**Highlights**
- Support [OmniSource](https://arxiv.org/abs/2003.13042)
- Support C3D
- Support video recognition with audio modality
- Support HVU
- Support X3D
**New Features**
- Support AVA dataset preparation ([266](https://github.com/open-mmlab/mmaction2/pull/266))
- Support the training of video recognition dataset with multiple tag categories ([235](https://github.com/open-mmlab/mmaction2/pull/235))
- Support joint training with multiple training datasets of multiple formats, including images, untrimmed videos, etc. ([242](https://github.com/open-mmlab/mmaction2/pull/242))
- Support to specify a start epoch to conduct evaluation ([216](https://github.com/open-mmlab/mmaction2/pull/216))
- Implement X3D models, support testing with model weights converted from SlowFast ([288](https://github.com/open-mmlab/mmaction2/pull/288))
**Improvements**
- Set default values of 'average_clips' in each config file so that there is no need to set it explicitly during testing in most cases ([232](https://github.com/open-mmlab/mmaction2/pull/232))
- Extend HVU datatools to generate individual file list for each tag category ([258](https://github.com/open-mmlab/mmaction2/pull/258))
- Support data preparation for Kinetics-600 and Kinetics-700 ([254](https://github.com/open-mmlab/mmaction2/pull/254))
- Add `cfg-options` in arguments to override some settings in the used config for convenience ([212](https://github.com/open-mmlab/mmaction2/pull/212))
- Rename the old evaluating protocol `mean_average_precision` as `mmit_mean_average_precision` since it is only used on MMIT and is not the `mAP` we usually talk about. Add `mean_average_precision`, which is the real `mAP` ([235](https://github.com/open-mmlab/mmaction2/pull/235))
- Add accurate setting (Three crop * 2 clip) and report corresponding performance for TSM model ([241](https://github.com/open-mmlab/mmaction2/pull/241))
- Add citations in each preparing_dataset.md in `tools/data/dataset` ([289](https://github.com/open-mmlab/mmaction2/pull/289))
- Update the performance of audio-visual fusion on Kinetics-400 ([281](https://github.com/open-mmlab/mmaction2/pull/281))
- Support data preparation of OmniSource web datasets, including GoogleImage, InsImage, InsVideo and KineticsRawVideo ([294](https://github.com/open-mmlab/mmaction2/pull/294))
- Use `metric_options` dict to provide metric args in `evaluate` ([286](https://github.com/open-mmlab/mmaction2/pull/286))
**Bug Fixes**
- Register `FrameSelector` in `PIPELINES` ([268](https://github.com/open-mmlab/mmaction2/pull/268))
- Fix the potential bug for default value in dataset_setting ([245](https://github.com/open-mmlab/mmaction2/pull/245))
- Fix the data preparation bug for `something-something` dataset ([278](https://github.com/open-mmlab/mmaction2/pull/278))
- Fix the invalid config url in slowonly README data benchmark ([249](https://github.com/open-mmlab/mmaction2/pull/249))
- Validate that the performance of models trained with videos have no significant difference comparing to the performance of models trained with rawframes ([256](https://github.com/open-mmlab/mmaction2/pull/256))
- Correct the `img_norm_cfg` used by TSN-3seg-R50 UCF-101 model, improve the Top-1 accuracy by 3% ([273](https://github.com/open-mmlab/mmaction2/pull/273))
**ModelZoo**
- Add Baselines for Kinetics-600 and Kinetics-700, including TSN-R50-8seg and SlowOnly-R50-8x8 ([259](https://github.com/open-mmlab/mmaction2/pull/259))
- Add OmniSource benchmark on MiniKineitcs ([296](https://github.com/open-mmlab/mmaction2/pull/296))
- Add Baselines for HVU, including TSN-R18-8seg on 6 tag categories of HVU ([287](https://github.com/open-mmlab/mmaction2/pull/287))
- Add X3D models ported from [SlowFast](https://github.com/facebookresearch/SlowFast/) ([#288](https://github.com/open-mmlab/mmaction2/pull/288))