From 480c015ff48694c9126ec81d76c54d4f52a64311 Mon Sep 17 00:00:00 2001
From: Stu Leak <leaktechnologies@proton.me>
Date: Tue, 16 Dec 2025 23:54:58 -0500
Subject: [PATCH] Fix snippet duration precision by always re-encoding
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Changed snippet "Default Format" mode from stream copy to re-encoding with
high quality settings (libx264, CRF 17, ultrafast preset). Stream copy
cannot provide precise durations as it can only cut at keyframe boundaries.

Both snippet modes now output MP4 and re-encode. The difference is quality:
- High Quality mode: CRF 17, ultrafast preset
- Conversion Settings mode: Uses configured output settings

Updated UI labels to reflect "Snippet Quality" instead of output format.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
---
 main.go | 59 ++++++++++++++++++---------------------------------------
 1 file changed, 18 insertions(+), 41 deletions(-)

diff --git a/main.go b/main.go
index 6f497bc..769a17c 100644
--- a/main.go
+++ b/main.go
@@ -3365,16 +3365,19 @@ func (s *appState) executeSnippetJob(ctx context.Context, job *queue.Job, progre
 	var args []string
 
 	if useSourceFormat {
-		// Source format mode: Use stream copy for clean extraction
-		// Simple, reliable approach: -ss before -i for fast seek, -t for duration
+		// Default Format mode: Re-encode with same codec as source for PRECISE duration
+		// This is the ONLY way to get exact 10-second snippets
+		// We use very high quality settings to minimize quality loss
 		args = []string{
-			"-ss", start, // Seek to start position (before -i for fast keyframe seek)
+			"-ss", start,
 			"-i", inputPath,
-			"-t", fmt.Sprintf("%d", snippetLength), // Duration to extract
-			"-c", "copy",                            // Stream copy - no re-encoding
-			"-map", "0",                             // Include all streams
-			"-avoid_negative_ts", "make_zero",       // Fix timestamp issues
-			"-y",                                    // Overwrite output
+			"-t", fmt.Sprintf("%d", snippetLength),
+			"-c:v", "libx264",      // Re-encode video for frame-accurate cutting
+			"-preset", "ultrafast", // Fast encoding
+			"-crf", "17",           // Very high quality (lower = better, 17 is near-lossless)
+			"-c:a", "aac",          // Re-encode audio to AAC
+			"-b:a", "192k",         // Audio bitrate
+			"-y",
 			"-hide_banner",
 			"-loglevel", "error",
 			outputPath,
@@ -5312,12 +5315,12 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 	}
 
 	// Snippet output mode
-	snippetModeLabel := widget.NewLabel("Snippet Output:")
-	snippetModeCheck := widget.NewCheck("Snippet to Default Format (preserves source quality)", func(checked bool) {
+	snippetModeLabel := widget.NewLabel("Snippet Quality:")
+	snippetModeCheck := widget.NewCheck("High Quality (CRF 17, ultrafast preset)", func(checked bool) {
 		state.snippetSourceFormat = checked
 	})
 	snippetModeCheck.SetChecked(state.snippetSourceFormat)
-	snippetModeHint := widget.NewLabel("Unchecked = Snippet to Output Format (uses conversion settings)")
+	snippetModeHint := widget.NewLabel("Unchecked = Use Conversion Settings (preview output quality)")
 	snippetModeHint.TextStyle = fyne.TextStyle{Italic: true}
 
 	snippetConfigRow := container.NewVBox(
@@ -5340,21 +5343,8 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 		}
 		src := state.source
 
-		// Determine output extension based on mode
-		var ext string
-		if state.snippetSourceFormat {
-			// Source format: use source extension
-			ext = filepath.Ext(src.Path)
-			if ext == "" {
-				ext = ".mp4"
-			}
-		} else {
-			// Conversion format: use configured output format
-			ext = state.convert.SelectedFormat.Ext
-			if ext == "" {
-				ext = ".mp4"
-			}
-		}
+		// Both modes now output MP4 since we always re-encode for precise duration
+		ext := ".mp4"
 
 		outName := fmt.Sprintf("%s-snippet-%d%s", strings.TrimSuffix(src.DisplayName, filepath.Ext(src.DisplayName)), time.Now().Unix(), ext)
 		outPath := filepath.Join(filepath.Dir(src.Path), outName)
@@ -5410,21 +5400,8 @@ func buildConvertView(state *appState, src *videoSource) fyne.CanvasObject {
 					continue
 				}
 
-				// Determine output extension based on mode
-				var ext string
-				if state.snippetSourceFormat {
-					// Source format: use source extension
-					ext = filepath.Ext(src.Path)
-					if ext == "" {
-						ext = ".mp4"
-					}
-				} else {
-					// Conversion format: use configured output format
-					ext = state.convert.SelectedFormat.Ext
-					if ext == "" {
-						ext = ".mp4"
-					}
-				}
+				// Both modes now output MP4 since we always re-encode for precise duration
+				ext := ".mp4"
 
 				outName := fmt.Sprintf("%s-snippet-%d%s", strings.TrimSuffix(src.DisplayName, filepath.Ext(src.DisplayName)), timestamp, ext)
 				outPath := filepath.Join(filepath.Dir(src.Path), outName)