- From: John Simmons <johnsim@microsoft.com>
- Date: Wed, 3 Apr 2013 20:05:06 +0000
- To: Janina Sajka <janina@rednote.net>
- CC: Mark Watson <watsonm@netflix.com>, Glenn Adams <glenn@skynav.com>, "Henri Sivonen" <hsivonen@iki.fi>, Steve Faulkner <faulkner.steve@gmail.com>, HTMLWG WG <public-html-media@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Hi Janina I am not sure when the term 'Late binding' first appears, but it was at least 2009, when the fragmented MP4 format was adopted by UltraViolet. The ultraviolet definition: http://www.uvvu.com/docs/public/tspec/CFFMediaFormat-1.0.5.pdf Late Binding ... The combination of separately stored audio, video, subtitles, metadata, or DRM licenses with a preexisting video file for playback as though the late bound content was incorporated in the preexisting video file. This feature works for live and on-demand streaming, as well, which is the most important use case for MSE/EME. The basic structure of CFF is what is used with DASH ISOBMFF Live and On-demand streaming. ISO MPEG Common Encryption means that late binding can occur from the same encrypted media streams even though different DRM (Key Systems) are in use. This addresses the "combinatorial complexity" problem on the encoding side, as well as the edge cache hit rate for media segments. The latter is very important for live media steams, when many devices will be consuming the same live television stream, but have different DRM (Key Systems) installed. John John C. Simmons | Media Platform Architect | Microsoft Corporation | direct 425-707-2911 | mobile 425-269-5759 -----Original Message----- From: Janina Sajka [mailto:janina@rednote.net] Sent: Wednesday, April 03, 2013 12:37 PM To: John Simmons Cc: Mark Watson; Glenn Adams; Henri Sivonen; Steve Faulkner; HTMLWG WG; HTML Accessibility Task Force Subject: Re: how does EME/DRM effect captioning John Simmons writes: > As a data point, the Common File Format used by UltraViolet (which is fragmented MP4 for a reason) prohibits the encryption of closed captioning. > > In general, the model that works best for the web is one where "late binding" of tracks from a variety of sources are combined together into a composition. One of those tracks could be captioning, and with late binding, there is no upper limit on the number of captioning tracks that can be defined to be included in that composition. > Excellent to hear, thank you. Also, I like the term "late binding." It's new to me. But, if that's the generally understood industry term, we'll update our User Accessibility Media Requirements doc accordingly: http://www.w3.org/TR/media-accessibility-reqs/ Also, as an additional data point, let me note that there are a myriad set of alternative media types that need to be bindable, not just captions. The above (emerging) W3C note addresses those. Janina > > John C. Simmons | Media Platform Architect | Microsoft Corporation | > direct 425-707-2911 | mobile 425-269-5759 > > > -----Original Message----- > From: Janina Sajka [mailto:janina@rednote.net] > Sent: Wednesday, April 03, 2013 8:50 AM > To: Mark Watson > Cc: Glenn Adams; Henri Sivonen; Steve Faulkner; HTMLWG WG; HTML > Accessibility Task Force > Subject: Re: how does EME/DRM effect captioning > > Mark Watson writes: > snip ... > > > ... we deliver captions/subtitles separately in a (unencrypted) TTML > > file. > > > > Seems to me this is the optimal approach. > > 1.) Minimizes any potential barriers for users > 2.) Benefits service providers by supporting open ansillary > services, like indexing. > > Am I wrong? Is there any actual use case for encrypting captions? What did I miss here? > > Janina > > > -- > > Janina Sajka, Phone: +1.443.300.2200 > sip:janina@asterisk.rednote.net > Email: janina@rednote.net > > Linux Foundation Fellow > Executive Chair, Accessibility Workgroup: http://a11y.org > > The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI) > Chair, Protocols & Formats http://www.w3.org/wai/pf > Indie UI http://www.w3.org/WAI/IndieUI/ > > > > -- Janina Sajka, Phone: +1.443.300.2200 sip:janina@asterisk.rednote.net Email: janina@rednote.net Linux Foundation Fellow Executive Chair, Accessibility Workgroup: http://a11y.org The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI) Chair, Protocols & Formats http://www.w3.org/wai/pf Indie UI http://www.w3.org/WAI/IndieUI/
Received on Wednesday, 3 April 2013 20:06:41 UTC