[Athen] captions for ios devices

Terrill Thompson tft at uw.edu
Fri Dec 28 13:01:24 PST 2012

Hi All,

I'm a little late joining this conversation, but just wanted to share
what we're doing at DO-IT:

We've created a custom media player that uses HTML5 as its primary
player, and JW Player as fallback for those who are using older
browsers that don't support HTML5. We've created a highly accessible
custom player that communicates with both the HTML5 media and JW
Player API's so all users - even those with older browsers - get
exactly the same experience and identical feature sets.

For video files, we're using MP4, which is now supported by most
browsers and will eventually be supported by Firefox (the last major
holdout). Until then, we're also delivering all our videos using Ogg
(older videos) or WebM (newer videos), since those are the formats
preferred by Firefox (and Opera, which only recently began supporting
MP4). JW Player also supports MP4, so that same file works in the
fallback player.

For captions, we start with an SRT caption file. The standard format
for HTML5 captions is WebVTT, which at its core is very similar to
SRT, so it's easy to convert the SRT file to WebVTT with just a couple
of edits in a text editor (there are also free tools available that
will do the conversion). Browsers are starting to build in support for
WebVTT captions in HTML5, but from my experience their implementation
is still a little buggy, so we decided to build caption support into
our custom controller rather than rely on browsers to do it.

We upload all our videos to YouTube in addition to showing them on our
own site. For YouTube, we upload the original SRT caption file. And
for iOS, we embed the SRT caption file into our MP4 video file using
Handbrake. It's great that iOS supports that because we're already
delivering an MP4 file, so we don't really have to do anything
extra-special - we just use that same MP4 file for all purposes,
including delivery of captions in iOS. I recently discovered that my
iPhone reports that it "Can't play the caption file" on at least one
of our videos, so the iOS caption parser is apparently a little fussy,
but most of the time it seems to work. iOS also supports multiple SRT
files within a single MP4, so that's an effective strategy for
delivering foreign-language subtitles. We aren't supporting subtitles
yet on our videos, but we do have a few of them translated so we're
working on implementing subtitles soon.

Since you mentioned audio description Ken, we're implementing that in
a couple of different ways:

First, we outsource audio description for all our videos. The
deliverable from vendors is a new video, with description mixed into
the program audio. They do a great job of placing description in the
best places so it's minimally intrusive plus they adjust volumes so
the description can easily be heard over background sounds. The media
player we've created includes a Description button that if clicked,
swaps the source media file so if the user is viewing the
non-described version the described version is loaded, and vice versa.

We also provide a text version of the description in a WebVTT file,
the same file format that's used for captions. This form of
description is supported by the HTML5 spec. No browsers support it
natively yet, but we built support into our custom player. The
description text is displayed at the appropriate times just like
captions are, but they're displayed in a box that's marked with ARIA
role="alert", which causes screen readers to read the description as
soon as it appears. This is off by default on our player since users
have the option of viewing a professionally described video, but
there's a Preferences button that allows users to experiment with
different ways of getting their description delivered.

One advantage of having a WebVTT-based description, at least as a
supplement to the professionally described alternative version, is
that the WebVTT description file can be used in conjunction with the
caption file to build a transcript. In our transcript we markup the
caption and description in such a way that they're visually distinct,
plus we've added the text "Description:" to the start of each block of
description content, hidden to everyone except screen reader users.

We're planning to make our custom media player available as an open
source project sometime in early 2013. The best place to stay abreast
of that is my blog: http://terrillthompson.com/blog


Terrill Thompson
Technology Accessibility Specialist
DO-IT, Accessible Technology
UW Information Technology
University of Washington
tft at uw.edu

On Thu, Dec 20, 2012 at 2:39 PM, Ken Petri <petri.1 at osu.edu> wrote:

> Hi Dean,


> The Handbrake method works just fine. But if you have a Mac iSubtitle gives

> you more options.


> Here's the too-long URL on how to do this with Handbrake:

> https://carmenwiki.osu.edu/display/10292/DIY+Captioning+Techniques#DIYCaptioningTechniques-AddingCaptions%28Subtitles%29toMP4VideoforUseiniTunesorVLC


> A short URL to the entire DIY Captioning Techniques page is:

> http://go.osu.edu/diy-captioning


> Other good info in this page as well. The info about how to add an audio

> description track is forth-coming. That technique does, however, require

> QuickTime Pro....



> ken

> --

> Ken Petri

> Program Director, OSU Web Accessibility Center

> 102D Pomerene Hall, 1760 Neil Avenue, Columbus, Ohio 43210

> Office: 614.292.1760 | Mobile: 614.218.1499 | Fax: 614.292.4190

> http://wac.osu.edu | petri.1 at osu.edu




> On Thu, Dec 20, 2012 at 5:10 PM, Sean J Keegan <skeegan at stanford.edu> wrote:


>> > I want to learn how to add captions for iOS devices. I found a

>> > vendor site that gives instructions, but it says it only works using

>> > QuickTime Pro on a Mac. I have been unsuccessful in searches to

>> > confirm this. Can someone please tell me whether this is accurate?


>> Hi Dean,


>> Generally speaking, there are two ways to add captions to iOS media:

>> embedding a caption file so that it requires the closed caption decoder; or,

>> embedding a caption file as a subtitle track.


>> The first method is what I call the "closed caption decoder" solution.

>> This requires that you create an SCC file and embed this file into the

>> original media file. In order to view these captions on an iOS device you

>> have to enable the closed caption decoder feature in the Videos menu

>> (Settings > Videos > Closed Captioning). The SCC file is the same file type

>> as is used for captioning VHS media content and is a bit of a pain. From

>> what I have found, you need to have Compressor (Mac only) in order to

>> integrate the SCC caption into the original media file.


>> The second method is what I call the "subtitle track" solution. This

>> involves using the subtitle track to embed caption information into the

>> media file. I have had much greater success using this solution as it is

>> far easier to deal with the SRT caption file and the application used to

>> embed the captions (as subtitles) into the original media. I have used the

>> application iSubtitle (Mac only) to perform this process. Subler, also Mac

>> only, also works.


>> For Windows, the options are varied. Wondershare Video Converter Ultimate

>> (http://www.wondershare.com/video-editing-tips/how-to-add-subtitles-to-mp4.html)

>> is one tool that you could try. Previous versions seemed to work with

>> getting a subtitle track into an MP4 media file, so that may be one option

>> (I only tried this tool years ago, so your mileage may vary).


>> Handbrake may be an option now that there is improved subtitle support for

>> MP4 media files. With a user created SRT caption file, you can run the

>> media file and caption file together through Handbrake to get soft or hard

>> subtitles (soft-subtitles can be enabled/disabled whereas hard-subtitles are

>> burned into the video itself). See https://trac.handbrake.fr/wiki/Subtitles

>> for more information. I have not tried this method myself (yet!).


>> Take care,

>> Sean


>> --

>> Sean Keegan

>> Associate Director, Assistive Technology

>> Office of Accessible Education - Stanford University

>> http://studentaffairs.stanford.edu/oae

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