[linux-dvb] Tuning/locking problems with PCTV 2000e

Jami Pekkanen jami.pekkanen at tkk.fi
Tue Oct 23 16:49:39 CEST 2007


Some more information:

When I use tzap to tune adapter1 to "YLE TV1" multiplex (the situation 
that gives a bad image), I get a high bit error rate:

tzap -r -a 1 "YLE TV1"
using '/dev/dvb/adapter1/frontend0' and '/dev/dvb/adapter1/demux0'
tuning to 562000000 Hz
video pid 0x0200, audio pid 0x028a
status 06 | signal ffff | snr 0000 | ber 001fffff | unc 00000000 |
status 1e | signal ffff | snr 0000 | ber 000007d0 | unc 00000012 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 000002c0 | unc 00000000 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 00000130 | unc 00000000 | 
FE_HAS_LOCK

However, with the another device, this stream has practically no error 
at all:

tzap -r -a 0 "YLE TV1"
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
tuning to 562000000 Hz
video pid 0x0200, audio pid 0x028a
status 06 | signal ffff | snr 0000 | ber 001fffff | unc 00000000 |
status 1e | signal ffff | snr 0000 | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 00000000 | unc 00000000 | 
FE_HAS_LOCK

And when trying to tune adapter0 to the multiplex it won't tune into 
("partial lock" in MythTV), there's a high amount of "uncorrected block 
error":

tzap -r -a 0 "MTV3"
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
tuning to 658000000 Hz
video pid 0x0131, audio pid 0x0231
status 02 | signal ffff | snr 0000 | ber 001fffff | unc 00000000 |
status 1a | signal ffff | snr 0000 | ber 00000000 | unc 00000120 | 
FE_HAS_LOCK
status 1a | signal ffff | snr 0000 | ber 00000000 | unc 000001a7 | 
FE_HAS_LOCK
status 1a | signal ffff | snr 0000 | ber 00000000 | unc 00000219 | 
FE_HAS_LOCK
status 1a | signal ffff | snr 0000 | ber 00000000 | unc 0000028b | 
FE_HAS_LOCK
status 1a | signal ffff | snr 0000 | ber 00000000 | unc 00000303 | 
FE_HAS_LOCK

Watching the same multiplex with adapter1 has no uncorrected error, but 
quite a lot of bit error, this doesn't influence the video quality though:

tzap -r -a 1 "MTV3"
using '/dev/dvb/adapter1/frontend0' and '/dev/dvb/adapter1/demux0'
tuning to 658000000 Hz
video pid 0x0131, audio pid 0x0231
status 06 | signal ffff | snr 0000 | ber 001fffff | unc 00000000 |
status 1e | signal ffff | snr 0000 | ber 00000490 | unc 00000000 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 00000300 | unc 00000000 | 
FE_HAS_LOCK
status 1e | signal ffff | snr 0000 | ber 00000350 | unc 00000000 | 
FE_HAS_LOCK

However, when I first tune adapter1 to "MTV3" (its "good" channel) and 
then adapter0 to the same multiplex (that doesn't show any image), the 
bit error rate goes to (near) zero also in adapter1.

One guess would be that the card's "diversity" feature state is 
internally somehow on, which prevents the tuners from working 
independently (which would also explain the better signal when both are 
tuned to same multiplex). Or then again it could be another bug 
altogether, but anyway it seems that the tuners aren't working fully 
independently.

I browsed through the driver code and found some code about the 
diversity in dib7000p.c and dib7000m.c, but my understanding of the 
hardware and DVB in general is quite lacking. It seems however that 
there's options to enable/disable the diversity through the driver 
(contrary to the documentation in the card's wiki entry), but I can't 
figure out how to get the configuration to the module (in insmod, ioctl, 
sys/proc fs ??).

- Jami



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