[BC] Analogue is better for many viewers

[Rik van Riel]

Harold Hallikainen wrote:
> I haven't studied 8VSB extensively. Is there any sort of fall-back system
> in it?

DVB-T has hierarchical modulation, which makes it possible to
fall back to decoding fewer bits (getting just the high priority
stream) in bad conditions and decoding more bits when the signal
is good.

This is done by mapping the most important bits to the QPSK
state of a 16QAM or 64QAM signal.  If the signal is bad, the
QPSK state can still be decoded (2 bits per symbol) and the
important bits can be used. The other 4 or 6 bits per symbol
can only be extracted if the signal is good.

ATSC is all-or-nothing.  All the error correction is done
in the digital stream, with no earlier fallbacks possible.

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