feat(subtitles): use loaded subtitles to guide generation timing (#249)

src/core/services/subtitle-generation-acceleration.ts

@@ -0,0 +1,62 @@
+import { execFile } from 'node:child_process';
+import { mkdtemp, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import type {
+  SubtitleGenerationAcceleration,
+  SubtitleGenerationToolStatus,
+} from '../../shared/subtitle-generation';
+
+function probe(command: string, args: string[], env: NodeJS.ProcessEnv) {
+  return new Promise<{ code: number; stdout: string; stderr: string } | null>((resolve) => {
+    execFile(
+      command,
+      args,
+      { env, timeout: 3000, killSignal: 'SIGKILL', maxBuffer: 64 * 1024, windowsHide: true },
+      (error, stdout, stderr) => {
+        const code = error?.code ?? 0;
+        if (typeof code !== 'number' || error?.killed || error?.signal) {
+          resolve(null);
+          return;
+        }
+        resolve({ code, stdout, stderr });
+      },
+    );
+  });
+}
+
+/** Require both a working NVIDIA driver and CUDA device discovery in the selected Whisper binary. */
+export async function detectSubtitleGenerationAcceleration(
+  whisper: SubtitleGenerationToolStatus,
+  env: NodeJS.ProcessEnv = process.env,
+): Promise<SubtitleGenerationAcceleration> {
+  const unavailable: SubtitleGenerationAcceleration = { kind: 'unavailable' };
+  if (whisper.kind === 'missing') return unavailable;
+  let directory: string | undefined;
+  try {
+    const nvidia = await probe('nvidia-smi', ['--query-gpu=name', '--format=csv,noheader'], env);
+    const gpuName = nvidia?.stdout.trim().split(/\r?\n/)[0]?.trim();
+    if (nvidia?.code !== 0 || !gpuName) return unavailable;
+
+    directory = await mkdtemp(path.join(tmpdir(), 'subminer-cuda-check-'));
+    const model = path.join(directory, 'probe.bin');
+    await writeFile(model, Buffer.alloc(4));
+    // whisper.cpp discovers backends before checking model magic. This deliberately invalid
+    // local file stops before allocating a model or decoding audio, even on a fresh install.
+    const result = await probe(whisper.path, ['-m', model, '-f', model], env);
+    if (
+      result &&
+      result.code !== 0 &&
+      /ggml_cuda_init:\s+found\s+[1-9]\d*\s+CUDA devices?\b/i.test(result.stderr) &&
+      /invalid model data \(bad magic\)/i.test(result.stderr)
+    ) {
+      return { kind: 'nvidia-cuda', gpuName };
+    }
+    return unavailable;
+  } catch {
+    // Detection is advisory; unsupported builds and driver failures must not block generation.
+    return unavailable;
+  } finally {
+    if (directory) await rm(directory, { recursive: true, force: true }).catch(() => {});
+  }
+}