Add HyperFrames skills (from heygen-com/hyperframes, Apache-2.0)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXVsD1DgdzZLiPuwtKzMSY

.claude/skills/media-use/scripts/transcript-cut.test.mjs

@@ -0,0 +1,341 @@
+import assert from "node:assert/strict";
+import { execFileSync, spawnSync } from "node:child_process";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import test from "node:test";
+import { fileURLToPath } from "node:url";
+
+const SCRIPT = fileURLToPath(new URL("./transcript-cut.mjs", import.meta.url));
+const HAS_FFMPEG =
+  spawnSync("ffmpeg", ["-version"], { stdio: "ignore" }).status === 0 &&
+  spawnSync("ffprobe", ["-version"], { stdio: "ignore" }).status === 0;
+
+const SAMPLE_RATE = 44100;
+// A continuous tone's own slope between samples never exceeds amplitude * 2*pi*f/rate
+// (~2054 for 440Hz at full scale here); a raw splice between two independently-cut
+// points on the same tone lands at two unrelated phases, so an unfaded join jumps far
+// past that. This threshold sits well above normal tone motion and well below a splice.
+const MAX_CONTINUOUS_STEP = 6000;
+const MIN_SUSPICIOUS_ZERO_RUN = 20;
+
+function fixture() {
+  const dir = mkdtempSync(join(tmpdir(), "media-use-transcript-cut-"));
+  return { dir, cleanup: () => rmSync(dir, { recursive: true, force: true }) };
+}
+
+function run(args) {
+  return spawnSync(process.execPath, [SCRIPT, ...args], { encoding: "utf8" });
+}
+
+function readPcm(filePath) {
+  const raw = execFileSync("ffmpeg", [
+    "-hide_banner",
+    "-loglevel",
+    "error",
+    "-i",
+    filePath,
+    "-f",
+    "s16le",
+    "-ac",
+    "1",
+    "-ar",
+    String(SAMPLE_RATE),
+    "-",
+  ]);
+  const samples = new Int16Array(raw.buffer, raw.byteOffset, raw.length / 2);
+  return samples;
+}
+
+// Three kept ranges, none starting or ending on a frame boundary of any rate below.
+const UNALIGNED_KEEP = "0.137-1.913,2.845-4.111,4.9-5.47";
+const UNALIGNED_KEPT_SECONDS = 1.776 + 1.266 + 0.57;
+
+function cutVideo(t, rate, keep = UNALIGNED_KEEP) {
+  const { dir, cleanup } = fixture();
+  t.after(cleanup);
+
+  const source = join(dir, "source.mp4");
+  execFileSync("ffmpeg", [
+    "-y",
+    "-hide_banner",
+    "-loglevel",
+    "error",
+    "-f",
+    "lavfi",
+    "-i",
+    `testsrc2=size=160x90:rate=${rate}:duration=6`,
+    "-f",
+    "lavfi",
+    "-i",
+    `sine=frequency=440:duration=6:sample_rate=${SAMPLE_RATE}`,
+    "-c:v",
+    "libx264",
+    "-preset",
+    "ultrafast",
+    "-pix_fmt",
+    "yuv420p",
+    "-c:a",
+    "aac",
+    source,
+  ]);
+
+  const transcriptPath = join(dir, "transcript.json");
+  writeFileSync(transcriptPath, JSON.stringify({ words: [{ text: "tone", start: 0, end: 6 }] }));
+
+  const output = join(dir, "out.mp4");
+  const result = run([
+    "--input",
+    source,
+    "--transcript",
+    transcriptPath,
+    "--keep",
+    keep,
+    "--out",
+    output,
+    "--json",
+  ]);
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+  return output;
+}
+
+function readVideoTimestamps(filePath) {
+  const probe = JSON.parse(
+    execFileSync(
+      "ffprobe",
+      [
+        "-v",
+        "error",
+        "-select_streams",
+        "v:0",
+        "-show_entries",
+        "stream=time_base:packet=pts",
+        "-of",
+        "json",
+        "--",
+        filePath,
+      ],
+      { encoding: "utf8" },
+    ),
+  );
+  const [tickNum, tickDen] = probe.streams[0].time_base.split("/").map(Number);
+  // Packets come in decode order; B-frames put that out of presentation order.
+  const pts = probe.packets.map((packet) => Number(packet.pts)).sort((a, b) => a - b);
+  return { tickNum, tickDen, pts };
+}
+
+for (const rate of ["30", "30000/1001", "60"]) {
+  test(
+    `puts every frame of a ${rate} fps video cut on the frame grid, with no gaps`,
+    { skip: !HAS_FFMPEG },
+    (t) => {
+      const [rateNum, rateDen = 1] = rate.split("/").map(Number);
+      const { tickNum, tickDen, pts } = readVideoTimestamps(cutVideo(t, rate));
+      assert.ok(pts.length > rateNum / rateDen, "expected several seconds of video");
+
+      // Frame i belongs at exactly i / rate seconds. Compared as integers, so a
+      // timestamp rounded to the millisecond (0.067 for 2/30) cannot pass.
+      const offGrid = pts.filter(
+        (value, index) => value * tickNum * rateNum !== index * rateDen * tickDen,
+      );
+      assert.equal(
+        offGrid.length,
+        0,
+        `${offGrid.length} of ${pts.length} frames are off the ${rate} fps grid (timestamps in units of ${tickNum}/${tickDen} s)`,
+      );
+    },
+  );
+}
+
+test(
+  "keeps the keyframes of a video cut no more than a second apart",
+  { skip: !HAS_FFMPEG },
+  (t) => {
+    // One kept range of almost four seconds, so only the encoder decides where keyframes go.
+    const output = cutVideo(t, "30", "0.137-4.111,4.9-5.47");
+    const probe = JSON.parse(
+      execFileSync(
+        "ffprobe",
+        [
+          "-v",
+          "error",
+          "-select_streams",
+          "v:0",
+          "-show_entries",
+          "packet=pts_time,flags",
+          "-of",
+          "json",
+          "--",
+          output,
+        ],
+        { encoding: "utf8" },
+      ),
+    );
+    const keyframes = probe.packets
+      .filter((packet) => packet.flags.startsWith("K"))
+      .map((packet) => Number(packet.pts_time))
+      .sort((a, b) => a - b);
+    const gaps = keyframes.slice(1).map((time, index) => time - keyframes[index]);
+    const widest = Math.max(...gaps);
+    // A frame of slack: the forced keyframe is the first frame at or after each second.
+    assert.ok(widest < 1.05, `keyframes are up to ${widest.toFixed(3)}s apart`);
+  },
+);
+
+test(
+  "does not pad the audio of a video cut with encoder priming at each splice",
+  { skip: !HAS_FFMPEG },
+  (t) => {
+    const seconds = readPcm(cutVideo(t, "30")).length / SAMPLE_RATE;
+    // The single AAC encode may round the end up by a frame or two (23 ms each).
+    // Encoding every segment separately instead adds about 25 ms per splice on top.
+    assert.ok(
+      Math.abs(seconds - UNALIGNED_KEPT_SECONDS) < 0.05,
+      `audio runs ${seconds.toFixed(3)}s for ${UNALIGNED_KEPT_SECONDS.toFixed(3)}s kept`,
+    );
+  },
+);
+
+test(
+  "keeps a spliced tone continuous at every cut, with no raw phase jump or silence gap",
+  { skip: !HAS_FFMPEG },
+  (t) => {
+    const { dir, cleanup } = fixture();
+    t.after(cleanup);
+
+    const source = join(dir, "tone.wav");
+    execFileSync("ffmpeg", [
+      "-y",
+      "-hide_banner",
+      "-loglevel",
+      "error",
+      "-f",
+      "lavfi",
+      "-i",
+      `sine=frequency=440:duration=6:sample_rate=${SAMPLE_RATE}`,
+      source,
+    ]);
+
+    const transcriptPath = join(dir, "transcript.json");
+    writeFileSync(transcriptPath, JSON.stringify({ words: [{ text: "tone", start: 0, end: 6 }] }));
+
+    const output = join(dir, "out.wav");
+    // Two "ugly" removal ranges: neither aligned to the 440Hz period, so the kept
+    // segments' cut edges land at unrelated phases of the same continuous tone --
+    // exactly the shape that clicks without a fade, and the shape jrusso1020's
+    // review proved this branch never actually fades.
+    const result = run([
+      "--input",
+      source,
+      "--transcript",
+      transcriptPath,
+      "--remove",
+      "1.37-1.83,3.29-3.71",
+      "--out",
+      output,
+      "--json",
+    ]);
+    assert.equal(result.status, 0, result.stderr || result.stdout);
+
+    const samples = readPcm(output);
+    assert.ok(samples.length > SAMPLE_RATE, "expected several seconds of audio");
+
+    let maxStep = 0;
+    let zeroRun = 0;
+    let maxZeroRun = 0;
+    for (let i = 1; i < samples.length; i++) {
+      const step = Math.abs(samples[i] - samples[i - 1]);
+      if (step > maxStep) maxStep = step;
+      if (samples[i] === 0) {
+        zeroRun++;
+        if (zeroRun > maxZeroRun) maxZeroRun = zeroRun;
+      } else {
+        zeroRun = 0;
+      }
+    }
+
+    assert.ok(
+      maxStep <= MAX_CONTINUOUS_STEP,
+      `largest sample-to-sample step was ${maxStep}, expected <= ${MAX_CONTINUOUS_STEP} (a raw, unfaded splice)`,
+    );
+    assert.ok(
+      maxZeroRun < MIN_SUSPICIOUS_ZERO_RUN,
+      `found a run of ${maxZeroRun} consecutive zero samples, expected < ${MIN_SUSPICIOUS_ZERO_RUN} (a priming-silence gap)`,
+    );
+  },
+);
+
+// Frame 32 at 30 fps sits at 1.0666666 s. A -ss rounded to 1.067 lands just past
+// it, so ffmpeg's accurate seek starts that segment on frame 33 and the cut comes
+// out a frame short from the join on.
+const THIRTY_FPS_FRAME_32 = 32 / 30;
+
+test("a kept range starting on a 30 fps frame keeps that frame", { skip: !HAS_FFMPEG }, (t) => {
+  const { dir, cleanup } = fixture();
+  t.after(cleanup);
+
+  const source = join(dir, "src.mp4");
+  execFileSync("ffmpeg", [
+    "-y",
+    "-hide_banner",
+    "-loglevel",
+    "error",
+    "-f",
+    "lavfi",
+    "-i",
+    "testsrc2=size=320x180:rate=30",
+    "-f",
+    "lavfi",
+    "-i",
+    `sine=frequency=440:sample_rate=${SAMPLE_RATE}`,
+    "-t",
+    "4",
+    "-c:v",
+    "libx264",
+    "-pix_fmt",
+    "yuv420p",
+    "-c:a",
+    "aac",
+    source,
+  ]);
+
+  const transcriptPath = join(dir, "transcript.json");
+  writeFileSync(transcriptPath, JSON.stringify([{ text: "a", start: 0.1, end: 3.9 }]));
+
+  const output = join(dir, "out.mp4");
+  const result = run([
+    "--input",
+    source,
+    "--transcript",
+    transcriptPath,
+    "--keep",
+    `0-1,${THIRTY_FPS_FRAME_32}-3`,
+    "--out",
+    output,
+    "--json",
+  ]);
+  assert.equal(result.status, 0, result.stderr || result.stdout);
+
+  // Frames 0-29 for 0-1s, then frames 32-89 for the second segment. Rounding
+  // -ss to the millisecond drops frame 32 and yields 87.
+  const frames = Number(
+    execFileSync(
+      "ffprobe",
+      [
+        "-v",
+        "error",
+        "-select_streams",
+        "v",
+        "-count_packets",
+        "-show_entries",
+        "stream=nb_read_packets",
+        "-of",
+        "csv=p=0",
+        "--",
+        output,
+      ],
+      { encoding: "utf8" },
+    ).trim(),
+  );
+  assert.equal(frames, 88, `expected 88 frames, got ${frames}`);
+});