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BMD Pocket Cinema Camera Stereoscopic Collaboration
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  • Another question, the Pocket has timelapse functionality right? Could we trigger this simultaneously on both bodies? How is it activated?

    I included microcontroller-based timelapse functionality on the custom controller for my GH2 rig: (that was the old hyper rig, it's all now on a much shorter bar from DealExtreme).

    But that was triggering the stills shutter, so the trigger came from an external clock (my controller) and wouldn't drift between two bodies. Would this even work on the Pocket without massively drifting?

  • Here are the supported LANC commands, courtesy of :

    LANC(0x18, 0x33); // REC

    LANC(0x28, 0x43); / /AUTO FOCUS

    LANC(0x28, 0xAF); // AUTO IRIS

    LANC(0x28, 0x45); // MANUAL FOCUS FAR

    LANC(0x28, 0x47); // MANUAL FOCUS NEAR

    LANC(0x28, 0x53); // IRIS+

    LANC(0x28, 0x55); // IRIS-

    If BMD could add ISO, shutter speed and a few other key params, we could remote control and match both bodies perfectly. The same controller can measure sync from LANC, and could simulate a lens connection if necessary.

    Theoretically it's probably even be possible for BMD to send a capture sync signal via LANC to the other body.

  • Thanks @kavadni. From skimming the datasheet, it seems much more capable than the standard composite sync separators, but it still only deals with analogue signals, correct? The Pocket doesn't have analogue, so the only option would be HDMI.

    If going that route I would want to do full image processing on two HDMI inputs to give live anaglyph and other stereo previews on a single HDMI monitor (and you could also display the sync directly on it). But I don't know how to do the HDMI interfacing ...

  • Thinking about it, you can do most of these tests with your Applied Logic readout. Here I would leave one camera connected and running, and try the above on the other cam. If the sync suddenly changes the capture clock is reset.

    You can also try manually start-stop recording one body several times. Does it change the sync?

  • If you get the Sync Tester running, there's a few things to try. You only need a single camera for these.

    I think this is right (correct me if I'm wrong as I haven't used the sync test method yet): no need to measure anything, you should just be able to see the CRT beam moving gradually up or down as the camera drifts. You want a fast shutter speed (to eliminate motion blur). Try to get the beam moving as little as possible. You might have to try different frame rates to get close to the beam refresh rate? I believe the default is 60Hz, so 30fps might be a good match.

    We're looking for anything that resets the capture clock, ie. that places the vertical beam position visually somewhere else suddenly:

    • power up, observe the beam position, then quickly power down and up again (keeping external power connect all the time). Is the beam still where you expect it?

    If yes, power cycling does NOT reset the clock, and connecting juice may sync bodies. You could verify this with two bodies - if you can feed juice to them at exactly the same time, but then power them up at slightly different times - are they actually in sync (beam positions in the same spot on both)?

    • same for Lens Reset - does it actually reset the capture clock (beam position changes)?

    • try to find any other setting that resets the clock. For example changing shutter speed, Rec709 <> film, Prores <> RAW, focus punch-in (as these may change the sensor mode) etc.

    • if you (or anyone) has a LANC controller, try if any of the commands it listens to reset the clock. It only supports a limited cmd set (see my next post later).

    If lens release or some lens pin manipulation works, we can probably simulate a lens connection with a little microchip - maybe just signalling the 'lens ready' pin would be enough (or something like it)

  • A quick test with a single BMPCC confirms Marcus's thought that the lens release button resets the camera's clock. At least I can say that the lens release button appears to put the camera though the same protocol as camera start. If I can get a moment this afternoon I will two cameras and the Applied Logic board to see if a common reset with the lens release buttons of two cameras will put them in sync. I have never set up Peter's synctest but hopefully the Applied Logic board's led read-outs will provide some information.

    I should point out, however, that the lens reset button understandably only works with an automatic lens.

  • Very valuable info @crunchy. I don't actually measure sync on my GH2's. I only recently started designing a circuit for it though (with a nice OLED display and everything), but if the Pockets work out I'll use LANC instead of VSYNC extraction.

    (on a tanget: Of course what I'd really like is HDMI decoding (you could also measure sync from that), but it's beyond my skillset. The idea is to build a small board that accepts two HDMI ins from cameras, and does custom image processing to a single HDMI out to show eg. anaglyph previews (and other types) on any cheap HDMI monitor. You could extend that with histograms etc. I can do the image processing, but HDMI signal handling seems very complex, and demands high-speed processors and suitable electronics, I have no experience with either.)

    Like you I find that with my Panny primes that sync is hit and miss - but when it works, it's usually perfect. As I suspected the lens calibration, I developed a routine where I pre-focus and expose my shot (I always use manual exposure), then power cycle the bodies first before recording. The idea was that as both lenses are already on the same focus & iris, the calibration time on both should be much closer. It seems to be working for me, in that I get good sync more often (which I determine from the audio waveforms of a click at recording start). I also take more time these days after power-up to let everything settle, so it may be a combination of things, or maybe the lenses really have nothing to do with it at all. I should have done scientific sync test on my GHs, but I just never got around to it as it worked well enough-ish (but I will with my Pockets).

    @MarcusWolschon, I didn't realise that m43 lenses use SPI (I've just coded SPI comms on an AVR for something else). That might give us another way in. Has anybody reverse-engineered the protocol?

    It would be much easier to hack the lens pins with manual lenses (not sure how that works out with a Speedbooster fitted?).

    Can someone try the LENS RELEASE to see if it resets the capture clock on a single body? The best way to test it (and dual-body sync) is with an old CRT monitor (has to be CRT) and Peter Wimmer's free software: , you can just see what's happening to sync in real-time.

  • @_gl "A second idea - as the power button is 'soft', something is already running when the camera is off. It may just be an interrupt that wakes the CPU, but it's possible that the master clock is already running from the moment you connect power. If so, then just delivering juice to the bodies, even when switched off, may be syncing them at that point."

    This seems possible. In this case, if the power is delivered to both cameras simultaneously, the cameras should remain in synch (for some period, of course) even if they are waken up afterwards by shortly clicking power buttons. David Wilson may check it if his cameras have common external power supply.

    Concerning manual and "auto" lenses, the situation is not so clear. Mostly I get synched shots with a pair of GH2s (or GH1s) with Panasonic lenses. However, there are still many shots (usually less than 50%) which are not in synch. I switch on the cameras with predefined time-delay in order to get longer "good-synch" interval. The missynch between the cameras is monitored via video out signal.

    David Cole measured the missynch between the GH cameras and reported that he's got bad synched videos even when video out signals from the cameras were perfectly in synch. On the other hand, I've got badly synched videos only when the video out signals were not in synch (during recording). Later on I discovered the reason. David Cole used NTSC video out format and I used PAL video out signal (in camera's menu). When using PAL settings, the video out signal changes from 60i (in steady-mode) to 50i (during recording video). If the cameras are actually not in synch, it will be perfectly seen in missynched video out signals as well. On the other hand, if using NTSC video out signal, nothing changes in video out signal when starting recording (even though the cameras are not in synch anymore).

    To make the story shorter: when using two GH2s (GH1s, GH3s?, GH4s?), set video out signal to PAL. If there is no difference between video out signals from the cameras when they start recording, the cameras are actually in synch, period. No matter what kind of lenses you have on the cameras...

    On the other hand, if you want repeatable guaranteed synch with GH1, GH2 (probably GH3 and GH4 as well) cameras with any kind of lenses, use NTSC type of camera and 60p mode (e.g. 720p60, 1080p60). If the cameras are in synch after power-on, the recorded video will remain in synch as well. There might be a difference of one or two full frames between the takes, but this is easily solved in post (when comparing sounds from both cameras).

    In short, manual lenses are not the limitation.

  • Try the LENS-RELEASE button in sync to sync the cameras. It does a proper lens shutdown and power-on via the SPI interface to the lens.

  • Many many thanks... any ideas that occur to you we would be very happy to try out here while you wait for your cameras.

  • OK, maybe there's another way to trick it.

    re. lenses I will confirm when I get my bodies. I have the 14mm and 20mm primes here, and I can tape the contacts to simulate manual lenses. (I also have the Lumix 3D lens which I tape up to shoot raw stills, it's mostly awful for video though).

  • Good idea to try pressing the power button and then applying power to the camera. The results are different but unfortunately not so helpful in that on applying power with the on-off button depressed, the camera simply remains off. In addition, the camera does not turn on when releasing the button. The camera seems to only turn on with a quick pressing of the on-off button with power already applied. The camera is shut down with a long pressing of the button.

    With regards to David Cole's discoveries concerning manual vs automatic lenses with the GH, we seem to find that we are able to achieve equally passable sync with both manual lenses and a pair of automatic Lumix 14mm pancake lenses we have on-hand.

  • A second idea - as the power button is 'soft', something is already running when the camera is off. It may just be an interrupt that wakes the CPU, but it's possible that the master clock is already running from the moment you connect power. If so, then just delivering juice to the bodies, even when switched off, may be syncing them at that point.

    On the GH's, David Cole found that simul-power sync was only reliable with manual lenses. The bodies do some kind of lens calibration at boot with native lenses (probably focus and/or iris), and that probably introduces a random delay (which also suggests that the capture clock is only initialised after this calibration, so the firmware can apparently reset the clock).

    We'll need to see if this is true for the Pocket aswell.

  • Great info David.

    OK, so taping the power button down won't work. Except that maybe if it is held before the camera gets power, it might not make it shutdown (depends how they programmed their button scanning). Could you try that?

    So, LANC cannot reset the clocks, but it can be used to measure sync differences. That's very useful. I've not used it before (I will program an AVR to try it), but I've just been told that the cameras determine the protocol timing (makes sense), so I guess you can measure that from a custom controller and so figure out real-time sync. I will try that too.

    There may yet be some way to get simul-power to work. Or maybe something else resets the clocks, like changing lenses, framerates etc.

    If the firmware can reset the capture clock in theory, then BMD could enable this with almost no work. I'd be very happy to beta test firmware like that - does anyone have a good BMD contact? John Brawley?

  • Very very good idea to begin this effort. We bought two BMPCCs pretty much as soon as they were released, primarily for stereo work. These are wonderful little cameras. If handled with care, they are capable of making beautiful images. There are, however, certainly limitations to the BMPCC and (at least for our purposes) the ability to control shutter (frame) sync is one of them.

    As GL suggests, the form factor of the camera is good for mounting side by side. There are 1/4-20 mounting points directly over and under the lens mount so building a side by side mount for the camera is pretty straight forward. We also have built a beam-splitter rig that works quite well. But the shutter sync issue remains...

    Powering the cameras simultaneously does seem to work in our experience and we have produced some quite good results. We have no plans, however, to take the BMPCC stereo rig to the horse-races any time soon.

    With regard to GL's thoughts, some things we've observed:

    A permanent press on the power button does not work in that a long press on the power button cycles the camera on and then immediately off.

    It is certainly possible to start the cameras simultaneously with LANC commands but sadly, the LANC start command does not reset the camera's internal clock. It would be wonderful if BMD were able to write that capability into a future firmware update.

    The work-around we have been using for shutter sync is through the use of the Applied Logic DUAL CAMERA LANC CONTROLLER

    This board is seems very well conceived, engineered and fabricated and is relatively inexpensive at 240 USD. The board offers control of Zoom out, Zoom in, Focus Auto/Man, Focus Near, Focus Far, Photo Capture, Record Start/Stop, and Power On, and Power Off. Sadly, of course, the Power On, and Power Off does not work with BMPCCs. The board does not shutter-sync the cameras but through a set of LEDs one can tell when the camera is within 5 milliseconds which we find is good for most applications this side of a horse-race.

    Very much looking forward to others thoughts and observations on the possibility of syncing these splendid little cameras.