Hi!

I have been following the KnoppMyth forums for quite a while and I always find them entertaining and sometimes downright funny. The lowrider project has been incredibly funny to me so to say "thanks!" I thought I'd post the notes from my latest project for your entertainment.

I keep bench notes during my KnoppMyth installs to help the inevitable reinstalls and tweaks to aid in maintenance and recovery. This document is basically a cleaned up set of those notes.

As far as I know lowrider is the lowest end computer MythTV has successfully run on or at least seen posted on the internet. If you see any lower end PCs running MythTV I would sure like to see it, please post links on this thread so we can compare notes.

It is amazing to me how well this old PC works as a MythTV box given its history and general state. I picked the name lowrider because this PC running MythTV reminded me of seeing the old model cars that some "lowrider" enthusiasts work on. They refurbish old cars into something completely different than how the car began and they perform wonderfully. I find it fascinating just to watch them.

I think it's a testament to how well designed Linux, MythTV, and Linux really is to operate so well in such a severely resource constrained environment. When all is said and done, this project has been a success and works well. I may post a machine description and a shortened version of these bench notes in Tier 2!


Enjoy!

Andrew Lynch


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Low End MythTV: Project lowrider

References

http://www.belynnandjeremy.xohost.com/m ... 's_Ear.htm
http://hawley.homeip.net/recycled-machine-mythtv.html

http://mysettopbox.tv/phpBB2


Howto install KnoppMyth on lowrider

This computer has had a rough and tumble history. It is built from parts that were essentially cast aside as trash and I have reclaimed them to assemble a decent if battered working machine. Previously, it ran Knoppix 3.7 which worked so well it just wasn't very challenging. So I decided to take on something a little bigger ... like MythTV.

First: describe the hardware. Fairly low end stuff. Not bad for 1997.

Pentium II, 266 MHz Klamath core
128 MB mixed EDO and SDRAM
PCCHIPS M720 Dual Pentium II (one CPU installed) motherboard
http://motherboards.org/mobot/motherboa ... hips/M720/

Generic ATX Case, power supply, keyboard, MS Mouse
generic 14" SVGA monitor (I think its dying as it turns blue occasionally)

8 GB EIDE HD hda
32x EIDE CD-ROM hdc (severely broken loading mechanism, I use a finishing nail to eject CDs!)

Creative SB16 ISAPNP soundcard
SYM53C416 ISAPNP SCSI card

10/100 Mbit PCI ethernet NIC
ATI TV Wonder VE PCI tuner
S3 Virge 4MB PCI video card



(Originally the sound card was a SB32 AWE but got swapped during testing and was never replaced. I am fairly sure it would still work right in final configuration -- once the parameters are right it should make little difference)

Boot from KnoppMyth R4V5 CD using special startup parameters

Follow KnoppMyth install instructions

This is a summary of prompts and responses while booting from the CD:
At “Boot” prompt, type “knoppmyth no-hlt vga=normal screen=640x480” for 640x480 compatible displays
Select “2. Auto Install” at KnoppMyth main-menu, ok.
Don't try and change the date settings, just select “ok”.
Select “Yes” at the Initialization dialog
Type full name, “Next”
Type user ID, “Next”
Type password, “Next”
Type password again, “Next”
Type root password, “Next”
Type root password again, “Next”
Type the host name, “Next”
Select “Yes” to proceed
Select “Yes” to continue
Select “Yes” again to continue
Wait...
At the successfully installed screen, select “ok”
Remove the CD when told and hit enter.
Wait...

At first boot press ctrl repeatedly so lilo will give boot menu and enter at "boot:" menu

linux no-hlt

Follow KnoppMyth install instructions and follow them to completion.

I selected the G.A.N.T. theme because it is easy to read at low resolution

I configured the default recording profile to record at 256x192 and live TV at 160x160



Exit MythTV frontend when done.






How to fix all the broken settings


1. lilo boot parameters

Press ctrl-alt-F1 to change to console

#vi /etc/lilo.conf

Add "no-hlt noisapnp" to list of kernel boot parameters in "Append ="

Close and save file

Run lilo to make changes to MBR

#lilo




2. fix ATI TV Wonder VE module parameters

Reverse order of tuner and bttv modules so that tuner is loaded first

#vi /etc/modules

Change the parameters for tuner (type=2) so bttv works right

#vi /etc/mythtv/modules/bttv

Add after first line of file

alias char-major-81-0 bttv
options tuner type=2
options bttv card=64 radio=0 tuner=2



Close and save file, and at command prompt:

#Update-modules ; depmod -a




3. Fix broken ISAPNP parameters

#pnpdump -c >/etc/isapnp.conf

edit ISAPNP configuration to suite your hardware

#vi /etc/isapnp.conf


4. fix X screen resolutions and mouse problem

go to /etc/X11 directory and make backup of current XF86Config-4

#mv XF86Config-4 XF86Config-4.bak

use xf86config tool to create new configuration file specifying
- mouse port (/dev/ttyS1)
- 320x240 resolution for MythTV
- configure a 640x480 resolution mode for setup debugging, etc and comment out later

#xf86config

rename old style XF86Config file so XFree86 4.x can use it

#mv XF86Config XF84Config-4



5. fix Alsa

I created a file (as root) /etc/modutils/alsa (because one did not exist) with the following code:

#vi /etc/modutils/alsa


alias char-major-116 snd
alias char-major-14 soundcore

options snd major=116 cards_limit=4

alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
alias /dev/dsp* snd-pcm-oss

alias snd-card-0 snd-sb16
options snd-sb16 index=0 id="SB-16" port=0x240 mpu_port=0x300 fm_port=0x388 irq=5 dma8=0 dma16=5 isapnp=0

alias snd-slot-0 snd-card-0
alias sound-slot-0 snd-slot-0




Close and save file

As root, update the modules and their dependencies

#update-modules ; depmod -a
#modprobe snd-sb16

Review the loaded modules to see if the Alsa modules loaded properly

#lsmod | less

#/etc/init.d/alsa-autoconfig
#/etc/init.d/Sound start



Check the mixer levels with alsamixer. Initially this gave me an error

"alsamixer: function snd_ctl_open failed for default: No such file or directory"

Alsamixer is easily fixed by creating the audio devices for linux alsa using

#alsa_snddevices

run the alsamixer

#alsamixer

make sure that master volume and pcm are turned up and line in are set to record and muted.


Results: Works great. Schedules and records TV shows like a champ and resulting playback is OK. Live TV is not so great and you can see the CPU strain under the load even at low resolution capture. Need to do some more experimenting to see what can be done to improve performance.




Remaining Tasks:

1. fix alsa so that it stores proper settings and then restores them on reboot.

(the forum says this is just doing an "alsactl store" and adding "alsactl restore" to /etc/init.d/Sound)

(update: since alsactl is not on my R4V5 box according to the forums, I'll have to add packages that break to get it. I'll stick with the manual procedure with alsamixer. No big deal.)

2. Try more exotic low resolution X modes like 256x192 and 240x180

(Since XF86Config-4 from xf86config does not contain any modeline settings, this may actually work. Not required but would improve video performance FPS.)

(update: after reviewing the XFree86.0.log it appears that my chipset "ViRGE 86c325" does not support default doublescan modes lower than 320x240. )

3. Configure as network frontend slave

(appears to be pretty straight forward from forum)

(update: this was trivially easy to do but disappointing. Just run mythtv-setup from the xterm and change the IP addresses in the General settings to the local IP and the MythTV backend server and restart the frontend. Works like a charm. Unfortunately, the CPU burden of displaying much higher resolution 720x480 MPEG2 files over a LAN was more than my CPU could bear and the quality was really badly choppy. Oh well, it was a neat idea. Save this for the next faster CPU frontend system)

4. Try recording in 320x240 mode

(probably pushing the CPU throughput limits but since 256x192 recordings look nice its worth a try)

(update: good news! 320x240 work great and look even better than 256x192. Sort of like SP VHS quality video. OK and definitely watchable. Doesn't even appear to drop frames on recorded videos. Nice!)

5. See if Xv is enabled and if not if enabling Xv would help playback performance

(need to find out if Xv is enabled by default or turned on using xvinfo)

(update: according to the XFree86 s3virge docs, my chipset "ViRGE 86c325" does not support Xv at all.
see: http://unixhelp.ed.ac.uk/CGI/man-cgi?s3virge+4
Bummer! xvinfo confirmed this by reporting "no adaptors found" at all resolutions. This video card makes me long for my NVidia GF440MX with its great linux drivers. Oh well. )

woudl be interesting to see how well this pc woudl work with a 2nd cpu

i even have a spare Pii 266 here in aus i'd give ya to find out pitty i'm not in the US hey

I tried running MythTV on a PIII/500 box and while I could get decent TV results... DVD playback was not watchable to me... prompting me to give up that ghost and use my 1.8ghz machine instead. DVD playback (through Xine... NOT mplayer) is VERY important to me on my Myth box.

anyone actually had luck with this?

_________________
...you pervy Windows™ fancier!

This thread described how a low end system was setup and used. You have issues/questions about playing DVDs. How do the two relate? If you search the forum and wiki, you'd know KnoppMyth now includes Xine. You can playback unencrypted DVDs w/o issue.

_________________
cesman

When the source is open, the possibilities are endless!

My myth box is running fine. What I was saying is that when i tried setting it up on a LOW END system, I had no luck getting DVD playback working smoothly on a LOW END system. To me DVD playback is just as important on a MthTV box as watching live TV.

I was inquiring as to whether or not those who had tried Myth on a LOW END system also saw this issue.

I have no issues running Xine on MythTV or Knoppmyth... it was to relate that I'd had been able to get MythTV running on a low end system but that DVD playback was bad at best.

_________________
...you pervy Windows™ fancier!