[linux-dvb] Budget DVB-C tuning problems

[Antti Kaihola <antti.kaihola@linux-aktivaattori.org>]

I'm having tuning problems on my budget DVB-C card. When I get a good
tuning, everything works perfectly. Unfortunately I get occasional
tuning failures all the time.

I've tried tuning with czap, dvbtune and mythtv, and they all show the
same behavior (see below).

My card is a VES1820-based Technotrend budget DVB-C with Philips
SAA7146, bought from USA-X / DVBSHOP.

I'm using dvb-kernel from CVS (2004-02-06) with
kernel-tmb-2.6.2-0.rc2.1.tmb.2mdk-1-1mdk from Mandrake Cooker
contributions.  I did a "make" in the dvb-kernel CVS tree, unloaded
any DVB modules and loaded these new modules with a modified
insmod.sh:
  videodev, evdev, v4l1-compat, v4l2-common, video-buf,
  dvb-core.ko, ves1820.ko verbose=1, saa7146.ko, ttpci-eeprom.ko,
  budget-core.ko, budget.ko

I had a similar behavior with the dvb-kernel drivers included in
kernels 2.4.22, 2.6.0, 2.6.1 and 2.6.2.  It seems to me that the
number of unsuccessful tunings is bigger with the current CVS driver
than with the older ones.

I've understood that the pwm setting has no effect on this card.
Trying different values for it when loading the ves1820 module has
indeed no effect at all to the AFC value (I get (3) always).

The unscrambled channels here (Turku, Finland) are on the frequencies
162MHz and 154MHz, so these are the frequencies I've been trying to
tune to.

One detail which has caught my eye is from the dvbtune output.  When I
tune successfully to, say, 162MHz, dvbtune reads back from the card a
frequency value of 172579786Hz (see dvbtune output attached below),
which equals to:
  162MHz + 10.6MHz - 20214Hz.
I understand that 20214Hz corresponds to my AFC value of 3, but where
does the 10.6MHz offset come from?

I've spent a fair amount of time reading this mailing list and found
no solutions to this problem.  I'd appreciate any suggestions about
how to debug and try to solve the problem.

Best regards,

Antti Kaihola



Output from lspci
-----------------

$ lspci -v

00:0d.0 Multimedia controller: Philips Semiconductors SAA7146 (rev 01)
	Subsystem: Technotrend Systemtechnik GmbH: Unknown device 1004
[snip]

$ lspci -vvnx

00:0d.0 Class 0480: 1131:7146 (rev 01)
	Subsystem: 13c2:1004
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B-
	Status: Cap- 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
	Latency: 32 (3750ns min, 9500ns max)
	Interrupt: pin A routed to IRQ 17
	Region 0: Memory at cfffbe00 (32-bit, non-prefetchable) [size=512]
00: 31 11 46 71 06 00 80 02 01 00 80 04 00 20 00 00
10: 00 be ff cf 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 c2 13 04 10
30: 00 00 00 00 00 00 00 00 00 00 00 00 0a 01 0f 26



Output from czap
----------------

An unsuccessful attempt:

# czap -n 1
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
  1 YLE1:162000000:INVERSION_OFF:6900000:FRC_NONE:QAM_128:512:650
  1 YLE1: f 162000000, s 6900000, i 0, fec -1, qam 4, v 0x200, a 0x28a
status 00 | signal e7e7 | snr 8f8f | ber 000001a4 | unc 00000000 |
status 00 | signal ffff | snr c0c0 | ber 000001a4 | unc ffffffff |
status 00 | signal ffff | snr bebe | ber 009ffff6 | unc ffffffff |
status 00 | signal ffff | snr bcbc | ber 009ffff6 | unc ffffffff |
status 00 | signal ffff | snr bcbc | ber 009ffff6 | unc ffffffff |
status 00 | signal ffff | snr baba | ber 009ffff6 | unc ffffffff |

Tuning success:

# /tmp/linuxtv-dvb-apps-1.1.0/util/szap/czap -n 1
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
  1 YLE1:162000000:INVERSION_OFF:6900000:FRC_NONE:QAM_128:512:650
  1 YLE1: f 162000000, s 6900000, i 0, fec -1, qam 4, v 0x200, a 0x28a
status 1f | signal 9b9b | snr e3e3 | ber 009ffff6 | unc ffffffff |
FE_HAS_LOCK
status 1f | signal ffff | snr eded | ber 009ffff6 | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr eded | ber 00077b82 | unc 00000000 |
FE_HAS_LOCK



Output from dvbtune
-------------------

An unsuccessful attempt:

# dvbtune -f 162000000 -s 6900 -qam 128 -I 0
Using DVB card "VES1820 based DVB-C frontend"
tuning DVB-C to 162000000, srate=6900000
frequency 162000000 inversion 0
symbol_rate 6900000 fec_inner 9 modulation 4
polling....
Getting frontend event
FE_STATUS: FE_TIMEDOUT
Not able to lock to the signal on the given frequency

Tuning success:

# dvbtune -f 162000000 -s 6900 -qam 128 -I 0
Using DVB card "VES1820 based DVB-C frontend"
tuning DVB-C to 162000000, srate=6900000
frequency 162000000 inversion 0
symbol_rate 6900000 fec_inner 9 modulation 4
polling....
Getting frontend event
FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
FE_HAS_SYNC
Event:  Frequency: 172579786
        SymbolRate: 6900000
        FEC_inner:  0
 
Bit error rate: 983670
Signal strength: 65535
SNR: 61166
FE_STATUS: FE_HAS_SIGNAL FE_HAS_LOCK FE_HAS_CARRIER FE_HAS_VITERBI
FE_HAS_SYNC



Output from ves1820 verbose=1
-----------------------------

This is the entry I get in /var/log/messages on a successful
tuning. The AFC value is occasionally 2, but almost always 3.

Feb  7 10:27:49 localhost kernel: DVB: VES1820(0): AFC (3) -20214Hz

 

System log messages when modules are loaded
-------------------------------------------

Feb  7 11:01:45 localhost kernel: saa7146: register extension 'budget
dvb'.
Feb  7 11:01:45 localhost kernel: saa7146: found saa7146 @ mem
e0945e00 (revision 1, irq 17) (0x13c2,0x1004).
Feb  7 11:01:45 localhost kernel: DVB: registering new adapter
(TT-Budget/WinTV-NOVA-C  PCI).
Feb  7 11:01:45 localhost kernel: DVB: VES1820(0): setup for tuner
sp5659c
Feb  7 11:01:45 localhost kernel: DVB: VES1820(0): pwm=0x48
Feb  7 11:01:45 localhost kernel: DVB: registering frontend 0:0
(VES1820 based DVB-C frontend)...
Feb  7 11:01:45 localhost kernel: TT-Budget/WinTV-NOVA-C  PCI adapter
0 has MAC addr = 00:d0:5c:02:57:16





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