paper in pdf format - Department of Systems and Control
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1. Another experiment has been conducted on two Sony DSC V1 still cameras The reset impulse of the same length 100ms was sent to both cameras Time disparity is shown in Figure 13 Since the closed loop control of time disparity is not possible the cameras cannot be kept in synchronisation 10 The accuracy of measured time disparity with 3D LANC Master was verified by shooting computer CRT monitor with two camcorders Camcorder shutter speeds were 1 10000s The monitor refresh rate was set to 100Hz and resolution to 768 horizontal lines Horizontal refresh frequency was 81 4kHz so electron beam takes about t 7 12 34s 4 V to draw one horizontal line on the screen synchronisation level us 200 wo switched into the closed loop 150H i JOO Hy eke Ok oe bed ew ences ae pale yeas aa a a a N e eh BEER a E E E E Sa aa 50H l 500 1000 1500 2000 2500 time s Figure 11 Time disparity of two camcorders Histogram of time disparity in time interval from t 1000s to t 2400s 2 Time disparity us Figure 12 Histogram of time disparity of two camcorders in time interval t 1000s to t 2400s 11 synchronisation level us 100 50 50 100 150 200 250 0 100 200 300 400 500 600 700 800 900 1000 time s Figure 13 Time disparity of two still cameras Figure 14 shows a part of one progressive frame from both camcorders when the shown time disparity on2. 3 4 C2 8V5 1u 15V 5 8v5 C4 C3 A 3 ee ey his wo O Si Q Q lt lt FY wo oO O a a ATMEGA8 XTAL1 C6 16MHz Ra a 8 5 C 22p a Ss 2 H C7 5V TT 5V 5V LSO MS O RSO s4 A SRA S2 4 s1 R13 R14 R15 ll sal Rel R3 R4 R6 R8 L_ 10K 110K 10K 10K M Pel fs fro fax fe NP INT INDE INE INT IN R MP IM IST IM x IX 5V 5V 5V L 1 L M R10 lt T S1A BC556B 5V BAT 3V6 NIMH 3 x AAA R T2 BC556B D3 HSCH1001 R11 2K2 QV Fig 5 Electronic circuit of 3D LANC Master 7 Fig 6 Bottom side of the circuit board with elements Fig 7 Upper side of the circuit board with elements Fig 8 Prototype of 3D LANC Master 8 4 4 Functions The basic HMI 4 buttons with LCD display offers the following functions synchronous power on off record pause pre trigger trigger for still cameras tele zoom focus far near menu functions on camcorders enter menu up down and submenu and 2 user defined LANC commands permanent synchronisation of two camcorders if the camcorder has settings for oscillator frequency selection of display mode time disparity in us or recommended shutter speed for stereoscopy 3D LANC Master can be configured via serial communication by using programme 3D LANC Communicator on PC computer 8 The following settings can be modified page address o
3. Fig 4 Block scheme of 3D LANC Master 4 2 Power supply 3D LANC Master is powered by internal rechargeable batteries 3x AAA NiMH in order to reduce power consumption of connected camcorders or still cameras the latter are usually more sensitive to additional power consumption The batteries can be re charged either by connected camcorders still cameras by applying external power supply 4 5 6V DC voltage on dedicated input or by charging the batteries in external battery charger Charging is controlled by switch SIA either 3D LANC Master is switched on or off The charging current is controlled by a current source transistors T and T2 The estimated battery capacity is shown on LCD display It is estimated that 3D LANC Master functions for about 10 hours with one charging The main switch is S2A The voltage from the batteries is increased and stabilised to 5V by using DC DC converter MAX619 4 3 Human Machine Interface On board Human Machine Interface HMI consists of keyboard and LCD display The keyboard has 4 keys 3 are function keys and one is SHIFT MENU key Display consists of two lines each with 16 characters Top line displays current commands associated to 3 buttons HCT05 version of the integral circuit is being currently tested 6 Several other functions of 3D LANC Master can be achieved by using serial communication with PC 8 5V RS232 D1 1N4148 O TPS O TP6 E TP7 C1 1u715V
4. The device is powered by internal recharging batteries in order to reduce power consumption of connected camcorders or still cameras the latter are more sensitive to additional power consumption 3D LANC Master works for about 10 hours with fully charged batteries which can be recharged in different ways Some internal parameters of 3D LANC Master can be configured by using programme 3D LANC Communicator The programme is written for PC computers and offers visual 13 inspection of time disparity as well Some camcorder s parameters can be modified with extreme caution by using programme 3D LANC Doctor It was shown that 3D LANC Master worked on a pair of Sony DCR TRV9OOE camcorders where permanent time disparity within 10us has been achieved Unfortunately permanent synchronisation can be achieved only on some camcorders according to Table 1 REFERENCES 1 Atmel Atmel Corporation http www atmel com 2 Bloss W ste fra LANC http www digi dat de produkte index_eng html 3 Boehmel M How SONY LANC protocol works http www boehmel de lanc htm 4 Crockett R LANC Shepherd http www ledametrix com index html 5 HP InfoTech http www hpinfotech com 6 Kovacevic M Enabling DV IN on D8 amp DV http lea hamradio si s5 1kg DV IN HTM 7 Vrancic D 2004 Synchronizing two camcorders http www e2 1s si damir vrancic personal trv900 Sync 8 Vran i D 2005 3D LANC Master http
5. synchronisation can be achieved by using some professional video camcorders which are equipped with connectors dedicated for synchronisation However those inputs are not available in consumer video equipment so taking quality stereoscopic video stays out of reach for ordinary amateur videographer Video frames are taken from camcorder s CCD chip about 25 PAL or 30 NTSC times per second The exact video frame rate depends on the frequency of camcorder s internal oscillator If the first camcorder s frame rate is f and the second one is f2 then time disparity S will change over time as follows sa hth t S 1 where denotes time and Spo is initial disparity at time origin t 0 For example if the frame rate of the first camcorder were f 25 000 Hz and the frame rate of the second camcorder were f2 25 001 Hz the time disparity would be 2 4ms after 1 minute provided that they were perfectly synchronised at time origin So 0 Recently some dedicated devices for synchronisation of still cameras and camcorders like LANC Shepherd 4 or ste fra LANC 2 have appeared on the market They are using the so called LANC or CONTROL L inputs on camcorders and still cameras to power up the cameras at the same instant Since both camcorders should be of the same type they become relatively well synchronised at time origin initial disparity So 1 becomes relatively small However since internal oscillators in both d
6. www e2 1s si 3 DLANCMaster 14
7. 1s a way but it applies only to some camcorders 2 LANC LANC Local Application Control Bus System is a protocol developed by Sony which enables video devices to be controlled externally usually from a connected LANC remote Remote controllers based on LANC protocol are frequently used by video enthusiasts and professionals for controlling zoom focus record pause commands etc The LANC protocol is similar to RS232 protocol with exception that video device is permanently sending so called LANC frames which have to be filled with command codes Shorter explanation of the LANC protocol timing and codes can be found in 3 Some specifics related to LANC communication with still cameras is given in 8 LANC protocol has also been used for hacking some Sony camcorders in order to remove DV input and video input protection on some European models or to enable several hidden functionalities However it is less known that LANC protocol can also be used to view and modify some camcorder s internal settings like white balance settings adjustments of brightness and contrast etc One of the most useful settings 1s oscillator adjustment More precisely LANC input can be used to modify frequency of the internal oscillator on some models of Sony camcorders How can it be done By sending specific codes to camcorder s LANC input basic camcorder functional settings can be altered by modifying data bytes stored on particular pages and a
8. LCD display was 180us It can be seen that the time difference between both pictures is 15 lines see left edge of the picture The actual time disparity is therefore tf 15 t 184us 5 which corresponds to the measured time disparity Another measurement was taken when both camcorders were under the closed loop control and the measured time disparity was 2us From frames in Figure 15 it can be seen that the difference between both pictures is about 1 vertical line According to 5 the actual time disparity is about tp 12us It corresponds to the measured disparity within less than one horizontal line 12us Figures 16 and 17 show the pictures taken by Sony DSC V1 still cameras measured disparity was between 50us and 100us Figure 14 Video frames of two camcorders when the measured time disparity was 180us 12 Figure 17 Left Right Left picture taken by two Sony DSC V1 still cameras 7 CONCLUSIONS A device named 3D LANC Master has been made for synchronisation of two camcorders or still cameras The device requires LANC signal on both camcorders in order to simultaneously power on both camcorders still cameras It can permanently keep some types of camcorders produced by Sony in synchronisation 3D LANC Master simultaneously sends LANC commands to camcorders or still cameras according to pressed buttons received commands from standard LANC commander or commands received via serial RS232 communication
9. R DVD100 B DCR DVD200 E DCR DVD300 DCR HC14E DCR HC15 E DCR HC16E DCR HC18E DCR HC20 E DCR HC30 E DCR HC85 B i o DCR PC106E DCR PC107E DCR PC108 E DCR PC330 E DCR PC350 E DCR TRV255E DCR TRV260 DCR TRV260 E DCR TRV360 DCR TRV361 DCR TRV460 E DCR TRV461E 0 DCR PC100E DCR TRV103 DCR TRV410 DVD201 E DVD301 E HDR HC1 DCR HC40 E DCR HC65 DCR HC1000 E DCR IP1 E DCR frame rate cannot be adjusted PC109 E Camcorder functional settings can be modified in two ways The settings can be modified temporary by changing data in camcorder s volatile RAM or permanently by changing data in non volatile e g E PROM camcorder s memory Temporary change of settings 1s relatively safe and the change is reset after switching off the camcorder On the contrary permanent change of data may stop the functioning of camcorder since the checksum of non volatile memory is calculated every time after turning on the camcorder If the calculated checksum is different from the previously calculated checksum data the camcorder stops functioning Usually frame rate settings are not protected by the checksum An experiment has been conducted where camcorder s frame rate has been changed modifying volatile or non volatile data at page F and address 1C for camcorder TRV9OOE In accordance with modified data the change of camcorder s frame rate has been detected 3 SPECIFICATIONS After promising result of th
10. SYNCHRONISATION OF TWO CAMCORDERS WITH PI CONTROLLER 3D LANC MASTER Damir Vran i Department of Systems and Control J Stefan Institute Jamova 39 SI 1000 Ljubljana Slovenia e mail damir vrancic ijs si Abstract A device which keeps two camcorders permanently in synchronisation has been developed The mentioned device uses LANC CONTROL L camcorder s inputs for synchronisation It enables controlling of two camcorders simultaneously via built in buttons by using external LANC remote controller and or by the PC via serial RS232 communication Since device requires LANC inputs on camcorders or still cameras it can be used on some camcorders produced by manufacturers Sony and Canon or some still cameras produced by Sony Permanent synchronisation can be achieved only on some camcorders produced by Sony The effectiveness of the proposed device is demonstrated by several experiments Keywords stereoscopy camcorder PI controller synchronization 1 INTRODUCTION Stereo 3D photography is almost as old as classical photography since the first stereoscopic camera with two lenses was made in 1849 The first stereoscopic film was made by brothers Lumi re in 1903 Popularity of stereoscopy had risen until the 1950s when CinemaScope wide angle format won over the stereoscopic films mainly due to reduced production costs and higher quality Today stereoscopic video cameras are again gaining in popularity due to cheaper ways o
11. ddresses as shown in Figure 3 There are 16 pages 0 F and each contains 256 addresses OO FF where 8 bit data is stored For example modifying data on Page F and Address 1C in camcorder Sony TRV 900E will change main oscillator s frequency and therefore camcorder s frame rate Particular pages and addresses which affect camcorder s frame rate for several other Sony s camcorder models are given in Table 1 The easiest way to alter camcorder functional settings through LANC input is to buy original Sony service remote and modify data at appropriate page address Cheaper way is to build simple electronic circuit and use parallel port of a PC and adequate software for emulating service remote controller 6 LANC is also known as Control L According to author s best knowledge this feature is not available on still cameras produced by Sony Note that free versions of emulation software are mostly running on WIN95 and WIN98 systems 3 Page F Page 1 Page 0 Address Data 00 00 01 00 02 00 FF 00 Fig 3 Camcorder functional settings stored on pages and addresses Table 1 Pages and addresses of the data which affects frame rate for several Sony camcorder models Camcorder model Page hex Address hex DCR TRV900 E VX2100 E DCR PC1E DCR PC2E DCR PC3 E DCR PC10E DCR TRV9 DCR DVD91E DCR DVD101 E DC
12. e previous experiment it has been decided to develop a portable device which is able to control and maintain synchronisation of two camcorders The control device should comply with or have two LANC ports for connecting two camcorders or still cameras additional LANC port for connecting external LANC remote controller HMI interface keys and LCD display with optional external keys serial RS232 connection with a PC configuration and measurements time offset measurement between two LANC frames with accuracy lt lIus versatile power management internal rechargeable batteries with long autonomy and different charging sources closed loop control of time disparity if camcorder has appropriate setting for modifying oscillator frequency commands for record pause tele zoom focus near far camcorder s menu operations etc and user defined speed for tele zoom operation and additional user defined LANC commands The block scheme of device is given in Figure 4 Since the author had previous experience with Atmel microcontrollers the microcontroller Atmel ATMega8 1 has been chosen It offers 16kB internal program memory IkB static RAM 512Bytes of E PROM 3 counters 10 bit ADC converter USART serial communication and several interrupt sources The microprocessor has been programmed by CodeVisionAVR Compiler 5 since it offers several pre defined functions and templates wizards for ATMega8 The dev
13. evices are running at slightly different frequencies the time disparity changes over time 1 and soon becomes unacceptable Drifting of time disparity can be eliminated by modifying oscillator s frequency of one camcorder Namely changing one frequency is enough to keep time disparity S as close as possible to 0 The question is how to modify the oscillator s frequency Straightforward solution is to open the camcorder find the oscillator s electronic circuit and apply control voltage to varicap diode connected to the oscillator s crystal Varicap diode changes its own capacitance according to the applied voltage which results in modified oscillator s frequency The additional requirement here is to have a controller which permanently keeps the time disparity at S 0 A practical example of proposed design can be found in 7 where time disparity was S 50ns However even though the achieved synchronisation was remarkable the approach has one major drawback 1 e it requires modification of existing camcorder s hardware Firstly this can only be done by a skilled electrical engineer with appropriate service manual Secondly unauthorised modifications incur warranty loss and additional plug has to be placed on camcorder s body for controlling camcorder s frame rate The question remained is if there exists any other way of modifying camcorder s frame rate by using existing standard plugs without opening a camcorder Yes there
14. f producing and showing stereoscopic content The stereoscopy is mostly used in geodesy medicine chemistry and in entertainment industry However amateur stereoscopic video maker is still faced with relatively high costs of stereoscopic video equipment One of the main requirements for making stereoscopic videos is that both camcorders are tightly synchronised Such synchronisation is required in order to correctly fuse left and right pictures of the moving objects into one stereoscopic 3D picture Figure 1 depicts the case when an object is moving horizontally If the cameras are not synchronised right picture is taken some time interval after the left one the right picture of the object is taken at position b instead of a so the fused stereoscopic image is created in incorrect position d instead of c The fused stereoscopic picture therefore appears righter and closer than in reality The second case is when the object is moving vertically see Figure 2 Due to non ideal synchronisation the right picture is taken in position b instead of a In this case the stereoscopic picture cannot be fused at all There appears double picture d instead of one stereoscopic picture c Fig 1 Horizontal displacement due to Fig 2 Vertical displacement due to shooting shooting time difference time difference Accurate synchronization of camcorders or still cameras is therefore very important in stereoscopy Precise
15. f the data responsible for frame rate adjusting duration and offset of power on signal separately for camcorder and still camera duration of power off signal during reset speed of tele wide commands for camcorders proportional and integral gain of the PI controller responsible for keeping permanent synchronisation between two camcorders and two additional LANC commands for camcorders 3D LANC Communicator can also be used for monitoring time disparity see Figure 9 The measured disparity can be saved as ASCII file or as Windows Meta File wmf picture 3D LANC Communicator 0 20 0 AG a Oj x Choose COM PORT le COM 1 F C COM2 meke Status OK Read Write to E2PROM Uscillator Page Value F Write to E2PROM E2PROM gt working Sync Graph Stop Measurement Save measurements Save picture Figure 9 Adjusting parameters of 3D LANC Master and monitoring time disparity can be done by 3D LANC Communicator Camcorder s internal settings data in pages addresses can be adjusted by programme 3D LANC Doctor 8 see Figure 10 The programme enables viewing and modifying the data in particular page address in volatile and non volatile memory 5 CLOSED LOOP CONTROL ALGORITHM In order to keep two camcorders synchronised the closed loop control has to be applied A PI controller structure has been selected u t Kpe t Kele dr 2 to where u i
16. ice has been named 3D LANC Master 4 3D LANC MASTER The electronic scheme of device is given in Fig 5 The core is microcontroller ATMega8 which is connected to LANC ports through open collector inverters 74LS05 and to serial port via MAX232 The microcontroller is directly connected to 2x16 display LMO16 and 4 keys by using pull up and pull down resistors The power is taken from rechargeable batteries and supplied by DC to DC converter MAX619 The electronic schemes layouts and programmes are given in 8 The circuit board is shown in Figures 6 and 7 and assembled prototype in Figure 8 4 1 Inputs and outputs There are three LANC connectors in 3D LANC Master Two are used for connecting two camcorders or still cameras and one for external LANC remote controller if desired The signals on LANC connector are the following ground power supply voltage about 5 5V and LANC signal LANC signal either LS RS or MS is connected to open collector inverters 74LS05 in order to separate voltage levels optical decouplers can be used as well but current consumption should be taken into consideration Serial communication RS232 with PC is enabled via 9 pin serial port DB9 and MAX232 In circuit ISP programming of the microcontroller is enabled by connector K2 Left camcorder Right camcorder In circuit programming Ait jing F Remote controller PC eet I 4 keys 2x16 LCD display
17. s controller output e is measured time disparity in us Kp is proportional gain and K is integral gain of the PI controller Signal u represents camcorder s data byte at particular page address depends on camcorder model see Table 1 Integration inside expression 2 is performed only when calculated u is between 0 and 255 otherwise u is limited to either 0 or 255 The initial value of the integrator is the first measured value of data byte Proportional gain Kp and integral gain K can be adjusted with programme 3D LANC Communicator by modifying proportional factor PF and integral factor IF oe i Kaa IF Select Seral Por le COM cama Status OK Fage E 0 Address 00 400 Data 200 400 Go to FagerAddr Change Data save data STOP Figure 10 3D LANC Doctor can modify camcorder s internal settings by changing data within camcorder 6 RESULTS When 3D LANC Master was built it was tested on two Sony DCR TRV9OOE camcorders First reset impulse of length 100ms was sent to camcorders After 20 seconds 3D LANC Master has been switched into the closed loop configuration PI controller became active PI controller parameters were Kp 0 25 PF 4 and Kj 0 005 IF 256 The corresponding time disparity is shown in Figure 11 and histogram of the signal is shown in Figure 12 It can be seen that time disparity remained within 10uUs after 200s and practically within 5us after 1000s
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