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Old June 17th, 2003, 09:31 AM   #1
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Pre-trigger recording

Very often in action shots I miss the action pressing record button few seconds after the action has begun.
I just thought it should be easy to add pre-recording memory for these situations. Such memory is basically a circular buffer storing few seconds of video and audio data. In stand-by mode this data is constantly overwritten, so as it always contain last few seconds of data.
Then, when one presses record button, the recording starts from this buffer data, that is few secons BEFORE the button is pressed.

It looks to me such a feature is extremely useful in action shots. It's also easy to implement. For instance, 5sec of data at 6Mb/s rate is about 30Mb of memory. This is dirt cheap these days.

Is there any camera that has this feature?
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Old June 17th, 2003, 10:12 AM   #2
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NOne that I am aware of. Most people simply press the trigger before the action. It helps if you remember the old saying

Lights.

CAMERA

Action!

Of course, that comes form the old pre-sound days. Now, you include sound in the roll call.
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Old June 17th, 2003, 10:36 AM   #3
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Great Idea. I know they do this now with digital audio recorders and for what it would cost, think it would be a great idea to add to video. Especially since even after you push record, it takes some time to spool up the tape drive and actually start recording.
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Old June 17th, 2003, 11:14 AM   #4
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The new FireStore FS-3 on-camera hard disk recorder has this function. We'll have more info and a review here on the website shortly.
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Old June 17th, 2003, 01:11 PM   #5
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Oh NO! Yet another reason I WANT one of those!
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Old June 17th, 2003, 02:15 PM   #6
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i believe sonys does the same thing, i think its 13 seconds..not sure
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Old June 17th, 2003, 02:40 PM   #7
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Thats a very good idea. I know I could sure use it, heh.

Richard, you can only say "action" if it's a movie your making with a cast and they are acting, not when your filming "action" stuff, such as skateboarding, and all the other sports. I know I always miss the good shots.
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Old June 17th, 2003, 03:13 PM   #8
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Yep, and wildlife also has a funny habit of missing its cues!
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Old June 17th, 2003, 03:32 PM   #9
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Nigel: Not if you shoot at the zoo.

Robert: Yes, the new-ish Sony DSR-DU1 disk recorder does have a pre-capture buffer of 8 seconds. Unfortunately, it also has a yen-scale price of $2,350.
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Old June 17th, 2003, 03:33 PM   #10
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To Robert Mann: What Sony do you mean? Hard disk recorder or camera?

I've just thought about one more implication of pre-trigger memory - a tape drive mechanism can be stopped completely in waiting mode. After the record button is pressed, memory recording gives few seconds for tape drive to wind-up. This can save excessive wear of the drive and tape and also might extend battery operating time.
My camera spends most of the time in waiting mode, so it might be a huge wear saver. Also, one could eliminate this annoying auto power-off thing that is supposed to save drive and tape.
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Old June 17th, 2003, 04:12 PM   #11
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Some of Sony's HD cameras have what's called "video cache recording" where the video signal is fed thru a buffer. The tape mechanism remains quiet until the "record" button is hit. At that point, the contents of the buffer is recorded to tape, followed by what's going on in real time.

The one I read about has a 7-second buffer.

I don't know if other models include this feature. But it would be handy for anything from baseball (to get that homerun hit without all the foul balls) to hard news (is that SWAT guy gonna shoot now?) to wildlife (is the whale breaching yet?). It's almost like having Nostradamus as a cameraman!

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Old June 17th, 2003, 04:26 PM   #12
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Guess it would pose some technical problems if you were recording to tape since the record mechanism would be required to double (or something faster than normal speed) record rate for the same amount of data as the buffer was recorded. OR it would just always record was was coming out the back end of the buffer and know to stop a specific time after you pushed the record button again. If it were to be added as a feature, I'm thinking I would want to be able to enable/disable it either way.
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Old June 17th, 2003, 05:13 PM   #13
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Rob,
I think on-the-fly speed change is relatively complex to implement. The second way when tape drive stops recording after a specific time is easier to implement.

One might think also what happens if one starts recording and stops it again in a second or two. Then it might be an option that camera just ignores it and records nothing. This might be helpful sometimes.

On the other hand, if one stops recording, but discovers in a moment that the action is still going on, then press record button again. In that case camera might ignore the pause and record continously. This also might be useful sometimes. It's good to have this as an option too.
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Old June 19th, 2003, 05:09 PM   #14
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For DV specifically, at 25 mbps, 10 seconds of buffering equals about 32M of memory, so this is not out of the question. It'd be a fantastic consumer camera feature, and I like the idea about bridging short on-off-on cycles.
///d@
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Old June 21st, 2003, 04:59 PM   #15
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Personally I just roll earlier. Very easy and almost cost nothing
extra. Better safe than sorry. Also I roll a bit longer after I yell
"cut"
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