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[linux-dvb] Re: DVB-T signal acquisition time...?



Robert Schlabbach wrote:
Hi,

has anyone here ever measured the signal acquisition time (time for the
demodulator to fully lock to a signal after a channel change) on DVB-T? I
find that with my TDA10045H card and (Windows) driver, it takes over 600ms
to fully lock to a signal - a bit too long for my taste.

Is that the best the TDA10045H (or even DVB-T) can do, or am I maybe doing
something wrong? For comparison, the STV0299B can acquire the signal in
less than 5ms, and the VES1820 typically in less than 50ms. These times are
negligible compared to the typical MPEG keyframe interval of about 500ms.
But the DVB-T signal acquisition time is not and significantly delays the
channel change times... :(
I never did absolute measurements but the 'perceived aquisition time' has been for all OFDM demodulators much higher than for cable or satellite demodulators. This sounded natural to me since the number of circuits that need to get synchronized increases significantly from QPSK to QAM and even more to COFDM.

Anyway - I can't tell you hard numbers, just the fact that I had the feeling that some well-designed DVB-T STBs are able to tune in about half a second in strong-signal receiption environments in most cases, so this matches your measurement of a signal aquisition time of a few hundret milliseconds...

Have you played with other alternative frontends?

Holger




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