video-audit: Скилл анализа и проверки качества видео

--- name: video-audit description: This skill should be used when the user asks to "audit this video", "analyze video quality", "check this video file", "is this video good quality", "should I reencode this", "what format is this video", or wants to understand a video file's technical properties and quality before working with it. --- # Video File Audit Analyze video files to understand their technical properties, identify quality issues, and recommend appropriate next steps (remux, reencode, or leave unchanged). ## Prerequisites Requires `mediainfo` CLI tool. Install via: - macOS: `brew install mediainfo` - Linux: `apt install mediainfo` or equivalent - Windows: Download from mediaarea.net ## Audit Workflow ### Step 1: Gather File Metadata Run MediaInfo to get comprehensive file information: ```bash mediainfo --Full "/path/to/video.mkv" ``` For quick summary: ```bash mediainfo "/path/to/video.mkv" ``` ### Step 2: Identify Container vs Codec Extract and report separately: **Container format** (file extension): mkv, mp4, webm, avi, mov, m2ts - Containers store and package video/audio streams - Changing container = remuxing (fast, lossless) **Video codec** (actual encoding): H.264 (AVC), H.265 (HEVC), VP9, AV1, ProRes - Codecs compress and encode the actual video data - Changing codec = reencoding (slow, quality loss) Key MediaInfo fields: - `Format` under "General" section = container - `Format` under "Video" section = codec ### Step 3: Check Color Space Parameters Examine these fields in MediaInfo's Video section: | Parameter | Expected Value | Problem Indicator | |-----------|---------------|-------------------| | Color primaries | BT.709 | BT.601 on HD content | | Matrix coefficients | BT.709 | BT.601 on HD content | | Transfer characteristics | BT.709 | Mismatched values | | Color range | Limited | "Full" on broadcast content | | Chroma subsampling | 4:2:0 | Unusual values | **Red flags:** - HD video (720p+) tagged as BT.601 instead of BT.709 - Mismatched matrix/primaries/transfer values - "Full" range on content that should be "Limited" For detailed color space information, consult `${CLAUDE_PLUGIN_ROOT}/references/color-space.md`. ### Step 4: Identify Quality Red Flags Check MediaInfo for these warning signs: **Encoding quality indicators:** - `Encoded_Library`: Look for x264/x265 (good) vs NVENC/QuickSync (lower quality for archival) - `Writing application`: Identify source (ffmpeg, Handbrake, etc.) - `Bit rate mode`: VBR preferred over CBR for quality **Suspicious characteristics:** - Resolution not matching source (e.g., 4K from 1080p source = upscaled) - Frame rate interpolated (e.g., 60fps from 24fps source) - Very high or very low bitrate for resolution - 10-bit encoding of 8-bit source content (acceptable, often more efficient) **Content red flags:** - HDR metadata on content never released in HDR (fake HDR) - Dolby Vision on SDR-only content - Unusual aspect ratios suggesting cropping or stretching ### Step 5: Provide Recommendations Based on findings, recommend one of: **Leave unchanged** when: - Container and codec match intended use - Color space parameters are correct - No quality red flags detected - File works with target application/device **Remux only** when: - Need different container (e.g., mkv→mp4 for compatibility) - Container change doesn't require reencoding - Color space just needs retagging (not conversion) **Reencode required** when: - Codec incompatible with target device - Source has fixable quality issues (wrong matrix applied, not just mistagged) - File size reduction needed (with quality tradeoff warning) **Avoid/warn** when: - Video already heavily compressed (reencoding will compound quality loss) - User wants to upscale resolution (quality loss, not gain) - User wants to interpolate frame rate (quality loss) ## Quick Reference: Container vs Codec | If user says... | They probably mean... | Actual operation | |-----------------|----------------------|------------------| | "Convert mkv to mp4" | Change container | Remux (fast, lossless) | | "Compress this video" | Reduce file size | Reencode (slow, quality loss) | | "Make it H.265" | Change codec | Reencode (slow, quality loss) | | "Fix the colors" | Depends on issue | Retag (fast) or reencode (slow) | ## Additional Resources ### Reference Files For detailed technical information, consult: - **`${CLAUDE_PLUGIN_ROOT}/references/quality-myths.md`** - Why resolution/bitrate don't equal quality - **`${CLAUDE_PLUGIN_ROOT}/references/color-space.md`** - Color matrices, range, chroma location - **`${CLAUDE_PLUGIN_ROOT}/references/tools.md`** - Recommended and discouraged tools - **`${CLAUDE_PLUGIN_ROOT}/references/encoding-commands.md`** - ffmpeg/mpv command templates