High Definition with Elphel model 333 camera

[Oscar Spierenburg]

Hi everyone,

I'm working on a detailed version of the rods support CAD model for the Elphel. I want to avoid having stuff machined that already exist.
One thing we don't want to make, are the handles on top and on the front. So we should be looking for things like this
(unless we would go for a handle with control buttons of course)


All ideas are welcome!

[Sebastian Pichelhofer]

Here is the summary from a discussion about battery packs were recently had:

Elphels power consumption (10349 - ElphelWiki) is around 5W at full load (streaming video and writing to internal HDD).

With the optional 9-36V Power supply (best efficiency at around 15V) we did an example with a 12 V battery pack (Pb batteries would do the job)

The maximum current with 12V would be around 400mA

If the battery pack has a capacity of around 4000mAh it would allow the camera to operate for a maximum of 9.5 hours (not considering DC-DC losses, degree of efficiency, etc).


An interesting reference for the power consumption of all different cameras and manufacturers can be found here: How to choose your battery

Sony PD 170: 8 Watts
Red One: 60 Watts

A quite detailed explanation here : http://www.antonbauer.com/downloads/2008Handbook.pdf

Their conclusion is probably to buy their own battery packs, but still an interesting read about batteries, specifically for video work.

An interesting project of building a though small Lithium Ion battery pack can be found here: HY Research - Simple Li battery power supply


Last not least its important to have a proper mount system for the battery pack that allows battery changing without screwing and plugin in multiple connectors.
Examples are the Sony V-Mount for their professional cameras or the Anton Bauer mount.

Conclusion:
LiPo batteries are to date the lightest available technology, though very expensive and rather dangerous as they easily catch fire if not charged or discharged properly.

LithIon are probably the most widely spread camcorder, still camera, laptop and cellphone battery packs today. Though they also thread a potential danger if not properly secured and monitored by protection circuits.

There are the heavy and cheap big Pb battery packs that hold a wast amount of power and can be charged rather easily compared to LiIon or LiPo packs. Their weight might help balance the front-heavy rigs (heavy lenses).


Does anyone know an open source / open hardware approach to design a general purpose battery pack?

[Oscar Spierenburg]

I bought a universal charger with integrated balancer (needed LiPo) so I can try different types of batteries if needed.
First I'll test out LiPo. They have two connectors to charge:

A balancer cable
A power cable

How about using some kind of a project box ( something like this or this )

The dimensions of the battery I have (pretty standard) are:
W= 50mm
H= 30mm
L= 90mm (maybe longer for higher capacity batteries)

If you have two batteries in an enclosure that mounts directly on the rods support, you only need to connect and disconnect the power cable. Would be like the shell design posted on the wiki, only other dimensions.

I also got a led that will light up if the battery runs down to 9v. I'd like to get a fully functional battery meter, but this is a beginning (to know when you have to change batteries, but also to spare the life of the battery)

[Sebastian Pichelhofer]

I spent many hours in the last 3 days to get the S65 LCD I bought for the camera buttons interface running . Without success so far. I don't have an oscilloscope to be able to properly monitor the ignition sequence. All I can do is measure if there is a signal and if the wiring is OK. I was so desperate I even tried to monitor the signal with the line-in of my sound card but 44KHz are simple not enough when dealing with a 8Mhz+ transmission. All I was able to verify was that there was indeed a signal being transferred.

I kind of gave up and instead of buying a (cheapest) 1000$ oscilloscope I decided to buy a 30$ ready built S65 LCD shield for the Arduino.

But finally a small success in a different area today. I managed to embed an MPlayer video canvas in a java application. It also already works with the cameras live stream!

Now we need a cool name for the viewfinder software that keeps me motivated to go on :)

[Oscar Spierenburg]

Great work! How about calling -this- Elphel Vision?

BTW: LiPo works perfectly with the camera. I don't know yet how long the battery will run the camera though.

[Oscar Spierenburg]

I've tested the camera interface and HDD recorder interface on the TabletPC in portrait mode(upright). Although the camera interface is normally a mess on this low resolution screen, in portrait mode it works surprisingly better! The window is scaled down better and the long 'tab' of camera controls fits the screen.

The HDD recorder interface (camogmgui) doesn't show up that well in portrait mode, but that's only because the layout is designed horizontally.

I guess the images below explain everything.

(I still feel this is a good setup, the preview image is small, somewhat like most camcorder LCD's, but you have a lot of space left for all the controls. But, the main reason is to save space on the rods support.)

[Sebastian Pichelhofer]

Very nice Oscar!

Both camvc and camogmgui as shown in your last post are actually just workarounds because we have no real cinema camera control software yet.

Calling THIS software "Elphel Vision" is a great idea between, at least it definitely got me motivated.

I did further tests for Elphel Vision and managed to draw text overlay on top of a live video feed from the camera in a java applet (using mplayer in slave mode). See attached image. (Yes it is "the very hungry caterpillar") :)

[Oscar Spierenburg]

I actually climbed on the roof today and shot some footage with the LiPo.

Cathedral on Vimeo - Yes, I have a cathedral in my backyard :)

I didn't use a 35mm adapter. The image is not sharp enough (too big aperture I guess). So clearly, focusing is difficult without a focus aid. There seem to be some frame drops, but it could also be that I couldn't fix the frame rate (must be something in the new firmware.)

The battery (2000 MaH) dropped from 12.8v to 11.8v after +/- 1,5 hour.

Hope to be testing "Elphel Vision" some time on the roof ;) It looks very promising.

[Andrey Filippov]

Oscar, you'd rather open camvc2.html in a new window (as the alert message says) - it will give you more room especially on the small screen. And camvc _is_ designed to work in the new window. When doing it first time you'll need to enable popup windows in Firefox
Next (it is also written in the alert box) open "about:config" in firefox, enter "dom" in the filter and edit several options so the camvc2 can:
- hide address field:
dom.disable_window_open_feature.location false
- hide status bar
dom.disable_window_open_feature.status false

In Linux you may save even more space - right-click on the title bar of the window, select "advanced->no border" (alt-F3 to be able to restore it back).

[Philippe Jadin]

Originally Posted by Oscar Spier

(I still feel this is a good setup, the preview image is small, somewhat like most camcorder LCD's, but you have a lot of space left for all the controls. But, the main reason is to save space on the rods support.)

Sorry if it has been asked before, but what is the "lag" of this setup? I mean, how much is the delay between live action and what you see on the screen ?

[Oscar Spierenburg]

Philippe, I think Sebastian had good results (semi real time), but I can't judge if the lag (about 1/2 sec.) I experience on the tabletPC is a result of the speed of the PC. On a fast laptop I was able to get almost real time preview. In the current camogmgui I can only choose 'update every 1 second' as live view, so that's not really workable. But as Sebastian says, it's a workaround interface and he is implementing mplayer now.

Battery update:
I've soldered a 'LiPo saver' on the battery wires and put everything in an improvised enclosure with rod support mount. The 'LiPo saver' is a LED light that lights up when the battery reaches 9v (3v per cell). This is because a LiPo battery must not be discharged under 2.5v per cell.
Maybe it would be possible to make a relay in stead of the LED and actually shut down the battery (or maybe it already exists)

[Sebastian Pichelhofer]

Originally Posted by Philippe Jadin

Sorry if it has been asked before, but what is the "lag" of this setup? I mean, how much is the delay between live action and what you see on the screen ?

The internal camera delay resulting from putting the full frame into memory and reading it out again for compression, image processing, etc. should be extremely small (maybe a single frame at 25fps if at all).

But I also get varying delays in the player displaying the video live stream from time to time that are very well noticeable.

VLC for example has built in caching so it will fill up a buffer of read data in advance to displaying it. Mplayer should be optimized for not causing any delay but as Oscar mentioned there still can be a short delay sometimes. We will need to do some investigation to solve this problem.

[Sebastian Pichelhofer]

Here is the first concept for the DICTATOR Camera Control Interface.

It will work together nicely with the touchscreen / laptop and the Elphel Vision Software.

But it can also be used standalone with the camera. There is just no direct way to view live video then.

What do you think?

[Philippe Jadin]

Originally Posted by Oscar Spier

Battery update:
I've soldered a 'LiPo saver' on the battery wires and put everything in an improvised enclosure with rod support mount. The 'LiPo saver' is a LED light that lights up when the battery reaches 9v (3v per cell). This is because a LiPo battery must not be discharged under 2.5v per cell.
Maybe it would be possible to make a relay in stead of the LED and actually shut down the battery (or maybe it already exists)

This looks great !

Other batteries types have a drop of voltage before being empty. Here an article with some nice curves : Battery monitoring

A great way to monitor battery level could be to feed the battery voltage to an analog to digital convertor (an analog input on the arduino?) then monitor the voltage of the battery and have some kind of meter shown on the lcd screen or on the web interface.

Different battery types have different discharge curves. The firmware of the camera should have one for each type of battery (nicd, nimh, lipo...), then the user could choose which battery type/ capacity is connected to the camera and have a precise meter of the remaining battery level.

I don't know if it works like this in other systems, but I think it could work. I guess other more intelligent systems (like stamina) have built in electronic in the batteries that have this curve and the initial capacity of the battery stored. All this can be done in camera I think.

[Philippe Jadin]

Have you guys at Elphel considered using a Beagle board to power the next camera ?

They look very interesting in the video department (and inexpensive). But I wonder if they are open source...

BeagleBoard.org - brief