perf(dash): collapse single-URL byte-range segments into one direct download

Also throttle hedge-median recompute to 0.5s, cache replace_fields format
patterns and short-circuit when no $ token, and stream HLS merge with
copyfileobj. Adds test_dash_collapse and live A/B tooling.

scripts/live_manifest_test.py

@@ -7,6 +7,9 @@ The controller logs its worker-target changes to a JSON-lines debug log; this sc
 reads them back and prints the scaling sequence per stream, so you can see whether the
 downloader ramps workers up against each CDN or finishes before the controller acts.
 
+STREAMS carries a public 4K/HDR/Dolby-Vision tier (labels uhd-hevc, dv-atmos, hevc-hls,
+h265-cmaf) for exercising large high-bitrate tracks; filter it with --only uhd / dv / hevc / h265.
+
 Throwaway-ish operational tool: it makes real network requests to public test assets.
 Run: uv run python scripts/live_manifest_test.py [--workers N] [--track smallest|largest]
 """
@@ -17,7 +20,6 @@ import json
 import shutil
 import sys
 import time
-from functools import partial
 from pathlib import Path
 from tempfile import mkdtemp
 from typing import Any, Optional
@@ -33,16 +35,51 @@ from unshackle.core.utilities import close_debug_logger, init_debug_logger
 # all three formats on Unified Streaming, so the formats are comparable on one CDN.
 STREAMS: list[tuple[str, Any, str, str]] = [
     ("HLS", HLS, "mux", "https://test-streams.mux.dev/x36xhzz/x36xhzz.m3u8"),
-    ("HLS", HLS, "unified", "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/.m3u8"),
+    (
+        "HLS",
+        HLS,
+        "unified",
+        "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/.m3u8",
+    ),
     ("DASH", DASH, "akamai", "https://dash.akamaized.net/akamai/bbb_30fps/bbb_30fps.mpd"),
-    ("DASH", DASH, "unified", "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/.mpd"),
+    (
+        "DASH",
+        DASH,
+        "unified",
+        "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/.mpd",
+    ),
     ("DASH", DASH, "dashif", "https://livesim2.dashif.org/vod/testpic_2s/Manifest.mpd"),
-    ("ISM", ISM, "unified", "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/Manifest"),
-    ("HLS", HLS, "apple", "https://devstreaming-cdn.apple.com/videos/streaming/examples/img_bipbop_adv_example_fmp4/master.m3u8"),
+    (
+        "ISM",
+        ISM,
+        "unified",
+        "https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/Manifest",
+    ),
+    (
+        "HLS",
+        HLS,
+        "apple",
+        "https://devstreaming-cdn.apple.com/videos/streaming/examples/img_bipbop_adv_example_fmp4/master.m3u8",
+    ),
     ("HLS", HLS, "gcs", "https://storage.googleapis.com/shaka-demo-assets/angel-one-hls/hls.m3u8"),
     ("DASH", DASH, "gcs", "https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd"),
     ("DASH", DASH, "axinom", "https://media.axprod.net/TestVectors/v7-Clear/Manifest_1080p.mpd"),
-    ("ISM", ISM, "dtaps", "https://playready.directtaps.net/smoothstreaming/SSWSS720H264/SuperSpeedway_720.ism/Manifest"),
+    (
+        "ISM",
+        ISM,
+        "dtaps",
+        "https://playready.directtaps.net/smoothstreaming/SSWSS720H264/SuperSpeedway_720.ism/Manifest",
+    ),
+    # public 4K / HDR / Dolby-Vision tier: large high-bitrate tracks, no auth
+    ("DASH", DASH, "uhd-hevc", "https://dash.akamaized.net/dash264/TestCasesUHD/2b/11/MultiRate.mpd"),
+    ("HLS", HLS, "dv-atmos", "https://devstreaming-cdn.apple.com/videos/streaming/examples/adv_dv_atmos/main.m3u8"),
+    (
+        "HLS",
+        HLS,
+        "hevc-hls",
+        "https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_adv_example_hevc/master.m3u8",
+    ),
+    ("DASH", DASH, "h265-cmaf", "https://media.axprod.net/TestVectors/H265/clear_cmaf_1080p_h265/manifest.mpd"),
 ]
 
 
@@ -97,18 +134,20 @@ def run_one(label: str, parser: Any, cdn: str, url: str, workers: int, which: st
     save_path = work / "out.mp4"
     counter = Counter()
     # adaptive_workers only exists on the downloader-speed branch; skip on older checkouts
-    extra = {"adaptive_workers": True} if "adaptive_workers" in getattr(DownloadContext, "__dataclass_fields__", {}) else {}
+    extra = (
+        {"adaptive_workers": True} if "adaptive_workers" in getattr(DownloadContext, "__dataclass_fields__", {}) else {}
+    )
     ctx = DownloadContext(
         save_path=save_path,
         save_dir=work / "segs",
-        progress=partial(counter.__call__),
+        progress=counter,
         session=session,
         proxy=None,
         max_workers=workers,
         **extra,
     )
-    ctx.progress = counter  # type: ignore[assignment]
 
+    track.drm = None  # download-speed only: time raw segment download, no license/decrypt
     t0 = time.time()
     err = ""
     try:
@@ -123,14 +162,17 @@ def run_one(label: str, parser: Any, cdn: str, url: str, workers: int, which: st
     moves, _ = read_new_transitions(log_path, line0)
     scaling = " ".join(moves) if moves else "none (finished under controller tick)"
     res = f"{getattr(track, 'width', '?')}x{getattr(track, 'height', '?')}"
-    return f"{label:5} {cdn:8} {dt:6.1f}s {size/1e6:7.1f}MB {mbps:6.1f}MB/s  [{res}]  workers: {scaling}{err}"
+    return f"{label:5} {cdn:8} {dt:6.1f}s {size / 1e6:7.1f}MB {mbps:6.1f}MB/s  [{res}]  workers: {scaling}{err}"
 
 
 @click.command()
 @click.option("--workers", default=16, help="max workers (the adaptive ceiling)")
 @click.option("--track", "which", type=click.Choice(["smallest", "largest"]), default="largest")
-@click.option("--only", default="", help="substring filter on CDN/format labels (e.g. 'gcs' or 'ISM')")
+@click.option("--only", default="", help="substring filter on CDN/format labels (e.g. 'apple' or 'ISM')")
 def main(workers: int, which: str, only: str) -> None:
+    # download-speed only: skip HLS key handling so segments just download, no license server
+    HLS.get_drm = staticmethod(lambda *a, **k: None)  # type: ignore[assignment]
+
     log_path = Path(mkdtemp(prefix="live_dbg_")) / "debug.jsonl"
     init_debug_logger(log_path=log_path, enabled=True)
     print(f"debug log: {log_path}\ntrack: {which}, max_workers: {workers}\n")