feat(video): 添加原始变速效果支持

- 在常量定义中新增 ospeed 效果类型用于兼容旧模板
- 在任务域中实现 get_ospeed_params 方法解析变速参数
- 修改视频渲染处理器合并 speed 与 ospeed 效果计算
- 更新时长计算逻辑以正确处理 ospeed 变速影响
- 新增 ospeed 参数验证和边界值处理机制
- 添加完整的 ospeed 效果单元测试覆盖各种场景

tests/unit/test_render_video_effects.py

@@ -82,3 +82,139 @@ def test_build_video_filters_zoom_and_camera_shot_stack_in_order(tmp_path):
     assert camera_shot_marker in filters
     assert zoom_marker in filters
     assert filters.index(camera_shot_marker) < filters.index(zoom_marker)
+
+
+# ---------- ospeed 测试 ----------
+
+def test_get_ospeed_params_with_valid_values():
+    effect = Effect.from_string('ospeed:2')
+    assert effect is not None
+    assert effect.get_ospeed_params() == pytest.approx(2.0)
+
+    effect2 = Effect.from_string('ospeed:0.5')
+    assert effect2 is not None
+    assert effect2.get_ospeed_params() == pytest.approx(0.5)
+
+
+@pytest.mark.parametrize(
+    'effect_str',
+    [
+        'ospeed:0',
+        'ospeed:-1',
+        'ospeed:nan',
+        'ospeed:inf',
+        'ospeed:abc',
+        'ospeed:',
+    ],
+)
+def test_get_ospeed_params_invalid_values_fallback(effect_str):
+    effect = Effect.from_string(effect_str)
+    assert effect is not None
+    assert effect.get_ospeed_params() == 1.0
+
+
+def test_get_ospeed_params_no_params():
+    effect = Effect.from_string('ospeed')
+    assert effect is not None
+    assert effect.get_ospeed_params() == 1.0
+
+
+def test_ospeed_does_not_trigger_filter_complex(tmp_path):
+    handler = _create_handler(tmp_path)
+    render_spec = RenderSpec(effects='ospeed:2')
+    output_spec = OutputSpec(width=1080, height=1920, fps=30)
+
+    command = handler._build_command(
+        input_file='input.mp4',
+        output_file='output.mp4',
+        render_spec=render_spec,
+        output_spec=output_spec,
+        duration_ms=6000,
+    )
+
+    assert '-vf' in command
+    assert '-filter_complex' not in command
+    # 验证 setpts 滤镜
+    vf_idx = command.index('-vf')
+    vf_value = command[vf_idx + 1]
+    assert 'setpts=2.0*PTS' in vf_value
+
+
+def test_ospeed_combined_with_speed(tmp_path):
+    handler = _create_handler(tmp_path)
+    # speed=2 → 1/2=0.5, ospeed=3 → 0.5*3=1.5
+    render_spec = RenderSpec(speed='2', effects='ospeed:3')
+    output_spec = OutputSpec(width=1080, height=1920, fps=30)
+
+    filters = handler._build_video_filters(
+        render_spec=render_spec,
+        output_spec=output_spec,
+        duration_ms=6000,
+        source_duration_sec=10.0,
+    )
+
+    assert 'setpts=1.5*PTS' in filters
+
+
+def test_ospeed_with_complex_effects(tmp_path):
+    handler = _create_handler(tmp_path)
+    render_spec = RenderSpec(effects='ospeed:2|zoom:1,1.2,2')
+    output_spec = OutputSpec(width=1080, height=1920, fps=30)
+
+    filters = handler._build_video_filters(
+        render_spec=render_spec,
+        output_spec=output_spec,
+        duration_ms=8000,
+        source_duration_sec=10.0,
+    )
+
+    # zoom 触发 filter_complex
+    assert '[v_base]' in filters
+    # setpts 在 base_chain 中
+    assert 'setpts=2.0*PTS' in filters
+    # zoom 正常处理
+    assert "overlay=0:0:enable='between(t,1.0,3.0)'" in filters
+
+
+def test_only_first_ospeed_is_used(tmp_path):
+    handler = _create_handler(tmp_path)
+    render_spec = RenderSpec(effects='ospeed:2|ospeed:5')
+    output_spec = OutputSpec(width=1080, height=1920, fps=30)
+
+    filters = handler._build_video_filters(
+        render_spec=render_spec,
+        output_spec=output_spec,
+        duration_ms=6000,
+        source_duration_sec=10.0,
+    )
+
+    assert 'setpts=2.0*PTS' in filters
+    assert 'setpts=5.0*PTS' not in filters
+
+
+def test_ospeed_affects_tpad_calculation(tmp_path):
+    handler = _create_handler(tmp_path)
+    # ospeed:2 使 10s 视频变为 20s 有效时长，目标 6s → 无需 tpad
+    render_spec = RenderSpec(effects='ospeed:2')
+    output_spec = OutputSpec(width=1080, height=1920, fps=30)
+
+    filters = handler._build_video_filters(
+        render_spec=render_spec,
+        output_spec=output_spec,
+        duration_ms=6000,
+        source_duration_sec=10.0,
+    )
+
+    assert 'tpad' not in filters
+
+    # 对比：无 ospeed 时 10s 视频 → 目标 15s → 需要 5s tpad
+    render_spec_no_ospeed = RenderSpec()
+    filters_no_ospeed = handler._build_video_filters(
+        render_spec=render_spec_no_ospeed,
+        output_spec=output_spec,
+        duration_ms=15000,
+        source_duration_sec=10.0,
+    )
+
+    assert 'tpad' in filters_no_ospeed
+    assert 'stop_duration=5.0' in filters_no_ospeed