There's already been some HD transmissions, but they've been on the existing DVB-T modulation. The current TV cards and set top boxes simply aren't capable of demodulating the signal.
Once the signal has been demodulated it then needs to be decoded. This can be done on a suitably powerful PC, or by the time the technology evolves, by a DSP on a set top box or a second/third generation TV card.
PCs are capable of decoding the new HD signals, but there's no hardware to demodulate the signal, other than some very expensive analogue to digital converters.
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Demodulation vs decoding
There's already been some HD transmissions, but they've been on the existing DVB-T modulation. The current TV cards and set top boxes simply aren't capable of demodulating the signal.
Once the signal has been demodulated it then needs to be decoded. This can be done on a suitably powerful PC, or by the time the technology evolves, by a DSP on a set top box or a second/third generation TV card.
PCs are capable of decoding the new HD signals, but there's no hardware to demodulate the signal, other than some very expensive analogue to digital converters.