Author Topic: Greater than 30fps in crop mode?  (Read 8772 times)

Thomas Worth

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Greater than 30fps in crop mode?
« on: April 03, 2014, 05:46:38 AM »
I'm working with a 7D and would love to be able to record greater than 30fps in crop mode. Is this possible?

ted ramasola

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Re: Greater than 30fps in crop mode?
« Reply #1 on: April 03, 2014, 06:23:21 AM »
Based on my tests the 60P mode does not work in crop mode. Only 30P.
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Re: Greater than 30fps in crop mode?
« Reply #2 on: April 03, 2014, 03:15:43 PM »
Yup it's a shame, 60p or even 48 fps in 2k would be CRAZY.
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Thomas Worth

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Re: Greater than 30fps in crop mode?
« Reply #3 on: April 04, 2014, 01:14:39 AM »
The problem is the aliasing is so bad in 720p mode that the footage is pretty much unusable. Is there no way to use crop mode when shooting 720p?

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Re: Greater than 30fps in crop mode?
« Reply #4 on: April 04, 2014, 02:56:15 AM »
Doesn't look like it, seems to be locked at 30p even with fps override on. Tested it in both 720p and 640x480 60p NTSC and 50p PAL. Would seem like the 7d would be capable of high frame rates with dual Digic, guess it's easier said than done though.
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a1ex

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Re: Greater than 30fps in crop mode?
« Reply #5 on: April 04, 2014, 07:50:11 AM »
There is a single crop mode, and it doesn't care about what FPS you have set in Canon menu.

Thomas Worth

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Re: Greater than 30fps in crop mode?
« Reply #6 on: April 05, 2014, 04:13:40 AM »
There is a single crop mode, and it doesn't care about what FPS you have set in Canon menu.
Is there any possibility of pulling data off the sensor in crop mode at any rate greater than 29.97? Even if it's at small resolutions?

a1ex

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Re: Greater than 30fps in crop mode?
« Reply #7 on: April 05, 2014, 08:12:58 AM »
Thing is... we don't know how to change the resolution (we are just cropping what Canon already gives us).

The closest thing is via ADTG: a few registers are related to vertical resolution, and if you change them (e.g. reduce them in half), the LiveView data will be filled with dark pixels in the second half.

Also note that FPS control is not yet fully understood, since we can't get 30 FPS overriden from 24, even if the resolution is the same. There's something else we need to change, besides the two timers.

Canon eos m

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Re: Greater than 30fps in crop mode?
« Reply #8 on: April 05, 2014, 05:50:15 PM »
Cant begin to imagine what would happen to the temperature if the camera did go up to 48 or 60fps i crop 
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Thomas Worth

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Re: Greater than 30fps in crop mode?
« Reply #9 on: April 05, 2014, 07:35:06 PM »
Thing is... we don't know how to change the resolution (we are just cropping what Canon already gives us).
Okay, so then you are reading the full output of the sensor and just deciding which parts to write to the card, e.g. based on the CF card speed? If that's what is happening, then you could window different areas of the sensor. Wait, aren't you already doing that with the white box / joystick control? The "resolution" of the output file would just be whatever resolution you decided to write to the card. Am I in the ballpark here?

rainless

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Re: Greater than 30fps in crop mode?
« Reply #10 on: April 06, 2014, 12:00:24 PM »
I have read now... literally... THOUSANDS of posts about this "crop mode"... and I still don't understand it.

I read about a hundred posts a day trying to wrap my head around it. I've read all the posts and stickies about it, I just don't understand it... so please... somebody break this down for me.

1. Are you saying that, if you press the "zoom" button in movie mode... then you can hit "record" and record from that ML Grayscale thing?
2. It's my understanding that if you record in crop mode, you can record at a higher resolution than you would normally be able to.
3.  You already have greater than 50fps... (I suppose in normal mode?) http://www.magiclantern.fm/forum/index.php?topic=10195.0 on the 7D. So, I'm assuming, that this thread is about having greater than 50fps in the higher resolution of crop mode.

Is that it?
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Audionut

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Re: Greater than 30fps in crop mode?
« Reply #11 on: April 06, 2014, 02:11:29 PM »
Yes, yes, and yes.

NedB

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Re: Greater than 30fps in crop mode?
« Reply #12 on: April 06, 2014, 02:17:10 PM »
@rainless: This is my understanding of what is known in ML and this forum as "crop mode".

1. Raw video is not created by ML. It is simply captured directly from the already-existing data stream which the camera sends to the LV display in Video mode.

2. Therefore, when you are in, let's call it "normal" mode (you haven't hit the Zoom button yet), you can get, as a maximum, the native video resolution of the LV display. This resolution has increased since the older cameras, so that the 50D, for example, can do "only" 1584x1058 whereas the 5D Mark III can do 1920x1080.

3. This represents the entire image sensor dimensions mapped onto the size of the LV display. For example, the entire 5760x3240 of the 5D Mark III sensor is mapped [via a black-box process we don't completely understand] to the dimensions of the LV display in Video mode (1920x1080 for this camera, less for other cameras.) This mapping is done in the camera, and ML has no control over how it is done. It simply uses the result.

4. BUT, once you press the "Zoom" button, it's another story. Now you go into "crop mode". By zooming into the image we see on the LV display in "normal" Video mode, we see objects larger than we did before. Exactly how much larger varies by camera. But what happens when you're running ML is that now the data stream sent to the LV display  can in effect be larger (or smaller) than the native video resolution of the LV display. That's why, in "crop mode", you can record, for example 2000x1080 on the 50D and 3584x1320 on the 5D Mark III. The difference is that now this rectangle you are recording is a 1-to-1 pixel mapping of only a portion of the image sensor, that is, a smaller rectangle which represents only part of the entire image sensor rectangle. The highest resolution you can record in "crop mode" depends on the camera model you have and is probably a hardware limitation in most cases.

5. The display, on the other hand, which you see when you are in "crop mode" is selectable. It is also ONLY a display, it is not what you are recording. Basically you have the choice between ML grayscale, which shows an accurate representation of the boundaries of the rectangle you are recording, but a low-frame-rate and low-pixel-count picture, and Canon internal, which displays in the correct frame rate and in color, but as far as I understand, with no guarantee that you are seeing the correct boundaries of what you are recording. You just have to pick which is more helpful to you while shooting, remembering that it's only the display and doesn't change what you are recording.

I hope others will chime in with corrections and/or additions, and that this helps a bit. Cheers.
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a1ex

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Re: Greater than 30fps in crop mode?
« Reply #13 on: April 06, 2014, 02:38:20 PM »
@NedB: your understanding is perfect. Some additions:

- When you move the zoom box, the captured (internal) raw buffer may or may not move. Try moving it as fast as you can - at some points you will see some jumps (delays). This is when the raw buffer gets moved (by Canon code). When it doesn't jump, only the preview (displayed) window is reconfigured (of course, in Canon code).

- The above explains why you can't always center the crop rectangle (especially at high resolutions): because you can't choose the raw crop window (Canon chooses it). ML does its best to center the recorded crop window (align it with the color image displayed by Canon code), but at some point it hits the edge of the raw buffer (of course, only if the crop window recorded by ML is larger than the one displayed by Canon).

- There is actually a way to move the raw crop window, via ADTG/CMOS registers, but the exact details are not yet fully understood. If you want to implement an extended digital dolly (that can travel over the entire sensor area), you will also have to understand the black level correction (or override it in post somehow).

- Crop advantage: no aliasing (it's 1:1 crop from the sensor).

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rainless

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Re: Greater than 30fps in crop mode?
« Reply #14 on: April 06, 2014, 04:28:07 PM »
Beautiful!  Thanks guys!

This is the most complete explanation I've found on the site. Someone with the power to do so should add these two posts to the "How to record cropped video" sticky.

Maybe a: "First... What IS cropped video?" kinda thing. :)
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