For ages I have been intending to write a program to produce a nice guide to a town or area based on OpenStreetMap data.
I finally decided that I knew enough about postgresql and python to have a go.
The result is a program called townguide.py. The idea is that you load the openstreetmap data into a postgresql database (like you do if you want to render it using Mapnik), then produce an xml file to tell townguide.py what you want rendering. It then goes and produces the nice output for you.
Version 0.1 is working and is on SVN. At the moment it only produces html output (because that is easy), and it is not very pretty.
The next stage is to make it produce postscript to give nice printable output on a defined paper size.
An example of the html output is at http://hartlepoolmap.webhop.net.
Having looked at the output it looks like it will be quite useful from a mapping point of view - if you know the area you can review the features that are summarised and look for missing banks, supermarkets etc.
Sunday, 4 October 2009
Saturday, 19 September 2009
Using a Graphics Tablet in Ubuntu 9.04
I have a cheap Trust graphics tablet that I used to use for drawing in Inkscape or Gimp.
It stopped working at some point (Can't remember which Ubuntu version), but I decided I needed to use it again, because drawing with a touchpad on a laptop is a pain in the thumb...
It was surprising that it didn't just work when you plug it in, because I'm sure a previous version of Ubuntu behaved like this.
I found the instructions at https://help.ubuntu.com/community/AiptekTablet.
You basically have to install the Aiptek xorg driver and put a configuration file in a directory under /etc/hal. I wondered where the X11 configuration was now that Xorg.conf is so small....
Anyway, it works now...
It stopped working at some point (Can't remember which Ubuntu version), but I decided I needed to use it again, because drawing with a touchpad on a laptop is a pain in the thumb...
It was surprising that it didn't just work when you plug it in, because I'm sure a previous version of Ubuntu behaved like this.
I found the instructions at https://help.ubuntu.com/community/AiptekTablet.
You basically have to install the Aiptek xorg driver and put a configuration file in a directory under /etc/hal. I wondered where the X11 configuration was now that Xorg.conf is so small....
Anyway, it works now...
Sunday, 6 September 2009
Progress with IP Camera Viewer
The Edimax IP Camera seems to work fairly well, but the video stream seems to get interrupted every now and again, which makes the player crash - vlc just hangs, and mplayer exits.
I decided that exiting was better so I have written a simple pyGTK front end for mplayer to play the screen. It also includes a wireless network link quality monitor to help understand why it is not working - it is here as 'bentv'.
Note that bentv uses a library that I have started work on (named ntpylib for want of a better name) - so far it only contains one class, 'prefs', which deals with saving and loading of simple key/value data from XML files. It includes a dialog box that GUI programs (such as bentv.py) can use to allow the user to edit the data. prefs.py and prefs.glade need copying or linking into the bentv directory to make it work - there is no clever installer!
I decided that exiting was better so I have written a simple pyGTK front end for mplayer to play the screen. It also includes a wireless network link quality monitor to help understand why it is not working - it is here as 'bentv'.
Note that bentv uses a library that I have started work on (named ntpylib for want of a better name) - so far it only contains one class, 'prefs', which deals with saving and loading of simple key/value data from XML files. It includes a dialog box that GUI programs (such as bentv.py) can use to allow the user to edit the data. prefs.py and prefs.glade need copying or linking into the bentv directory to make it work - there is no clever installer!
Sunday, 23 August 2009
Embedded Linux Firmware Binary Files
I have always struggled to understand the format of the binary files that store the firmware upgrades.
They tend to be a mixture of some simple text labels, a kernel image and one or more mountable filesystems.
I have written a little script that goes through a file in a brute force (one byte at a time) way and attempts to mount it as various filesystem types (script stored here).
I used the information found by this script, and the source code provided by Edimax to work out some information about the internals of the IC-3010WG IP Camera - it is written up here.
They tend to be a mixture of some simple text labels, a kernel image and one or more mountable filesystems.
I have written a little script that goes through a file in a brute force (one byte at a time) way and attempts to mount it as various filesystem types (script stored here).
I used the information found by this script, and the source code provided by Edimax to work out some information about the internals of the IC-3010WG IP Camera - it is written up here.
Saturday, 22 August 2009
Practical Experience using the Edimax IP Camera
We were away on holiday last week so I got to try using the Edimax IP camera 'for real' as a monitor to keep an eye on our disabled son - known as 'BenTV-ng' (next generation) to distinguish it from 'BenTV' which was the old analogue system I used to use.
I gave up on using ad-hoc networking and instead took my wireless access point with me. This had the added advantage of improving the range of transmission because I could arrange for the access point to be between the camera and the computer. The computer I used was a Toshiba netbook running Ubuntu Linux.
The first thing I noticed was that when I powered everything up, nothing happened. At first I thought it was because the access point needed to see a wired connection as well as a wireless one, because when I connected the computer to it using a wire things started to work. I soon realised that the range was awful - it stopped working as soon as you were outside of his room. This turned out to be my fault because I had also switched on the analogue camera, which transmitted on the same frequency as the wireless network, so the noise level was huge. Things got better when I switched off the analogue camera.
At first everything appeared to work - vlc rtsp://admin:1234@bentv/ipcam.sdp played the video stream with sound.
I soon noticed that if the network got interrupted vlc froze, giving an apparently good picture, but no movement, which was no use to me. Instead I changed to mplayer - at least if that got into trouble it crashed and closed the video playback window so you knew something was wrong.
I set up a simple shell script that loops indefinitely starting mplayer then when mplayer exits it re-boots the ip camera, waits for 30 seconds and starts mplayer again.
This approach worked pretty well - the 30 second interruptions during the re-boot were not usually too troublesome.
We did find some problems when the video stream only worked for a few seconds before mplayer exited and the re-boot sequence started again, which was no good at all. The only way I found to cure this was to power off the camera all together - a software re-boot via the web interface did not cure it. I'll set up a little test at home now to see how long it takes to get into this state, and whether it makes a difference if you use wireless or wired networking.
The code to achieve this is stored at http://code.google.com/p/ntmisc/source/browse/bentv/
I gave up on using ad-hoc networking and instead took my wireless access point with me. This had the added advantage of improving the range of transmission because I could arrange for the access point to be between the camera and the computer. The computer I used was a Toshiba netbook running Ubuntu Linux.
The first thing I noticed was that when I powered everything up, nothing happened. At first I thought it was because the access point needed to see a wired connection as well as a wireless one, because when I connected the computer to it using a wire things started to work. I soon realised that the range was awful - it stopped working as soon as you were outside of his room. This turned out to be my fault because I had also switched on the analogue camera, which transmitted on the same frequency as the wireless network, so the noise level was huge. Things got better when I switched off the analogue camera.
At first everything appeared to work - vlc rtsp://admin:1234@bentv/ipcam.sdp played the video stream with sound.
I soon noticed that if the network got interrupted vlc froze, giving an apparently good picture, but no movement, which was no use to me. Instead I changed to mplayer - at least if that got into trouble it crashed and closed the video playback window so you knew something was wrong.
I set up a simple shell script that loops indefinitely starting mplayer then when mplayer exits it re-boots the ip camera, waits for 30 seconds and starts mplayer again.
This approach worked pretty well - the 30 second interruptions during the re-boot were not usually too troublesome.
We did find some problems when the video stream only worked for a few seconds before mplayer exited and the re-boot sequence started again, which was no good at all. The only way I found to cure this was to power off the camera all together - a software re-boot via the web interface did not cure it. I'll set up a little test at home now to see how long it takes to get into this state, and whether it makes a difference if you use wireless or wired networking.
The code to achieve this is stored at http://code.google.com/p/ntmisc/source/browse/bentv/
Friday, 24 July 2009
Ad-Hoc Wireless Network Troubles
Now that I have the Edimax IP Camera working I want it to connect to my Toshiba NB100 netbook computer as simply as possible - the idea is to use it when we are away on holiday so I don't want to have to set up a whole network with an access point etc. Instead I just want to set up an ad-hoc network between the computer and the IP Camera.
According to the instructions this should be easy - I tell the IP Camera to connect to an ad-hoc network called 'bentv', and then use NetworkManager in the Ubuntu desktop of the netbook to create the ad-hoc network.
This works fine on my main laptop, but fails on the netbook.
It turns out that NetworkManager is not capable of putting the wireless card into ad-hoc mode.
The work around was to have the script to start the VLC viewer shutdown network manager and set up the network manually as follows:
This is based on information I found here.
This seems to work, but the wireless networking is a bit iffy after the script exits - I might have to do the wlanconfig destroy bit again to put it into infrastructure mode.
According to the instructions this should be easy - I tell the IP Camera to connect to an ad-hoc network called 'bentv', and then use NetworkManager in the Ubuntu desktop of the netbook to create the ad-hoc network.
This works fine on my main laptop, but fails on the netbook.
It turns out that NetworkManager is not capable of putting the wireless card into ad-hoc mode.
The work around was to have the script to start the VLC viewer shutdown network manager and set up the network manually as follows:
#!/bin/sh
/etc/init.d/NetworkManager stop
ifconfig ath1 down
wlanconfig ath1 destroy
wlanconfig ath1 create wlandev wifi0 wlanmode adhoc
iwconfig ath1 essid bentv
iwconfig ath1 channel 1
iwconfig ath1 192.168.1.35
iwconfig ath1 netmask 255.255.255.0
ifconfig ath1 up
vlc --fullscreen rtsp://192.168.1.17/ipcam.sdp
/etc/init.d/NetworkManager start
This is based on information I found here.
This seems to work, but the wireless networking is a bit iffy after the script exits - I might have to do the wlanconfig destroy bit again to put it into infrastructure mode.
Sunday, 12 July 2009
More on Edimax IP Camera
I think we're getting somewhere. Searching around for references to IP cameras and mplayer yielded this thread which suggested the following:
Progress!
Just need to get sound working now....
Well, I did a bit more hunting around in the camera web set-up and realised I had missed a section about RTSP. The default was for RTSP to be enabled on port 554 with a rtsp path of ipcam.sdp.
When I tried
I got pictures AND sound!
I had tried rtsp before, but had missed the ipcam.sdp bit. Mplayer complains that my little netbook is too slow to play the stream, so there is a bit more work to do, but it looks promising. I'll try VLC now.
This seems to work ok - there is a bit of a delay in the video, but probably ~0.1 sec, which is acceptable.
mkfifo fifo.mpeg4
wget -q http://admin:1234@192.168.1.117:4322 -Ofifo.mpeg4 &
mplayer -V -demuxer 35 fifo.mpeg4
Progress!
Just need to get sound working now....
Well, I did a bit more hunting around in the camera web set-up and realised I had missed a section about RTSP. The default was for RTSP to be enabled on port 554 with a rtsp path of ipcam.sdp.
When I tried
mplayer rtsp://192.168.1.117:554/ipcam.sdp
I got pictures AND sound!
I had tried rtsp before, but had missed the ipcam.sdp bit. Mplayer complains that my little netbook is too slow to play the stream, so there is a bit more work to do, but it looks promising. I'll try VLC now.
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