This article is a guide to uploading an already-prepared closed captions for on demand web videos using a desktop upload workflow.
You have two different choices for how to publish your web closed captions via manual upload. You can either embed your captions in your video file, or provide captions stored as a separate file.
BLOX VMS supports the following formats for your source video with embedded captions:
MP4 with caption track in CEA-608 format
MP4 with caption track in CEA-708 format
MP4 with caption track in MPEG-4 Part 17 format
3GP with caption track in 3GPP Timed Text format
MPEG-2 with caption track in CEA-608 format
ASF with caption track in CEA-608 format
Captions stored as a separate (sidecar) file
BLOX VMS supports the following formats for your video with sidecar captions:
MP4 with a sidecar file in DFXP (TTML) format
MP4 with a sidecar file in SRT format
MP4 with a sidecar file in WebVTT format
BLOX VMS currently supports the following formats for caption outputs:
MP4 with a WebVTT sidecar file
MP4 with CEA-608 caption track
If captions are embedded in the video file on upload, the output MP4 will contain embedded captions, as well as a VTT sidecar. If captions were in a sidecar on upload, the output MP4 will contain embedded captions, and BLOX VMS also stores a WebVTT sidecar.
The SMPTE-TT extension of DFXP/TTML is the FCC “safe harbor” interchange and delivery format.
Remember to save your file with the extension dot xml (.XML) before uploading.
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xml:lang="en">
<body
<div>
<p begin="0:00:02.00" end="0:00:05.00">This is a caption about robots attacking a city.</p>
</div>
</body>
</tt>
BLOX VMS will display that sidecar caption file in the player along with the transcoded video file. You can also view your sidecar caption file in the manager or view any sidecar files created from embedded captions.
