T2 or T Tuner

logie110

Hi guys..what's the difference between a saorview box with a T2 tuner as opossed to a box with a T tuner??

Gerry Wicklow

T2 is the newer more efficient transmission standard. It is currently only used in UK for it's HD muxes. If you are within range of a Welsh or NI HD transmitter, you should be able to view FreeView HD. It is unlikely to be adopted here for some time yet.

logie110

Gerry Wicklow wrote: »

T2 is the newer more efficient transmission standard. It is currently only used in UK for it's HD muxes. If you are within range of a Welsh or NI HD transmitter, you should be able to view FreeView HD. It is unlikely to be adopted here for some time yet.

Hi gerry..if and when T2 is adopted here will a box with a T tuner still be compaitible?

gerryo

logie110 wrote: »

Hi gerry..if and when T2 is adopted here will a box with a T tuner still be compaitible?

Don't think so.
T2 is backwards compatible with T, but I don't think T works with T2.

Given the huge effort required to jump from analogue to digital TV, I think it may be quite a while before Ireland switches again.

And whose to say it will be T2 if we do.

The Cush

logie110 wrote: »

if and when T2 is adopted here will a box with a T tuner still be compaitible?

Not with any service carried on a T2 mux. There are no plans to change over to DVB-T2. The only possibility for T2 mux(s) would be if a pay DTT service launched at some point in the future.

reslfj

gerryo wrote: »

Don't think so.
T2 is backwards compatible with T, but I don't think T works with T2.

And whose to say it will be T2 if we do.

It will be DVB-T2, but other parts of the receive-chain in the box/IDTV may change - e.g. the MPEG-4 compression may change to the new HEVC standard.
The BBC was not happy with the present "MPEG-4 High Profile Level 4.0" (720p50/1080interlace) FreeviewHD spec., but MPEG-4 FullHD (1080p50) chips were not available, at the time the FreeviewHD standard had to be frosen (in early 2009).

The procedures for EPG and channel scans should also - IMHO - follow the same mandatory standard in both the ROI and the UK.
Wasn't that a part of the MOU between the two governments ?

Lars

PS! I'm sure Saorview will continue with DVB-T for a number of years. More likely some muxes from NI will change - maybe some of the UK-COM muxes. Pay DTT - I am afraid - will not be a viable option in the present state of the economy.

winston_1

And once again there is NO SUCH THING as a DVT-T or DVB-T2 tuner. It's the decoder that decides not the tuner.

reslfj

winston_1 wrote: »

And once again there is NO SUCH THING as a DVT-T or DVB-T2 tuner. It's the decoder that decides not the tuner.

Well up to a point but - only half true -. In a strict RF terminology a tuner selects the RF frequency (band) to be received, filters (removes) adjacent frequencies and maybe changes the frequency to an IF and amplifies the signal.
Large parts of this is now often done with digital processing within analogue 'tuner' chips.

But the initial processing step in DVB-T/T2 (and DVB-C2) selects each individual COFDM carrier by doing a digital FFT (Fast Fourier transform) on the incoming signal. The result is a (complex) value for each carrier - some used to estimate the RF TX-RX channel, but most values are later used by a 'detector' to extract the I, Q values (or amplitude/phase) and the bits transmitted.

This first part of DVB-T/T2/C2 is as much a 'tuner' as anything - except maybe it should be called 'tuners' as up to 32k frequencies are 'tuned' in one FFT process.

Agreed the DVB-T/T2 (and C2) standards includes a lot of processing without a direct relation to being a 'tuner' - e.g. time interleaving or FEC calculations.
But I find it rather OK to call these DVB standards 'digital tuners'.


Lars

PS! MPEG-2/4 is, however, not a 'tuner' but compression/decompression methods for video etc.

watty

Not exactly true.
Strictly speaking the T or T2 uses a demodulator in the Tuner Module with digital out or a separate chip or in a do everything inc MPEG chip from a zero IF tuner head.

MPEG uses a decoder after the T or T2 demodulator.

[Edit: crossed with reslfj who is saying same thing in detail]

ardmacha

Would it be wrong/naive to say that DVB-T/T2 relates to signal coding/compression and MPEG 4 to image coding/compression?

watty

DVB-T/T2 relates to signal Modulation scheme of arbitrary data, which has ALL the channels of a Mux.

MPEG2 / MPEG4 is decompression of error corrected data into digital video after it's demultiplexed. The Arbitrary data is is usually a serial multiplexed MPEG2 Transport stream containing any mix of Teletext, MP2 audio, AAC audio, AC3 Audio, Subtitles, EPG, MHEG5, MPEG2 video, MPEG4 video and even UDP IP data for any number of channels.

Confusingly MPEG2 TS is the name of the stream and MPEG2 video is also a codec. MPEG4 video is carried along with MP2 or AAC Audio etc in an MPEG2 Transport Stream.

reslfj

ardmacha wrote: »

Would it be wrong/naive to say that DVB-T/T2 relates to signal coding/compression ....

Except there is very little compression* in these DVB transmission standards. Data are just moved - errorfree - from A to B.

If fact the useful date 'bits' are expanded by the addition of the FEC coding 'bits'. But this i just playing with words - I guess.

Lars

* a little shared signaling and "null packet deletion" in DVB-T2 is all - AFAIR.