fix(engine): tune VP9 cpu-used across render paths (#1614)

* fix(engine): tune VP9 cpu-used across render paths

* fix: address VP9 review feedback

packages/cli/src/background-removal/pipeline.test.ts

@@ -45,6 +45,7 @@ describe("background-removal/pipeline — buildEncoderArgs", () => {
     const args = buildEncoderArgs("webm", 1920, 1080, 30, "/tmp/out.webm");
     expect(args).toContain("libvpx-vp9");
     expect(args).toContain("yuva420p");
+    expect(args[args.indexOf("-cpu-used") + 1]).toBe("4");
     // The alpha_mode metadata must be present; without it Chrome ignores the alpha plane.
     const idx = args.indexOf("-metadata:s:v:0");
     expect(idx).toBeGreaterThan(-1);

packages/cli/src/background-removal/pipeline.ts

@@ -18,6 +18,7 @@ import { extname } from "node:path";
 import { findFFmpeg, findFFprobe, getFFmpegInstallHint } from "../browser/ffmpeg.js";
 import { createSession, type Session } from "./inference.js";
 import { type Device, type ModelId } from "./manager.js";
+import { DEFAULT_VP9_CPU_USED } from "@hyperframes/engine";
 
 export type OutputFormat = "webm" | "mov" | "png";
 
@@ -159,6 +160,8 @@ export function buildEncoderArgs(
       "good",
       "-row-mt",
       "1",
+      "-cpu-used",
+      String(DEFAULT_VP9_CPU_USED),
       "-auto-alt-ref",
       "0",
       "-pix_fmt",