add --to-mp4 argument to resize_videos.py

[makecent]

Motivation

Current resize_videos.py doesn't support resizing .webm videos.

1. It can be solved by change the -c:v libx264 to -c:v libvpx:

   mmaction2/tools/data/resize_videos.py

   Line 34 in cf15d56

   f'-c:v libx264 {"-g 16" if args.dense else ""} '

2. Or just outputting .mp4 videos, which is what this PR does.

I choose the second solution because I found writing .mp4 files saved lots of time. BTW, it requires lots of extra time to write the resized videos (which run in the background) after the python script execution is finished.

Modification

Add --to-mp4 argument, to output .mp4 files.

Others

I had tested it on the ActivityNet dataset, which contains .mkv, .webm abd .mp4 videos.

[CLAassistant]

All committers have signed the CLA.

[kennymckormick]

@dreamerlin Better to have lint passed before merging.

[makecent]

@dreamerlin Better to have lint passed before merging.

My bad. I used the Pycharm to run commit. Do you know how to enable pre-commit in Pycharm?

[dreamerlin]

run pre-commit run --all-files in command line

[dreamerlin]

ref: https://github.com/open-mmlab/mmcv/blob/master/CONTRIBUTING.md

[makecent]

ref: https://github.com/open-mmlab/mmcv/blob/master/CONTRIBUTING.md

Thx. I solved it by sudo apt install ruby. A new pull request #1026 was created to solve the format issue.

[yaqi0510]

Dear makecent,

First of all, we want to express our gratitude for your significant PR in the MMAction2 project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.

If you are Chinese or have WeChat，welcome to join our community on WeChat. You can add our assistant ：openmmlabwx. Please add "mmsig + Github ID" as a remark when adding friends：）

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Thank you again for your contribution❤

Best regards！@makecent