2 seconds OBD data delay in video

[Falc09]

Hello!

Today I recorded a video at the Eurospeedway Lausitz. I also recorded OBD Data. Communication with OBD Dongle and everything was fine. Later I selected the laps from one session and hit 'overlay'. The exported video is quite nice exept a 2 seconds delay in OBD Data. Actually OBD Data are 2 seconds ahead of the rest. (video+sound+GPS are synchron)

Is there a possibility to adjust this offset in laptimer app before rendering the final video-file?

Hardware is a Galaxy S4. I used internal GPS Sensor and an external ELM327 OBD Bluetooth Sensor. Car is a 2014 Evolution so Harry's laptimer grabbed a lot of PID's.

Any help would be appreciated!

[Harry]

Hi,

Humans are very sensible on missing video / audio and visual overlay sync. Mostly it is about 0.5 seconds which feel like a lot more. Anyway, please search the forum for "video delay" to find numerous threads on this. Google search is even better, try "video delay site:forum.gps-laptimer.de" as search term. In short, you will need to adjust the Overlay Synchronization / Video delay in LapTimer Expert Settings. With OBD data ahead (or video behind), you need to increase this setting by the gap. Start with small values - really. To verify the setting, revert the lap overlaid to the original video (in Lap Details), and repeat the process.

- Harry

[Falc09]

Thanks for your quick reply.

I searched the Forum before and found this solution. Unfortunately adjusting the video delay looses the sync of GPS data with the video. So I may have to find a compromise between OBD advance on the one hand and GPS delay on the other hand and place the video right in the middle of this gap. I know I can adjust this particular sensor befor recording the next laps but this time I have no choice...

With OBD data ahead (or video behind), you need to increase this setting by the gap.

increase?

[gplracerx]

Look at the speed chart for a lap. (Select a lap by touching the lap time in the lap list, scroll down to preview and touch the circled i, then select charts). The first chart is the speed chart. The OBDII speed is a dotted line and the GPS speed is a solid line. If the two lines are offset on the distance axis, your OBDII delay is off. If they are synchronized, then it is your video delay that's the problem. You can fix the video delay after the fact. You can't change the OBDII delay after the fact.

[Harry]

increase?

Yes, video is behind - which means the delay between reality and video recording is even higher = increase.

Harry

[Falc09]

Thank you gplracerx

In the chart its obvious that obd is far ahead of gps. I will adjust sensor delays and test before recording next laps.

During the track session all overlays were synchron in the live preview.

[gplracerx]

You can get a good estimate of the time difference on the speed chart as well. Find a feature, like a peak or a minimum on the speed graph. Set the cursor on that feature for the OBDII data by tapping the graph and then drag the cursor to where you need it. Write down the time in the list of data from the cursor. Then move the cursor to the same feature on the GPS speed. The difference in the time should be how much you need to increase the OBD delay.

[Falc09]

I have to come back to this:

increase?

Yes, video is behind - which means the delay between reality and video recording is even higher = increase.

Harry

I found out that decreasing 'video delay' reduces time gap between the recordings. I cut together a short video showing the effect of increasing and decreasing video delay

[youtube]www.youtube.com/watch?v=vyD_Qs9D23Y[/youtube]
http://www.youtube.com/watch?v=vyD_Qs9D23Y

Its not my intention to complain, I just want to give feedback that might help improving further releases.

The minimum "video delay" setting of 0.0 limits the adjustment. Acording to my particular situation a video delay option of -0.7 (minus 0.7) would be a good improvement.

However, I may resolve this issue for the future by adjusting sensor delays.

My current values are 'factory settings':
gps: 1.5 obd: 1.0 accelerator: 0.5

How do I have to change these values regarding the postet video:
Does increasing the obd sensor delay setting from 1.0 to 2.4 fix my problem or do I need a theoretical -0.4 Value that is actually not possible to set-up?

Many thanks for the quick support. I will be on the track next saturday and test again...

[Harry]

The delay is always the time between the point in time something happens and the point in time the corresponding measurement arrives for processing. This means a negative delay makes no sense. In case it is necessary to decrease a delay below 0, you should increase all other delays instead.

Harry

[gplracerx]

If you could export your data as a .csv file and post it here or post a link to it, I can check your data delay settings. The accelerometer delay can be checked by either integrating the lineal acceleration to get speed or differentiating the speed data to get lineal acceleration. Lateral acceleration can be calculated from GPS data using the yaw rate and speed.