fix(producer): normalize padded audio on sample timeline

packages/engine/src/services/chunkEncoder.test.ts

@@ -373,29 +373,6 @@ describe("encodeFramesChunkedConcat ffmpegEncodeTimeout", () => {
 });
 
 describe("muxVideoWithAudio audio codec handling", () => {
-  it("caps copied audio to the encoded video duration", async () => {
-    const { spawn, calls } = createSpawnSpy();
-    vi.resetModules();
-    vi.doMock("child_process", () => ({ spawn }));
-
-    const { muxVideoWithAudio } = await import("./chunkEncoder.js");
-    const muxPromise = muxVideoWithAudio(
-      "/tmp/video-only.mp4",
-      "/tmp/audio.duration-normalized.m4a",
-      "/tmp/output.mp4",
-      undefined,
-      { audioCodec: "aac", durationSeconds: 16.066667 },
-      { num: 30, den: 1 },
-    );
-
-    await flushMuxCodecResolution();
-    expect(calls[0]!.args).toContain("-shortest");
-    expect(calls[0]!.args).toContain("-t");
-    expect(calls[0]!.args).toContain("16.066667");
-    emitClose(calls[0]!.proc, 0);
-    await expect(muxPromise).resolves.toMatchObject({ success: true });
-  });
-
   it("copies HyperFrames AAC sidecars into MP4 instead of re-encoding", async () => {
     const { spawn, calls } = createSpawnSpy();
     vi.resetModules();

packages/engine/src/services/chunkEncoder.ts

@@ -80,7 +80,6 @@ export interface MuxVideoWithAudioOptions extends Partial<
   /** Preserve a priming edit list known to have been created by AAC re-encoding. */
   preserveAudioPrimingEditList?: boolean;
   /** Hard cap copied audio to the already-encoded video's exact duration. */
-  durationSeconds?: number;
 }
 
 async function shouldCopyAacSidecar(
@@ -708,16 +707,6 @@ export async function muxVideoWithAudio(
     // output container metadata. `-c:v copy` is retained; no re-encode.
     args.push("-r", fpsToFfmpegArg(fps));
   }
-  if (config?.durationSeconds !== undefined) {
-    // Stream-copying a normalized AAC sidecar can preserve a longer packet
-    // timeline than its container/edit-list duration.  `-t` alone limits the
-    // output timestamp window but does not prevent the copied audio stream's
-    // tail from extending the MP4 timeline.  When an explicit video-derived
-    // duration is supplied, also stop at the shortest stream so the final
-    // mux boundary is deterministic.
-    args.push("-shortest");
-    args.push("-t", String(config.durationSeconds));
-  }
   args.push("-y", outputPath);
 
   const processTimeout = config?.ffmpegProcessTimeout ?? DEFAULT_CONFIG.ffmpegProcessTimeout;