share-social: Скилл оптимизации видео для соцсетей

--- name: share-social description: > This skill should be used when the user asks to "optimize for Instagram", "YouTube Shorts format", "make it 9:16", "square video", "TikTok format", "Reels format", "prepare for social media", "encode for Twitter", "optimize for Facebook", "LinkedIn video", "crop for portrait", or mentions any platform-specific video format or upload requirements. allowed-tools: - Bash(ffprobe:*) - Bash(ffmpeg:*) - AskUserQuestion --- # 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 | | Facebook | 16:9 or 9:16 | 1920×1080 | 240min | 4 Mbps | AAC 128k | | LinkedIn | 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 ```bash ffprobe -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 "$OUTPUT" ``` **Square (1:1) from 16:9 — center crop:** ```bash ffmpeg -i "$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.