[linux-dvb] AVerMedia AverTV DVB-T USB 2.0 (A800) signal reporting (tzap versus mythtv)

Doug Scoular dscoular at cisco.com
Sun Mar 5 01:59:17 CET 2006


Hi All,
    I'm wondering if there is a problem with the signal reporting on
    the AverMedia AverTV DVB-T USB 2.0 (A800) driver. This
    is on a genkernel generated 2.6.15-gentoo-r5 kernel.

    This appears to result in mythtv 0.19 failing to tune.

    When I run tzap or use xine dvb://1 I have no problems tuning
    and obtaining a good quality stream, however on close inspection
    I notice that tzap gives me 0 for signal, ber and unc (my Nova-T
    PCI card rarely gets 0 for ber and the signal is commonly c4c4).

bash-2.05b# tzap -c ~/nova-t-channels.conf -a 1 'TEN DIGITAL'
using '/dev/dvb/adapter1/frontend0' and '/dev/dvb/adapter1/demux0'
reading channels from file '/root/nova-t-channels.conf'
tuning to 219500000 Hz
video pid 0x0200, audio pid 0x028a
status 03 | signal 8d12 | snr 0002 | ber 001fffff | unc 0000ffff |
status 1f | signal 8d14 | snr 0002 | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK
status 1f | signal 0000 | snr ffff | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK
status 1f | signal 0000 | snr ffff | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK
status 1f | signal 0000 | snr ffff | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK

    Post lock, signal is reported as 0000... and according to the tzap 
README:

status 0x1f              --- The demodulator status bits. 0x1f means all 
bits set, everything ok.
signal [0x0000...0xffff] --- Signal Strength. Values above 0x8000 should 
be ok.
snr [0x0000...0xffff]    --- Signal/Noise Ratio. Values above 0x8000 are ok.
ber [0...0xffffffff]     --- Bit Error Rate. The less the better.
unc [0...0xffffffff]     --- Number of Uncorrectable Blocks. Small 
numbers are Preferable.

    So a reported signal of 0000 should be a bad thing.

    It appears MythTV expects to get reports on the following:

2006-03-05 11:10:47.320 SM(1)::AddFlags: Seen() Match() 
Wait(Sig,SNR,BER,UB,)

    And because signal is 0 it never succeeds in tuning the A800.

    Any thoughts on whether signal is being misreported for the A800 ?

    Cheers,

    Doug



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