[OSM-talk] JOSM Audio Mapping - Technical Issues

David Earl david at frankieandshadow.com
Fri Jan 2 12:17:55 GMT 2009

JOSM Audio is designed to sync *continuous* audio with the GPX track. 
This means you don't have to fiddle with the recorder buttons every time 
you want a voice note, you can just leave it in a pocket; but nor do you 
have to listen to inordinate amounts of heavy breathing.

See the JOSM help file at 
http://josm.openstreetmap.de/wiki/Help/HowTo/AudioMapping for details 
(or use Help while in JOSM, same thing).

I too have an Olympus recorder. The clock on mine is about 0.15% out, 
which means that a continuous sound track can be many tens of metres out 
after an hour's recording, so make sure you at least check whether you 
need to calibrate (as described in the help). I guess the time stamps 
for multiple files will suffer from the same problem too unless the 
recorder sampling rate and the time stamps run off a different clock.

Note that in the long play mode the Olympus recorder (well, my model, so 
I guess all of them) records 4 bit audio, so you'll need to convert it 
to 8-bit using Audacity or similar before it is usable in JOSM. This is 
quick and easy for one long file, but a bit tedious if you have to do it 
for many small files.

It would be relatively simple to extend the existing functionality to 
also process a folder full of time-stamped WAV files, one for each GPX 
waypoint; but really it is much easier just to record one long session - 
easier to record, easier to preprocess and easier to handle in JOSM.

Someone mentioned that someone has broken audio in a recent JOSM 
version. I haven't had a chance to check yet, but I have made no changes 
to the audio recently.

On a bike, I suggest using a cheapo PC headset (with a bit of sponge 
over the mic) rather than the built-in mic as it is completely hands 
free then.


On 01/01/2009 16:58, Gregory wrote:
> I got a new olympus digital voice recorder for Christmas, which means I 
> have to use http://code.google.com/p/odvr/ to download the recordings to 
> my linux/ubuntu computer. Unfortunatly when downloading the wav files 
> the recorded date gets lost, but a table of the times can be displayed 
> on the command prompt.
> How does JOSM Audio get the date/time of the wav files?
> I tried changing the linux files atime and mtime (last accessed/modified 
> time), but the location marker for the audio does not change. Is it 
> using the ctime (created time)? I can not change the ctime and it gets 
> set to the time the files were downloaded off the voice recorder.
> I have filled an issue with the odvr downloader, but I want to confirm 
> that it is the ctime that needs to be right for JOSM. I was recording 
> ~2sec comments as I passed a location, so I have a trip with 60 
> recordings waiting to be mapped.
> My final idea is maybe I could make a JOSM plugin (now I've learnt some 
> Java) that takes a fixed-width txt table of time stamps and names, and 
> match the times to an open gpx file to create waypoints. This would mean 
> I have to open audio files outside of josm, but at least I would know 
> where they were recorded. Such a plugin may help people with other media 
> problems, ao I wonder has something along those lines already been done?
> I've been told audio mapping is more amazing than photo mapping, and it 
> would be ideal cycling in these cold winter months. Sadly it's not going 
> to well yet, so I hope to get this sorted.
> Gregory Marler
> http://www.livingwithdragons.com
> ------------------------------------------------------------------------
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk

More information about the talk mailing list