webvtt-py

webvtt-py is a Python library for reading, writing and converting WebVTT caption files. It also features caption segmentation useful when captioning HLS videos.

Documentation is available at http://webvtt-py.readthedocs.io.

$ pip install webvtt-py

import webvtt

for caption in webvtt.read('captions.vtt'):
    print(caption.identifier)  # cue identifier if any
    print(caption.start)       # cue start time
    print(caption.end)         # cue end time
    print(caption.text)        # cue payload
    print(caption.voice)       # cue voice span if any

from webvtt import WebVTT, Caption

vtt = WebVTT()

vtt.captions.append(
    Caption('00:00:00.500', '00:00:07.000', 'Caption line 1\nCaption line 2')
)
vtt.captions.append(
    Caption('00:00:07.000', '00:00:11.890', ['Caption line 1', 'Caption line 2'])
)

vtt.save('captions.vtt')

# or get the content without writing a file
print(vtt.content)

import webvtt

webvtt.segment('captions.vtt', 'output/path')

Supported formats:

• SubRip (.srt)
• YouTube SBV (.sbv)

import webvtt

# write captions.vtt next to captions.srt
vtt = webvtt.from_srt('captions.srt')
vtt.save()

# alternatively in a single line
webvtt.from_sbv('captions.sbv').save()

Caption segmentation, shifting and synchronizing are also available from the command line with the webvtt executable. Given captions.vtt:

WEBVTT

00:00:01.000 --> 00:00:04.000
Hello and welcome.

00:00:06.000 --> 00:00:12.000
This caption spans two segments.

00:00:14.500 --> 00:00:18.000
Thanks for watching!

Segment it into 10 second segments:

$ webvtt segment captions.vtt --output out
$ ls out
fileSequence0.webvtt  fileSequence1.webvtt  prog_index.m3u8

The playlist out/prog_index.m3u8 lists the segments:

#EXTM3U
#EXT-X-TARGETDURATION:10
#EXT-X-VERSION:3
#EXT-X-PLAYLIST-TYPE:VOD
#EXTINF:10.00000,
fileSequence0.webvtt
#EXTINF:10.00000,
fileSequence1.webvtt
#EXT-X-ENDLIST

A caption crossing a segment boundary is included in every segment it overlaps, out/fileSequence1.webvtt:

WEBVTT
X-TIMESTAMP-MAP=MPEGTS:900000,LOCAL:00:00:00.000

00:00:06.000 --> 00:00:12.000
This caption spans two segments.

00:00:14.500 --> 00:00:18.000
Thanks for watching!

Use -d to change the segment duration and -m to change the MPEG-TS value.

Show the captions 1.5 seconds earlier, writing them to a new file:

$ webvtt shift captions.vtt -1.5 --output shifted.vtt

Without --output the shifted captions are written to standard output. Use --start to only shift the captions starting at or after a timestamp.

Fix captions that drift out of sync by moving two or more points, here the caption at 00:14.500 to 00:15.850 keeping the first one in place, or by changing the frame rate they are timed for:

$ webvtt sync captions.vtt -p 00:01.000 00:01.000 -p 00:14.500 00:15.850
$ webvtt sync captions.vtt --fps 25 23.976 -o captions.vtt

For all the options, run webvtt segment --help, webvtt shift --help, webvtt sync --help or man webvtt, or see the CLI documentation.

Licensed under the MIT License.