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285 posts

Ultimate Geek


Topic # 24320 21-Jul-2008 14:46
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Hi Geeksters

I have some questions about digital TV; specifically with regards to cable.


Some time ago (I did not pay much attention as I'm a Sky Satellite subscriber) Telstra announced they were going digital with their TV transmission.


I assume this means that there is now a single (or multiple?) electrical-digital singals running through the coax cable that connects into my house. Can anyeone add any clarity into how this mechanism works?


Based on previous threads I've read, it sounds like there are now two types of STB's in use: Analog and Digital. I assume the analog STB's represent the old mechanism -which is still being supported? Any new connection I would assume defaults to a digital STB?


I know for a fact (I have a splitter on my coax cable) that I can hook Telstra's cable (via an RF plug adapter) into my PC's "analog" TV tuner and am able to pick up/decode a number of free-to-air channels -which is great, as it works well with Windows Media Centre and I was even able to set up a web-based EPG using revens XML converter (see www.reven.co.nz).


Would it also be possible to use a digital TV tuner (in my PC) and decode these channels via the digital feed?


HD content. Can I assume any move by Telstra to join the HD bandwagon is going to require a STB upgrade for existing digital subscribers?

Note that as I live in Wainui, I've not even bothered looking at the freeview HD option, UHF reception sucks in this lovely little valley, which is why I went with satellite originally.





"There is no way to Peace -Peace is the Way" (A. J. Muste)

 


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  Reply # 149915 21-Jul-2008 15:45
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Yes, there is now analogue cable tv carriers and digital cable tv carriers on the same cable.

Yes, two set top boxes... Analogue uses several different types of set top box (Usually General Instrument/Motorola).
Digital Cable TV requires a different set top box (ADB).

No, you cannot use any PC card to decode Digital TV, in fact you shouldn't really connect anything other than provided hardware to the cable.

The current set top box does not support HD.. a different set top box would be required.

Cheers,
Grant

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  Reply # 149917 21-Jul-2008 15:54
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Freeview|HD should be good in most parts of Wainui as there is a transmitter on Mt Fitzherbert (the mast at the end of the valley above Naenae)

 
 
 
 


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  Reply # 149923 21-Jul-2008 16:06
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A cable network is a private little RF propagation system, just like the big outside world, but enclosed within the cable and the network thereof. As such analog TV is transmitted in the same manner as normal TV transmissions, albeit to a frequency plan decided by TCL not MED, and each channel has a normal analog TV frequency occupancy of 7MHz (although I understand TCL uses a US plan of 6MHz). Digital transmissions on cable networks use the DVB-C standard, which places a 6Mhz wide QPSK or more commonly QAM carrier in a desired TV channel, this has a useable bitrate or around 30-40Mb/s, and carries DVB compliant transport streams which within are all the various elements (ie mpeg2 video, mpeg1 audio, Service Info streams and various tables of information). DVB transport streams consist of a constant rate of DVB packets each 204bytes long, 188 are actual payload the rest are wrapper overheads.  The cable network may carry 10 or more QAM carriers, each with 6or more SD channels within.

The DOCSIS cable broadband system essentailly packets IP traffic up into mpeg frames and then into DVB compliant transmissions, so appear like an the DVB-C digital TV carriers, but carrying data. All the downstream DOCSIS carriers and digtial TV carriers are in the band from 50MHz upward, and upstream transmissions from your cable modem are in the 5-45MHz band.

DOCSIS3 allows channels bonding, this means that a very wide (upto 24MHz) slot of 2,3 or4 adjacent channels can be combined to carry one large symbol rate QAM carrier that can carry 200Mb/s.

Cyril



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  Reply # 150101 22-Jul-2008 08:42
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Thanks guys, every response above was helpful and insightful.

sbiddle, sounds like I was wrong about the Wainui reception issue -I will seriously consider getting a quality external UHF arial installed.  My preference is to use a digital tuner on my PC (as versus a setop box) and my understanding is that this is possible with freeview HD.

Cheers





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  Reply # 150183 22-Jul-2008 11:26
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Quidam:

Thanks guys, every response above was helpful and insightful.

sbiddle, sounds like I was wrong about the Wainui reception issue -I will seriously consider getting a quality external UHF arial installed.  My preference is to use a digital tuner on my PC (as versus a setop box) and my understanding is that this is possible with freeview HD.

It is possible to get a digital DVB-C cable tuner card for your PC, plus you would need an Irdeto CAM to put your TCL Digital Smartcard into.  It's not for the faint of heart or short of time as the whole setup process can be considerable.  However I do know a few guys in Wellington who have done this and it integrates nicely into GB-PVR and Media Portal, the EPG can be problematic due to TCL only sending over the DVB signal the current + next program, but there are ways around that as well.  I personally don't do this as I have a different solution, but have seen a number of very sweet setups doing this.  It is however against the TCL T&C's as you are not allowed to connect anything other than TCL supplied hardware to the TCL Cable network for the reasons Cyril detailed above.






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  Reply # 152209 28-Jul-2008 21:21
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As Steve said,the majority of Wainui gets a good UHF signal,PM me if you 
you are interested in an install  


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  Reply # 152226 28-Jul-2008 22:16
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Cyril, TCL uses 8Mhz 64-QAM, starting at 570Mhz going up to 682Mhz and they seem to have 10 video streams per transponder, more if it's got only radio stations on tp.  You see most of it when the ADB box boots and it scans all the transponders.







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  Reply # 152294 29-Jul-2008 08:48
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Brunzy:

As Steve said,the majority of Wainui gets a good UHF signal,PM me if you 
you are interested in an install  



I've PM'd you.

Would be brilliant if I was able to get the Olympics in HD.

I would want to feed the signal into a HTPC.

I already feed sky into it via a svideo/RCA inputs.  Am running SageTV and use the plug-in Placeshifter which means I can share the picture to other PC's in the house.  (This means we can watch Sky on other TV's but can only change channels etc via the STB)

I envisage using a digital tuner card so I can fully make use of SageTV/Place shifter

ps. The PC in question is probably the lowest spec machine in my house.  It's running a Pentium-M (with a CT-479 adapter kit) overclocked to about 2.5ghz on an Asus desktop motherboard.  These were probably the best of the single-core cpu's and were the basis for the Conroe design.  I have a 8800GTS 320meg Video card installed.  I'm just slightly concerned about system performance when handling a Hi def signal -but I assume the Video Card should offer hardware assistance for the decoding  (I have the purevideo plug-in installed)




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  Reply # 152295 29-Jul-2008 08:51
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Cyril, TCL uses 8Mhz 64-QAM, starting at 570Mhz going up to 682Mhz and they seem to have 10 video streams per transponder, more if it's got only radio stations on tp.  You see most of it when the ADB box boots and it scans all the transponders.


Hi, yes but there Docsis carriers are 6MHz ones not EuroDocsis, so much for standards.

Cyril

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  Reply # 152299 29-Jul-2008 09:10
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Quidam:
I already feed sky into it via a svideo/RCA inputs.  Am running SageTV and use the plug-in Placeshifter which means I can share the picture to other PC's in the house.  (This means we can watch Sky on other TV's but can only change channels etc via the STB)


Just one small issue here - SageTV still had no support for H.264 DVB-T broadcasts so you would need to change TV software.





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  Reply # 152921 31-Jul-2008 10:39
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sbiddle:
Quidam:
I already feed sky into it via a svideo/RCA inputs.  Am running SageTV and use the plug-in Placeshifter which means I can share the picture to other PC's in the house.  (This means we can watch Sky on other TV's but can only change channels etc via the STB)


Just one small issue here - SageTV still had no support for H.264 DVB-T broadcasts so you would need to change TV software.




Thanks, -I was kind of bummed to read this.  In fact I sent a email to SageTV customer support about this issue and they repliied saying Sage does support DVB-T H.264, assuming the TV card supports it.  They also said they support our sound codec, and would provide email support if I have problems setting it up.

Obviously I remain sceptical about whether it will work, as I imagine you had good reason for saying SageTV doesn't support it.  Along those lines, I am looking to get the install done next Friday, and will probably go with a setop box, and then experiment with a feed into my PC.

ps. exact contents of response from SageTV:

If your tuner supports DVB-T H.264, SageTV shouldn't have a problem with
that, SageTV internally supports H.264 format video plus AAC-HE audio
(NewZealand).

if you have any problem, send us a mail.




"There is no way to Peace -Peace is the Way" (A. J. Muste)

 


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