From 95f467b4adb1f3e2aab624138ef503fbe63cd73b Mon Sep 17 00:00:00 2001
From: Victor Kuznetsov <kuznetsov.va@gmail.com>
Date: Fri, 28 Aug 2026 19:44:25 -0700
Subject: [PATCH] Register the Doubao video mark with a corpus-calibrated
 single-floor policy

detect_doubao_frame reuses the image engine's synthetic doubao alpha as its
video template, so the glyph cannot drift between registries. The policy is
seedance-style single-floor, calibrated by sequential decode over 39
TC260-confirmed Doubao corpus videos and 25 negatives: a 12-frame stable run
at 0.35 accepts 33/39 positives and 0/25 negatives (0.30 already accepted a
negative), and through the shipped arbiter identify_video selects 32/39 with
no false selection. Also documents the measured impossibility of a bare-pill
removal arm with the current detector (68 OCR-confirmed pills max 0.317 vs
clean negatives max 0.353 -- no separating threshold exists).
---
 data/fixtures/visible/doubao/example.mp4  | Bin 0 -> 96689 bytes
 docs/cli.md                               |   4 +-
 docs/module-internals.md                  |  38 +++++++++++-
 docs/supported-signals.md                 |   1 +
 scripts/render_visible_examples.py        |   2 +
 src/remove_ai_watermarks/video.py         |   3 +-
 src/remove_ai_watermarks/video_visible.py |  68 ++++++++++++++++++++++
 tests/test_video.py                       |  10 ++--
 8 files changed, 115 insertions(+), 11 deletions(-)
 create mode 100644 data/fixtures/visible/doubao/example.mp4

diff --git a/data/fixtures/visible/doubao/example.mp4 b/data/fixtures/visible/doubao/example.mp4
new file mode 100644
index 0000000000000000000000000000000000000000..46781ed7740a57f17f51bfa3e0be0bae89704df4
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diff --git a/docs/cli.md b/docs/cli.md
index e7aa169..ff99e4d 100644
--- a/docs/cli.md
+++ b/docs/cli.md
@@ -327,8 +327,8 @@ provider provenance may relax the visual score only for registered
 provenance-aware marks; metadata alone never creates a detection.
 
 `--mark auto` is the default. It evaluates all providers in one decode pass and
-selects the first stable match in specificity order: Sora, Veo, Seedance, Dola,
-Hailuo AI, then Kling AI. Their confidence scores are independently calibrated and
+selects the first stable match in specificity order: Sora, Veo, Seedance,
+Doubao, Dola, Hailuo AI, then Kling AI. Their confidence scores are independently calibrated and
 are not compared across providers. Pass an explicit `--mark` to scan only that
 provider.
 
diff --git a/docs/module-internals.md b/docs/module-internals.md
index 90e8305..3e17577 100644
--- a/docs/module-internals.md
+++ b/docs/module-internals.md
@@ -296,7 +296,7 @@ from the gate. The full-clip oracle floor is
 detected while `0.15` did not.
 
 [`video_visible.py`](../src/remove_ai_watermarks/video_visible.py) implements
-the first pixel stages for Sora, Veo, Seedance, Dola, Hailuo AI, and Kling AI. The
+the first pixel stages for Sora, Veo, Seedance, Doubao, Dola, Hailuo AI, and Kling AI. The
 Sora detector searches a normalized frame with a fully synthetic
 mascot-and-text silhouette at several scales. The Veo detector uses separate
 synthetic silhouettes for the current four-point diamond and legacy `Veo`
@@ -327,8 +327,8 @@ carries `accepts_provenance`, which forces `provenance=False` for Hailuo AI and
 — they have no metadata that could confirm them, and the guarantee used to be
 structural (their wrappers took no `provenance` parameter at all). Provenance can relax a low-contrast run only
 after recurring visual evidence exists. Sora transition frames follow the
-nearest confirmed moving position only with Sora provenance. Seedance, Dola,
-Hailuo AI, and Kling AI additionally require candidates to remain anchored to the
+nearest confirmed moving position only with Sora provenance. Seedance, Doubao,
+Dola, Hailuo AI, and Kling AI additionally require candidates to remain anchored to the
 start of a run. This rejects slowly drifting scene details that still have
 high frame-to-frame overlap. Hailuo AI and Kling AI do not infer provenance from
 technical encoder tags; their confirmed public samples carried no provider
@@ -855,6 +855,22 @@ two-line mark can be light on dark scenes or dark on light scenes. Its detector
 and footprint both use the same best-match box. The separate one-line overlay
 variant is not covered.
 
+#### Bare-upload pill arm: measured impossible with the current detector (2026-08-28)
+
+`_keep_pill` never removes a metadata-bare pill, and the question "can a bare arm
+(score + footprint-flatness) be opened" was measured to a closed NO over the local
+spaces corpus: 68 OCR-confirmed bare pills (an independent pixel-level label: the
+band sweep read a flush-left `AI生成`) score p50 0.181 / max 0.317, while 799 clean
+no-signal negatives reach 0.353 and 18 of them already pass the shipped 0.22 raw
+gate. The true-pill and clean distributions overlap completely -- there is no
+threshold -- and the engine's own high scores (0.34-0.48 on the flagged cohort)
+correlate with textured corners, not with pills: the edge-NCC keys on "text-like
+structure top-left". As with the Jimeng wordmark's silhouette, no threshold repairs
+this; a bare arm needs a detector that keys on the pill's rounded-rectangle
+geometry, and until one exists the bare-arm question is settled by this
+measurement, not by gate tuning. Harness: `data/spaces/_pill_bare_measure.py`
+(cohorts A/B/C over the no-signal pool).
+
 The capture-less Jimeng pill lives in
 [`pill_engine.py`](../src/remove_ai_watermarks/pill_engine.py). It uses a
 synthetic silhouette for detection and a fixed top-left footprint.
@@ -866,6 +882,22 @@ Shared behavior is covered by:
 - [`test_text_mark_faint_mask.py`](../tests/test_text_mark_faint_mask.py)
 - [`test_text_mark_memory.py`](../tests/test_text_mark_memory.py)
 
+#### Doubao video mark (2026-08-28 registration)
+
+`detect_doubao_frame` reuses the image engine's synthetic `doubao_alpha.png` as
+its video template (same `豆包AI生成` run, bottom-right) through
+`_asset_template`, so image and video cannot drift apart on the glyph. Search
+profile: heights 3.2-6.0 percent of the short side from origin (0.60, 0.76),
+measured on the corpus. Policy is seedance-style single-floor: weak 0.35 /
+strong 0.55 / anchor IoU 0.80, calibrated by sequential decode over 39
+TC260-confirmed Doubao videos and 25 negatives -- a 12-frame stable run at 0.35
+accepts 33/39 positives and 0/25 negatives, while 0.30 already accepted one
+negative, so the bar stays at 0.35. Through the shipped arbiter
+(`identify_video`): 32/39 selected as doubao, 0/25 false; the remainder split
+between no stable run (5) and cross-template ties handed to earlier table
+entries (sora 1, kling 1) -- the registry's known order-decides behavior, not a
+doubao-specific defect. Harness: `data/spaces/_doubao_seq_measure.py`.
+
 ### Fill backends and region erasing
 
 [`region_eraser.py`](../src/remove_ai_watermarks/region_eraser.py) implements the
diff --git a/docs/supported-signals.md b/docs/supported-signals.md
index 6c9f5b5..f6d5274 100644
--- a/docs/supported-signals.md
+++ b/docs/supported-signals.md
@@ -40,6 +40,7 @@ detectors' canonical geometry and house style, not vendor raster fidelity.
 | --- | --- | --- | --- |
 | `sora` | Sora 2 mascot and wordmark | Moves among frame positions | Requires a temporally recurring visual match; the older Sora Turbo corner swirl is a different unsupported mark. |
 | `veo` | Current four-point diamond and legacy `Veo` text | Fixed bottom-right corner | Uses separate silhouettes and requires a recurring match; learned fill is preferable on structured backgrounds. |
+| `doubao` | `豆包AI生成` text run | Fixed bottom-right corner | Reuses the image engine's synthetic alpha as the template; a stable 12-frame run above 0.35 is required. |
 | `seedance` | Boxed `AI` label | Fixed bottom-right corner | Requires an anchored recurring match; the full localized box is filled because a thinner synthetic shape mask leaves the real translucent rim behind. |
 | `dola` | `Dola AI` text | Fixed bottom-right corner | Requires an anchored recurring match; ByteDance or BytePlus provenance can relax only an existing visual run. |
 | `hailuo` | `MINIMAX \| hailuo AI` composite label | Fixed lower edge | Uses a synthetic waveform, text, separator, and ring silhouette; the complete recurring label box is filled. A TC260 label naming MiniMax as producer can relax only an existing stable run. |
diff --git a/scripts/render_visible_examples.py b/scripts/render_visible_examples.py
index 55918c7..d4fa65a 100644
--- a/scripts/render_visible_examples.py
+++ b/scripts/render_visible_examples.py
@@ -187,6 +187,8 @@ def _video_mark_frame(key: str, w: int, h: int) -> np.ndarray:
         return _composite_light(base, cv2.resize(tmpl, (tw, th)).astype(np.float32) / 255.0, x, y, 250)
     elif key == "seedance":
         tmpl, scale, x, y = templates["seedance"], 0.095, int(w * 0.74), int(h * 0.80)
+    elif key == "doubao":
+        tmpl, scale, x, y = templates["doubao"], 0.048, int(w * 0.72), int(h * 0.82)
     elif key == "dola":
         tmpl, scale, x, y = templates["dola"], 0.036, int(w * 0.70), int(h * 0.88)
     elif key == "hailuo":
diff --git a/src/remove_ai_watermarks/video.py b/src/remove_ai_watermarks/video.py
index aac4900..3266c5e 100644
--- a/src/remove_ai_watermarks/video.py
+++ b/src/remove_ai_watermarks/video.py
@@ -25,7 +25,7 @@ if TYPE_CHECKING:
     from remove_ai_watermarks.video_visible import VideoScan
 
 VIDEO_EXTENSIONS: frozenset[str] = frozenset({".mp4", ".mov", ".m4v", ".webm", ".mkv", ".avi", ".flv"})
-VIDEO_VISIBLE_MARKS = ("sora", "veo", "seedance", "dola", "hailuo", "kling")
+VIDEO_VISIBLE_MARKS = ("sora", "veo", "seedance", "doubao", "dola", "hailuo", "kling")
 _ISOBMFF_VIDEO_EXTENSIONS: frozenset[str] = frozenset({".mp4", ".mov", ".m4v"})
 _EBML_VIDEO_EXTENSIONS: frozenset[str] = frozenset({".webm", ".mkv"})
 _RIFF_VIDEO_EXTENSIONS: frozenset[str] = frozenset({".avi"})
@@ -178,6 +178,7 @@ _VISIBLE_PLATFORM = {
     "sora": "OpenAI Sora",
     "veo": "Google Veo",
     "seedance": "ByteDance Seedance",
+    "doubao": "ByteDance Doubao",
     "dola": "ByteDance Dola",
     "hailuo": "MiniMax Hailuo AI",
     "kling": "Kuaishou Kling AI",
diff --git a/src/remove_ai_watermarks/video_visible.py b/src/remove_ai_watermarks/video_visible.py
index 0ce442b..46bc91e 100644
--- a/src/remove_ai_watermarks/video_visible.py
+++ b/src/remove_ai_watermarks/video_visible.py
@@ -313,6 +313,28 @@ def _top_hat(gray: NDArray[Any]) -> NDArray[Any]:
 
 
 @lru_cache(maxsize=1)
+def _asset_template(name: str) -> NDArray[Any]:
+    """Load a package asset as a video detect template (white glyph on black).
+
+    The image-registry alpha maps are the same synthetic silhouettes the image
+    engines match; a video mark that shares the glyph reuses the asset instead of
+    re-rendering it. No source frame contributes pixels.
+    """
+    from pathlib import Path as _P
+
+    from remove_ai_watermarks.image_io import imread as _imread
+
+    at = _imread(str(_P(__file__).parent / "assets" / name), 2)
+    if at is None:
+        raise RuntimeError(f"missing video template asset: {name}")
+    return at
+
+
+@lru_cache(maxsize=1)
+def _doubao_template() -> NDArray[Any]:
+    return _asset_template("doubao_alpha.png")
+
+
 def _template_sources() -> dict[str, NDArray[Any]]:
     """Return every immutable synthetic template by detector-local key."""
     sora_word, sora_icon = _sora_templates()
@@ -326,6 +348,9 @@ def _template_sources() -> dict[str, NDArray[Any]]:
         "dola": _dola_template(),
         "hailuo": _hailuo_template(),
         "kling-logo": _kling_logo_template(),
+        # The Doubao video mark is the same "豆包AI生成" run the image engine
+        # matches (its synthetic alpha asset), bottom-right on video frames.
+        "doubao": _doubao_template(),
     }
     sources.update({f"kling-{index}": template for index, template in enumerate(_kling_templates())})
     return sources
@@ -606,6 +631,32 @@ def detect_seedance_frame(
     )
 
 
+def detect_doubao_frame(
+    image_bgr: NDArray[Any],
+    *,
+    frame_index: int = 0,
+    prepared: _PreparedFrame | None = None,
+) -> FrameLocalization:
+    """Locate the strongest fixed Doubao "豆包AI生成" text candidate.
+
+    The ByteDance Doubao mark registered for IMAGES also appears burned into the
+    bottom-right of Doubao VIDEO exports; this detector reuses the image engine's
+    synthetic alpha as the template. Search profile measured on the local spaces
+    corpus (48 TC260-confirmed Doubao videos, 2026-08-28): the run sits at
+    cx 0.83-0.90 / bottom-flush, heights swept 3.2-6.0 percent of the short side.
+    """
+    return _detect_fixed_mark(
+        image_bgr,
+        "doubao",
+        relative_heights=tuple(value / 1000 for value in range(32, 61, 4)),
+        search_origin=(0.60, 0.76),
+        kernel_fraction=0.14,
+        prefer_larger_within=0.04,
+        normalized=None if prepared is None else (prepared.normalized_gray, prepared.normalized_scale),
+        frame_index=frame_index,
+    )
+
+
 def detect_dola_frame(
     image_bgr: NDArray[Any],
     *,
@@ -952,6 +1003,22 @@ VISIBLE_MARK_POLICIES: dict[str, VisibleMarkPolicy] = {
         padding_fraction=0.0,
         mask_style="box",
     ),
+    "doubao": VisibleMarkPolicy(
+        # One floor at either trust level (seedance-style: the TC260 producer
+        # confirms the vendor inside the arbiter; the confidence bar does not
+        # move). Floors measured 2026-08-28 on the local spaces corpus with
+        # sequential decode: a >=0.35 stable run of 12+ frames accepts 33/39
+        # TC260-confirmed Doubao videos and 0/25 no-Doubao negatives; 0.30
+        # already accepted 1 negative, so the bar stays at 0.35.
+        weak_floor=0.35,
+        strong_floor=0.55,
+        transition_floor=0.30,
+        min_stable_frames=_MIN_FIXED_MARK_STABLE_FRAMES,
+        cover_after_confirmation=True,
+        anchor_iou=0.80,
+        padding_fraction=0.0,
+        mask_style="box",
+    ),
     "dola": VisibleMarkPolicy(
         weak_floor=_DOLA_STRICT_WEAK_CONFIDENCE,
         provenance_weak_floor=_DOLA_PROVENANCE_WEAK_CONFIDENCE,
@@ -1181,6 +1248,7 @@ def scan_video_marks(
                 detect_sora_frame,
                 detect_veo_frame,
                 detect_seedance_frame,
+                detect_doubao_frame,
                 detect_dola_frame,
                 detect_hailuo_frame,
                 detect_kling_frame,
diff --git a/tests/test_video.py b/tests/test_video.py
index d210de6..e51125c 100644
--- a/tests/test_video.py
+++ b/tests/test_video.py
@@ -924,7 +924,7 @@ class TestVideoProvenanceApi:
         assert report.visible_mark == "sora"
         assert report.visible_detected_frames == 5
         assert report.total_frames == 5
-        assert tuple(VIDEO_VISIBLE_MARKS) == ("sora", "veo", "seedance", "dola", "hailuo", "kling")
+        assert tuple(VIDEO_VISIBLE_MARKS) == ("sora", "veo", "seedance", "doubao", "dola", "hailuo", "kling")
 
     def test_reports_unknown_instead_of_clean(self, tmp_path: Path):
         from remove_ai_watermarks.video import identify_video
@@ -2085,10 +2085,10 @@ class TestVideoVisibleScan:
 
         scans = scan_video_marks(
             tmp_path / "synthetic.mp4",
-            ("sora", "veo", "seedance", "dola", "hailuo", "kling"),
+            ("sora", "veo", "seedance", "doubao", "dola", "hailuo", "kling"),
         )
 
-        assert set(scans) == {"sora", "veo", "seedance", "dola", "hailuo", "kling"}
+        assert set(scans) == {"sora", "veo", "seedance", "doubao", "dola", "hailuo", "kling"}
         assert all(scan.timestamps == (0.25,) for scan in scans.values())
         assert len(prepared_ids) == 6
         assert len(set(prepared_ids)) == 1
@@ -2576,7 +2576,7 @@ class TestVideoVisibleApi:
         )
 
         def fake_scan(_source: Path, marks: tuple[str, ...]):
-            assert marks == ("sora", "veo", "seedance", "dola", "hailuo", "kling")
+            assert marks == ("sora", "veo", "seedance", "doubao", "dola", "hailuo", "kling")
             return {
                 "sora": sora_scan,
                 "veo": sora_scan,
@@ -2792,7 +2792,7 @@ class TestVideoVisibleCli:
 
         assert result.exit_code == 0, result.output
         assert "temporally stable" in result.output
-        assert "auto|sora|veo|seedance|dola|hailuo|kling" in result.output
+        assert "auto|sora|veo|seedance|doubao|dola|hailuo|kling" in result.output
         assert "--temporal-consistency" in result.output
 
     def test_reports_removed_frames(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch):