[linux-dvb] Re: How to understand DVB tools

[Q <raid517@fairadsl.co.uk>]

OK this is as far as I got. I have no idea how you pulled any of the
data you detailed from this.

This is my transmitter/s.

http://www.ofcom.org.uk/static/reception_advice/digital_trans_guide/show_transmitter.asp-siteID=32.html

My immediate impressions are these:

How can i tell from looking at this whether I have an offset or not. For
Offsets all I can see are some + and minus signs. Are they indicating
that if I see an offset symbol which is a minus - sign that I should
subtract 167kHz from the total frequency and if I see a plus sign I
should add it? Where and how should I add or subtract this 167khz? Am i
right to assume that this should be done as follows:

Multiplex 1 BBC
Channel	30 = 510 - 167 = 343MHZ
Offset	- 
ERP	0.02

Multiplex A SDN
Channel	25 = 475 + 167 =  592MHZ
Offset	+ 
ERP	0.02

Multiplex C Crown Castle
Channel	32 = 544 + 167 = 711MHZ
Offset	+ 
ERP	0.02

Multiplex 2 Digital 3&4
Channel	22 = 374 +167 = 541MHZ
Offset	+ 
ERP	0.02

Multiplex B BBC
Channel	28 = 476 + 167 = 643MHZ
Offset	+ 
ERP	0.02

Multiplex D Crown Castle
Channel	57 = 969 + 167 = 1136MHZ
Offset	+ 
ERP	0.02

And this is where I loose it:

Quote:

"T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
T 474000000 8MHz 1/2 NONE QAM16 2k 1/32 NONE"

How on earth did you derive this information from the information above?
Indeed again I have to confess I don't know what any of these values
mean, let alone how to formulate accurate channel settings for them.

Television is simply something I have never had to think all that hard
about in the past. It has just been there, you switch it on and you
don't even have to care how it works.

As forthe additional data you requested, it's fairly lengthy, so I hope
you don't mind. With regard to OS, I am running Gentoo Linux. (Again
notoriously fiddly to set up - but very easy once it is done to
maintain).

I have an Nforce 2.0 motherboard (Abit). and a 2.2-ish GHZ processor
with 512 MB DDR 

ls PCI Gives the following output:

sh-2.05b# lspci
00:00.0 Host bridge: nVidia Corporation nForce2 AGP (different version?)
(rev c1)
00:00.1 RAM memory: nVidia Corporation nForce2 Memory Controller 1 (rev
c1)
00:00.2 RAM memory: nVidia Corporation nForce2 Memory Controller 4 (rev
c1)
00:00.3 RAM memory: nVidia Corporation nForce2 Memory Controller 3 (rev
c1)
00:00.4 RAM memory: nVidia Corporation nForce2 Memory Controller 2 (rev
c1)
00:00.5 RAM memory: nVidia Corporation nForce2 Memory Controller 5 (rev
c1)
00:01.0 ISA bridge: nVidia Corporation nForce2 ISA Bridge (rev a4)
00:01.1 SMBus: nVidia Corporation nForce2 SMBus (MCP) (rev a2)
00:02.0 USB Controller: nVidia Corporation nForce2 USB Controller (rev
a4)
00:02.1 USB Controller: nVidia Corporation nForce2 USB Controller (rev
a4)
00:02.2 USB Controller: nVidia Corporation nForce2 USB Controller (rev
a4)
00:04.0 Ethernet controller: nVidia Corporation nForce2 Ethernet
Controller (rev a1)
00:05.0 Multimedia audio controller: nVidia Corporation nForce
MultiMedia audio [Via VT82C686B] (rev a2)
00:06.0 Multimedia audio controller: nVidia Corporation nForce2 AC97
Audio Controler (MCP) (rev a1)
00:08.0 PCI bridge: nVidia Corporation nForce2 External PCI Bridge (rev
a3)
00:09.0 IDE interface: nVidia Corporation nForce2 IDE (rev a2)
00:0d.0 FireWire (IEEE 1394): nVidia Corporation nForce2 FireWire (IEEE
1394) Controller (rev a3)
00:1e.0 PCI bridge: nVidia Corporation nForce2 AGP (rev c1)
01:08.0 Multimedia audio controller: Creative Labs SB Audigy (rev 04)
01:08.1 Input device controller: Creative Labs SB Audigy MIDI/Game port
(rev 04)
01:08.2 FireWire (IEEE 1394): Creative Labs SB Audigy FireWire Port (rev
04)
01:09.0 Multimedia controller: Philips Semiconductors SAA7146 (rev 01)
01:0b.0 RAID bus controller: Silicon Image, Inc. (formerly CMD
Technology Inc) Silicon Image Serial ATARaid Controller [ CMD/Sil
3112/3112A ] (rev 02)
02:00.0 VGA compatible controller: ATI Technologies Inc RV350 NJ [Radeon
9800 XT]
02:00.1 Display controller: ATI Technologies Inc RV350 NJ [Radeon 9800
XT] (Secondary)

So my WinTV Nova-T card is fully recognised.

Ls mod gives me:

Module                  Size  Used by
sr_mod                 13988  0
fglrx                 213324  7
cdemu                  11404  0
vmnet                  31440  12
vmmon                 157068  0
snd_intel8x0           30024  0
snd_mpu401_uart         6144  1 snd_intel8x0
snd_emu10k1            91656  0
snd_rawmidi            19876  2 snd_mpu401_uart,snd_emu10k1
snd_ac97_codec         66436  2 snd_intel8x0,snd_emu10k1
snd_util_mem            3264  1 snd_emu10k1
snd_hwdep               7172  1 snd_emu10k1
snd_pcm_oss            49128  0
snd_pcm                84936  3 snd_intel8x0,snd_emu10k1,snd_pcm_oss
snd_page_alloc          8968  3 snd_intel8x0,snd_emu10k1,snd_pcm
snd_timer              21124  1 snd_pcm
snd_mixer_oss          17344  1 snd_pcm_oss


But again you should note tha DVB support is 'compiled in' rather than
having been built in my kernel as a module.

In any case since I am a proficient Googler, I did a search with regard
to there being no frontend0 and I found that this is the case in many
distros. (there were though the three devices listed in my earlier
mail). Morever several other devices were not present like video.o and
audio.o and so on. After reading around for a while I found that in fact
what I needed to do was create them using a script.

So I used the following script:

#!/bin/sh
# Create device nodes for the Linux DVB API with DVB_API_VERSION 2.
# The devices created are suitable for most current PC DVB cards,
# i.e. cards having one frontend, one demux and optionally one
# MPEG decoder.
# The script creates devices for four cards by default.

if [ -e /dev/.devfsd ]; then
echo "It seems you are using devfs. Good!"
exit 0
fi

# get rid of old DVB API devices; do it twice for good measure...
rm -rf /dev/ost
rm -rf /dev/ost
rm -rf /dev/dvb
rm -rf /dev/dvb

mkdir /dev/dvb
chmod 755 /dev/dvb

for i in `seq 0 3`; do
echo "Creating DVB devices in /dev/dvb/adapter0$i"
mkdir /dev/dvb/adapter$i
chmod 755 /dev/dvb/adapter$i
mknod -m 0660 /dev/dvb/adapter0$i/video0 c 250 `expr 64 \* $i + 0`
mknod -m 0660 /dev/dvb/adapter0$i/audio0 c 250 `expr 64 \* $i + 1`
mknod -m 0660 /dev/dvb/adapter0$i/frontend0 c 250 `expr 64 \* $i + 3`
mknod -m 0660 /dev/dvb/adapter0$i/demux0 c 250 `expr 64 \* $i + 4`
mknod -m 0660 /dev/dvb/adapter0$i/dvr0 c 250 `expr 64 \* $i + 5`
mknod -m 0660 /dev/dvb/adapter0$i/ca0 c 250 `expr 64 \* $i + 6`
mknod -m 0660 /dev/dvb/adapter0$i/net0 c 250 `expr 64 \* $i + 7`
mknod -m 0660 /dev/dvb/adapter0$i/osd0 c 250 `expr 64 \* $i + 8`
chown root.video /dev/dvb/adapter0$i/*
done

but the issue I found with this was that it was pointing to
/dev/dvb/adapter and not /dev/dvb/adapter0, so I edited it to reflect
where my other dvb devices (mounted by the kernel) were all located. I
am not so sure though if any of the applications will be able to find
them there or if doing this is likely to cause me to run into trouble?

Anyway the script didn't wotrk too well as it kind of crapped out after
it said it has found I was using /devfs and congradulated me. So
assuming that since the tools were still asking for these devices they
were probably needed I decided to just use use mknod from the CL and
make them anway.

But the question is now what? It is entirely non obvious to me how to
derive the correct information from the above statisticsin order to
write a working configuration file. I note that one of those who
graciously responded to my previous mail hinted that they 'had to
guess'FEC (the 1/2 field)' because none of the vaues they tried worked -
but I have to ask for your understanding here in that the 'FEC' and '1/2
field' are just meaningless terms for me. So if he/you had to 'guess' I
don't see how you stand a chance of guessing anything.

If you guys think I'm a complete dumbass for asking this stuff then I'm
sorry. I would like to learn it - and I am sure I can. I just need a
somehwat clearer explanation than has been possible so far.

Your input in this regard is very much appreciated.

GJ