New decoder Question - how will it take to change a channel
hb
digital (satellite) box say it takes a while. Will my channel surfing be
seriously disrupted by the digital (cable) box ?
Anybody (perhaps people from UK) know ?
hb
word.
Me - The Real one!
"hb" <ben...@bigpond.net.au> wrote in message
news:ZVbJb.74128$aT.5...@news-server.bigpond.net.au...
> I meant to ask how LONG it takes to change a channel - damn left out key
> word.
>
yep
> !> "hb" <ben...@bigpond.net.au> wrote in message
No it wasn't. Read it again. Changing channels takes just a little bit
longer than finding the remote. The serious question is - what are you
going to change channels for ? Is there something worthwhile to watch ?
If so please post results here , as I for one have been waiting some
time for this to occur.
--
yep
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Me - The Real one!
"yep" <yep....@no-mx.forums.eyo.com.au> wrote in message
news:yep....@no-mx.forums.eyo.com.au...
>
> > !> "hb" <ben...@bigpond.net.au> wrote in message
> > news:ZVbJb.74128$aT.5...@news-server.bigpond.net.au...
> > > I meant to ask how LONG it takes to change a channel - damn left
> > out key
> > > word.
> > >
> > It was in your subject so we know what you were asking. :)
>
> No it wasn't. Read it again.
Well I understood it, as I'm sure many others did.
poiuytrewqasd...@pqowieurytghfjdkslazmxncv.com
hb wrote:
> I meant to ask how LONG it takes to change a channel - damn left out key
> word.
anywhere between 1.5secs to 3 secs.
Why?
The digital modulation signal is QAM64 (standard)
The Digital Mhz signal is above 1500 (or 1.5Ghz)
Also, with digital (here is the trick) you STU is receiving 1 channel at any
given time, unlike analogue which broadcasts all the signals.
Also that is why the stu needs a return path (for PPV - NVOD reports, + other
data Foxtel will learn about yor veiwing habits)
Thomas 'bacco|007' Baxter
poiuytrewqasd...@pqowieurytghfjdkslazmxncv.com wrote:
> The digital modulation signal is QAM64 (standard)
QAM has fuck all to do with channel changes doofus.
Quadrature Amplitude Modulation. In basic terms, this means that instead of
sending a single bit in one go you can transmit many. More bits means more
bandwidth and hence more channels.
Higher the QAM value, higher the susceptibility to poor quality
transmissions
poiuytrewqasd...@pqowieurytghfjdkslazmxncv.com
Thomas 'bacco|007' Baxter wrote:
> On Sun, 04 Jan 2004 21:40:39 +1100,
> poiuytrewqasd...@pqowieurytghfjdkslazmxncv.com wrote:
>
> > The digital modulation signal is QAM64 (standard)
>
> QAM has fuck all to do with channel changes doofus.
> Quadrature Amplitude Modulation. In basic terms, this means that instead of
> sending a single bit in one go you can transmit many. More bits means more
> bandwidth and hence more channels.
Hence more procesing time to find the fucking right Digital Mrz frequency.
Example:
QPSK: Analogue frequency: bigpond cable users the high 580Mhz range for its
download channel and the low 25Mhz range for its uploading channel.
Which is why Bigpond Cable has such a limited range in terms of speed
(uploading and downloading) but on the other hand can handle more uploading
speed on the back end frequency (side B and C of the Data over Copper channel)
Much in the same way its ADSL network runs.
.
>
>
> Higher the QAM value, higher the susceptibility to poor quality
> transmissions
No not correct, well not with Digital Cable anyway.
Anywehere between 64 to 128 to 256 is aceptable via Digital cable as only 1
side of the data channel is receiving.
foo
news:3FF7EDA7...@pqowieurytghfjdkslazmxncv.com:
>
>
> hb wrote:
>
>> I meant to ask how LONG it takes to change a channel - damn left
>> out key
>> word.
>
> anywhere between 1.5secs to 3 secs.
>
> Why?
Because a digital STU has a LOT more work to do; it has to figure out where
the channel you just asked for actually *is*. This can be quite complex.
It has to potentially
a) stop the current video/audio
b) change the RF tuner to the new frequency
c) tune to, lock onto and demodulate the digital signal.
d) find out how to decrypt the video and audio streams.
e) decrypt the video and audio streams
f) pump the decrypted video and audio out.
Some of these jobs may take a few seconds - depending on things like how
long it takes for the EPG to figure out where to go, how long the RF takes
to lock onto the new carrier, how long the STU takes to pull all the pieces
of data it needs from the stream, how long it takes to talk to the
smartcard, how long the picture sequence is [MPEG2 allows for long
sequences of pictures which can't be decoded without the first one] and so
on.
>
> The digital modulation signal is QAM64 (standard)
DVB permits different "standard" digital cable broadcast modulation
schemes. QAM 64 is just one of them.
> The Digital Mhz signal is above 1500 (or 1.5Ghz)
On TELSTRA's HFC network system the downstream is 85-750Mhz.
1.5GHz is more appropriate for an upconverted satellite signal.
But that's not usually QAM, it's QPSK.
> Also, with digital (here is the trick) you STU is receiving 1 channel
> at any given time, unlike analogue which broadcasts all the signals.
Both analogue and digital broadcast systems broadcast all of the content
all of the time. An STU only ever tunes to demodulate one carrier at a
time per tuner - analogue OR digital. [PVRs have multiple tuners..]
The big difference is the analogue system carries 1 TV channel per
demodulated carrier whereas a 7 MHz Digital carrier with QAM64 can carry
about 10 TV channels.
Navigating between services on the same carrier is faster than navigating
to services on a different carrier, because no RF tuning needs to take
place. On satellite there is also potentially polarity and bandswitching
of the LNB to deal with when RF tuning, but all of these actions can be
done at the same time.
> Also that is why the stu needs a return path (for PPV - NVOD reports,
> + other data Foxtel will learn about yor veiwing habits)
An STU needs a return path *only if needs to send data back*.
Digital systems which support order-ahead PPV for instance, dont need a
return path for PPV.
foo
news:3FF90A83...@pqowieurytghfjdkslazmxncv.com:
>
>
> Thomas 'bacco|007' Baxter wrote:
>
>> On Sun, 04 Jan 2004 21:40:39 +1100,
>> poiuytrewqasd...@pqowieurytghfjdkslazmxncv.com wrote:
>>
>> > The digital modulation signal is QAM64 (standard)
>>
>> QAM has fuck all to do with channel changes doofus.
>> Quadrature Amplitude Modulation. In basic terms, this means that
>> instead of sending a single bit in one go you can transmit many. More
>> bits means more bandwidth and hence more channels.
>
> Hence more procesing time to find the fucking right Digital Mrz
> frequency.
No, actually, one QAM constellations acquisition time is much the same as
another. Tuning to the RF is the tricky bit in the RF/demod chain.
> Example:
>
> QPSK: Analogue frequency: bigpond cable users the high 580Mhz range
> for its download channel and the low 25Mhz range for its uploading
> channel.
>
> Which is why Bigpond Cable has such a limited range in terms of speed
> (uploading and downloading) but on the other hand can handle more
> uploading speed on the back end frequency (side B and C of the Data
> over Copper channel) Much in the same way its ADSL network runs.
>
Which has nothing to do with the time it takes to figure out how to tune to
a service.
>>
>> Higher the QAM value, higher the susceptibility to poor quality
>> transmissions
>
> No not correct, well not with Digital Cable anyway.
Yes it *is* correct, *especially* with digital cable.
Noise affects QAM signals by making the demodulator guess wrongly what
symbol is being transmitted.
The more symbols transmitted per symbol period [eg the higher the QAM
number] the smaller the distance between them and the greater the chance of
causing an error in demodulation.
Draw a grid of dots in 8x8 [qam 64] and a 16x16 grid [qam 256] in the same
size square. Then think about how far apart the dots are.
Thats the difference between qam64 and qam256.
> Anywehere between 64 to 128 to 256 is aceptable via Digital cable as
> only 1 side of the data channel is receiving.
"only 1 side of the data channel is receiving." has exactly nothing to do
with noise susceptibility in the broadcast QAM channels.
cb
It takes a while because it has to decode the mpeg2 from mid stream,
there is only a keyframe sent every 15 frames, it needs that frame to
know the rest, so it waits on that, on windows its diff coz it finds the
previous ones and decodes all until it finds it. Try seeking mid stream
in an internet streaming file.
Technically mpeg2 can insert more I B frames before a P frame, so who
knows what they do , might be dynamic.
Jay wrote:
> Anyone with Austar knows.
> It takes about 5 seconds per channel change.
>
> Yes, you will have to adjust because your channel surfing will be seriously
> disrupted. Also, if Austar is any guide, you will not be able to set your
> box to skip stupid channels that you have absolutely no interest in.
>
> Austar used to have that feature, but they removed it.
> They claimed it was too confusing for customers but I suspect
> that it was too confusing for their inept help desk people.
>