[linux-dvb] How can I ever succeed using DVB-T on Gentoo Linux?

Jesper Taxbøl jesper at taxboel.dk
Tue Jan 22 21:07:06 CET 2008


Hi guys,

I have been trying to get DVB working under Gentoo for quite some time
now. At first my goal was to receive encrypted DVB-S through a PCI
card. That adventure took me through a list of cards:

Terratec Cinergy  without a CAM module - this could recieve Free TV
Pinnacle systems card with a CAM module - This could only recieve free TV
Hauppauge-NEXUS-S card without a CAM module
Hauppauge-NOVA-S with a CAM module.

I actually made the last one work, but it could only tune for about 15
minutes and I often needed to coldstart the PC. I gave up on the DVB-S
units almost a year ago and have now moved toward DVB-T cards, hoping
that life without a CAM module is easier. Denmark recently started
DVB-T services. This adventure has now taken me through 4 different
cards.

A pinnacle stick (USB ID: eb1a:2870) that only seem to reveal a analog
tuner. So no luck with that yet.
A AGK stick (USB ID: 15a4:9020), that is recognized as an af9005
device, but it cant scan any services.
Two Hauppauge Nova-T-USB sticks (2040:7070). that could scan and tune,
but had alot of noise in the signal. I tried variuous firmwares that
finally ended up killing one of the units.
A Hauppauge NOVA-T-PCI, which sort of works but there is a lot of
noise in the signal.

I feel I am getting closer, but it is very frustrating to spend alot
of time and money getting nowhere. So i figured I would try to explain
what I have done, hoping for someone to point out some obvious
mistake.

I have tried a range of PC's using Gentoo on all of them. The one I
use now is a Core2 Duo running "i686 mode". (I tried installing an
Amd64 profile, but that really made the mercurial v4l-dvb package
complain.)

I do a normal gentoo stage3 install following
http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?full=1.
On top of that i have installed "vanilla-sources", so my kernel is 2.6.23.9.

Then I fetch the v4l-dvb and dvb-apps packages (as root) using:

hg clone http://linuxtv.org/hg/v4l-dvb

hg clone http://linuxtv.org/hg/dvb-apps

then i do make && make install in both of the directories and reboot.

Then I enter the v4l-dvb directory and do a "make reload". This seem
to load modules, but with very mixed results.

I read "dmesg" to see if my device has been detected.

If this wakes up one of my devices I usually do a scan for channels using:

scan /usr/share/dvb/dvb-t/dk-All
(I usually use one device at a time, to avoid mixups)

This evening this procedure revealed a poor subset of the channels I
know is available in my signal. All very noisy.

I try to record using:

gnutv -out file test.mpg -timeout 5400 DR1

Thereafter i play it using VLC

vlc test.mpg

This reveals a noisy video stream. Sound is skipping and the image is
very distorted.

I have some ideas on where the error lies, but not the knowledge to
proceed so I have cooked up some questions:

1) What is the right kernel to use with the latest v4l-dvb checkout,
and where can I figure out which to use.

2) What is the proper firmware for DVB cards. I killed a Nova-T-USB
stick trying a bad firmware, and I suspect bad firmwares to be partly
responsible for some of my problems. How do I make sure I have the
right firmware?

3) Is the ForwardErrorCorrection algorithm not supported by the
v4l-dvb drivers. I get crisp images on Windows, but noisy on Linux?

4) What is the proper procedure for rebuilding and installing the
v4l-dvb modules.

"Make menuconfig" in the v4l-dvb directory gives me some options. What
should I enable. And perhaps more important what should be disabled in
the kernel menuconfig.

Should I do something after the modules are built?

What is the proper way to give modules options?

How do I clean out old modules?

I sure could use some guidance here.

I hope my explanation pops up some obvious reason for my poor results
and perhaps some answers.

Thank you in advance, and sorry for the lengthy mail.

Jesper Taxbøl



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