gui-video-clipper/chat-summaries/2026-09-21_13-27-hybrid-download-defocus-input-summary.md

Hybrid Download Model + Auto-Defocus URL Input

Task Description

Two user-requested improvements:

1. Hybrid download model: Download a low-resolution (≤360p H.264+AAC) version for immediate preview/scrubbing/waveform/thumbnail generation, while downloading the best available quality in the background for export. Clips are cut from the best-quality file.
2. Auto-defocus URL input: After pasting a URL and triggering submit, blur the input field so keyboard shortcuts (I, O, etc.) don't accidentally modify the URL.

Changes Made

Session State Refactor (src/lib/stores/videoSession.svelte.ts)

• Replaced single localFilePath/downloadProgress/downloadStatus with dual-track state:
  • previewFilePath/previewProgress/previewStatus — for the 360p preview
  • exportFilePath/exportProgress/exportStatus — for the best-quality export
• Preview format: bv*[vcodec^=avc1][height<=360]+ba[acodec^=mp4a]/b[ext=mp4][height<=360]/worst[ext=mp4]/worst
• Export format: bv*+ba/b (best available, any codec since ffmpeg handles export)
• beginDownload() now:
  1. Checks cache for preview → downloads if needed → triggers post-processing (waveform, thumbnails, keyframes)
  2. Checks cache for export → downloads in background (fire-and-forget)
• Files stored in separate subdirectories: video-clipper/preview/ and video-clipper/export/

Rust Backend (src-tauri/src/commands/video.rs)

• start_download now accepts format_spec and variant parameters
• check_cached_download now accepts a variant parameter to check the correct subdirectory
• Helper variant_dir() builds $TEMP/video-clipper/{variant}/ paths
• Diagnostic logging includes variant name for easier debugging

Download Manager (src-tauri/src/services/download_manager.rs)

• start_download now accepts format_spec: &str parameter instead of hardcoding format selection
• Format string passed through from the frontend call

Frontend Bindings (src/lib/bindings/video.ts)

• startDownload now takes formatSpec and variant parameters
• checkCachedDownload now takes a variant parameter

VideoPlayer (src/lib/components/VideoPlayer.svelte)

• Uses previewFilePath/previewStatus instead of old single-track fields
• Download progress shows "Downloading preview…" label

ExportDialog (src/lib/components/ExportDialog.svelte)

• Uses exportFilePath/exportStatus/exportProgress for export readiness
• Shows "Downloading best quality (X%)…" while export download is in progress

StatusBar (src/lib/components/StatusBar.svelte)

• Shows dual progress: preview download → export download → ready to export
• Contextual status messages for each download phase

UrlInput (src/lib/components/UrlInput.svelte)

• Added bind:this={inputEl} reference to input element
• blurInput() called at the start of handleSubmit() — defocuses immediately on paste/enter
• Keyboard shortcuts (I, O, etc.) now work immediately after submitting a URL

Lessons Learned

• Storing preview and export files in separate subdirectories (preview/, export/) keeps cache management clean and avoids filename collisions between quality variants.
• Fire-and-forget pattern for background export download (.catch() at call site) keeps the preview flow responsive without blocking on the best-quality download.
• The variant parameter threading from frontend → Rust command → download manager keeps the API clean and extensible for future quality tiers.

Follow-Up Items

• Consider showing export download progress in the timeline/player area as a subtle indicator
• The export format bv*+ba/b may download VP9/WebM — this is fine for ffmpeg export but won't play in WKWebView. The preview file handles playback.
• Old flat video-clipper/ cache was cleared; users with existing caches in the old location won't get cache hits (harmless — just re-downloads)