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Re: text-format discussion from today's call

From: Geoff Freed <geoff_freed@wgbh.org>
Date: Fri, 6 Aug 2010 07:24:48 -0400
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
CC: Judy Brewer <jbrewer@w3.org>
Message-ID: <C8816940.F752%geoff_freed@wgbh.org>

Comments inline.

On 8/5/10 8:07 PM, "Silvia Pfeiffer" <silviapfeiffer1@gmail.com> wrote:

Hi Geoff,

This is all very interesting indeed.

I do wonder, however, how much "automatism" can be in there from saying because "SMPTE is using TTML as their transcoding format for IP delivery of captions" to saying "TTML also has to be supported by the Web". The problem about this statement is implementation support in Web browsers. If no Web browser is implementing support for TTML, TTML will not mean much on the Web, no matter how many TTML documents exist from repurposed broadcast captions.

I'm saying that the decision to recommend a text-display format in HTML5 should not be made without taking note of, and making accommodations for, events in progress elsewhere, especially from the source of the greater percentage of video material that lands on the Web.  I'm not saying that TTML must be supported on the Web.  I am saying that it should not be ignored.  I'll add that you should not  ignore, or merely toss aside with a cavalier "I'm not worried" flick of the wrist the possible ramifications of what you are saying in light of this new legislation.  I'm happy to hear that you're not worried about continuing to transform caption files to various formats.  I'm worried about it because it's been a headache for a very long time and I had hoped that the problem would have been solved by now.  I'm worried that the use of a new text-display format, added to the giant pool of existing and disparate text-display formats, is not going to make things any easier for getting captions onto the Web.

But, to be honest, I do not see that as a big problem. Transcoding from one text format to another is not a big issue where those formats support the same functionality. I believe that whatever format will be chosen for HTML5, it will support all the TTML features, so there should be no problem in transcoding. In fact, even the proposed draft WebSRT by the WHATWG is already capable of supporting almost all of TTML, so I am not worried about this.

In fact, if I was a broadcaster, I would probably just create both file types from my existing broadcast captions and use them as appropriate. It has been done with video before and is a much bigger problem there since transcoding in video means data loss. This is not the case for text, so won't be much of an issue, IMHO.

I guess that as a broadcaster, or even as a captioning agency, you're not worried about keeping track of which caption files are compatible with which players, and what happens when you want to use a new player that doesn't support your old text format, etc.  Your statement  fails to address the long-standing problem faced by captioning agencies and broadcasters:  text format and player incompatibility.  You're saying that we must continue to transform caption source files to multiple formats to accommodate whatever permutations browsers and multimedia players want to support.  Well, then, there has been no progress.

On Fri, Aug 6, 2010 at 2:52 AM, Geoff Freed <geoff_freed@wgbh.org> wrote:

Greetings, all:

Regarding the conversation on the call today about timed-text formats, I'd like to offer some further thoughts regarding the format eventually recommended by the a11y group and/or HTML5 and how it may affect others.  At a minimum these comments may further complicate matters.  Sorry...

Some on the list may be aware that SMPTE (Society of Motion Picture and Television Engineers) is coming close to completing a standard for the repurposing of broadcast captions for IP delivery.  This standard, called SMPTE-TT, is based almost entirely on TTML.  SMPTE-TT will provide broadcasters a clearly defined method for converting huge libraries of existing captions for Web delivery.

Many here may also be aware of legislation making its way through the U.S. Congress that will, in some form, mandate the inclusion of captions and descriptions on some types of video material on the Web, most likely related to material that originates in the broadcast sphere and is then transferred to the Web.  The U.S. House of Representatives passed its version of the bill (HR3101, The 21st-Century Communications and Video Accessibility Act; http://www.coataccess.org/node/9733) last week, and the Senate is still debating its version but is expected to complete its work soon.

Among its many provisions, HR3101 contains the following language:

(1) CLOSED-CAPTIONING REPORT.-Within 6 months after the date of the first meeting of the Advisory Committee, the Advisory Committee shall develop and submit to the Commission a report that includes the following:

(A) An identification of the performance objectives for protocols, technical capabilities, and technical procedures needed to
permit content providers, content distributors, Internet service providers, software developers, and device manufacturers to
reliably encode, transport, receive, and render closed captions of video programming delivered using Internet protocol.

(B) An identification of additional protocols, technical capabilities, and technical procedures beyond those available as of the
 date of enactment of this Act for the delivery of closed captions of video programming delivered using Internet protocol that
are necessary to meet the performance objectives identified under subparagraph (A).

(C) A recommendation for any regulations that may be necessary to ensure compatibility between video programming
delivered using Internet protocol and devices capable of receiving and displaying such programming in order to facilitate
access to closed captions.

C is most relevant here:  it's stating that the committee must recommend a format for IP delivery of captions.  The committee specified in (1) will probably have significant representation from the broadcast world, and my educated guess is that broadcasters are probably going to push for SMPTE-TT as the standard to specify in the regulations.  If there is a disconnect between this recommendation and what is recommended in HTML5, it could create a significant headache for the broadcast industry.  In short, harmonization of the text-display formats would be ideal.

It's important to keep this specific issue in mind while debating the text-format problem, and I raise it just to remind everyone that a good deal of video on the Web, especially captioned video, originates elsewhere and will continue to do so for some time.  The amount of captioned programming repurposed from the broadcast world is significant, and we should be paying close attention to what is happening there.  Broadcasters will probably favor a single conversion format for captions from terrestrial/cable to Web.  In other words, if they're already having to convert from CEA-608/708 to SMPTE-TT (not a done deal), they're probably not going to want to do another conversion, with potentially different results or limitations, to whatever format is recommended by HTML5 and its implementers.


Received on Friday, 6 August 2010 11:26:58 UTC

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