Thread Subject: Re: thoughts from another discussion (related)

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From: Larry Goldberg
Date: Thu, Feb 08 2007 10:20 AM

One solution to the situation as described by Sean is to have the DVD
players decode the caption data like set-top boxes do. That (STB decoding)
was a solution imposed by the FCC and it works - though the user interface
for set-top box captioning controls leaves much to be desired.

In light of the fact that the US is not likely to, in fact cannot, drop
608/708, we need to live with these standards and support them in the way we
can. There is a vast amount of equipment, regulations and investment in the
608/708 platforms and the effort by the 508 Refresh committee to take global
harmonization of standards into account in its deliberations should not mean
that any problematic, but embedded, US standard should be tossed aside in
favor of yet-to-be-determined international approaches.

I'd like to point all concerned to two pieces of information on this issue -
one from the FCC and the other from the HDMI standards consortium. Both of
the following statements clearly indicate that the solution lies in proper
handling and decoding of 708 captions by all video source devices (including
DVD players):

Section 53 of the July 31, 2000 FCC Report and Order on DTV captioning
stated the following:

"53. Other Devices. Although we did not propose closed caption
decoder requirements for television interface devices whose primary function
is other than delivering television programming, such as VCRs, DVD players,
or personal video recorders, we know that these devices are used by
consumers in connection with their television sets to view closed caption
programming. In order for viewers to receive closed captions when using
these devices, it is not necessary for these devices to have decoding
capability. Rather, all that is required is for the device to pass through
the closed caption information to the decoder in the television set. We
expect that such devices, and any other similar new devices, will pass
through closed captions unaltered and intact to the decoder in the attached
digital television. Manufacturers of such devices should ensure that this
continues to be the case as the transition to digital television
progresses."

[Larry here again]:
So the FCC justified not requiring video source devices to decode captions
based on the assumption that they would pass through the data. Clearly
BluRay and HD-DVD are not doing what the FCC expected, so there needs to be
a Plan B. This paragraph implies that the Plan B would be for all video
sources to decode caption data and pass the open captions to the display.

Then we have the problem with the fact that the HDMI connector can't pass
caption data anyway. When asked, here is what one of the chief authors of
the HDMI spec had to say about this issue:

> HDMI does not carry, nor need to carry, closed caption data. Nor does
> component analog video. It's not needed because the source device (STB, DVD
> player) is required to "open" the captions. "Closed" captions are a hidden
> stream of text characters that are not normally visible but are carried with
> the video stream. "Open" captions are actually visible: displayed on the
> screen.
> So, the source needs to take the hidden text stream ("closed") and draw those
> characters on the image data if the user turns on Closed Caption. This happens
> upstream of HDMI so HDMI only needs to carry the video signal, not the hidden
> closed caption data.
> Another way of thinking of this is that it's the tuner that handles closed
> captions. For normal TV signals, the tuner is inside the TV and so it decodes
> and displays the data if the user selects it. For HDTV, the tuner is in the
> set-top-box (STB) so it's the STB that does the decode.
> The assumption of the
> founders has been that the source device will decode and display the captions
> and teletext.

[back to Larry:]
So clearly the authors of the HDMI spec thought the DVD players would decode
captions - they even mistakenly believed that they were required to do so.
Many of the members of the HDMI consortium are also members of CEA and were
involved in developing the BluRay and HD-DVD specifications. And if a next
generation DVD player happens to include a tuner, it would automatically be
subject to FCC rules requiring it to decode 708 caption data.

So, here we have a situation where the right hand didn't know what the left
hand was doing - and deaf consumers and others who rely on closed captioning
are faced with acceptance of either a lower quality image (composite video
and last generation DVDs), an inflexible substitute (subtitles), and loss of
an advanced technology (which allows user control) that they worked so hard
to implement (the 708 caption specification).

Let's continue this discussion.

- Larry



Sean Hayes wrote:

> That's right, and for these reasons, as well as the fact that both Blu-Ray and
> HD-DVD need to apply to a global market rather than just to the US, closed
> captions in those formats are not encoded in CEA608 or 708, but (for HD DVD at
> least), either in DVD subtitles or as subtitle applications. The devices can
> turn these on and off and the TV acts as a pure monitor. Even if 608 was
> encoded in the video using the same hack as was used for DVD, it could not be
> carried over any of the proscribed interconnects from the player to the TV.
>
> The same issue is going to be true for internet delivery of captioning to
> TV's, it is not practical to convert to 608 or 708 on reception, and even if
> carriage of these over IP was possible in internet streaming formats, it would
> not be globally applicable requireing multiple encodings at the server.
>
> Unfortunately the captioning story around the world has siloed into lots of
> different and incompatible formats, which is not to the benefit of the users.
> The European Broadcasting Union has an activity underway to attempt to address
> this, and the Timed Text DFXP format does offer the possibility of a truly
> global captioning format, unfortunately it is not likely to see widespread
> adoption in time for 508.
>
> The rest of the world is not going to adopt 608 or 708 for many technical and
> political reasons, so the question for the US is whether they would join an
> international effort to get to a single world standard, and give up on 608/708
> or to enforce these specific formats as an extra tax on all imported equipment
> and lobby Hollywood and the consumer electronics industry to change the HDMI
> standard.
>
> Sean Hayes
> Standards and Policy Team
> Accessible Technology Group
> Microsoft
> Phone:
> mob +44 7977 455002
> office +44 117 9719730
>
> -----Original Message-----
> From: = EMAIL ADDRESS REMOVED =
> [mailto: = EMAIL ADDRESS REMOVED = ] On Behalf Of Larry Goldberg
> Sent: 07 February 2007 19:15
> To: TEITAC AV list; TEITAC Web/Software Subcommittee
> Subject: Re: [teitac-video] [teitac-websoftware] thoughts from another
> discussion (related)
>
> Not quite - the DVD players need to reconstitute the caption data that was
> written onto the disks in the video user bits and encode it onto line 21 for
> transmission to and decoding by the displays' caption decoding circuitry.
> The original (1st gen) DVD players were not able to do this but later models
> fixed that design flaw.
>
> Now we are facing the same situation with BluRay and HD-DVD - the hardware
> cannot "sense" nor reconstitute caption data for transfer to the HD display
> and the high-end connections make this impossible too. So the DVD would need
> to decode the captions to make this work - like cable set-top boxes and other
> HD receivers that are external to the display.
>
> - Larry
>
>
> David Poehlman wrote:
>
>> Greg, DVD players have nothing to do with capttions, it's the dvds
>> themselvs which have or do not have them. If they are available, dvd
>> players will honor them if asked.
>>
>> On Feb 7, 2007, at 4:17 PM, Gregg Vanderheiden wrote:
>>
>>
>>
>>>> /This article states that most DVD players don't support closed
>>
>>>> captions.
>>
>>
>>
>>> Ugh.
>>
>>
>>
>>> On a similar note, I learned this morning that the strict definition
>>> of
>>
>>> "podcast" doesn't allow video files to be captioned. From what I
>>
>>> understand, if a QuickTime file includes a text track (which is how
>>> you
>>
>>> include captions for this format), then it can't be downloaded via
>>
>>> iTunes or played on an iPod...
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Gregg
>>
>> ------------------------
>>
>> Gregg C Vanderheiden Ph.D.
>> Professor - Depts of Ind. Engr. & BioMed Engr.
>> Director - Trace R & D Center
>> University of Wisconsin-Madison
>> < <http://trace.wisc.edu/> http://trace.wisc.edu/> FAX 608/262-8848
>>
>> DSS Player at http://tinyurl.com/dho6b
>>
>> <http://trace.wisc.edu:8080/mailman/listinfo/>
>>
>>
>>
>>
>>
>>

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