refactor: invoke ffmpeg without deprecated wrapper

src/audio/ffmpegProcess.ts

@@ -0,0 +1,61 @@
+import { spawn } from "child_process";
+
+export interface MuxFfmpegArgsOptions {
+  inputs: string[];
+  filter: string;
+  output: string;
+  codec: string;
+  audioFrequency?: number;
+  audioChannels?: number;
+}
+
+/**
+ * Builds ffmpeg argument array for muxing audio clips.
+ */
+export function buildMuxFfmpegArgs(options: MuxFfmpegArgsOptions): string[] {
+  const args: string[] = ["-y"];
+
+  for (const input of options.inputs) {
+    args.push("-i", input);
+  }
+
+  args.push("-filter_complex", options.filter);
+  args.push("-map", "[out]");
+  args.push("-codec:a", options.codec);
+
+  if (options.audioFrequency !== undefined) {
+    args.push("-ar", String(options.audioFrequency));
+  }
+
+  if (options.audioChannels !== undefined) {
+    args.push("-ac", String(options.audioChannels));
+  }
+
+  args.push(options.output);
+
+  return args;
+}
+
+/**
+ * Runs ffmpeg with the given arguments.
+ * Resolves on successful (code 0) exit, rejects on error or non-zero exit.
+ */
+export function runFfmpeg(args: string[]): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const proc = spawn("ffmpeg", args, {
+      stdio: ["ignore", "inherit", "inherit"],
+    });
+
+    proc.on("close", (code) => {
+      if (code === 0) {
+        resolve();
+      } else {
+        reject(new Error(`ffmpeg exited with code ${code}`));
+      }
+    });
+
+    proc.on("error", (err) => {
+      reject(err);
+    });
+  });
+}