Live telemetry overlay on your onboard video, no render first

A track day gives you an hour of onboard footage and maybe two clips you’d show anyone. The rest is for you: where you lifted, why the delta opened up in the second half of the lap, whether that was really the line you thought you drove.

Reviewing that footage with the data next to it is one thing. Reviewing it with the data on the picture is another — speed, lap time and the delta to your best lap in the frame, so you don’t look at a video and then at a chart. The usual way to get there is to render an overlay video first and watch it afterwards. Rendering takes minutes, and you only learn after the render that you picked the wrong lap.

This post covers a different order in ApexLog, the tool I build, so read the tool-specific parts with that in mind: review with the overlay drawn live over the file, and render only the clip you decided to publish.

The overlay, live, without rendering

Open a session, go to the Telemetry tab and play the original GoPro file from disk — the same file the overlay render reads, straight off the SD card or from a folder you linked. The overlay is drawn on the picture while it plays:

• Speed, with the running lap time and delta against the session’s fastest other lap: the best lap, or the second-fastest while you’re on the best one.
• The track map with the car’s position.
• The G meter, in Broadcast and Classic; Strip leaves it out.
• The OBD channels you’ve chosen, if the session has them.

Nothing is rendered and nothing is saved. The overlay is a layer over the player, driven by the sync the file already has with the session’s telemetry. It follows what you do: pause and it freezes on that frame, seek and it jumps to the matching moment, and when a long recording rolls over from one GoPro chapter to the next, the overlay goes with it.

Two small controls in the player head:

• Overlay turns it off and on. The browser remembers your choice, so if you prefer bare footage it stays that way.
• Fullscreen shows the video with the overlay across the whole screen. The player’s own fullscreen button shows the bare video, because the overlay is a layer on top of the player. To watch with the data on, use the Fullscreen next to Overlay.

Set it up once, in the player

Overlay settings, next to Overlay, changes the style, the elements and the OBD channels without leaving the player. The styles are the same three as in the render — Broadcast, Strip and Classic — with the same element switches and channel picker.

The settings are shared with Overlay video, the render panel. What you pick while watching is what the render uses, so the file you save looks like what you saw live. There’s no second set of preferences to keep in step.

Render this clip

When a lap turns out to be worth publishing, Render this clip in the player head opens Overlay video with that clip already loaded:

• no second file pick,
• no second read of the GPS inside the file,
• the same sync you were watching with.

If you linked a footage folder, it takes the chapter that is playing. From there the render works as described in the overlay post: choose the range, the output size, and render, in a desktop browser on your own computer.

That’s the point of the order: watching is instant, so you can go through every lap with the data on, and the minutes of rendering go only into the one clip you’d send to somebody.

One small change that came along: the overlay’s bottom row (speed, G) no longer sits under the player’s own controls when you pause or hover.

What it doesn’t do

• YouTube videos don’t get the live overlay yet. It needs a file played from disk. A synced YouTube onboard still gives you the map, the trace and the readout beside the video, not on it.
• It’s a viewing layer, not a video. To get the overlay into a file you can post, you render. The live view can’t be saved or shared.
• Desktop. The render panel is desktop-only, and I’ve only used the live overlay on a computer.
• Sync depends on the camera. For a GoPro with GPS (I’ve tested a HERO13) it is automatic; for other cameras you place one sync point by hand, as described in the overlay post.
• OBD parts only appear if the session has OBD. Without it you get speed, lap timing, map and, except in Strip, G.

What you need

• A session in ApexLog with GPS telemetry, imported from a RaceChrono export, a RaceBox CSV or a VBO file (RaceChrono import, RaceBox import, VBO import).
• The original video file from the camera.
• A desktop browser. Chrome (or Edge) is the one to use: it remembers the folder and the file between visits and renders faster than Safari. Safari and Firefox play from disk too, but you pick the file again each visit.

The live overlay is available on every plan.

Try it with one session

Import a session, open the Telemetry tab, pick the video file and press play:

Import a session and watch it with the overlay →

Free during beta.