[Feature] Support MAE metric

[Yshuo-Li]

No description provided.

[codecov]

Codecov Report

Merging #871 (d310a8c) into master (1f1e9bc) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #871      +/-   ##
==========================================
+ Coverage   83.12%   83.18%   +0.06%     
==========================================
  Files         220      221       +1     
  Lines       12453    12508      +55     
  Branches     2017     2031      +14     
==========================================
+ Hits        10351    10405      +54     
- Misses       1785     1786       +1     
  Partials      317      317              

Flag	Coverage Δ
unittests	83.14% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmedit/core/__init__.py	100.00% <100.00%> (ø)
mmedit/core/evaluation/__init__.py	100.00% <100.00%> (ø)
mmedit/core/evaluation/metrics.py	97.07% <100.00%> (+0.28%)	⬆️
...edit/models/backbones/vfi_backbones/tof_vfi_net.py	94.18% <0.00%> (-4.66%)	⬇️
mmedit/core/evaluation/eval_hooks.py	61.53% <0.00%> (-0.63%)	⬇️
mmedit/datasets/__init__.py	100.00% <0.00%> (ø)
mmedit/datasets/vfi_vimeo90k_7frames_dataset.py	100.00% <0.00%> (ø)
mmedit/datasets/pipelines/augmentation.py	98.89% <0.00%> (+0.39%)	⬆️
mmedit/datasets/pipelines/formating.py	99.05% <0.00%> (+1.88%)	⬆️

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[wangruohui]

Should this function assume bgr input? Should it accept rgb too?

I suggest convert_to be some string like 'bgr2y' or 'rgb2y', and the mmcv.bgr2ycbcr is retrieved from a str to function dict.

func = convert_dict['rgb2y']
img1 = func(img1, y_only=True)