6 replies to this topic

[manthony121]

I use the Mobius Action Cam for my in-car video, and an Aim Solo as my lap timer.  At the end of a weekend, I use Race Render to combine my videos and overlay them with the Aim data.  However, it seems that the camera and lap timer are running at slightly different speeds.  I take great care to line up the data and video at one point during the race, but at other times, they are clearly out of sync.  And, it is not a constant drift in one direction.  It's almost as if one of the units is not running at a consistent speed.

 

I just put up my latest video on Youtube: , which clearly shows the problem.  The AIM had turned itself off while waiting on the grid, so data doesn't start until 09:30.  The next few turns are clearly out of sync, with the data lagging several seconds behind the video.  I synced at a point close to the middle of the race.  Some laps are spot on, while other laps have the data traces just a little behind the video.

 

I presume the AIM is very precise, making measurements every 0.1 seconds, which get exported as a CSV file to Race Render.  I suppose the cameras might have some error in their frame rate due to compression artifact.  I suppose Race Render could also be messing up the video frame rate.  It makes me wonder if some of the software components are in conflict over frame rates during compression/decompression? 

 

Does anyone have a similar setup, and have you noticed this problem with your videos and data?

[Martinracing98]

Unfortunately I think it's Mobius that has overlap between each of it's 15 minute files. Something like 150ms of recording in file 1 is in file 2 also and so on. It is a real pain. I had to use something before Render to trim off overlap. Then use Render. I went back to GoPro that does not have that problem

[manthony121]

Unfortunately I think it's Mobius that has overlap between each of it's 15 minute files. Something like 150ms of recording in file 1 is in file 2 also and so on. It is a real pain. I had to use something before Render to trim off overlap. Then use Render. I went back to GoPro that does not have that problem

No, the entire race is in a single file.  I believe it is recording at 30 fps, but I'll have to check to make sure.

[Steve Scheifler]

FWIW - We used those cameras with Traqmate but I don’t recall seeing what you describe.

[Tom Hampton]

If the video is running slow then either the internal clock is running slow, or the framerate is higher than what you've put into racerender. Pretty much all clocks these days are way more accurate than 0.1% (more like 0.001%), so my money would be on framerate.

The error appears to be roughly 3s in 30min. Roughly 0.1%. Interestingly, that's about the same % as the difference between ntsc framerate (29.97 fps) and true 30.0 fps. Perhaps the video is encoded at 30fps, but racerender thinks it's 29.97?

[manthony121]

If the video is running slow then either the internal clock is running slow, or the framerate is higher than what you've put into racerender. Pretty much all clocks these days are way more accurate than 0.1% (more like 0.001%), so my money would be on framerate.

The error appears to be roughly 3s in 30min. Roughly 0.1%. Interestingly, that's about the same % as the difference between ntsc framerate (29.97 fps) and true 30.0 fps. Perhaps the video is encoded at 30fps, but racerender thinks it's 29.97?

I'm wondering if it's something like that.  But I don't think there's a setting in Race Render for the video framerate.  At least, I haven't seen one.  I'll have to look more closely.

[DmitryZ]

If the video is running slow then either the internal clock is running slow, or the framerate is higher than what you've put into racerender. Pretty much all clocks these days are way more accurate than 0.1% (more like 0.001%), so my money would be on framerate.

The error appears to be roughly 3s in 30min. Roughly 0.1%. Interestingly, that's about the same % as the difference between ntsc framerate (29.97 fps) and true 30.0 fps. Perhaps the video is encoded at 30fps, but racerender thinks it's 29.97?

You can change those in Mobius settings I think - I would also make sure that you don't have anything strange checked on like motion detect or have video data rate set to "low"