Record video using sensor region of interest (like EOS600D) - Feature Requests - CHDK Forum
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Record video using sensor region of interest (like EOS600D)

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Offline Davo

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Record video using sensor region of interest (like EOS600D)
« on: 23 / February / 2020, 08:40:45 »
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The Canon EOS600D has a feature that allows video to be recorded using only the central portion of the sensor rather than the full sensor width. This allows you to shoot video with an optical zoom factor of 2.7x. Magic Lantern have enabled this feature on other EOS models as well like the 650D. Note that this is not digital zoom because only the central 1920x1080 pixels are used with no interpolation.
Would it be possible to do this with CHDK? It would give me an extra 2.4x optical zoom on my SX530HS which would take it to an optical zoom of 120x or a 35mm equivalent focal length of 2880mm - better than most telescopes.  This would be great for birding videos and astronomy captures of the Moon, Sun and planets.
Being greedy, manual settings of video FPS, shutter speed, ISO and aperture would make it even better for astronomy. Also great would be user defined region of interest for planetary captures. Dedicated astro cameras use small regions of interest for planets which allows them to increase the FPS while keeping video bandwidth the same. More captured frames gives better final results after stacking.
I have SX230HS and SX530HS cameras and would be a very active tester if someone takes this up.
Fingers crossed.
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Offline reyalp

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #1 on: 23 / February / 2020, 16:22:08 »
It might be possible in theory, but would at a minimum require a lot of reverse engineering. So it's unlikely to happen until someone with significant reverse engineer skill decides to spend a bunch of time on it.

The existence of a similar feature in ML (I guess you mean https://www.magiclantern.fm/forum/index.php?topic=17021.0) does not necessarily help much, because the P&S codebase is quite different from the SLRs.

Some work has been done on manual controls in video https://chdk.fandom.com/wiki/Manual_Exposure_Control_for_Video_Recording
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Offline Davo

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #2 on: 24 / February / 2020, 06:04:36 »
Many thanks for the helpful reply. I wasn't aware of that ML thread - I just knew about the 650D work. I do have the movie manual control setting script on my cameras.
I might have a go at this myself as the reward will be a pocketable video camera with a 3 metre focal length lens. Worth going for I think.
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Offline Davo

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #3 on: 24 / February / 2020, 06:49:51 »
Embarrassingly, I got involved in the exact same question back in 2013 but I had forgot all about it. I didn't find it on a forum search but it popped up in the related posts below. Time for a lie down.


https://chdk.setepontos.com/index.php?topic=9527.0
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Offline Davo

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #4 on: 25 / February / 2020, 09:51:27 »
I checked out the changes in propcases between the various video modes on my SX530 using the script linked below. I thought there might be some pattern that I could crack but I certainly can't see any logic.

Propcase     FHD       HD       VGA
67              2000       -1       732
173                  5        4           2
202              405       58       353
251            2000        -1       732
254              843     876        851
273              543     567        567
277              972     963        966

My thinking was that there might be a 'function' in the camera like this:
setVideoMode(sensorRectangle, videoWidth, videoHeight, FPS)
that we could call using propcases to give the zoomed video.

https://chdk.fandom.com/wiki/PropertyCaseDump
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Offline srsa_4c

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #5 on: 25 / February / 2020, 14:03:35 »
Quote from: Davo on 25 / February / 2020, 09:51:27
My thinking was that there might be a 'function' in the camera like this:
setVideoMode(sensorRectangle, videoWidth, videoHeight, FPS)
IMHO things are way more complicated than that.

The EOS M models do support reading out a smaller rectangle of the sensor, but only for live view magnification. Recording that smaller area is not supported. On the m10, enabling/disabling live view magnification is possible via logical events. Unfortunately, those events are ignored during video recording.
On PowerShots, partial sensor readout is used when digital zoom is active.

From reyalp's link, 1 -> 2, setting ADTG and CMOS registers might be the way to achieve your goal.

A while back, I identified a function that looks like 'adtg_write', its address is 0xFC427E40 in m3 101a, 0xFC231308 in m10 110d. But that's just one function, the CMOS related counterpart is still TODO. Other than finding that function, I have not done any experiments.
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Offline Davo

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Re: Record video using sensor region of interest (like EOS600D)
« Reply #6 on: 26 / February / 2020, 13:51:10 »
Thanks for the links but I am obviously way out of my depth here so I think I should drop this idea. Instead, I am going to run some tests with video between 50x optical and 200x digital on my SX530. This will include tweaking the CHDK video quality and bitrate settings to see what the best video zoom my camera can provide. I will post results here.
Thanks for all the advice.
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