[opendtv] Re: Speaking of MPEG-4 ...
- From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 16 Sep 2008 16:31:19 -0700
Yeah, but the majority of the payload in analog caption is captions. IIRC,
there is only a small sliver of channel 1 that can contain non-text data,
and only half of the second channel.
John Willkie
_____
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Adam Goldberg
Enviado el: Tuesday, September 16, 2008 4:23 PM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: Speaking of MPEG-4 ...
"analog captions" = "captions for analog video", CEA-608
"digital captions" = "captions for digital video", CEA-708
(and yes, of course, 708 packets can carry 608 data)
Don't take the 'analog' literally. Heck, don't take the 'captions'
literally either - CEA-608 includes lots of other stuff, too: XDS, CGMS-A,
etc.
----- Original Message ----
From: Tom Barry <trbarry@xxxxxxxxxxx>
To: opendtv@xxxxxxxxxxxxx
Sent: Tuesday, September 16, 2008 6:31:25 PM
Subject: [opendtv] Re: Speaking of MPEG-4 ...
John Willkie wrote:
> Tom;
>
> I'm sorry, you've disintermediated yourself from reality. Have you ever
> read CEA-608?
>
Yes, for one project I wrote software to create the needed Line 21
waveform for a D/A converter. I still have my copy of CEA-608C.
And you can go re-intermediate yourself by seeing section 5.2 of the
same document which begins "Figure 2 shows the signal waveform. The
Clock Run-in is a symmetrical sine wave with its maximum and minimum
amplitudes being equal to the logic "1" and "0" levels respectively of
the encoded data. ...". Then there is a pretty picture in Figure 2 to
explain it.
Smells pretty digital to me. ;-)
- Tom
> Here's from section 1.1
>
> "CEA-608-D is a technical standard and guide for using or providing Closed
> Captioning services or other data services embedded in line 21 of the
> vertical blanking interval of the NTSC video signal."
>
> Does that sound "analog enough" for you? Vertical blanking intervals and
> NTSC are "characteristics of analog video" and are distinguishable from
> characteristics of digital video.
>
> You see, I wasn't referring to how the captions are coded, but what
CEA-608
> captions describe: words spoken in an analog television channel. The
> carriage of analog captions in 8-VSB program services will last long after
> analog television sunsets.
>
> In industry shorthand, there are "analog" and "digital" captions,
> corresponding to CEA-608 and CEA-708, respectively.
>
> Using your argument, there is no digital television, since all modulation
is
> -- by definition and reality -- analog. (With the possible exception of
> dit-dah over a telegraph line.)
>
> John Willkie
>
>
>
> -----Mensaje original-----
> De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
> nombre de Tom Barry
> Enviado el: Tuesday, September 16, 2008 3:14 AM
> Para: opendtv@xxxxxxxxxxxxx
> Asunto: [opendtv] Re: Speaking of MPEG-4 ...
>
> Technically I'm not sure EIA-608 captions ever really were analog. IIRC,
> the line-21 waveform is decoded to represent 2 binary bytes per field.
> Does that make it analog, any more than ATSC? It seems more like early
> digital to me, just not very dense.
>
> - Tom
>
>
> Ron Economos wrote:
>> I'm not sure what you mean by "no analog captions". Seems like
>> EIA-608 fields in EIA-708 user_data_registered_itu_t_t35 packets
>> are still allowed.
>>
>> Also, stream_type 0x1B isn't exactly "new". It was added to H.222.0
>> in 2004.
>>
>> Ron
>>
>> John Willkie wrote:
>>> Correction: stream_type 27/ 0x1B.
>>>
>>>
>>>
>>> John Willkie
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> *De:* opendtv-bounce@xxxxxxxxxxxxx
>>> [mailto:opendtv-bounce@xxxxxxxxxxxxx] *En nombre de *John Willkie
>>> *Enviado el:* Monday, September 15, 2008 1:54 PM
>>> *Para:* opendtv@xxxxxxxxxxxxx
>>> *Asunto:* [opendtv] Speaking of MPEG-4 ...
>>>
>>>
>>>
>>> The ATSC today announced the publication of ATSC Standard A/72, in two
>>> parts (part 1 <http://www.atsc.org/standards/a_72_part_1.pdf>) and
>>> (part 2 <http://www.atsc.org/standards/a_72_part_2.pdf>) providing for
>>> the carriage of AVC (MPEG-4, part 10) video within ATSC A/53 transport
>>> streams. I suspect that the first real use of AVC will not be in A/53
>>> transport streams, in no small part due to the inability of legacy
>>> digital receivers to deal with AVC (for the most part.) For what that
>>> use will be, you will have to stay tuned.
>>>
>>>
>>>
>>> But, note that there is now a new stream_type for AVC (28 / 0x1B) ,
>>> and how this information is conveyed in PSIP.
>>>
>>>
>>>
>>> A few highlights: finally support for still pictures, and NO ANALOG
>>> CAPTIONS, just digital ones.
>>>
>>>
>>>
>>> There is a press release. If you'd like a copy, and it isn't
>>> available from the ATSC web site, send me an email and I'll forward it
>>> to you. I tend to not read press releases on this type of stuff.
>>>
>>>
>>>
>>> I'll have support for AVC to my PSIP generator, EtherGuide Emissary,
>>> and test the changes, before the day is out. (Turn on a dime, and
>>> give nine cents change.)
>>>
>>>
>>>
>>> John Willkie
>>>
>>>
>>>
>>>
>>>
>
>
>
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