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Video Ground Station - Recording Advise?

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Hi all, I need some advise and direction on building a decent portable ground station; particularily the recording side. I have read threads with respect to this, but need some input from those experienced with what really works. The station has to setup, shoot, and pack up fairly quickly. I initially plan to contain most of the compoments in something like a Pelican case; except for external antenna(s). The video system is a 2.4 ghz 500mw on a Logo10. I will use a my 9CHPS to trigger a Canon A640 camera with "BLIP" switch.

I am looking at using my existing laptop to record. I did think about using something like the Archos 604 with the DVR Travel Adapter. However, I think a laptop would be better due to greater control, HD space, quality recording capability, etc. The 604 has only a 4.3 screen and limited hard drive, although it would probably be great for carry around recording.

As far as I can figure, the components will consist of:

1. Laptop (View & Record) I will test the video card well first.

2. Digital Video Converter: Plextor ConvertX PX-M402U (Acts as a go-between for the laptop and receiver). Also allows for MPEG-4 and DivX recording compression.

3. Video Receiver (2.4ghz)

4. Power Source. (Unknown battery type and capacity)

5. External Antenna. (I first plan to use a single 8 or 14 dbi patch. I will gradually add a Diversity Receiver to the internal components as well).

6. FPV flying; will gradually add something like the I-VIsion 922 or Argo+PC glasses. I also can't avoid getting an RC-Tech Gyrocontrol unit.

Okay...questions:

1. Am I good to go with using a laptop for recording?.

2. Are there any issues I should be aware of? I would kind of like to skip the initial "trial & error hump" and get exactly what will work.

3. Anything missing; anthing to add?

I did read JMS's recent thread which helped alot. I will certainly look forward to advise from those who have pursued a similar avenue of approach. Thx!

Edited by qb7

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Well, I said about all I could in the other thread.

DivX recording will need a very powerful laptop (Core Duo at least), and thus eat the battery quickly if the capture interface doesn't do hardware encoding, which is not clearly specified. You'd better go with DV , the quality will better too.

Edited by Kilrah

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Roger that Kilrah; you definately provided good input there. Appreciate the heads up regarding power situation, as that is my primary concern. But I guess that's where the "trial & error" part comes in to play. Will check hardware encoding specs on the interface and look at sticking with DV.

Thank you!

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For power, I know my laptop will run for 2hrs -AT-100% CPU usage, and 3h-3h30 if idling. I've especially ordered a 2nd battery for extended field sessions when buying it as it was only ~$80... pretty good for a 3s3p 7600mAh pack! :blink:

I absolutely don't know how it was so cheap as I'm used to $250+ figures for laptop batteries, but what I'm sure about is that I didn't hesitate at all :P

Edited by Kilrah

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For power, I know my laptop will run for 2hrs -AT-100% CPU usage, and 3h-3h30 if idling. I've especially ordered a 2nd battery for extended field sessions when buying it as it was only ~$80... pretty good for a 3s3p 7600mAh pack! :blink:

I absolutely don't know how it was so cheap as I'm used to $250+ figures for laptop batteries, but what I'm sure about is that I didn't hesitate at all :P

Dell batteries are pretty cheap as well, i ordered 2 batteries for the laptop which should be arriving on friday because its so cheap.

I'm starting to think that pulling a few laptop batteries apart will be cheaper than buying them from hobby shops, assuming they put out enough amps hehe

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That's what I actually thought about when writing my last post :P

So I just checked the Dell website, the one for my laptop is indeed $200. I guess they did an offer as I was buying a $2500 laptop from them ;)

There is one other type of the same capacity that is about $100 though, might be cool.

That is the point, laptop batteries will not like being discharged at more than ~2C. You can forget about that for slowflyers, but for long flight time applications if you want to fly for 45mins or more that would be perfect. 3s/15Ah for $200 sounds good indeed :)

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My laptop is about 3 years old, and kind of plan to use it specifically for outdoor AP untill it dies of old age (It's seen better days!) I have no idea how much battery time I get on running 100% capacity, but will have to buy a new batt before trying. The laptop batt now is the original, so probably won't get more than 10 minutes at best! :D

I will see if I can power the laptop with an external battery with higher capacity to provide longer run time. The existing battery is rated 14.8V at 4400maH. I should be able find a fairly decent capacity gel-cell that will fit the pelican case and not be too heavy. If I solder in a regulator and it should be good to go. (Big talk for someone who is "electronically challenged") :lol:

Not sure, but I think it would probably be best to run each component (receiver, convertor, etc) off of independent batteries opposed to wiring all into one. I believe the less internal wiring and regulator use the better; keep it simple.

Edited by qb7

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Which laptop did you get Kilrah? I got the lattitude D820, however i get discounts through work. A spare 9 cell 85Whr battery cost me $AU150, normally around $AU192 though.

Cheapest high capacity battery i could find there was:

Dell Kit - 9-Cell 85 WHr Lithium Ion Spare Primary Battery for Inspiron XPS M121 - Dell SKU : CG039 for $AU145.20. Websites are saying these are 8500mAh which is quite huge. I'm guesing these are 3S3P for the 9 cells. Considering i get wholesale 2200mAh 3S batteries for $AU70 thats a considerable jump. However the cells i use are 20-30C.

Sorry for de-railing the thread :)

Back to the original thread topic anyway... I use a DLink capture device which does high quality divx compression or various mpeg types within itself, i find it to be quite reasonable. The only problem with it is that it adds a 1.5 second or so delay so you cant really watch the data "live" for flying. Might be good for simulating satellite feed latency though haha. This is on my 1.2ghz centrino laptop though (Toshiba Tecra S1) so it may actually be the CPU generously providing the lag. The device cost me about $AU270 wholesale, if your in australia i can get them cheap for you too - no commision :) The DLink code is DUB-AV300, there is a higher quality one but i really dont see the point in spending the extra money.

If your going to be ripping directly to your laptop though, i'd high recommend getting at least 1gb of ram if your on XP, or 3gb+ if your on vista. The more ram you have the better you are for ripping. If possible also drop a 7200rpm disk into your laptop rather than the 5400rpm that most 2.5" disks are. While CPU speed is important, being able to actually write the data and process it in memory rather than in page file is extremely important.

The only thing i don't like about using a laptop is that you have to cart 1-4kg around depending on your model.

My sony handycam won't do video in recording, at least that i'm aware of - it's a DCR-HC36 so if your looking at it, great cam otherwise - but no AV in.

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I have an XPS M1210, with 2GHz Core 2 duo and 2Gb RAM, 100Gb 7200rpm SATA drive (especially asked for the 7200rpm version and paid extra). I think you spotted my battery, however the product no is different. Maybe some country-related stuff. It's a 9-cell 85Wh too.

You're right, I forgot to mention hardware encoders will always introduce a delay, for the simple reason that most modern codecs use bidirectional analysis, each delta frame will be calculated from a few frames coming before, but also from ones coming AFTER. So it obviously needs to wait the arrival of subsequent images before giving a result. There are buffers to damp slowdowns in transfer rates between the device and the PC too. If you want to have a real live view to fly by viewing the screen you should go for a simple model that doesn't do any treatment but just sends the raw digitized data to the PC for it to do the encoding.

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I have an XPS M1210, with 2GHz Core 2 duo and 2Gb RAM, 100Gb 7200rpm SATA drive (especially asked for the 7200rpm version and paid extra). I think you spotted my battery, however the product no is different. Maybe some country-related stuff. It's a 9-cell 85Wh too.

You're right, I forgot to mention hardware encoders will always introduce a delay, for the simple reason that most modern codecs use bidirectional analysis, each delta frame will be calculated from a few frames coming before, but also from ones coming AFTER. So it obviously needs to wait the arrival of subsequent images before giving a result. There are buffers to damp slowdowns in transfer rates between the device and the PC too. If you want to have a real live view to fly by viewing the screen you should go for a simple model that doesn't do any treatment but just sends the raw digitized data to the PC for it to do the encoding.

My laptop arrived today :) whee.

The hardware encoders generally don't let you grab the video stream through DirectX or the Windows API for anyone who is a software developer - i was most disappointed.

I too think that the most simple of encoders is the way to go, especially if you are hoping to do some image processing or display the image onto a headset like the Z800.

I wonder what sort of amp draw we can give these batteries before they go pop. Anyone got an old dying li-ion cell or just a li-ion cell they do not want?

I found the inspirion batteries are cheaper than the lattitude and xps batteries, must be the way their cases are built to incur the extra $AU30-$AU50 for the same Wh and cell count.

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As I said, I had dismounted an old laptop batttery, found the cell datasheet and they were rated as 2C. Maybe the newer cells can give more, but I really doubt. There's a manufacturing tradeoff between capacity and current handling, and laptop batteries clearly need the highest possible capacity, while they'll never be discharged at more than 1C...

You're right with hardware encoders, you can forget 3rd party software too ans usually stuck with the manufacturer's solution. That's not including the DV encoders with firewire output of course.

Price differences are strange for Dell batteries. There are models with the same characteristics, but some are twice the price than others...

Edited by Kilrah

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Well, I guess my first step will definately be upgrading my old laptop with an extra 512 ram and look for a 7200rpm HD. If I had some money to throw around, I would look at buying the Quick Capture A2D. Definately not cheap at approx $1200 for their smallest 40GB. But it would be ideal for portable AP recording application.

It's worth taking a look at it.

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