Key Decisions
- Always include
-movflags +faststart— relocates the moov atom to the file start, enabling progressive playback before full download. Required for all social platforms. - Crop vs. pad: default to crop for talking-head or centered subjects; default to pad for wide scenic shots or text-heavy content. When the user says "don't cut anything off", use pad. When uncertain with off-center subjects, ask before running.
- Never upscale: if source is smaller than target resolution, scale to fit within bounds or keep original dimensions.
