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Why do SA HD boxes delay SD?

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Anonymous
June 6, 2005 9:14:51 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

This is just a curiosity question. I recently
discovered that both of my HDTV set top boxes -
Scientific Atlanta 3250HD and 8300HD - delay analog SD
signals by about 3 seconds. This is an impressive
buffering feat because it is done without encoding the
SD into a data stream and with no hard drive on the
3250. (I can tell there is no encoding because the SA
encoders are not very good, and I would easily detect
the compression artifacts if an encoder were in the
loop. The video quality is not degraded.) Anyway, I
am just wondering WHY DO THEY DO IT? In contrast,
digital broadcasts are delayed by only a reasonable
half second or so, and this is the context in which
you would expect that some delay is actually required
for decoding the data stream and synchronizing the
output.

Please help solve this mystery for me.

Regards,
David V.

More about : boxes delay

Anonymous
June 6, 2005 12:35:26 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"David Vanderschel" <DJV4@Austin.RR.com> wrote in message
news:fZQoe.23152$PR6.830@tornado.texas.rr.com...
> This is just a curiosity question. I recently
> discovered that both of my HDTV set top boxes -
> Scientific Atlanta 3250HD and 8300HD - delay analog SD
> signals by about 3 seconds. This is an impressive
> buffering feat because it is done without encoding the
> SD into a data stream and with no hard drive on the
> 3250. (I can tell there is no encoding because the SA
> encoders are not very good, and I would easily detect
> the compression artifacts if an encoder were in the
> loop. The video quality is not degraded.) Anyway, I
> am just wondering WHY DO THEY DO IT? In contrast,
> digital broadcasts are delayed by only a reasonable
> half second or so, and this is the context in which
> you would expect that some delay is actually required
> for decoding the data stream and synchronizing the
> output.
>
> Please help solve this mystery for me.
>
> Regards,
> David V.
>
There is actually MORE processing done on a SD analog picture than Digital
if you use the component input and are inputing at 1080 or 720P.

Digital data streams have delays before transmitting and delays after
receiving. Analog is delayed by the processing that takes place to convert
it to digital, then the upconversion to 1080i or 720p then the conversion to
analog to be input to your TV via the component input.
June 6, 2005 7:35:28 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

There is A/D conversion time and then there is latency at the encoder
to make the signal part of the stream of packets that represent all of
the signals being broadcast by that station on their digital
transmitter. The receiver has a defined buffer size for video and audio
and the encoder models those buffers so as not to underflow or overflow
them.
Related resources
June 6, 2005 10:55:51 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

On 6 Jun 2005 15:35:28 -0700, "Tree" <roy547@msn.com> wrote:

>There is A/D conversion time and then there is latency at the encoder
>to make the signal part of the stream of packets that represent all of
>the signals being broadcast by that station on their digital
>transmitter. The receiver has a defined buffer size for video and audio
>and the encoder models those buffers so as not to underflow or overflow
>them.


3 seconds of delay?
Thumper
Anonymous
June 7, 2005 3:33:24 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Jeff Rigby" <jeffg212@comcast.net> wrote in message
news:<7fadnXwVmOSP3jnfRVn-3w@comcast.com>...
> There is actually MORE processing done on a SD
> analog picture than Digital if you use the component
> input and are inputing at 1080 or 720P.

Well, yes, it must be digitized. But that must
clearly proceed at a synchronized rate which allows
the box to keep up. So it should not delay things
perceptibly. In my case, I operate the box in Pass
Through mode, so, when tuned to an analog SD station,
it puts out 480i on the component cables. However, I
recognize that, in general, it must allow for the
possibility that it may have to upconvert.

Once the signal has been digitized, I don't see how
there is any more work remaining for the box to do
before I see the picture than if the box started with
digital SD. Can you explain?

> Digital data streams have delays before transmitting
> and delays after receiving. Analog is delayed by
> the processing that takes place to convert it to
> digital, then the upconversion to 1080i or 720p then
> the conversion to analog to be input to your TV via
> the component input.

All the above is true enough. But I don't see how it
can possibly explain 2.5 seconds of _additional_ delay
as compared to the rendering of a digital data stream.

Regards,
David V.
ð
Anonymous
June 7, 2005 3:33:25 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"David Vanderschel" <DJV4@Austin.RR.com> wrote in message
news:835pe.28190$j51.23766@tornado.texas.rr.com...
>
> All the above is true enough. But I don't see how it
> can possibly explain 2.5 seconds of _additional_ delay
> as compared to the rendering of a digital data stream.

David..could you please describe your method of comparison. What are
comparing the SD signal to that is 2.5 seconds ahead of it? I know this is
not your situation, but if I compare my SD local channels coming from Direct
TV via satellite there is considerable delay from the same program via OTA
signal.
Anonymous
June 7, 2005 3:44:04 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Tree" <roy547@msn.com> wrote in message
news:1118097328.773128.195840@g47g2000cwa.googlegroups.com...
> There is A/D conversion time

Which it must be able to do at 30 frames per second
and for which process it must not (indeed, does not)
get behind. This cannot explain noticeable delay.

>and then there is latency at the encoder to make the
>signal part of the stream of packets that represent
>all of the signals being broadcast by that station on
>their digital transmitter.

I'm sorry; but this makes no sense to me. As I stated
clearly in my initial post, there is no encoding going
on here. Digitization, yes, but no compression. This
is not about anything transmitted digitally. It is
about analog SD signals on the cable.

>The receiver has a defined buffer size for video and
>audio and the encoder models those buffers so as not
>to underflow or overflow them.

Yes, but 3 seconds seems like it offers a safety
margin an order of magnitude greater than required to
assure no underflow or overflow. For me, the mystery
remains.

Regards,
David V.
Anonymous
June 7, 2005 11:51:44 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Charles Tomaras" <tomaras@tomaras.com> wrote in message
news:8MmdnfQIBs-ibjnfRVn-pw@comcast.com...
>
> "David Vanderschel" <DJV4@Austin.RR.com> wrote in message
> news:835pe.28190$j51.23766@tornado.texas.rr.com...
> >
> > All the above is true enough. But I don't see how it
> > can possibly explain 2.5 seconds of _additional_ delay
> > as compared to the rendering of a digital data stream.
>
> David..could you please describe your method of comparison. What are
> comparing the SD signal to that is 2.5 seconds ahead of it? I know this is
> not your situation, but if I compare my SD local channels coming from
Direct
> TV via satellite there is considerable delay from the same program via
OTA
> signal.

I have a splitter before my cable box so that I can
look at straight analog RF off the cable with my TV or
any of several VCRs. I also have an extra little TV
along side my big one. (Picture outside a picture. :) 
With the little one monitoring RF straight off the
cable and the big one monitoring the output from an SA set
top box, I can watch both renderings of the very same
RF feed simultaneously. I got into such a
configuration once unintentionally, and that was when
I discovered the surprising 3 second delay.

I determined the delay for digital signals in a less
controlled way: I compared analog ESPN via RF to
ESPN-HD coming through the box. I assumed that there
was essentially no delay with the analog SD version.
The HD feed was only about half a second behind, which
seems reasonable taking into account the need both for
encoding on ESPN's end and for decoding on my end.

Your experience with the satellite is not relevant,
since we know there are delays going through DTV's
system and space. The effect I am talking about is
something that occurs entirely in the set top box
after the signal gets to me.

Regards,
David V.
Anonymous
June 7, 2005 11:51:45 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

David Vanderschel wrote:
>
> I have a splitter before my cable box so that I can
> look at straight analog RF off the cable with my TV or
> any of several VCRs. I also have an extra little TV
> along side my big one. (Picture outside a picture. :) 
> With the little one monitoring RF straight off the
> cable and the big one monitoring the output from an SA set
> top box, I can watch both renderings of the very same
> RF feed simultaneously. I got into such a
> configuration once unintentionally, and that was when
> I discovered the surprising 3 second delay.
>
> I determined the delay for digital signals in a less
> controlled way: I compared analog ESPN via RF to
> ESPN-HD coming through the box. I assumed that there
> was essentially no delay with the analog SD version.
> The HD feed was only about half a second behind, which
> seems reasonable taking into account the need both for
> encoding on ESPN's end and for decoding on my end.
>
> Your experience with the satellite is not relevant,
> since we know there are delays going through DTV's
> system and space. The effect I am talking about is
> something that occurs entirely in the set top box
> after the signal gets to me.

Perhaps not. I don't know what cable system you're on or how they map
the channels, but here in my area Adelphia remaps the channels via their
SA8000 cable box. Yes, the regular analog channels are on the cable, so
I can watch our locals (3, 5, and 8) here on my regular TV just as you
do. But if instead, I tune those same exact channels (3, 5, and 8) on my
SA8000, I do NOT see the analog versions of those channels - instead, I
get the digital versions that Adelphia is broadcasting on a completely
different frequency. The SA8000 remaps the channel numbers internally.

So any difference in timing between the two is not due to my cable box,
but to the cable system itself. (Incidentally, I note about a 1 second
delay in the digital version of the channels here.)
Anonymous
June 7, 2005 1:10:52 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"David Vanderschel" <DJV4@Austin.RR.com> wrote in message
news:8d5pe.28242$j51.13765@tornado.texas.rr.com...
> "Tree" <roy547@msn.com> wrote in message
> news:1118097328.773128.195840@g47g2000cwa.googlegroups.com...
>> There is A/D conversion time
>
> Which it must be able to do at 30 frames per second
> and for which process it must not (indeed, does not)
> get behind. This cannot explain noticeable delay.

You are confusing phase delay vs frequency. For the first frame to be
processed, ie; SA to SD then upconverted to 720p or 1080I then conversion to
analog for the component inputs in your set may take from (Guess) .3 to 1
sec. Thereafter each additional frame takes the same or less. This output
is buffered and come out at a constant rate which matches the scan rate you
have chosen.
>
>>and then there is latency at the encoder to make the
>>signal part of the stream of packets that represent
>>all of the signals being broadcast by that station on
>>their digital transmitter.
>
> I'm sorry; but this makes no sense to me.

IF we are talking about a digital SD signal of any resolution then another
facet of digital transmission is that the processed digital signal is sent
as packetts and these packetts are not sent sequentially but are semi
random, or rather packets are sent so that the average signal appears to be
random. This makes better use of the RF energy and extends the range of the
broadcasts as well as helps keep them within the 6 mhz bandwidth better than
analog signals do.

As I stated
> clearly in my initial post, there is no encoding going
> on here. Digitization, yes, but no compression. This
> is not about anything transmitted digitally. It is
> about analog SD signals on the cable.
>
>>The receiver has a defined buffer size for video and
>>audio and the encoder models those buffers so as not
>>to underflow or overflow them.
>
> Yes, but 3 seconds seems like it offers a safety
> margin an order of magnitude greater than required to
> assure no underflow or overflow. For me, the mystery
> remains.
>
> Regards,
> David V.
>
>
Anonymous
June 8, 2005 3:49:44 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Jim Gilliland" <usemylastname@cheerful.com> wrote in message
news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...
> David Vanderschel wrote:
> > Your experience with the satellite is not relevant,
> > since we know there are delays going through DTV's
> > system and space. The effect I am talking about is
> > something that occurs entirely in the set top box
> > after the signal gets to me.

> Perhaps not. I don't know what cable system you're on or how they map
> the channels, but here in my area Adelphia remaps the channels via their
> SA8000 cable box. Yes, the regular analog channels are on the cable, so
> I can watch our locals (3, 5, and 8) here on my regular TV just as you
> do. But if instead, I tune those same exact channels (3, 5, and 8) on my
> SA8000, I do NOT see the analog versions of those channels - instead, I
> get the digital versions that Adelphia is broadcasting on a completely
> different frequency. The SA8000 remaps the channel numbers internally.

"Perhaps" is the operative word here. Your proposed
theory does not apply in my case. Time Warner Austin
does not replicate any of its analog channels in
digital. (Many of us wish they would.)

It seems that the thrust of most of the comments here
has been to question the validity of my observation.
It never occurred to me that folks would be so
unwilling to believe. When I say that I am observing
two different renderings of the SAME RF SIGNAL
directly off the raw cable, I know what I am talking
about. The delay is DEFINITELY occurring in the cable
box. At least this sort of response reaffirms my
feeling that this is mysterious behaviour - so
mysterious that many folks are unwilling to believe
that it is even happening.

Regards,
David V.
Anonymous
June 8, 2005 3:49:45 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

David Vanderschel wrote:
> "Jim Gilliland" <usemylastname@cheerful.com> wrote in message
> news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...
>
>>David Vanderschel wrote:
>>
>>>Your experience with the satellite is not relevant,
>>>since we know there are delays going through DTV's
>>>system and space. The effect I am talking about is
>>>something that occurs entirely in the set top box
>>>after the signal gets to me.
>
>
>>Perhaps not. I don't know what cable system you're on or how they map
>>the channels, but here in my area Adelphia remaps the channels via their
>>SA8000 cable box. Yes, the regular analog channels are on the cable, so
>>I can watch our locals (3, 5, and 8) here on my regular TV just as you
>>do. But if instead, I tune those same exact channels (3, 5, and 8) on my
>>SA8000, I do NOT see the analog versions of those channels - instead, I
>>get the digital versions that Adelphia is broadcasting on a completely
>>different frequency. The SA8000 remaps the channel numbers internally.
>
>
> "Perhaps" is the operative word here. Your proposed
> theory does not apply in my case. Time Warner Austin
> does not replicate any of its analog channels in
> digital. (Many of us wish they would.)
>
> It seems that the thrust of most of the comments here
> has been to question the validity of my observation.
> It never occurred to me that folks would be so
> unwilling to believe. When I say that I am observing
> two different renderings of the SAME RF SIGNAL
> directly off the raw cable, I know what I am talking
> about. The delay is DEFINITELY occurring in the cable
> box. At least this sort of response reaffirms my
> feeling that this is mysterious behaviour - so
> mysterious that many folks are unwilling to believe
> that it is even happening.

You asked for an explanation, and several of us provided reasonable
explanations that may, or may not, explain what you've observed. As for
whether or not you're actually observing what you think you are, I can't
say. However, I _can_ report that my SA box does not appear to have the
same behavior. And it appears that others here might have come to the
same conclusion. If yours is the only one that acts that way, and if
there's no good explanation for its behavior, then you might want to
consider other possibilities. But that's up to you.

People are always going to trust their own observations over those
reported by others. That applies to the rest of us just as much as it
does to you.
Anonymous
June 8, 2005 3:49:46 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

On Time Warner Houston, I notice a distinct (probably two or three
seconds) delay on my SA8300HD when compared to an analog tuner on a
plain old TV connected directly to the cable, no cable box...

In article <42a64717$0$1582$c3e8da3@news.astraweb.com>, Jim Gilliland
<usemylastname@cheerful.com> wrote:

> David Vanderschel wrote:
> > "Jim Gilliland" <usemylastname@cheerful.com> wrote in message
> > news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...
> >
> >>David Vanderschel wrote:
> >>
> >>>Your experience with the satellite is not relevant,
> >>>since we know there are delays going through DTV's
> >>>system and space. The effect I am talking about is
> >>>something that occurs entirely in the set top box
> >>>after the signal gets to me.
> >
> >
> >>Perhaps not. I don't know what cable system you're on or how they map
> >>the channels, but here in my area Adelphia remaps the channels via their
> >>SA8000 cable box. Yes, the regular analog channels are on the cable, so
> >>I can watch our locals (3, 5, and 8) here on my regular TV just as you
> >>do. But if instead, I tune those same exact channels (3, 5, and 8) on my
> >>SA8000, I do NOT see the analog versions of those channels - instead, I
> >>get the digital versions that Adelphia is broadcasting on a completely
> >>different frequency. The SA8000 remaps the channel numbers internally.
> >
> >
> > "Perhaps" is the operative word here. Your proposed
> > theory does not apply in my case. Time Warner Austin
> > does not replicate any of its analog channels in
> > digital. (Many of us wish they would.)
> >
> > It seems that the thrust of most of the comments here
> > has been to question the validity of my observation.
> > It never occurred to me that folks would be so
> > unwilling to believe. When I say that I am observing
> > two different renderings of the SAME RF SIGNAL
> > directly off the raw cable, I know what I am talking
> > about. The delay is DEFINITELY occurring in the cable
> > box. At least this sort of response reaffirms my
> > feeling that this is mysterious behaviour - so
> > mysterious that many folks are unwilling to believe
> > that it is even happening.
>
> You asked for an explanation, and several of us provided reasonable
> explanations that may, or may not, explain what you've observed. As for
> whether or not you're actually observing what you think you are, I can't
> say. However, I _can_ report that my SA box does not appear to have the
> same behavior. And it appears that others here might have come to the
> same conclusion. If yours is the only one that acts that way, and if
> there's no good explanation for its behavior, then you might want to
> consider other possibilities. But that's up to you.
>
> People are always going to trust their own observations over those
> reported by others. That applies to the rest of us just as much as it
> does to you.

--
---
Anonymous
June 8, 2005 10:48:05 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

Brian Hall wrote:
> On Time Warner Houston, I notice a distinct (probably two or three
> seconds) delay on my SA8300HD when compared to an analog tuner on a
> plain old TV connected directly to the cable, no cable box...

Right, and I explained below exactly how that can happen. David is
unwilling to accept my explanation (which is fine with me), perhaps you
are as well. If so, please feel free to extend your own explanation.

It's easy enough to check for yourself. Just put the SA box into its
diagnostic mode (while it's on) and go through the channels in question.
The diagnostic summary screen will tell you exactly what frequency the
box is receiving (in the RF section on the very first page), and it'll
even tell you if it is an analog signal.

On my system here, channels 3, 4, 5, 6, and 8 are all received in digital
on a frequency of 585MHz. All of the other low channels (2, 7, and 9
through 13) are received on their regular analog frequencies (ranging
from 57MHz to 213MHz). Adelphia is putting digital signals for five SD
channels into a single QAM broadcast, decoding them back into individual
channels once they get to my cable box.

When I tune those same channels 3, 4, 5, 6, and 8 from the same cable on
an analog TV, it receives them on their usual frequencies - 63, 69, 79,
85, and 182 MHz, respectively. So there's definitely a timing difference
between the two, and it's easy to see why.

You'll have to check for yourself to see what's going on on your system.
But I do suggest that you check for yourself rather than taking the
word of a service rep.

> In article <42a64717$0$1582$c3e8da3@news.astraweb.com>, Jim Gilliland
> <usemylastname@cheerful.com> wrote:
>
>
>>David Vanderschel wrote:
>>
>>>"Jim Gilliland" <usemylastname@cheerful.com> wrote in message
>>>news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...
>>>
>>>
>>>>David Vanderschel wrote:
>>>>
>>>>
>>>>>Your experience with the satellite is not relevant,
>>>>>since we know there are delays going through DTV's
>>>>>system and space. The effect I am talking about is
>>>>>something that occurs entirely in the set top box
>>>>>after the signal gets to me.
>>>
>>>
>>>>Perhaps not. I don't know what cable system you're on or how they map
>>>>the channels, but here in my area Adelphia remaps the channels via their
>>>>SA8000 cable box. Yes, the regular analog channels are on the cable, so
>>>>I can watch our locals (3, 5, and 8) here on my regular TV just as you
>>>>do. But if instead, I tune those same exact channels (3, 5, and 8) on my
>>>>SA8000, I do NOT see the analog versions of those channels - instead, I
>>>>get the digital versions that Adelphia is broadcasting on a completely
>>>>different frequency. The SA8000 remaps the channel numbers internally.
>>>
>>>
>>>"Perhaps" is the operative word here. Your proposed
>>>theory does not apply in my case. Time Warner Austin
>>>does not replicate any of its analog channels in
>>>digital. (Many of us wish they would.)
>>>
>>>It seems that the thrust of most of the comments here
>>>has been to question the validity of my observation.
>>>It never occurred to me that folks would be so
>>>unwilling to believe. When I say that I am observing
>>>two different renderings of the SAME RF SIGNAL
>>>directly off the raw cable, I know what I am talking
>>>about. The delay is DEFINITELY occurring in the cable
>>>box. At least this sort of response reaffirms my
>>>feeling that this is mysterious behaviour - so
>>>mysterious that many folks are unwilling to believe
>>>that it is even happening.
>>
>>You asked for an explanation, and several of us provided reasonable
>>explanations that may, or may not, explain what you've observed. As for
>>whether or not you're actually observing what you think you are, I can't
>>say. However, I _can_ report that my SA box does not appear to have the
>>same behavior. And it appears that others here might have come to the
>>same conclusion. If yours is the only one that acts that way, and if
>>there's no good explanation for its behavior, then you might want to
>>consider other possibilities. But that's up to you.
>>
>>People are always going to trust their own observations over those
>>reported by others. That applies to the rest of us just as much as it
>>does to you.
>
>
Anonymous
June 9, 2005 5:48:17 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Jim Gilliland" <usemylastname@cheerful.com> wrote in message
news:42a64717$0$1582$c3e8da3@news.astraweb.com...
> David Vanderschel wrote:
> > "Jim Gilliland" <usemylastname@cheerful.com> wrote in message
> > news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...

> >>David Vanderschel wrote:

> >>>Your experience with the satellite is not relevant,
> >>>since we know there are delays going through DTV's
> >>>system and space. The effect I am talking about is
> >>>something that occurs entirely in the set top box
> >>>after the signal gets to me.


> >>Perhaps not. I don't know what cable system you're on or how they map
> >>the channels, but here in my area Adelphia remaps the channels via their
> >>SA8000 cable box. Yes, the regular analog channels are on the cable, so
> >>I can watch our locals (3, 5, and 8) here on my regular TV just as you
> >>do. But if instead, I tune those same exact channels (3, 5, and 8) on
my
> >>SA8000, I do NOT see the analog versions of those channels - instead, I
> >>get the digital versions that Adelphia is broadcasting on a completely
> >>different frequency. The SA8000 remaps the channel numbers internally.


> > "Perhaps" is the operative word here. Your proposed
> > theory does not apply in my case. Time Warner Austin
> > does not replicate any of its analog channels in
> > digital. (Many of us wish they would.)

Well, I must eat crow. I was so certain that TW was
not digitally replicating any analog channels that I
did not even bother to check when Jim first offered
this explanation. However, it turns out that, with no
fanfare whatsoever, TW has started offering a QAM feed
for ESPN and ESPN2 - interestingly enough on 585MHz.
(Of all their analog channels, the only other one with
a digital duplicate is a relatively obscure local
access channel. I suppose it was their initial
experiment at doing this.)

What seems strange to me is that there are other
channels which are much more subject to ingress
interference and which would be better candidates for
the digital alternative. And, for ESPN, we already
had a digital feed in the form of ESPN-HD. (I wonder
if, in its negotiations with TW to provide HD feeds,
ESPN did not insist that its SD feeds be distributed
digitally also.) The encoder they are using does not
do a perfect job, so it is a matter of choosing
between analog noise and compression artifacts for me
now. For high speed sports action, I think I will
still tend to favor the analog noise. Since I got my
DVR, I have consistently recorded the ESPN and ESPN2
SD feeds using a VCR since it makes a better recording
than do the encoders in the SA boxes (even at EP
speed!). Now that the box no longer needs its
encoder, I can use the DVR when I don't mind the
relatively mild encoder problems of the encoder TW is
using for the system digital feed.

Jim, I apologize. Since you behaved so calmly in face
of my contradiction, I figured I better go look at the
diagnostics myself.

Anyway, the mystery is now solved. As it turns out,
SA boxes still do not delay analog feeds. But sometimes
they have a delayed digital alternative.

Thanks,
David V.
Anonymous
June 9, 2005 5:48:18 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

David Vanderschel wrote:
> "Jim Gilliland" <usemylastname@cheerful.com> wrote in message
> news:42a64717$0$1582$c3e8da3@news.astraweb.com...
>
>>David Vanderschel wrote:
>>
>>>"Jim Gilliland" <usemylastname@cheerful.com> wrote in message
>>>news:<42a57b5b$0$26338$c3e8da3@news.astraweb.com>...
>
>>>>David Vanderschel wrote:
>
>>>>>The effect I am talking about is
>>>>>something that occurs entirely in the set top box
>>>>>after the signal gets to me.
>
>>>>Perhaps not. I don't know what cable system you're on or how they map
>>>>the channels, but here in my area Adelphia remaps the channels via their
>>>>SA8000 cable box. Yes, the regular analog channels are on the cable, so
>>>>I can watch our locals (3, 5, and 8) here on my regular TV just as you
>>>>do. But if instead, I tune those same exact channels (3, 5, and 8) on
>>>>SA8000, I do NOT see the analog versions of those channels - instead, I
>>>>get the digital versions that Adelphia is broadcasting on a completely
>>>>different frequency. The SA8000 remaps the channel numbers internally.
>
>>>"Perhaps" is the operative word here. Your proposed
>>>theory does not apply in my case. Time Warner Austin
>>>does not replicate any of its analog channels in
>>>digital. (Many of us wish they would.)
>
> Well, I must eat crow. I was so certain that TW was
> not digitally replicating any analog channels that I
> did not even bother to check when Jim first offered
> this explanation. However, it turns out that, with no
> fanfare whatsoever, TW has started offering a QAM feed
> for ESPN and ESPN2...
>
> Jim, I apologize. Since you behaved so calmly in face
> of my contradiction, I figured I better go look at the
> diagnostics myself.
>
> Anyway, the mystery is now solved. As it turns out,
> SA boxes still do not delay analog feeds. But sometimes
> they have a delayed digital alternative.

No apology necessary. I had no way of knowing what T/W does in your area
- I was just explaining what happens here. Since it seemed to fit your
scenario rather closely, I thought it a likely explanation. The only
other thing that was hidden in my comment was the idea that the reps of
the cable company may well not know many of the technical details of
their own systems.
!