[linux-dvb] Tuning broken in development branch, 2.6.20 for lowest freq channel with TT DVB-C 1500

Kari Salmela Kari.Salmela at lanwan.fi
Mon Apr 16 16:52:01 CEST 2007


Hello

 

Hardware: Technotrend DVB-C 1500, CI, Conax CAM, Asus P5B

 

Am I the only one left alone without working system with current
development v4l tree? Somewhere between 2.6.18.1 and 2.6.20 (and current
mercurial, also) something changed, and tuning to Discovery channel no
longer works at least for me. With 2.6.18.1 plain vanilla kernel,
Discovery channel on 138 Mhz works fine:

 

mythtv:/home/mythtv/.czap# czap -a 1 -c disco.conf "Discovery"

using '/dev/dvb/adapter1/frontend0' and '/dev/dvb/adapter1/demux0'

reading channels from file 'disco.conf'

  1
Discovery:138000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_128:900:901:406

  1 Discovery: f 138000000, s 6900000, i 2, fec 0, qam 4, v 0x384, a
0x385

status 1f | signal 0324 | snr 1224 | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

status 1f | signal 0325 | snr 0fbd | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

status 1f | signal 0325 | snr 104c | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

status 1f | signal 0325 | snr 1107 | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

status 1f | signal 0325 | snr 1154 | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

status 1f | signal 0325 | snr 10da | ber 00000000 | unc 00000000 |
FE_HAS_LOCK

 

but if I try with 2.6.20 or v4l mercurial:

 

mythtv:/home/mythtv/.czap# czap -a 1 -c disco.conf "Discovery"

using '/dev/dvb/adapter1/frontend0' and '/dev/dvb/adapter1/demux0'

reading channels from file 'disco.conf'

  1
Discovery:138000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_128:900:901:406

  1 Discovery: f 138000000, s 6900000, i 2, fec 0, qam 4, v 0x384, a
0x385

status 00 | signal 0329 | snr 2368 | ber 00000000 | unc 00000000 |

status 00 | signal 0329 | snr 06fc | ber 00000000 | unc 00000000 |

status 00 | signal 032a | snr 07eb | ber 00000000 | unc 00000000 |

status 00 | signal 032a | snr 07e4 | ber 00000000 | unc 00000000 |

status 00 | signal 0328 | snr 0678 | ber 00000000 | unc 00000000 |

 

.. no lock, no picture ..

 

All the other multiplexes work ok with both setups, except for one HD
channel with QAM256, which has some artifacts, but that's a different
issue...  It seems that on the problematic set, SNR is large on first
seconds and drops fast after that. Possibly a timing issue?? Anyone have
ideas how to debug this?

 

--Kari

 

 

 

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