55 lines
3.2 KiB
Markdown
55 lines
3.2 KiB
Markdown
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# Fix: Video Codec Compatibility + Timeline Pan/Scroll + Minimap
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**Date:** 2026-09-21 12:56
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**Task:** Fix video playback (black screen despite play state), add timeline panning when zoomed, add minimap overview.
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## Root Causes & Fixes
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### 1. Video playback: WKWebView doesn't support VP9/WebM
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The downloaded file was VP9+Opus in WebM container (yt-dlp format 399+251). Apple's WKWebView on macOS does NOT support VP9 codec. The `<video>` element accepted `.play()` but had no decodable frames.
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**Fix:** Added `-f "bv*[vcodec^=avc1]+ba[acodec^=mp4a]/bv*[ext=mp4]+ba[ext=m4a]/b[ext=mp4]/b"` to the yt-dlp download command in `download_manager.rs`. This selects H.264 (avc1) video + AAC (mp4a) audio, producing an MP4 file playable by WKWebView. Deleted the cached WebM file.
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### 2. Timeline: no scroll/pan when zoomed
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Mouse wheel only triggered zoom. No way to scroll horizontally when zoomed in.
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**Fix in `Timeline.svelte`:**
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- **Horizontal scroll → pan:** `deltaX` from trackpad/shift+wheel now calls `panBy()` to shift the visible window
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- **Vertical scroll → zoom** (unchanged)
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**New `panBy()` in `interactions.ts`:** Computes new `visibleStart`/`visibleEnd` from pixel delta, clamped to `[0, duration]`.
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### 3. Minimap overview bar
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Added a minimap canvas that appears when zoomed in:
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- Shows the full waveform at a glance
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- Highlights the current viewport with a blue border
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- Dims regions outside the viewport
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- Click to center viewport, drag to pan
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- Playhead indicator
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### 4. Other fixes applied this session (cumulative)
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- **stdout/stderr swap:** yt-dlp sends status messages to stdout, not stderr
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- **`[Merger]` path parsing:** Correctly captures final merged file path
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- **"Already downloaded" parsing:** Handles `has already been downloaded` message
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- **Cache check:** `checkCachedDownload(title)` checks temp dir before invoking yt-dlp
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- **Parallel processing:** Waveform/thumbnails/keyframes results applied individually as they complete
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- **Asset protocol scope:** Added `/private/var/**` and `/var/**` for macOS symlink paths
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## Files Changed
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- `src-tauri/src/services/download_manager.rs` — H.264 format selection
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- `src/lib/components/Timeline.svelte` — Minimap + horizontal pan support
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- `src/lib/timeline/interactions.ts` — Added `panBy()` function
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- `src-tauri/src/commands/video.rs` — Cache check, diagnostic logging
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- `src-tauri/src/commands/media_analysis.rs` — Diagnostic logging
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- `src-tauri/src/lib.rs` — Registered `check_cached_download` command
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- `src-tauri/tauri.conf.json` — Expanded asset protocol scope
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- `src/lib/stores/videoSession.svelte.ts` — Cache check before download, parallel results
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- `src/lib/bindings/video.ts` — `checkCachedDownload` binding
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- `src/lib/components/VideoPlayer.svelte` — Local file playback with progress UI
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## Lessons Learned
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1. **WKWebView codec support is limited.** VP9/AV1/WebM don't work. Must use H.264+AAC in MP4.
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2. **macOS `/var` is a symlink to `/private/var`.** Asset protocol scope must cover both paths.
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3. **`Promise.allSettled` blocks all results until the slowest completes.** Use individual `.then()` chains when you want progressive rendering.
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4. **yt-dlp sends status to stdout, warnings to stderr.** Not the other way around.
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