User:GerryLight
Contents |
Werkzeug
OpenMoko Neo Freerunner
Bevorzugtes Gebiet
Laufach, Hain, Frohnhofen
Some personal thoughts about video mapping
In April 2010, I started some experiments with three HD-WebCams in a car. Goals was good video quality with low-budget equipment (including my car ;), relative) Here is a dirty "braindump". Need to find a nice wiki place for that and clean up.
Software:
- guvcview to record the video streams; runs in parallel multiple instances; setting save- and loadable as profiles; well communication with program author.
- TangoGPS to record gps-track; Trip function can be used „where have we already been today“, OpenStreetBUgs loadable as POIs
- Could be combined with more features in own software in the long term. Timestamps of video and GPS can easily kept synchronized due unique computer system time (no need for complicated manual sync).
Filecontainerformat/Compression:
AVI: NoGo! Limited to 2GB (specification), longest 4GB (technical, 32Bit-Pointer). MKV: Pros: Timestamp per frame (nice for synchronization), metadata per frame (GPS-Position could be allocated to each frame!), open and documented format (fits mood of osm). Cons: Not supported by every software. Power-Fail produces file corrupt and enforces therefore a complicated restore procedure, because frameindex is not been written at end of file (← maybe program author could provide a solution)
MPEG2, Theora, H264 definitely to slow or to worse quality for realtime-HD-encoding on today's hardware uncompressed YUV, RGB needs too much disk space (think of USB/Harddisk transfer rates, too) MJPG best compromise; beeing delivered by many WebCams directly (no further CPU usage)
Ideal weather conditions:
Sunshine (→ light!, GPS-receiption) (TODO: Test rainy/cloudy day, optimize guvcview-parameters)
What is possible?
Street name signs, street signs, lanes, house numbers, nearly any POIs (→ TODO: upload pictures)
Hardware
Logitech C300
- Properties: 1.3 Mpixel, plastic lens, manual focus (lens adjustable by winding), max. resolution: 1280x1024 @ 15 fps (Hardware MJPEG)
- Price: about 35€
- Subjective: Suitable as frontview, satisfying as sideview. Readability of (german) street name signs: <10m distance. Side house numbers: satisfying.
Logitech C500
- Product properties: 1.3Mpixel, glass lens, no focus (Fixfocus with good depth of sharpness), max. resolution 1280x1024 @ 15 fps (Hardware MJPEG)
- Price: about 45€
- Subjective: Suitable as frontview, satisfying as sideview. Quality similar to C300, but lens has wider angle as C300.
Logitech Quickcam Pro for Notebooks
- Properties: 2.0 Mpixel, Karl-Zeiss-lens, autofocus or manual software driven, max. resolution: 1600x1200 @ 5 fps (YUV) or 960x720@15fps (MJPEG)
- Very small and inconspicious.
- 5fps too less as sidecam, suitable as frontcam
Common to all these cams:
- Most Logitech webcams are supported by linux very well.
- Webcams normally have a low-cost CMOS-sensor, whitch features a weak dynamic, meaning bright and dark parts of the picture getting lost rather rapid.
- The exposure driven by firmware is optimized for in-house usage. Wide parts of bright sky in the picture result in underexposure of object of interest. Idea: Client-side exposure regulation for better results. Should feature:
- Optimized for short exposure times in general by using a higher gain (→ pay with noise), to reduce motion blur (thats only necessary on not-ideal weather conditions);
- Use only down half of picture to determine exposure to get most information of POIs(→ pay with overexposured/outshining sky);
- Faster regulation algorithm (→ doesn't need to look nice in running video, but get out most information out of picture)
- TODO direct picture comparsion of cams
- Supported resolutions of logitech cama see <http://www.quickcamteam.net/devices/logitech_uvc_frame_format_list.pdf>
Ordanary still image camera:
Fujifilm S9600 (640x480 @ 30fps) good enough as frontview on motorways: Street signs, lanes, limits cognizable. Not good enough for reading street names und house numbers. Main disadvantage: Abort after 2GB (->AVI, FAT), flash memory capacity limited and expencive. Still usable as an workaraound.
Keep in observation:
HD-(still- or movie-)Cams, Canon cams: Hacked Firmware.
Views:
Front, Back, Left, Right (F,B,L,R)
- Frontview: Most important. Steet-/navigation-/limit signs, POIs, lanes, side-attached house numbers.
- Rightview: Important to determine position of POIs mor accurate („which timestamp the GPS is in height of POI), house numbers, branches of small ways that can be overseen easily otherwise and so on
- Important enrichement.
- Leftview: Recommendable. Can be omitted if same trip is driven backward (not necesseraly possible!). Usage analog to right view.
- Backview: Not installed, but could be helpful to get more side-attached house numbers. Can be omitted if same way driven back..
- Also think of: Diagonal views. Pro: Needs less cameras. Contra: Objekt positionen can not be determined accurate.
Camera-Installation:
- Hidden-secretly / demonstrative-provoking?
- Care of polarized, light killing glass in modern cars (best open windows)
- Care of mirroring objects and dust in glass
- TODO: Photos and comments of my personal installation
other Hardware (TODO Schema graph):
- car supply → inverter 12V - 230V → notebook power supply → notebook
- Notebook → Camera 1 (USB)
- Notebook → Camera 2 (USB)
- ...further Cameras…
- Notebook → GPS (USB)
- GPS → external Antenna
- OBD → serial
- USB → notebook (Inkremental sensors of front wheel) realizable?
TODO Hints for mounting cables
Executing tours:
- Alone: Possible. Keep notebook out of sight of driver because of safety, police.
- With codriver: Probably very advisable (techical supervising; route planning „where have we already been“ „where is the next bug“; temporally as „walker“ for footway and so on., technical equipment has to be supervised against theft; have more fun; change of roles possible)
- Problem bicycle: Energy supply?
Conclusion:
Positive surprising results. MultiCam-Videomapping can be a good solution for fetching almost all details also as for bulk mapping far-away areas. Precondition is having fun evaluating video material in slow motion - will probably multiple times than the survey itself. Teamwork is recommandable - cams can be lend to other people while evaluating.
