Tagged with synchronization - Personal View Talks https://www.personal-view.com/talks/discussions/tagged/synchronization/feed.rss Mon, 29 Apr 24 04:50:10 +0000 Tagged with synchronization - Personal View Talks en-CA Kdenlive topic https://www.personal-view.com/talks/discussion/3429/kdenlive-topic Thu, 31 May 2012 17:02:57 +0000 karl 3429@/talks/discussions Good news from the developers of the free video editing software "kdenlive":

  • Their fund raising campaign for one developer to devote two full man months on some long desired re-factoring succeeded - and quickly!

  • kdenlive 0.9.2 was just released, addressing some regressions from the 10 days old 0.9 release, which introduced numerous interesting features (see http://kdenlive.org/discover/0.9 for a list).

Two new features I found especially notable:

  • The availability of a second video stabilizing filter (which was ported from "transcode"), which offers numerous parametrization options (that the first stabilizer, "vstab" is somewhat lacking).

  • Automatic synchronization of video tracks taken from different cameras at the same time (by using the audio track similarities).

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BMD Pocket Cinema Camera Stereoscopic Collaboration https://www.personal-view.com/talks/discussion/10902/bmd-pocket-cinema-camera-stereoscopic-collaboration Mon, 28 Jul 2014 06:34:39 +0000 _gl 10902@/talks/discussions After the success of our old Panny GH Collaboration, let's see if we can sync two BMD Pocket Cinema Camera (BMPCC) for stereoscopic 3D. I've got two on backorder (ETA 2 weeks), so I'll be able to run sync tests. If you're interested in shooting quality 3D on the Pocket or have one to try stuff on, join in!

The Pocket is only $500 USD / £390 UKP this summer (very limited availability, buy now!) .

Frame Sync is the big problem:

Syncing two cams for 3D cannot be done in post - they need to be synced at the pixel level, ie. each camera should begin each frame at exactly the same time. In other words, this is a fractional-frame problem; but you can only correct whole frames in post (not counting pixel interpolators like Twixtor which can cause unacceptable artifacts in 3D).

Pro cameras are synced with 'Genlock' - basically a connection between the two cameras that tightly synchronises frame capture. Without this, the cameras have a random gap between frame starts, anywhere up to 1/2 frame. So if you shoot 24p, the cameras will be randomly out up to 1/48th of a second, and you have no way to predict what that error will be at any given time. In 3D this is catastrophic, at least if there is any significant motion in the frame. The delay pushes moving objects forwards or backwards in 3D, and can also cause a weird shimmering effect. And forget high motion which looks awful.

Solutions:

1) hardware mod: do true genlocking by linking the cameras' capture timers or master clocks somehow at the circuit board level). This is perfect, but tricky/risky and requires skill and experience.

2) Simul-power workaround (this is what we use on the Panny GHs, and works on many others): you power-up both cameras at exactly the same time (usually with external power and a dual-switch or a custom circuit). Many cameras synchronize their frame capture from a global running clock, which is initialised at boot and never changes. So it doesn't actually matter when you trigger record - the first frame capture is always locked to that clock (ie. it waits for the next frame 'slot' before starting recording). By simul-powering the bodies, those clocks start in sync on both bodies and frames are synced.

we don't know if this works on the Pocket yet.

Downside: as no two digital clocks run at exactly the same speed, the bodies slowly drift out of sync. How fast depends on how closely matched the bodies are - people usually try to get consecutive serial nos., hoping that the eletronics components are likely from the same batch and so a close match. My badly matched (2 month apart) GH2's are good for about 4-5 mins before the drift becomes bad. Apparently some drift far less. So you have to keep power-cycling.

Problem: The Pocket only powers up when a button is pressed ('soft' power). It needs to power instantly as soon as external juice is on (one idea, permanently tape the power button down - does it work?).

3) LANC. The Pocket apparently responds to the LANC 'record' command (but not power cmds). If we're really lucky and this resets the frame capture timers (unlikely), it might be enough.

4) Firmware:

If the capture timers are NOT reset by capture start, BMD could add this to a firmware update. Then LANC-initiated record would always start in sync (subject to gradual drift) - much nicer than having to power-cycle all the time. This might be super-easy for BMD to do.

Of course some kind of true hardware sync option (maybe via the USB or LANC ports) would be best! BMD could probably do it if they wanted to - contact them if you want this: http://www.blackmagicdesign.com/uk/support (without demand it's unlikely to happen):

Exposure / Zoom sync:

Frame sync is the most important, but it would also be much nicer if exposure (iris, ISO, shutter-speed), focus etc settings could also be synchronised, ideally in real-time (one body acts as master, one as slave). Firmware or LANC command additions could do this.

With the pocket's small size, ultra-light and compact SBS (side-by-side) 3D rigs are possible. With 'body stacking', you can even get the lenses as close as around 70mm! With Speedboosters and fast lenses you can do lowlight and shoot wide (my target), and you have 10bit ProRes and 12bit RAW. Let's make it happen!

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Youtube videos re slightly out of sync. Why? https://www.personal-view.com/talks/discussion/13614/youtube-videos-re-slightly-out-of-sync.-why Wed, 26 Aug 2015 12:03:59 +0000 dlzn 13614@/talks/discussions I've noticed my videos are now slightly not-synchronized, after they have been uploaded for months, for an unknown reason. I mostly view them in Google Chrome. But I don't think it's browser related.

I shoot with a hacked Panasonic GH2, mostly Flowmotion V2. My upload codecs are usually h264 .mp4 varying from 24fps to 50fps. Nothing too extreme. When rendered and exported everything is pretty much synced. But on Youtube they are off.

I work on a Macbook Pro Retina (late 2014) 2.2 Ghz Intel Core i7, 16GB RAM

Does anyone know why or how to fix this? Or is it just me and am I going crazy.

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