Add encoder preset descriptions with speed/quality trade-offs

This commit enhances the encoder preset selector with detailed information
about speed vs quality trade-offs for each preset option.

Preset Information:
- Ultrafast: ~10x faster than slow, ~30% larger files
- Superfast: ~7x faster than slow, ~20% larger files
- Very Fast: ~5x faster than slow, ~15% larger files
- Faster: ~3x faster than slow, ~10% larger files
- Fast: ~2x faster than slow, ~5% larger files
- Medium: Balanced baseline (default)
- Slow: ~2x slower than medium, ~5-10% smaller (recommended)
- Slower: ~3x slower than medium, ~10-15% smaller
- Very Slow: ~5x slower than medium, ~15-20% smaller

UI Enhancements:
- Dynamic hint label below encoder preset dropdown
- Updates automatically when preset changes
- Visual icons for different speed categories:
  - ⚡ Ultrafast/Superfast/Very Fast (prioritize speed)
  - ⏩ Faster/Fast (good balance)
  - ⚖️ Medium (baseline)
  - 🎯 Slow/Slower (recommended for quality)
  - 🐌 Very Slow (maximum compression)

Implementation:
- updateEncoderPresetHint() function provides preset details
- Called on preset selection change
- Initialized with current preset on view load
- Positioned directly under preset dropdown for visibility

Benefits:
- Helps users understand encoding time implications
- Shows file size impact of each preset
- Recommends "slow" as best quality/size ratio
- Prevents confusion about preset differences
- Enables informed decisions about encoding settings

Technical:
- All presets already supported by FFmpeg
- No changes to command generation needed
- Works with all video codecs (H.264, H.265, VP9, etc.)
- Preset names match FFmpeg standards

DONE.md

@@ -17,6 +17,16 @@ This file tracks completed features, fixes, and milestones.
   - Proper handling for videos without black bars
   - 30-second timeout protection for detection process
 
+- ✅ **Frame Rate Conversion UI with Size Estimates**
+  - Comprehensive frame rate options: Source, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60
+  - Intelligent file size reduction estimates (40-50% for 60→30 fps)
+  - Real-time hints showing "Converting X → Y fps: ~Z% smaller file"
+  - Warning for upscaling attempts with judder notice
+  - Automatic calculation based on source and target frame rates
+  - Dynamic updates when video or frame rate changes
+  - Supports both film (24 fps) and broadcast standards (25/29.97/30)
+  - Uses FFmpeg fps filter for frame rate conversion
+
 - ✅ **Compare Module**
   - Side-by-side video comparison interface
   - Load two videos and compare detailed metadata

TODO.md

@@ -11,10 +11,10 @@ This file tracks upcoming features, improvements, and known issues.
   - 15-30% file size reduction with zero quality loss
   - Add manual crop override option
 
-- [ ] **Frame rate conversion UI**
-  - Dropdown: Source, 24, 25, 29.97, 30, 50, 59.94, 60 fps
+- [x] **Frame rate conversion UI** (v0.1.0-dev13 - COMPLETED)
+  - Dropdown: Source, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60 fps
   - Auto-suggest 60→30fps conversion with size estimate
-  - Show file size impact (40-45% reduction for 60→30)
+  - Show file size impact (40-50% reduction for 60→30)
 
 - [ ] **HEVC/H.265 preset options**
   - Add preset dropdown: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow

main.go

@@ -1999,12 +1999,44 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 	})
 	videoCodecSelect.SetSelected(state.convert.VideoCodec)
 
-	// Encoder Preset
+	// Encoder Preset with hint
+	encoderPresetHint := widget.NewLabel("")
+	encoderPresetHint.Wrapping = fyne.TextWrapWord
+
+	updateEncoderPresetHint := func(preset string) {
+		var hint string
+		switch preset {
+		case "ultrafast":
+			hint = "⚡ Ultrafast: Fastest encoding, largest files (~10x faster than slow, ~30% larger files)"
+		case "superfast":
+			hint = "⚡ Superfast: Very fast encoding, large files (~7x faster than slow, ~20% larger files)"
+		case "veryfast":
+			hint = "⚡ Very Fast: Fast encoding, moderately large files (~5x faster than slow, ~15% larger files)"
+		case "faster":
+			hint = "⏩ Faster: Quick encoding, slightly large files (~3x faster than slow, ~10% larger files)"
+		case "fast":
+			hint = "⏩ Fast: Good speed, slightly large files (~2x faster than slow, ~5% larger files)"
+		case "medium":
+			hint = "⚖️ Medium (default): Balanced speed and quality (baseline for comparison)"
+		case "slow":
+			hint = "🎯 Slow (recommended): Best quality/size ratio (~2x slower than medium, ~5-10% smaller)"
+		case "slower":
+			hint = "🎯 Slower: Excellent compression (~3x slower than medium, ~10-15% smaller files)"
+		case "veryslow":
+			hint = "🐌 Very Slow: Maximum compression (~5x slower than medium, ~15-20% smaller files)"
+		default:
+			hint = ""
+		}
+		encoderPresetHint.SetText(hint)
+	}
+
 	encoderPresetSelect := widget.NewSelect([]string{"ultrafast", "superfast", "veryfast", "faster", "fast", "medium", "slow", "slower", "veryslow"}, func(value string) {
 		state.convert.EncoderPreset = value
 		logging.Debug(logging.CatUI, "encoder preset set to %s", value)
+		updateEncoderPresetHint(value)
 	})
 	encoderPresetSelect.SetSelected(state.convert.EncoderPreset)
+	updateEncoderPresetHint(state.convert.EncoderPreset)
 
 	// Bitrate Mode
 	bitrateModeSelect := widget.NewSelect([]string{"CRF", "CBR", "VBR", "Target Size"}, func(value string) {
@@ -2198,6 +2230,7 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 		videoCodecSelect,
 		widget.NewLabelWithStyle("Encoder Preset (speed vs quality)", fyne.TextAlignLeading, fyne.TextStyle{Bold: true}),
 		encoderPresetSelect,
+		encoderPresetHint,
 		widget.NewLabelWithStyle("Quality Preset", fyne.TextAlignLeading, fyne.TextStyle{Bold: true}),
 		qualitySelect,
 		widget.NewLabelWithStyle("Bitrate Mode", fyne.TextAlignLeading, fyne.TextStyle{Bold: true}),