Video and data different playback speed?

[Merlin]

Hi all I am experiencing a problem with RaceRender, although it probably isn't RaceRender's fault.

When trying to sync up my video to my data overlay provided by my Hondata S300 ECU's data logging facility, I cannot get them to play at the same speed. I can get them sync however they quickly become un-synced as it seems one plays faster then the other. I do not get this problem when using the data output from my RaceLogic PerformanceBox.

Does it have to do with the sample rate of the Hondata S300? I currently have it set to 10Hz. The FPS of the video is 30FPS.

Does RaceRender play only a specified number of frames per second from the data log? Do I need to make sure that the sampling frequency of the data log is high enough to populate a complete seconds worth of data so that RaceRender frame shift reads the data in real time with the video? I hope that makes sense.

Or

Do I set the data logging frequency to 30hz in the hope that it will match my video?

Any ideas?

[Weston@HPTuners]

The data sample rate typically shouldn't matter, being that it should be providing the timing data in the file, so RaceRender can know how to interpret it. The rendering will automatically adapt to any data sample rate, and will interpolate up to the output video rate to make the display movements appear much smoother.

We sometimes do see some data systems and/or cameras that just don't keep time very well, and those cases typically result in a loss of sync that continues to drift further apart. Because of that, RaceRender 3 includes the option to adjust the playback speed of any input file... For example, if you find that your data file is playing back faster than it should, you could set the "Play Speed" to 0.98 to make it play 2% slower. The setting is available in the synchronization tool, and a value of 1.0 represents normal/default playback speed, while 1.02 would be 2% faster. It will take some fine-tuning to find the right rate to use for your situation, but that should greatly improve most of these cases.

If the playback speed is off by a huge amount (ie 100x, 1000x, etc), then the timing data may just be getting interpreted in the wrong unit, such as milliseconds instead of seconds. This can happen with short data files as well as very long data files. The solution in that case is to double-click the data file in the "Input Files" list, manually choose the data field for the "Session Time" selection, and then set the correct "Time Units Per Second" for it... use 1 if the time data is in seconds, 1000 if it's in milliseconds, etc.