[Improvement] Add warnings of uninstalling mmdet and supplementary do…

…cuments (#624)

* update

* remove mmdet bound

* fix bugs

README.md

@@ -47,6 +47,8 @@ The master branch works with **PyTorch 1.3+**.
 
   - For temporal action localization, we implement BSN, BMN, SSN.
 
+  - For spatial temporal detection, we implement SlowOnly, SlowFast.
+
 - **Well tested and documented**
 
   We provide detailed documentation and API reference, as well as unittests.

docs/install.md

@@ -113,7 +113,7 @@ pip install mmcv-full
 
 **Important:** You need to run `pip uninstall mmcv` first if you have mmcv installed. If mmcv and mmcv-full are both installed, there will be `ModuleNotFoundError`.
 
-d. Clone the MMAction2 repository
+d. Clone the MMAction2 repository.
 
 ```shell
 git clone https://github.com/open-mmlab/mmaction2.git
@@ -133,6 +133,12 @@ If you build MMAction2 on macOS, replace the last command with
 CC=clang CXX=clang++ CFLAGS='-stdlib=libc++' pip install -e .
 ```
 
+f. Install mmdetection for spatial temporal detection tasks.
+
+This part is **optional** if you're not going to do spatial temporal detection.
+
+See [here](https://github.com/open-mmlab/mmdetection#installation) to install mmdetection.
+
 Note:
 
 1. The git commit id will be written to the version number with step d, e.g. 0.6.0+2e7045c. The version will also be saved in trained models.

mmaction/models/builder.py

@@ -74,6 +74,10 @@ def build_model(cfg, train_cfg=None, test_cfg=None):
         return build_recognizer(cfg, train_cfg, test_cfg)
     if obj_type in DETECTORS:
         return build_detector(cfg, train_cfg, test_cfg)
+    model_in_mmdet = ['FastRCNN']
+    if obj_type in model_in_mmdet:
+        raise ImportError(
+            'Please install mmdet for spatial temporal detection tasks.')
     raise ValueError(f'{obj_type} is not registered in '
                      'LOCALIZERS, RECOGNIZERS or DETECTORS')