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Swarm Recording

Swarm Recording

 Ever hear of this?

Swarm Recording - the process of using a number of synchronized cameras and/or microphones to record an event. Nothing to do with bees, except of course if they are a logical part of the event. ;-)

For example,  the better modern cell phones contain pretty fair still/video cameras and microphones. The microphones may be  more limited, but high quality bypasses of them are possible.

AFAIK if the cell phones are all on the cell system, or running off of a common WiFi Hotspot, they are automatically time synchronized with each other. Precisely!

Basically you have a bunch of cell phones that are each pointed at one of the various people that are involved in an event, or at least the most important ones or at least the overall event from as many angles as desired or possible. You set them up to record video as desired and press the start buttons. You run the event.  When the event is over, you download all the videos and/or audio tracks and edit them into a usual multi-camera and/or multiple microphone recording.

The way this is economical is that you can now get really pretty good used cell phones for about $100 each. Not a bad price for a mic and a video camera.  If you synchronize them to a WiFi Hotspot they don't need SIM cards. BTW, VOIP still works on them, even without SIM cards. They work like small WiFi Android tablets. In terms of local storage, they can be expanded up to the uSD capacity of the phone, which may be 128 GB.

Re: Swarm Recording

Reply #1
The "megabuck" version of this has shown up at a few major sporting events:
IntelĀ® 360 Replay Technology

Lately I've seen it in some TV commercials; probably will happen more as cost comes down.

Re: Swarm Recording

Reply #2
The "megabuck" version of this has shown up at a few major sporting events:
IntelĀ® 360 Replay Technology

Lately I've seen it in some TV commercials; probably will happen more as cost comes down.


Interesting. One difference is that their system is real-time although the same thing could be done on a more limited scale in the Android context by possibly exploiting Chromecast.

Re: Swarm Recording

Reply #3
AFAIK if the cell phones are all on the cell system, or running off of a common WiFi Hotspot, they are automatically time synchronized with each other. Precisely!

While you could make a phone that worked like this, the A/D+D/A clocks are not going to be derived from the remote Wifi or 4G signal in a typical phone.  Instead they'll be derived from the same oscillator as the CPU.  Usually you don't actually have access to the underlying RF clocks on a SOC, so time aligning audio will be complex (but of course entirely possible in post processing). 

FWIW, I have wondered if anyone would consider making a SOC that worked like you're proposing for stuff like a Chromecast where you want to do multiroom audio.  You're right that it should be possible. 

Re: Swarm Recording

Reply #4
Genlock (generator locking) is a common technique where the video output of one source, or a specific reference signal from a signal generator, is used to synchronize other television picture sources together. The aim in video applications is to ensure the coincidence of signals in time at a combining or switching point. When video instruments are synchronized in this way, they are said to be generator-locked, or genlocked. ~ http://en.wikipedia.org/wiki/Genlock
Quis custodiet ipsos custodes?  ;~)

Re: Swarm Recording

Reply #5
Genlock (generator locking) is a common technique where the video output of one source, or a specific reference signal from a signal generator, is used to synchronize other television picture sources together.

Yes this is what Arnold is referring to, although for audio clocks rather than video.  The problem is that there is not an easy way to get at this signal given how most SOCs are designed.  Usually anything running off an RF clock is isolated from the rest of the system by FIFOs. 

I think the reason for this is that RF signals are intermittent and subject to interference, and high frequency digital circuits are extremely sensitive to clock errors and/or glitches, so it is probably easier to just keep everything running from a known good oscillator. 

Re: Swarm Recording

Reply #6
Genlock (generator locking) is a common technique where the video output of one source, or a specific reference signal from a signal generator, is used to synchronize other television picture sources together.

Yes this is what Arnold is referring to, although for audio clocks rather than video.  The problem is that there is not an easy way to get at this signal given how most SOCs are designed.  Usually anything running off an RF clock is isolated from the rest of the system by FIFOs. 

I think the reason for this is that RF signals are intermittent and subject to interference, and high-frequency digital circuits are extremely sensitive to clock errors and/or glitches, so it is probably easier to just keep everything running from a known good oscillator.

Obviously, RF systems can be time-synchronized to a high degree, because that is key to the operation of Cell Phones and GPS.

However, for multitrack recording of audio and video, tolerances in the integer millisecond range would suffice.

 
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