feat(streamer): ffmpeg rtmp encoder spawn

streamer/src/ffmpeg.ts

@@ -0,0 +1,58 @@
+import { ChildProcessWithoutNullStreams, spawn } from "node:child_process";
+import { EventEmitter } from "node:events";
+import { Writable } from "node:stream";
+
+export interface FfmpegOpts {
+  rtmpUrl: string;
+  width: number;
+  height: number;
+  framerate: number;
+  videoBitrate: string;
+  audioBitrate: string;
+}
+
+export class Ffmpeg extends EventEmitter {
+  private proc: ChildProcessWithoutNullStreams | null = null;
+
+  constructor(private opts: FfmpegOpts) { super(); }
+
+  start(): { videoIn: Writable; audioIn: Writable } {
+    const args = [
+      "-loglevel", "warning",
+      // video in (mjpeg pipe on fd 3)
+      "-f", "image2pipe", "-c:v", "mjpeg",
+      "-r", String(this.opts.framerate), "-i", "pipe:3",
+      // audio in (s16le pcm pipe on fd 4)
+      "-f", "s16le", "-ar", "48000", "-ac", "2", "-i", "pipe:4",
+      // video encode
+      "-c:v", "libx264", "-preset", "veryfast",
+      "-pix_fmt", "yuv420p",
+      "-b:v", this.opts.videoBitrate,
+      "-maxrate", this.opts.videoBitrate, "-bufsize", "9000k",
+      "-g", String(this.opts.framerate * 2), "-keyint_min", String(this.opts.framerate * 2),
+      "-r", String(this.opts.framerate),
+      // audio encode
+      "-c:a", "aac", "-b:a", this.opts.audioBitrate, "-ar", "48000",
+      // output
+      "-f", "flv", this.opts.rtmpUrl,
+    ];
+
+    this.proc = spawn("ffmpeg", args, {
+      stdio: ["ignore", "pipe", "pipe", "pipe", "pipe"],
+    }) as unknown as ChildProcessWithoutNullStreams;
+
+    const stdio = (this.proc as unknown as { stdio: Writable[] }).stdio;
+    const videoIn = stdio[3]!;
+    const audioIn = stdio[4]!;
+
+    this.proc.stderr.on("data", (d) => this.emit("log", d.toString()));
+    this.proc.on("exit", (code) => this.emit("exit", code));
+
+    return { videoIn, audioIn };
+  }
+
+  stop(): void {
+    this.proc?.kill("SIGTERM");
+    this.proc = null;
+  }
+}