From 03eec79b4c06aa985a8b242d585dfad72ebfea1e Mon Sep 17 00:00:00 2001
From: Claude Fable 5 <fable-5@waidele.info>
Date: Sat, 29 Aug 2026 21:11:42 +0200
Subject: [PATCH] Fix duplicated text in Markdown from YouTube auto-captions

Rolling auto-caption cues repeat the previous line as plain text and
carry the new text in lines with inline word-timing tags. Keep only the
tagged lines in such cues (JS module and Python CLI); skip writing
Markdown files whose content is identical to one already written.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 scripts/subtitle_to_markdown.py    | 12 +++++++++++-
 src/lib/subtitle.js                | 14 ++++++++++++--
 src/routes/api/download/+server.js |  6 ++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/scripts/subtitle_to_markdown.py b/scripts/subtitle_to_markdown.py
index f882e49..c0af6e0 100755
--- a/scripts/subtitle_to_markdown.py
+++ b/scripts/subtitle_to_markdown.py
@@ -9,6 +9,13 @@ def strip_html(text):
     return re.sub(r'<[^>]+>', '', text)
 
 
+# YouTube auto-captions use rolling cues: the previous line is repeated as
+# plain text while the new line carries inline word timings (<00:00:00.200>,
+# <c>…</c>). Only the tagged lines contain new text.
+def has_inline_timing_tags(line):
+    return re.search(r'<\d{2}:\d{2}:|<c[.\w]*>', line) is not None
+
+
 def parse_vtt(content):
     blocks = re.split(r'\n{2,}', content.strip())
     cues = []
@@ -23,9 +30,12 @@ def parse_vtt(content):
         ts_idx = next((i for i, l in enumerate(lines) if '-->' in l), None)
         if ts_idx is None:
             continue
+        text_lines = lines[ts_idx + 1:]
+        if any(has_inline_timing_tags(l) for l in text_lines):
+            text_lines = [l for l in text_lines if has_inline_timing_tags(l)]
         text = ' '.join(
             strip_html(l).strip()
-            for l in lines[ts_idx + 1:]
+            for l in text_lines
             if strip_html(l).strip()
         )
         if text:
diff --git a/src/lib/subtitle.js b/src/lib/subtitle.js
index c5a58ab..3ed6022 100644
--- a/src/lib/subtitle.js
+++ b/src/lib/subtitle.js
@@ -5,6 +5,13 @@ function stripHtml(text) {
 	return text.replace(/<[^>]+>/g, '');
 }
 
+// YouTube auto-captions use rolling cues: the previous line is repeated as
+// plain text while the new line carries inline word timings (<00:00:00.200>,
+// <c>…</c>). Only the tagged lines contain new text.
+function hasInlineTimingTags(line) {
+	return /<\d{2}:\d{2}:|<c[.\w]*>/.test(line);
+}
+
 function parseVtt(content) {
 	const blocks = content.split(/\n{2,}/);
 	const cues = [];
@@ -15,8 +22,11 @@ function parseVtt(content) {
 		if (lines[0].startsWith('NOTE') || lines[0].startsWith('STYLE')) continue;
 		const tsIdx = lines.findIndex(l => l.includes('-->'));
 		if (tsIdx === -1) continue;
-		const text = lines
-			.slice(tsIdx + 1)
+		let textLines = lines.slice(tsIdx + 1);
+		if (textLines.some(hasInlineTimingTags)) {
+			textLines = textLines.filter(hasInlineTimingTags);
+		}
+		const text = textLines
 			.map(l => stripHtml(l).trim())
 			.filter(Boolean)
 			.join(' ');
diff --git a/src/routes/api/download/+server.js b/src/routes/api/download/+server.js
index fc1cb28..c66ce40 100644
--- a/src/routes/api/download/+server.js
+++ b/src/routes/api/download/+server.js
@@ -105,12 +105,18 @@ async function runDownload(videoUrl, audioOnly, send, signal) {
 		}
 	}
 
+	const writtenMd = new Set();
 	for (const subPath of subtitlePaths) {
 		if (!existsSync(subPath)) continue;
 		send('info', `Converting: ${basename(subPath)}`);
 		try {
 			const md = convertSubtitleToMarkdown(subPath);
 			const mdPath = subPath.replace(/\.(vtt|srt)$/, '.md');
+			if (writtenMd.has(md)) {
+				send('info', `Skipped (identical): ${basename(mdPath)}`);
+				continue;
+			}
+			writtenMd.add(md);
 			writeFileSync(mdPath, md, 'utf-8');
 			send('info', `Saved: ${basename(mdPath)}`);
 		} catch (err) {