[Bugfix] Avoid enlarging MiniMax H3 reference images and videos (#8253)

Signed-off-by: lishunyang12 <lishunyang12@users.noreply.github.com>
Co-authored-by: lishunyang12 <lishunyang12@users.noreply.github.com>
Co-authored-by: Roger Wang <hey@rogerw.io>

tests/diffusion/models/minimax_h3/test_minimax_h3_contract.py

@@ -138,7 +138,7 @@ def test_local_encoder_modes_preserve_validated_text_and_unified_handoff(task, t
         (image.height // 32) * (image.width // 32), 96
     )
     pipeline.audio_vae = Mock()
-    prompt = {"prompt": "A person waves."}
+    prompt: dict[str, Any] = {"prompt": "A person waves."}
     if task != "t2va":
         prompt["multi_modal_data"] = {"image": Image.new("RGB", (256, 256))}
     if text_key is not None:
@@ -1487,19 +1487,39 @@ def test_rainfusion_packed_padding_stays_mask_free_on_unaligned_lengths():
     assert metadata.extra["valid_kv_length"] == 5
 
 
-def test_reference_image_resize_contract():
+@pytest.mark.parametrize(
+    ("size", "expected"),
+    [
+        ((1344, 768), (1344, 768)),
+        ((640, 384), (640, 384)),
+        ((2688, 1536), (2688, 1536)),
+        ((1536, 2688), (1536, 2688)),
+        ((3072, 3072), (3072, 3072)),
+        ((1080, 1440), (1088, 1440)),
+        ((648, 392), (640, 384)),
+    ],
+)
+def test_reference_image_resize_contract(size, expected):
     from PIL import Image
 
     from vllm_omni.model_executor.models.minimax_h3.preprocessing import (
         resolve_minimax_h3_reference_image_shape,
     )
 
-    assert resolve_minimax_h3_reference_image_shape(Image.new("RGB", (1080, 1440))) == (
-        2048,
-        2720,
+    assert resolve_minimax_h3_reference_image_shape(Image.new("RGB", size)) == expected
+
+
+def test_reference_image_resize_rejects_invalid_input():
+    from PIL import Image
+
+    from vllm_omni.model_executor.models.minimax_h3.preprocessing import (
+        resolve_minimax_h3_reference_image_shape,
     )
+
     with pytest.raises(ValueError, match="aspect ratio"):
         resolve_minimax_h3_reference_image_shape(Image.new("RGB", (100, 501)))
+    with pytest.raises(ValueError, match="dimensions"):
+        resolve_minimax_h3_reference_image_shape(Image.new("RGB", (128, 128)))
 
 
 def test_fl2va_supports_first_last_and_explicit_frame_index_contracts():
@@ -1678,13 +1698,26 @@ def test_encoder_forward_forwards_video_inputs():
     )
 
 
-def test_reference_video_shape_uses_h3_adapt_shape_policy():
+@pytest.mark.parametrize(
+    ("size", "expected"),
+    [
+        ((640, 384), (640, 384)),
+        ((384, 640), (384, 640)),
+        ((1280, 720), (1280, 704)),
+        ((1344, 768), (1344, 768)),
+        ((1920, 1152), (1280, 768)),
+        ((1152, 1920), (768, 1280)),
+        ((3844, 2160), (1344, 768)),
+        ((2160, 3844), (768, 1344)),
+        ((2048, 2048), (768, 768)),
+    ],
+)
+def test_reference_video_shape_caps_large_inputs_without_enlarging_small_inputs(size, expected):
     from vllm_omni.model_executor.models.minimax_h3.reference_video import (
         _reference_video_shape,
     )
 
-    assert _reference_video_shape(1280, 720) == (1344, 768)
-    assert _reference_video_shape(3844, 2160) == (1344, 768)
+    assert _reference_video_shape(*size) == expected
 
 
 def test_text_encoder_stub_constructs_without_group_or_weights():
@@ -2398,20 +2431,22 @@ def test_ref2va_reference_count_validation_preserves_client_error_metadata():
 
 
 @pytest.mark.parametrize(
-    ("case", "start_time", "expected_duration"),
+    ("case", "start_time", "expected_duration", "input_size", "expected_size"),
     [
-        ("R7", None, 10.0),
-        ("R8", 4.0, 6.0),
+        ("R7", None, 10.0, (3844, 2160), (1344, 768)),
+        ("R8", 4.0, 6.0, (640, 384), (640, 384)),
     ],
 )
-def test_r7_r8_ref2va_video_segment_matrix(monkeypatch, tmp_path, case, start_time, expected_duration):
+def test_r7_r8_ref2va_video_segment_matrix(
+    monkeypatch, tmp_path, case, start_time, expected_duration, input_size, expected_size
+):
     from vllm_omni.diffusion.models.minimax_h3 import reference_video as reference_video_module
 
     source = tmp_path / f"{case}.mp4"
     source.touch()
     metadata = {
-        "width": 1280,
-        "height": 720,
+        "width": input_size[0],
+        "height": input_size[1],
         "fps": 24.0,
         "frame_count": 240,
         "duration": 10.0,
@@ -2440,6 +2475,8 @@ def test_r7_r8_ref2va_video_segment_matrix(monkeypatch, tmp_path, case, start_ti
     assert prepared[0]["start_time_seconds"] == pytest.approx(start_time or 0.0)
     assert transcode_calls[0][1]["duration_seconds"] == pytest.approx(expected_duration)
     assert transcode_calls[0][1]["target_frame_count"] == 209
+    assert (prepared[0]["width"], prepared[0]["height"]) == expected_size
+    assert (transcode_calls[0][1]["target_width"], transcode_calls[0][1]["target_height"]) == expected_size
 
 
 def test_ref2va_transcode_zero_frame_count_keeps_video_stream(monkeypatch, tmp_path):