Support Forced Subtitles

[joncameron]

Description

Avalon doesn't currently support forced subtitles, which are sometimes provided as external files. The ability to designate a file as "forced" in the listing of captions on a masterfile should be available to meet this use case.

Forced Subtitles

Forced subtitles are common on movies and only provide subtitles when the characters speak a foreign or alien language, or a sign, flag, or other text in a scene is not translated in the localization and dubbing process.

https://en.wikipedia.org/wiki/Subtitles#Categories

On our service, Forced Narrative subtitles are only displayed if Subtitles and CC are set to "off" in the user's playback settings. When the user activates a full Subtitle or SDH/CC file, the FN subtitle does not display and for this reason, we require that all Forced Narrative events are also included in each full Subtitle and SDH/CC file.

https://partnerhelp.netflixstudios.com/hc/en-us/articles/217558918-Understanding-Forced-Narrative-Subtitles

Done Looks Like

• "Forced" binary option (checkbox?)
• Only one caption file can be set to "Forced" at a time
• When timed text display is disabled in the media player and a "Forced" subtitle track exists for the masterfile, the forced subtitle track is displayed

[joncameron]

Implemented as tags "captions" and "forced" in the supplemental files, probably. A Ramp ticket will also need to be created to make sure nothing looks selected when forced captions are going.

Videojs text tracks has a 'default' setting that could work for the initial loading of the video, as long as Ramp initializes the text track with that option. Hopefully this works as advertised.

Ramp currently stores this information in local storage; this could override the current Ramp behavior.

This will also need to be represented in the manifest. Another behavior attribute, or looking to the URL scheme to denote this? We can use the same approach as is currently used for the "machine-generated" tag (current in with the label in the manifest).

[masaball]

The behavior attribute has a list of accepted values and none of them seem quite right for this case. However, metadata is able to be used at any level of a manifest and can contain arbitrary data. @joncameron What do you think of adding a metadata entry to the caption annotation to denote a forced subtitle?

[joncameron]

@masaball metadata is more meant for user-facing presentation data, so I'm a bit hesitant to put it there. What do you think about a magic string like "forced" or "[Forced]" in one of the existing fields? Examples of what I was thinking:

"label": {
  "fre": ["Lunchroom Manners in French", "forced"],
  "none": ["lunchroom_manners french.mp4.vtt"]
}

Or appending " [Forced]" to the label string and keying in on that in Ramp:

"label": {
  "fre": ["Lunchroom Manners in French [Forced]"],
  "none": ["lunchroom_manners french.mp4.vtt"]
}

[masaball]

That works, but I hesitate a bit over how that would work with the machine generated label. Currently that gets appended to the label, so "Lunchroom manners (machine generated)".

A forced caption that's also machine generated would be something like "Lunchroom manners (machine generated) [Forced]"?

[joncameron]

After discussion, we can put this into the string label. It seems like the most reasonable place to put this information given a lack of places to put this in the IIIF manifest document.

Label in the player is long because we're not currently stripping the "(machine generated)" text. Users might not see this in the drop-down but it's still present in the value. The text could also be stripped from the label.