VISTAL: A visualization tool for temporal action localization

A lightweight tool for visualizing temporal action localization results. It generates .ass subtitle files containing timelines for videos.

Installation

pip install vistal

Tutorial

Import the library

from vistal import vistal, ColourScheme, Colour

By now this tool supports non-overlapping localization results, i.e. action segmentation results. Pack these temporal labels into a list of tuple(start, end, label_id), for example:

prediction = [
    # start, end, label_id
    ( 0,     2,     0),
    ( 2,     3,     1),
    ( 3,     5,     2),
    ( 5,     6,     3),
]

start and end are integers or floats in seconds, and label_id are integer IDs for each action.

And the actual temporal label, for example, is

ground_truth = [
    ( 0,     1,     0),
    ( 1,     1.8,   3),
    ( 1.8,   3.7,   1),
    ( 3.7,   4.5,   3),
    ( 4.5,   6,     2),
]

And another dict maps from label IDs to their names:

label_names = {
    0: 'foo',
    1: 'bar',
    2: 'baz',
    3: 'background',
}

Now we create a colour scheme to determine what colour to represent each action:

colour_scheme = ColourScheme(
    colours=[
        Colour(b=255, g=0,   r=0),
        Colour(b=0,   g=255, r=0),
        Colour(b=0,   g=0,   r=255),
        Colour(alpha=255),
    ]
)

Or, we can generate some random colours. The last action is background, therefore it should be transparent.

colour_scheme = ColourScheme(n_colours=4, transparent_id=3)

Suppose the video resolution is 1280x720, and it lasts for 6 seconds:

display_width = 1280
display_height = 720
video_duration = 6

The main function vistal creates a subtitle object:

sub = vistal(
    temporal_list_dict={
        'gt  ': ground_truth,
        'pred': prediction
    },
    label_names=label_names,
    colour_scheme=colour_scheme,
    video_duration=video_duration,
    display_width=display_width,
    display_height=display_height,
    timeline_height=72,
    font_size=72,
    font_name='Ubuntu Mono',
    show_legend=True,
)

Save to an .ass file:

sub.save('tutorial.ass')

Finally, play the video and load the subtitle to the player. Make sure your video player supports .ass subtitle, for example VLC media player and PotPlayer. Here is how it looks like on a blank video:

For another complete example, see example.py.