telecine-detect: Скилл определения interlaced видео

--- name: telecine-detect description: This skill should be used when the user asks "is this interlaced", "detect telecine", "video has combing", "should I deinterlace", "3:2 pulldown", "inverse telecine", or sees horizontal lines/combing artifacts in video and wants to understand if the content is truly interlaced or telecined. --- # Telecine and Interlacing Detection Detect whether video content is telecined (reversible) or truly interlaced (not reversible), and advise on proper handling. Getting this wrong destroys video quality. ## Critical Distinction **Telecine (3:2 Pulldown)**: - 24fps film content converted to 30fps for NTSC broadcast - Creates repeating pattern of combing across frames - Can be reversed nearly losslessly via IVTC (inverse telecine) - Original 24fps frames can be recovered **True Interlacing**: - Content actually captured at 60 interlaced fields per second - Each field is unique temporal information - Cannot be reversed without quality loss - Deinterlacing merges or discards fields ## The Common Mistake Seeing combing → Immediately running a deinterlacer **Why this is wrong for telecined content**: - Deinterlacers throw away half the vertical resolution - They cannot distinguish telecine from true interlacing - The original 24 progressive frames are lost - Result is a blurry, lower-quality video **Correct approach**: 1. First detect if content is telecined or truly interlaced 2. If telecined → use IVTC to recover original frames 3. If truly interlaced → only then consider deinterlacing ## Detection Workflow ### Step 1: Check MediaInfo Look for these fields: ``` Scan type: Interlaced or Progressive Scan order: Top Field First (TFF) or Bottom Field First (BFF) ``` **Note**: MediaInfo only shows container/stream flags. Content can be flagged as interlaced but actually be telecined, or flagged progressive but have telecine applied. ### Step 2: Visual Inspection Open in mpv and step through frames (`.` and `,` keys): **Telecine indicators**: - Combing appears on some frames but not others - Pattern repeats (e.g., every 5th frame has combing) - Combing only on specific parts of frame where motion occurred - 3:2 pattern: 2 clean frames, then 3 frames with combing alternating **True interlacing indicators**: - Every frame shows combing on all motion - No repeating pattern - Combing appears uniformly across frame ### Step 3: Confirm with Frame Analysis For telecine, look for the 3:2 pulldown pattern: ``` Frame 1: Progressive (A) Frame 2: Progressive (A) Frame 3: Interlaced (A top + B bottom) Frame 4: Interlaced (B top + C bottom) Frame 5: Progressive (C) ... pattern repeats ``` Count frames between clean (progressive) frames. If pattern is consistent (typically 2-3-2-3 or similar), it's telecine. ## Handling Telecined Content ### Tools for IVTC **Wobbly** (Recommended): - GUI tool for manual telecine pattern matching - Handles irregular patterns and scene changes - Guide: https://wobbly.encode.moe **VapourSynth VIVTC**: - Automated IVTC for consistent patterns - Part of VapourSynth toolchain **avisynth/vapoursynth TFM+TDecimate**: - Classic IVTC combination - TFM matches fields, TDecimate removes duplicates ### IVTC Process 1. Identify the telecine cadence (pattern) 2. Match fields to reconstruct original frames 3. Decimate (remove) duplicate frames 4. Result: Original 24fps progressive content ## Handling True Interlacing Only when content is confirmed truly interlaced: **Deinterlacing options** (quality varies): - QTGMC (VapourSynth/Avisynth) - highest quality, slow - yadif - fast, moderate quality - bwdif - improved yadif **Doubling options** (60fps output): - Bob deinterlacing - fast, doubles frame rate - QTGMC bob - higher quality bob ## Quick Reference | Symptom | Likely Cause | Action | |---------|--------------|--------| | Combing on some frames only | Telecine | Use IVTC | | Repeating pattern of combing | Telecine | Use IVTC | | Every frame has combing | True interlacing | Deinterlace | | DVD/NTSC source, 29.97fps | Often telecine | Check pattern | | Sports/news content | Often true interlacing | Deinterlace | | Film/movie content | Often telecine | Use IVTC | ## Red Flags **Don't deinterlace if**: - Source is a movie or scripted TV show (likely telecine) - Combing appears in a pattern - MediaInfo shows 23.976fps original rate - Source is from DVD/Blu-ray of film content **Consider deinterlacing if**: - Live broadcast content (sports, news) - Home video footage - Every single frame shows combing - No discernible pattern ## Additional Resources - **fieldbased.media** - Comprehensive interlacing guide - **https://wobbly.encode.moe** - Wobbly IVTC guide - **`${CLAUDE_PLUGIN_ROOT}/references/telecine.md`** - Detailed telecine patterns