[whatwg] Forced subtitles

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Thu Apr 11 15:54:22 PDT 2013

I think Eric is right - we need a new @kind="forced" or
@kind="forcedSubtitles" value on track elements, because they behave
differently from the subtitle kind:
* are not listed in a track menu
* are turned on by browser when no other subtitle or caption track is on
* multiple forced subtitles tracks can be on at the same time (see
discussion at https://www.w3.org/Bugs/Public/show_bug.cgi?id=21667 )

I only wonder how the browser is meant to identify for which language it
needs to turn on the forced subtitles. If it should depend on the language
of the audio track of the video rather than the browser's default language
setting, maybe it will need to be left to the server to pick which tracks
to list and all forced tracks are on, no matter what? Did you have any
ideas on this, Eric?


On Fri, Apr 12, 2013 at 4:08 AM, Eric Carlson <eric.carlson at apple.com>wrote:

>  In working with real-world content with in-band subtitle tracks, I have
> realized that the spec doesn't accommodate "forced" subtitles. Forced
> subtitles are used when a video has dialog or text in a language that is
> different from the main language. For example in the Lord of the Rings,
> dialog in Elvish is subtitled so those of us that don't speak Elvish can
> understand.
>  This is only an issue for users that do not already have
> subtitles/captions enabled, because standard caption/subitle tracks are
> expected to mix the translations into the other captions in the track. In
> other words, if I enable an English caption track I will get English
> captions for the dialog spoken in English and the dialog spoken in Elvish.
> However, users that do not typically have subtitles enabled also need to
> have the Elvish dialog translated so subtitle providers typically provide a
> second subtitle track with *only* the forced subtitles.
>   UAs are expected to automatically enable a forced-only subtitle track
> when no other caption/subtitle track is visible and there is a forced-only
> track in the same language of the primary audio track. This means that when
> I watch a version of LOTR that has been dubbed into French and I do not
> have a subtitle or caption track enabled, the UA will automatically show
> French forced subtitles if they are available.
>  Because forced subtitles are meant to be enabled automatically by the UA,
> it is essential that the UA is able to differentiate between "normal" and
> "forced" subtitles. It is also important because forced subtitles are not
> typically listed in the caption menu, again because the captions in them
> are also in the "normal" subtitles/captions.
>  I therefore propose that we add a new @kind value for forced subtitles.
> "Forced" is a widely used term in the industry, so I think "forced" is the
> appropriate value.
> eric

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