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Turn LCD ON/OFF during video recording

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Offline Barnacules

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Turn LCD ON/OFF during video recording
« on: 21 / January / 2009, 11:08:05 »
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Right now even with CHDK I can only record 1 hour of video tops because my battery goes dead. The LCD screen consumes more then 50% of the total usage battery power during operation. When I record video I simply point the camera and usually cover the LCD with my hand holding the camera anyways so this is a waste.

Feature
I would like to see an option where once video recording starts I can push a button to turn the LCD screen on and off while the video is recording, this way I can line up my shot and then turn off the LCD and set the camera down or tripod mount it at birthday parties and double my recording time. I don't know if CHDK can do this, now sure what level of access it has to the LCD control on the screen but this feature would be fantastic!
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Offline fbonomi

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Re: Turn LCD ON/OFF during video recording
« Reply #1 on: 21 / January / 2009, 12:49:31 »

On cameras where the photo/video switch is available via script, I have seen that even if you turn the LCD off, when you switch to video mode the LCD turns back on.

without being too much informed, that the video feed is very strictly connected to the LCD feed, and this is therefore impossible.

you can anyway plug a jack in the "video out" plug, this should turn the LCD off while keeping other circuitry on.. That means some power saving..

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Offline fudgey

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Re: Turn LCD ON/OFF during video recording
« Reply #2 on: 21 / January / 2009, 15:34:19 »
Video recording in these cameras uses the LCD live view image. Disabling LCD actually also disables the sensor (and whatever support circuitry it has), which accounts for quite a bit of the power consumption that you may think is going to the LCD.

But there are some good news for you: In very recent CHDK autobuilds there is a command to disable LCD backlight. It's already accessible from scripts, and you can probably run a script that calls this command after you start video record. The camera likes to turn on the backlight sometimes (every time it readjusts the live view image after shooting, for instance), but it's likely that it will stay dark work for the entire duration of a single video record session.

See http://chdk.setepontos.com/index.php/topic,2744.0.html for some power consumption results and info about the new script command and Phyrephox's example script (metronome.lua).

I don't know if anyone's tried this during video record yet, please report back your findings. :D
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Offline Barnacules

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Re: Turn LCD ON/OFF during video recording
« Reply #3 on: 21 / January / 2009, 23:24:40 »
Nice, I found the set_backlight option and included it in a script and it works like a charm on my SD950, now I have a script that can turn off the backlight when I click it. Now I'm trying to do some motion capture stuff with the video and I found some scripts but the problem is there is a md_detect_motion function but not a counterpart function (that I can find) to return when no motion is detected. My goal is to do this, if someone knows how please let me know, otherwise I have to set a max length for each video clip and segment it.

md_detect_motion
press "shoot_full"
set_backlight 0
loop
   md_detect_absent_motion (threshhold)
endloop
press "shoot_full"
set_backlight 1
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Offline fudgey

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Re: Turn LCD ON/OFF during video recording
« Reply #4 on: 22 / January / 2009, 02:18:05 »
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Offline Barnacules

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Re: Turn LCD ON/OFF during video recording
« Reply #5 on: 22 / January / 2009, 02:33:13 »
That article is good, but it only covers how to detect motion not how to detect when motion has stopped. When you take still photos it works because you can test for motion between each shot, no motion, not shot. With video however you cannot do this, you need to start recording, then test until movement is no longer visible and then continue after no movement is detected for a period of time. If there was a way to get the mp_detect_motion to return "motion or no motion" after a period of time instead of blocking until it occurs definitely I would be able to do this :)

EDIT: Nevermind, I read more of the article and it appears that md_detect_motion bails out after 30 seconds of inactivity. Since this is the case I can base stopping off this result. I'll give it a try and see what happens.
« Last Edit: 22 / January / 2009, 02:36:31 by Barnacules »
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Offline Ailurus fulgens

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Re: Turn LCD ON/OFF during video recording
« Reply #6 on: 22 / January / 2009, 03:08:59 »
perhaps you can also kind of "benchmark" your sessions, as to how much energy you can save with the lcdoff command?
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Offline Camineet

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Re: Turn LCD ON/OFF during video recording
« Reply #7 on: 29 / March / 2010, 07:48:38 »
I also need a script to turn off the LCD backlight on my SD 780 after video recording begins.  Would someone be kind enough to give me one?  I'm new to CHDK, and this is the only reason why I have spent a couple of hours so far getting to know the firmware enhancement.  I would really appreciate some help with this.


Many Thanks,
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Offline Camineet

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Re: Turn LCD ON/OFF during video recording
« Reply #8 on: 29 / March / 2010, 07:50:15 »
actually, a script that would allow me to use a button to turn the LCD on and off during video recording is what I really need.  You know, the still shot mode on this camera allows for that functionality by simply pressing the Disp button.  But Cannon, in all of their wisdom, have disabled it for video mode.
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