Hi,
I am using Race render to overlay my rally videos (3x GoPro Hero2 cams) and my data acquired from a Race Technology DL1 logger.
The Cameras are Running at 25Hz and the Logger at 100hz.
I can synchronize the data at the beginning of the video, but at the end of the video, the data have drifted. The longer the video, the more the drift. I know the Play speed trim, but it doesn't seem logical, because of the frequency ratio between video and data.
Any hints?
Thanks
Just to clarify, you import 3 video files and one data log file into RR 3. All files are continuous; no stop/start of the videos or data log (no segments). The videos and data log are synched at the beginning and the ends are trimmed to match at the end. Are my assumptions correct? How long does the video have to be before you notice the drift?
You are correct. It starts to be noticeable over 12-14min and it gets worse with the combined go pro videos, which usually split at around 20mins and RR combines automatically.
If you load just one video file and the data log; synch them to the same length, do you still get the drift?
I think yes, but I need to double check
While you are checking. Does this drifting happen while you are editing the video or only when you render it or both?
It happens both in editing and in final video. Editing the end of the video is particularly difficult due to massive lagging. The longer the video, the more the lagging
Can I assume your video plays normally to the end but the gauges overlay starts to fall behind?
I cannot be sure about that but I do not notice any obvious video delay. Here is an example of minor drifting. https://youtu.be/dPt6CoISm0A
These are 3 single continuous videos and one single continuous data file. Size / length is moderate. It's more obvious if you focus on the gas pedal.
I'm not sure how your data log works but would you not multiply the play speed by 4. For example say you shoot a video at 25 frames per second and shoot a second video at 100 fps but play the second video at 25 fps. Mathematically it would play 4 times slower than the first video.
Great video. Like I said I don't know your data logger and I'm not a race car driver to appreciate all the quick changes the driver is making but your video makes the whole experience very exciting for the viewer. Anyway, it must be something to do with the play speed of the video versus the data log and you may want to play with the speed setting of the data log. Hopefully someone with more experience with your particular logger can provide additional advice.
Thanks! RR is really helping to make those videos! Please subscribe to the channel 😎
In my understanding, it should not be a play speed issue. The logger is just playing 4 frames at the same time the video plays 1. As long as the 1st frame is synchronised, then the 4th should be also. I will try with a single long video, as well as with a 25hz log file and get back to you. I am using high frequency exactly to have better resolution for synchronisation...
Btw, a feature which would offer great help for synchronizing the videos is the sound wave synchronisation. I have used it in professional video editing software and is really a life saver, especially if the cameras have no common view field, but record sound from the same place. Look into it!
Hi Armaki,
Well maybe the following solution will help solve both your problems. During the next race honk your car horn to capture the wave sound. To edit, import only the data log and add a "green screen" to your gauges project. Render this video. Using a third party video editor, import your videos and green screen video. You can synch all the videos by looking at the sound waves attached to each video. Synching the green screen would have to be visual (ie brake gauge vs foot movement) unless your data logger also captures external sound. Render the final video in the 3rd party video editor. This solution will solve your sound wave synch and possibly solve your gauge drift. This is my current workflow. In my opinion, RR 3 is the best video telemetry software currently available in the world today. But its not an professional video editor. For 95% of the users it is fine, but for guys like me I use anther video editor to put together my final video. I only use RR 3 to green screen my gauges. Use the best tools for the job.
Last edited by Candive; 09-30-2018 at 09:19 PM.
My wife watched your video. She was wondering if the passenger (navigator) was reading the local sunday paper.
Hahaha I am actually the navigator, and no, that's not the Sunday paper! I don't know how familiar you are with rallying, but those are pacenotes of the road ahead. There is no chance going rallying without them! It's interesting to know that I look so relaxed though!
Regarding your workflow, I agree that it's the most high end way to go with, but the efforts included are quite high. In addition, the sound synchronisation is good, but not perfect, because of the very noisy environment. On tarmac rallies it works well, but gravel is a gamble. I might give it a try though, if I get my hands on high end video editor.
Synchronizing the data to one of the videos (main maybe) would be my way to go, to take advantage of the sync wizard of the RR, which helps a lot! It only takes some clicks to fine tune afterwards and that only on gravel.
In fact, all my 3 gopros and the logger are hardwired to start with one button, but the latency of the cameras is never the same and they practically never start in the same order.
Hi Armaki,
My video editor is Corel Video Studio. I wouldn't call it high end like Davinci Resolve but it does the job. In my work flow what I tend to do is synch the data file with my video clip where I want the gauges to enter and then exit out of the video (they are not displayed throughout the video) then I green screen and render just that portion and use it as an overlay in Video Studio. I can't help think that your problem is related to the speed of the playback file of your data log. I don't have this problem because my camera produces the video and data log so they are running at the same time and speed.
If you load your video and data log and synch the two at the beginning in RR 3, when you run your scrubber along the bottom (or just hit play) does your video end (black screen) and the data display keep on going? And if it does, how long does it approximately go for?
Last edited by Candive; 10-01-2018 at 01:00 AM.
Hi thanks for your suggestions.
It does play longer, but that's because those are practically 4 different files. The difference in length is between minimal up to almost 10 secs, but the drift on a synchronised video is never more than some tenths and I have only noticed drift between data and video, never between the videos.
Ok, unless some one else has a bright idea; here are my two bits worth. I have two suggestions for you to try. I'll use a simple example. Your video runs for 20 minutes. This is equal to 1200 seconds. Your data log runs 10 seconds longer - 1210 seconds. Divide 1210 by 1200 equals 1.008333. You increase the speed of your data log by this amount to see if it makes a difference.
My second suggestion is not as straight forward. It appears that the synch is initially ok but half way through the video it starts to drift. So you import the video and data log. Synch them. You then trim the data log's end point to the point where you notice the drift. You then import the same datalog again (RR 3 will automatically add a sequential number to the file name). You then trim the beginning of the 2nd data log to bring the synch back in line. For a twenty minute video, you may need to import the data log 2-3 times and line them up to keep the data in synch. I hope you understand the concept. For my videos, I have one long data log but I shoot segments of video (not continuous). To match the video clips and data, I have to import the same data log a number of times and trim each one to correspond to each video clip.
Last edited by Candive; 10-01-2018 at 02:15 AM.
Here is more detail from a previous post;
The trick is to import the data log more than once. Say you had 4 video clips;you import the same log, 4 times. Then you trim each log according to the start and duration of each clip. You join the videos in a group and you join the logs together in the same sequence as the video clips. The data is now in synch with the video! If the programmers for RaceRender develop some simple transitions in a future version, a nice video can be created. Hint Hint
I'll provide a simple example for other newbies out there. Say I go out for a 60 minute trail ride on my bike. I start my log and video capture the first 10 minutes of the ride. I then turn off the video for the next 45 minutes (the data logging remains on) For the final 5 minutes, to the finish, I turn the video capture back on. So my data log is 60 minutes, and I have 15 minutes worth of video; 10 min at the beginning and 5 min at the end.
In RaceRender, I create a new project and import both video clips. I also import the data log twice (RR will number them sequentially). For the first data log, I trim the log to the first 10 minutes. in the second log I trim it to the last 5 minutes. I join the two video clips into a group and I do the same for the data logs. The videos and data are in synch and I render the final video.
Yes I understand both concepts and will try them. What I don't really get is the relation between the longer or shorter files and the drift. I never synchronise the files at the very beginning, but 30-60 seconds in, and I never use the complete files, but stop the rendering 10-20 seconds before the file end.
I usually don't trim the files, since those loose ends help with synchronisation, especially when the RR is lagging, but I use the green and red flags to mark the start and finish.
Thanks anyway
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