GPS Overlay Test

Testing converting my GPX(or TCX) data to SRT(subtitles) to overlay details.

I have only done GPX so far, so I can overlay long/lat, alt, speed, bearing(cardinal and degrees). GPX doesn't store HR or CAD, so I will use Garmins TCX xml format for that later on.

Problems/thoughts so far...
1) SRT embedding is a pain in Windows Movie Maker (well, it just doesn't work). So for now I need to burn the subtitles in VDubMod (after converting to SSA since my VDub is buggered). And then I can cut/caption/encode in WMM. Or for raw video cut in VDubMod and encode first.

This isn't such an issue if you just want to save the .srt along side your raw videos, as it will just play in most decent players as normal subtitles would.

2) I have my garmin updating in smart mode. It only logs a point when HR/CAD/Direction/Speed/Alt changes, which could be a few seconds, so it doesn't seem to be responsive. So if it doesn't update for 3 seconds, my speed was the same for the 3 seconds it shows that speed.
I can set it to record 1 per second regardless, but this limits my recording to 3.5 hours I think (which I might start changing too for shorter rides).

2b) You might see that the alt is 102 then jumps to 100 (say 4 seconds later). This is because at 2 seconds in the middle its 101m and the GPS knows it. Because the change is linear (it must do this with speeds too, as long as direction is assumed the same from previous).

So when a line/graph is drawn, it's still accurate. This means that I can myself, calculate the difference every second between, and calculate the alt, and make it update even more rapidly... granted this is later date stuff.

3) I have a wheel speed/cadence sensor, my speed/cad will be more accurate than erratic GPS speed.

4) I also have the 305 which unlike some units has barometric alt, which calibrated over time or manually is much more accurate than GPS. If you compare my baro alt to say a garmin trek 101 which has no barometer, the GPS alt is very erratic.
The 305 705 has barometric, the 205 doesnt... I am not sure about other models, this is well worth considering when buying a unit, so is the speed sensors.

5) I'm slow :(

6) YouTube allows you to upload subtitles for videos, not embedded. And you can turn these on using the menu in the bottom right. This is okay if your video is properly synced to the subtitles... which isn't so easy if you cut the video, even without captions/credits.

7) Syncing your position on the video can be hard to the subtitles. For this one, I saw on the video I started the GPS 19 seconds in. So in my script to convert I marked the offset as 19s.
How to get around this...
a. Start GPS and video at the same time.
b. voice you are starting your gps on the video (or tap the camera, it will show a spike in the audio waveform).
c. find your location on the video on a map and check that position with the time/position in your gps

then check that the speed slows down at junctions etc...

7b) If you use autopause, or stop and start your gps manually, you can still sync the video using the original gps start time, so long as you don't stop your video.

Category:

Autos & Vehicles

Tags:

• gps
• subtitle
• srt
• overlay
• cyclist
• garmin
• edge
• 305

[rarosalion]

Stupid question, possibly, but... what are you using to convert the gps tracks to SRT? I know GPS babel converts lots of gps log format types, but I wasn't aware of SRT being an output format!

[drsquirrel0]

@rarosalion I did it myself, using my own coding and own calculations (to a stupidly high accuracy :p). The script was written in PHP so it could be hosted if I wanted, but as I have mentioned before I have no use for it - and the syncing to video is a big issue so its useless unless you specifically want it.

[39stonecyclist]

Thats awesome mate

[drsquirrel0]

You don't specifically need a 305, anything that can track with GPS and give a "decent" readable output (anything that gps babel can read would be a sensible way to call it) can do the above and the other video.

We both do it the same almost, I use flat text subtitles, they use "graphic" sub pictures (which dvd sub titles are, not text... graphics)

[drsquirrel0]

@outithewoods I have that info of course, I just decided not to post them on this vid. Not that i'm exactly paranoid or overly anonymous, I just don't want my home lats being on the interwebs :p

I've slightly abandoned this, too lazy mainly, but it's awkward to sync and I would only really do it if I wanted to show a video for some reason, coding is mostly done, bit more for inter point accuracy (ie. point refresh).

btw check out SLpb9oWnsqU

[drsquirrel0]

I'm not working now, but I was starting to commute 10 miles (each way, luckily on the back roads not this one).

I always give/plan myself 40 minutes, I can do it close to say 35 minutes (inc slow down for a mile in town). A lot of people could do this faster, I do need a little more stamina.

Shows that distance really is a small point when considering work commuting. But, I guess commuting on bike more suits the city boys rather than rural as it is, faster by car ;)

[Drivingyarns]

OK then, with speeds like that there is little need to drive, as long as you can consume enough pasta and bananas

[drsquirrel0]

What? Speeds like that? I'm slooooooooow.

First was up hill, second part was down and I was taking my time. I would usually be doing around 25mph on flat and 30mph on a slight down hill.

[Drivingyarns]

That's a good result, and a good idea too.

Anyway, I can certainly see the point of cycling if you can get speeds like that