Real Time Live Streaming With TrackAddict Telemetry

[Robertsmania]

I have setup a system to live stream autocross and track days on Twitch from my car.

It uses a Windows 10 laptop, OBS software, two webcams and an iPhone running TrackAddict.

To get the iPhone display with TrackAddict to show up on the stream I'm using the iOS Screen Mirroring feature and AirServer software running on the PC.

What I find is that for the outlap and first timed lap, the display from the phone lags behind real time by quite a bit. Then at the end of the first timed lap something happens with TrackAddict and it always disconnects from AirServer.

Here's a video of when it finishes the first timed lap on TrackAddict, but in reality I'm already up by turn 3.

[Robertsmania]

Then if I re-start the iOS Screen Mirroring then on subsequent laps, the TrackAddict display is pretty well synchronized and keeps up.

[Robertsmania]

From the behavior I observe, it seems like the initial out lap has the video feed and is drawing the track map from the GPS - during that phase is when it lags and when that stops is when the Screen Mirroring gets disrupted.

I would really like to be able to just start TrackAddict and have it display consistently for the whole run group.

Any thoughts on existing configuration options to keep the telemetry display the same, or feature enhancements to the app to make this kind of use more feasible?

[Weston@HPTuners]

This looks like it could be a CPU resource issue when you are attempting to use iOS Screen Mirroring. The first lap where the track map is being drawn as you drive does take more CPU than subsequent laps, because it has to rescale and regenerate the whole thing upon each new GPS data sample. Your video showing the app's display lagging and updating less frequently certainly fits that theory as well. This CPU use would also be increased if you are using an external GPS with a higher sample rate than the phone's internal 1 Hz GPS, being that it's getting more samples per second.

You might try turning off TrackAddict's own video recording, if you have other cameras capturing the action. That could save some processing time.

The next app update (v4.0.5) will aim to reduce the CPU load during this first lap. The map's first lap refresh rate was cranked up for many of the newer phones, so I'll back that down a bit.

At some point, I do hope to automatically save the lap data points into the user track database, so that you'd have a complete track map from the very start if you've driven that track/configuration previously. That may also come with an option for predictive lap timing data to persist between sessions. That's been on my to-do list for a while now, but we've had a few other things that needed to be done first.

[Robertsmania]

This looks like it could be a CPU resource issue when you are attempting to use iOS Screen Mirroring. The first lap where the track map is being drawn as you drive does take more CPU than subsequent laps, because it has to rescale and regenerate the whole thing upon each new GPS data sample. Your video showing the app's display lagging and updating less frequently certainly fits that theory as well. This CPU use would also be increased if you are using an external GPS with a higher sample rate than the phone's internal 1 Hz GPS, being that it's getting more samples per second.

You might try turning off TrackAddict's own video recording, if you have other cameras capturing the action. That could save some processing time.

The next app update (v4.0.5) will aim to reduce the CPU load during this first lap. The map's first lap refresh rate was cranked up for many of the newer phones, so I'll back that down a bit.

Thank you for the reply!

I did some experiments this weekend at an autocross event, and like the first lap of a circuit it just lags terribly behind the real time video.



If there is a way to reduce the CPU utilization or otherwise improve it, it would be awesome to get the time data to show up if nothing else.

I do certainly want to keep having the phone do its video recording. My usual routine is to have TrackAddict record the lap, then do a WiFi transfer to an iPad and review that before I go out to drive my next lap. And for analysis and stuff after the event, the quality of the TrackAddict recording is significantly better than what my crazy system streams live.

For my application, just having the time display would be satisfactory. I dont know if showing the video window and map creation on the phone display is expensive at all, but they are not necessary for what I'm trying to do. I guess in a perfect world, showing the time, speed, rpm and throttle in would be great and add valuable information to the stream.

[Weston@HPTuners]

Yup, the same thing is happening on segment and trail runs as on lap 1 of circuits, so the upcoming adjustment should improve all of those. I'm hoping to have that app update out later this week...

[libertyforall1776]

Which iPhone model are you using? It may be time to get a newer version with beefier processor to do more, more efficiently...

[Robertsmania]

I just saw the update, thank you! I will test it out.

For my TrackAddict phone I am using an old iPhone5 and it’s always been satisfactory for the video recording and processing. I do have a more modern phone but it’s being used for the data uplink while streaming. I need to have the TrackAddict iPhone on a separate wifi network for transferring the lap data/video to my iPad for review between runs.