[Rock-dev] ROCK loging and dataset creation.

Wed Sep 9 11:04:41 CEST 2015

Hi and welcome Evangelos,

i'm not sure what the revived time should be. Maybe this is a deprecated 
feature of the logging.
The Time stamps are created in different ways. Sometimes the are set 
from a camera itself. sometime from the driver.
I assume (without logging into the code) that the camera-firewire 
creates the timestamp when the driver received it.

Because of the scheduling they cannot be the same. If you are using a 
fixed-freqency you should consider the TimestampEstimater, it eliminates 
several aspects.
http://rock-robotics.org/stable/documentation/data_processing/timestamping.html

The idea of syncronizing times in rock is done by the stream-aligner.
http://rock-robotics.org/stable/documentation/data_processing/stream_aligner.html

It takes care of interpolation and synchronizing different data streams 
as they are typical in robotic systems.

I hope this solves all your questions, otherwise you are welcome for 
further questions.

Best,
Matthias

P.S. Moved this topic to rock-users...

On 08.09.2015 20:02, Evangelos.Boukas at esa.int wrote:
> Dear ROCK devs,
>
> I am at ESTEC/ESA and we are using ROCK on our new robot named:"HDPR". 
> We are close to the state that we can go on the field to collect a 
> dataset but, since I'm a fairly new user/dev, I  have a question:
>
> I am using a custom build stereo camera, with two firewire ptgrey 
> connected on the same IEEE 1394 bus. So, using the inherent 1394 
> properties, the two cameras are synchronised.
> Now, software-wise I am using in a ruby script the 
> "_drivers/orogen/camera_firewire_ 
> <http://rock-robotics.org/stable/pkg/drivers/orogen/camera_firewire/index.html>" 
> component twice for the each camera and then the 
> "_perception/orogen/stereo_ 
> <http://rock-robotics.org/stable/pkg/perception/orogen/stereo/index.html>" 
> to produce the disparity like this:
>
> Ptgrey_camera_1->camera_firewire_orogen-----|-->stereo_orogen->disparity
>               |
> Ptgrey_camera_2->camera_firewire_orogen-----|
>
> A struct view of the cameras in the rock-display reveals that there is 
> a timestamp from each camera like this:
> Left PanCam:
> Time: 28 Aug 2015 17:23:33.993947
> Received time: 1 Jan 1970 01:00:00.0
> Right PanCam:
> Time: 28 Aug 2015 17:23:33.993943
> Received time: 1 Jan 1970 01:00:00.0
>
> I assume by now that "Time" means sampled time and "Received time 
> means" time saved to disk/ram! Then we log the data in a .log file. In 
> order to export the data to useful .png files I use the following 
> commands:
> $ rock-export hdpr_perception.0.log --stream /pancam_left.frame 
> --filename "Pancam_#TIME_0.png"
> $ rock-export hdpr_perception.0.log --stream /pancam_right.frame 
> --filename "Pancam_#TIME_2.png"
>
> _Question one:_
> Even thought the images are actually synchronised (I can see it from 
> the product), the timestamps i am getting are not the same because of 
> the aforementioned struct properties. Is there an official way of 
> fixing this issue and have the images reported with exactly the same 
> timestamp, or should I create another component (or alter the stereo 
> one) in order to "fake" the timestamps to match? Something like theROS 
> time synchronzer 
> <http://wiki.ros.org/message_filters#Time_Synchronizer>would be perfect.
>
> _Question two:_
> The fact is that we are using several sensors on the rover (2 Stereo, 
> IMU, TOF, DGPS) and in the best case we would like to have them all 
> synchronised (at some point since they've got different frequencies) 
> or at least real-time like, i.e. to know exactly when to expect the 
> images. Is there any "easy" (obviously, that is not easy) way to do 
> this in ROCK, since we cannot hardware trigger all of the sensors?
>
> Thank you for your help and your time,
> Evangelos Boukas
> =========================================================================
>
> Dip.Eng | M.Sc. in E.E.|Computer Vision & Robotics Researcher | 
> European Space Agency NPI
> Laboratory of Robotics and Automation | School of Engineering | 
> Democritus University of Thrace
> evanbouk at pme.duth.gr | http://robotics.pme.duth.gr 
> <http://robotics.pme.duth.gr/boukas>| http://robotics.pme.duth.gr/boukas
>
> ESA - European Space Agency
> TEC-MMA - Automation and Robotics Section
>
>
> ESTEC - European Space research and TEchnology Centre
> Keplerlaan 1, PO Box 299
> NL-2201 AZ Noordwijk, The Netherlands
> Evangelos.Boukas at esa.int | http://www.esa.int/TEC/Robotics/
> Tel. +31 71 565 5499
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