refactor(youtube): extract subtitle generation pipeline

2026-03-20 12:11:28 -07:00 · 2026-03-08 16:10:56 -07:00
parent 9e46176519
commit 4c0575afe0
11 changed files with 876 additions and 467 deletions
--- a/launcher/youtube/audio-extraction.ts
+++ b/launcher/youtube/audio-extraction.ts
@@ -0,0 +1,84 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+import type { Args } from '../types.js';
+import { YOUTUBE_AUDIO_EXTENSIONS } from '../types.js';
+import { runExternalCommand } from '../util.js';
+
+export function findAudioFile(tempDir: string, preferredExt: string): string | null {
+  const entries = fs.readdirSync(tempDir);
+  const audioFiles: Array<{ path: string; ext: string; mtimeMs: number }> = [];
+  for (const name of entries) {
+    const fullPath = path.join(tempDir, name);
+    let stat: fs.Stats;
+    try {
+      stat = fs.statSync(fullPath);
+    } catch {
+      continue;
+    }
+    if (!stat.isFile()) continue;
+    const ext = path.extname(name).toLowerCase();
+    if (!YOUTUBE_AUDIO_EXTENSIONS.has(ext)) continue;
+    audioFiles.push({ path: fullPath, ext, mtimeMs: stat.mtimeMs });
+  }
+  if (audioFiles.length === 0) return null;
+  const preferred = audioFiles.find((entry) => entry.ext === `.${preferredExt.toLowerCase()}`);
+  if (preferred) return preferred.path;
+  audioFiles.sort((a, b) => b.mtimeMs - a.mtimeMs);
+  return audioFiles[0]?.path ?? null;
+}
+
+export async function convertAudioForWhisper(inputPath: string, tempDir: string): Promise<string> {
+  const wavPath = path.join(tempDir, 'whisper-input.wav');
+  await runExternalCommand('ffmpeg', [
+    '-y',
+    '-loglevel',
+    'error',
+    '-i',
+    inputPath,
+    '-ar',
+    '16000',
+    '-ac',
+    '1',
+    '-c:a',
+    'pcm_s16le',
+    wavPath,
+  ]);
+  if (!fs.existsSync(wavPath)) {
+    throw new Error(`Failed to prepare whisper audio input: ${wavPath}`);
+  }
+  return wavPath;
+}
+
+export async function downloadYoutubeAudio(
+  target: string,
+  args: Args,
+  tempDir: string,
+  childTracker?: Set<ReturnType<typeof import('node:child_process').spawn>>,
+): Promise<string> {
+  await runExternalCommand(
+    'yt-dlp',
+    [
+      '-f',
+      'bestaudio/best',
+      '--extract-audio',
+      '--audio-format',
+      args.youtubeSubgenAudioFormat,
+      '--no-warnings',
+      '-o',
+      path.join(tempDir, '%(id)s.%(ext)s'),
+      target,
+    ],
+    {
+      logLevel: args.logLevel,
+      commandLabel: 'yt-dlp:audio',
+      streamOutput: true,
+    },
+    childTracker,
+  );
+  const audioPath = findAudioFile(tempDir, args.youtubeSubgenAudioFormat);
+  if (!audioPath) {
+    throw new Error('Audio extraction succeeded, but no audio file was found.');
+  }
+  return audioPath;
+}