GitLab

Summary:
This commit adds fields to OutputStream, which shows the result
of fitlers, such as width and height after filtering.

Before

```
OutputStream(
    source_index=0,
    filter_description='fps=3,scale=width=320:height=320,format=pix_fmts=gray')
```

After

```
OutputVideoStream(
    source_index=0,
    filter_description='fps=3,scale=width=320:height=320,format=pix_fmts=gray',
    media_type='video',
    format='gray',
    width=320,
    height=320,
    frame_rate=3.0)
```

Pull Request resolved: https://github.com/pytorch/audio/pull/3155

Reviewed By: nateanl

Differential Revision: D43882399

Pulled By: mthrok

fbshipit-source-id: 620676b1a06f293fdd56de8203a11120f228fa2d