[linux-dvb] SNR problem with Twinhan VP-3040 (DTT-CI)

Fredrik Ax xmltv at axnet.nu
Fri Nov 17 10:42:36 CET 2006


Hi,

I have a Signal/Noise Ratio problem with my VP-3040 (DTT-CI) card.

I would like to start with pointing out that the reception in my area is
excellent and that the problem does no occur if I use the same card in
the same computer, with the same antenna, etc, using Windows.

The problem does occur only for some transponders / frequencies. 

For example does all channels defined by
"482000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_4:HIERARCHY_NONE:1029:1028:5110"
work perfectly, whilst channels at
"506000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_3_4:FEC_1_2:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_4:HIERARCHY_NONE:1049:1048:1040"
do have this problem.


Now for the actual problem description:

When doing a tzap to the channels on the affected transponders the SNR
periodically drops to zero, causing the viewed stream to slow / freeze
/ be distorted. If I increase the cache in e.g. mplayer it takes a bit
longer until the cache is emptied and the stream gets distorted and
eventually freezes. (See below of example output from tzap both for
problematic transponder and good one).

I'm running a Debian (etch) system with an 2.6.18.2 kernel, but I have
had the same problem with all kernels and cvs / hg checkouts I've
tried (I think I started playing around with a 2.6.12 kernel with the
latest CVS from linuxtv.org back in August 2005).

It would be great if you had a clue about what might be wrong ... 
and even better if you got a possible solution in store :-)


Thanks in advance,
Fredrik Ax




Below follows output from modul-loading and tzap.


The modules load fine according to the syslog:

Nov 16 21:42:01 localhost kernel: Linux video capture interface: v2.00
Nov 16 21:42:01 localhost kernel: bttv: driver version 0.9.16 loaded
Nov 16 21:42:01 localhost kernel: bttv: using 8 buffers with 2080k (520 pages) each for capture
Nov 16 21:42:01 localhost kernel: bttv: Bt8xx card found (0).
Nov 16 21:42:01 localhost kernel: ACPI: PCI Interrupt 0000:02:0d.0[A] -> GSI 21 (level, low) -> IRQ 217
Nov 16 21:42:01 localhost kernel: bttv0: Bt878 (rev 17) at 0000:02:0d.0, irq: 217, latency: 64, mmio: 0xf7efe000
Nov 16 21:42:01 localhost kernel: bttv0: detected: Twinhan VisionPlus DVB [card=113], PCI subsystem ID is 1822:0001
Nov 16 21:42:01 localhost kernel: bttv0: using: Twinhan DST + clones [card=113,autodetected]
Nov 16 21:42:01 localhost kernel: bttv0: gpio: en=00000000, out=00000000 in=00f500fd [init]
Nov 16 21:42:01 localhost kernel: bttv0: using tuner=4
Nov 16 21:42:01 localhost kernel: bttv0: add subdevice "dvb0"
Nov 16 21:42:01 localhost kernel: bt878: AUDIO driver version 0.0.0 loaded
Nov 16 21:42:01 localhost kernel: bt878: Bt878 AUDIO function found (0).
Nov 16 21:42:01 localhost kernel: ACPI: PCI Interrupt 0000:02:0d.1[A] -> GSI 21 (level, low) -> IRQ 217
Nov 16 21:42:01 localhost kernel: bt878_probe: card id=[0x11822],[ Twinhan VisionPlus DVB ] has DVB functions.
Nov 16 21:42:01 localhost kernel: bt878(0): Bt878 (rev 17) at 02:0d.1, irq: 217, latency: 64, memory: 0xf7eff000
Nov 16 21:42:01 localhost kernel: DVB: registering new adapter (bttv0).
Nov 16 21:42:01 localhost kernel: dst(0) dst_get_device_id: Recognise [DTT-CI]
Nov 16 21:42:01 localhost kernel: DST type flags : 0x1000 VLF 0x10 firmware version = 2
Nov 16 21:42:01 localhost kernel: dst(0) dst_get_mac: MAC Address=[00:08:ca:14:0f:00]
Nov 16 21:42:01 localhost kernel: dst(0) dst_get_tuner_info: DST TYpe = MULTI FE
Nov 16 21:42:03 localhost kernel: dst_ca_attach: registering DST-CA device
Nov 16 21:42:03 localhost kernel: DVB: registering frontend 0 (DST DVB-T)...


--- tzap output from good transponder:
> tzap -r -c frax-channels.conf SVT1
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file 'frax-channels.conf'
tuning to 482000000 Hz
video pid 0x03fb, audio pid 0x03fa
status 1f | signal 8000 | snr 5a00 | ber bffa1aec | unc 10000000 | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bffa1b00 | unc b7ee0e3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bffa1b00 | unc b7ee0e3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bffa1b00 | unc b7ee0e3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bffa1b00 | unc b7ee0e3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bffa1b00 | unc b7ee0e3a | FE_HAS_LOCK
...

--- tzap output from problematic transponder:

> tzap -r -c channels.conf TV4    
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file 'frax-channels.conf'
tuning to 506000000 Hz
video pid 0x0419, audio pid 0x0418
status 1f | signal 8000 | snr 5a00 | ber bf94448c | unc 10000000 | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 3200 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 3200 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 0000 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
status 1f | signal 8000 | snr 5a00 | ber bf9444a0 | unc b7f3ee3a | FE_HAS_LOCK
....





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