[Bugfix][MiniCPM-o] Bind omni-duplex video frames to the unit they close (#6404)

Signed-off-by: amy-why-3459 <wuhaiyan17@huawei.com>

tests/e2e/features/fullduplex/test_client.py

@@ -18,6 +18,10 @@ from vllm_omni.experimental.fullduplex.client import (
 from vllm_omni.experimental.fullduplex.minicpmo45.policy import (
     MiniCPMO45DuplexPolicy,
 )
+from vllm_omni.experimental.fullduplex.video_stacking import (
+    concat_frames,
+    unit_subframe_offsets,
+)
 
 pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
 
@@ -418,3 +422,62 @@ def test_realtime_client_pcm16_wav_round_trip(tmp_path):
         assert wav_file.getnchannels() == 1
         assert wav_file.getframerate() == 16_000
     assert read_pcm16_wav(path) == pcm16
+
+
+def _stack_test_image(color, size=(40, 30)):
+    from PIL import Image
+
+    return Image.new("RGB", size, color)
+
+
+def test_video_stacking_tiles_a_units_subframes_into_one_image():
+    frames = [_stack_test_image((255, 0, 0)), _stack_test_image((0, 255, 0))]
+
+    composite = concat_frames(frames)
+
+    # Landscape cells stack into a column because that canvas is squarer, and
+    # the interior seam carries the separator band that lets the model tell the
+    # sub-frames apart.
+    assert composite.size == (40, 30 * 2 + 6)
+    assert composite.getpixel((20, 30 + 3)) == (0, 0, 0)
+
+
+def test_video_stacking_picks_the_squarest_grid():
+    portrait = [_stack_test_image((255, 0, 0), size=(20, 60)) for _ in range(2)]
+    four = [_stack_test_image((0, 0, 255)) for _ in range(4)]
+
+    # A portrait clip tiles side by side, four frames always tile 2x2.
+    assert concat_frames(portrait).size == (20 * 2 + 6, 60)
+    assert concat_frames(four).size == (40 * 2 + 6, 30 * 2 + 6)
+
+
+def test_video_stacking_skips_the_subframe_that_duplicates_the_base_frame():
+    # Official samples stack_frames=5 as 0.2/0.4/0.6/0.8 s: offset 0 is the base
+    # frame, already sent as frame_list[0].
+    assert unit_subframe_offsets(5) == pytest.approx([0.2, 0.4, 0.6, 0.8])
+    assert unit_subframe_offsets(1) == []
+
+
+def test_realtime_client_sends_each_units_composite_beside_its_base_frame():
+    sent: list[dict] = []
+
+    class _Client(RealtimeDuplexClient):
+        def __init__(self):
+            pass
+
+        async def send(self, event):
+            sent.append(event)
+
+    asyncio.run(
+        _Client().stream_pcm16(
+            b"\x01\x00" * (16_000 * 3),
+            chunk_ms=200,
+            realtime=False,
+            video_frames=["f0", "f1"],
+            stacked_video_frames=["s0", None],
+        )
+    )
+
+    # A composite belongs to the unit it was captured in, so it rides the same
+    # append as that unit's base frame; a unit without one sends the base alone.
+    assert [event["video_frames"] for event in sent if "video_frames" in event] == [["f0", "s0"], ["f1"]]