Home Made HD Cinema Cameras - Technical Discussion

[Rob Scott]

<<<-- Originally posted by Rob Lohman : Netgear gigabit pcmcia network card -->>>

Rob ... did you get my most recent e-mail about the SourceForge project?

[Rob Lohman]

Yes I sure did and I'm walking through our e-mail conversation
to see which things we where talking about earlier. Sorry to not
get back to you earlier (as promised). I will be gone from friday
morning till somewhere sunday again but will try to get it done
by somewhere thursday (my time) at the latest.

Now if I could just quit my day job.... <g>

[Rob Scott]

Rob Lohman wrote:
Now if I could just quit my day job....

I hear you! I've been thinking about that one myself :-)

[Juan M. M. Fiebelkorn]

Don't know really but let suppose this:
you have 1280x720 at 10 bits and 250 fps.

If it is not Bitpacked (so it is at 16 bit) it gives:

439.45 MBytes/s

if it is bitpacked it is:

274.65 MBytes/s

So first if you wanna record direct to disk, you'll need a PCI-X 133 MHZ FG (= expensive) and enough disks to support that bandwith.(I think at least 20 if 2.5 inch would be ok).Also another controller for those disks which needs to be also PCI-X 133 MHZ.
So you need a motherboard with support for two independent PCI-X 133MHz buses.
Other solution would be using a FG with embedded RAID controller (again $$$$$).


Second option would be using a FG with processing capabilities able to process that amount of data and a disk controller for PCI-X 66MHZ.
So less disks to record but again an expensive FG.

Hope this helps...

[Wayne Morellini]

Lets say we go for packed 8 bit mode (just to fit into a cheaper 266MB/s 64bit or 66Mhz PCI-? card, and 4-8 3.5inch drive Main board raid canbe used). Sorry, I thought you were going to give realistic, unpadded, figures (this is when I am getting annoyed). See what I mean, it is a specialist camera not really requiring the best portability (even just transposrtable), (though using 20 2.5 inch drives over 4-8 3.5inch drives, you don't really save money, space, or power).

Well, talking a bit down the track (after the normal motion camera project is handled, and prices of drives, sensors and memory drop, and processing power increases (I am not PC limited here, I have something of much higher in performance in mind, lower powered and cheaper etc), the project could be made to support slow motion in this way (apart from a seperate slow motion camera):

Cheap option:
Normal camera + high speed sensor with 200fps+ 720p 8-bit capable FG 66Mhz or 64-bits (or cheaper 120fps 720p Altasens based system), biggest memory to buffer short sequences for film which are then saved.

Performance configuration:
As above, but with an extra module to attach extra raid drives for long slow motion sequences.

No bayer filtering/compression at these speeds, done in post.

(Processing requirements is up in the air for the moment, as I don't know what low powred dual core, dual processing systems they are planning, but a lot more advanced then now. Using the fastest low poprocessor may not be a problem, power wise, provided it has modern speed/power saving features. So during normal filming the power consumption canbe dropped and the attached/external drive module disconnected).

Only an idea!

So what do you think Jaun?

[Juan M. M. Fiebelkorn]

First my name is J u a n, the same as John.So if it is easier for you just call me John ;) (kidding)

Well the 20 disks are for over 400 MBytes/s, you don't need that for 280 Mbytes/s.
But you are right, I guess 8 Raptors with an Intel RAID card can get that (RAID 0)

I've never talked about portability, did I?

I don't understand what you call "packed 8 bit",sorry.
If you mean getting 8 bit directly from the camera that is ok for me, but if you are talking about any kind of packing (as putting two 12 bit pixels together inside three bytes or 24 bits) that is a different thing cause then again you would need an expensive card which supports the packing.

Sorry, but I'm not understanding what you are trying to say.
So I think it's up to you to define the needs for a high speed system cause I can't help.

[Jason Rodriguez]

Slow-motion at those frame-rates is a pretty specialized field. Why don't you just rent that slow-motion digital camera from Band-Pro (or someone else who has it)? Seems like you're going to be spending a lot of money and hassle for a dubious amount of gain.

[Steve Nordhauser]

I don't know how VGA would up-sample to HD, but we have a 640x480, 250fps 8/10 bit camera with global shutter and 9.9 micron pixels. The data rate is 80Mpix/sec so even at 160Mpix (unpacked) that isn't too scary. This will be supported on GigE in a bit (or when a customer demands it) which will include 2 pixels in 3 bytes. The max GigE rate is 100MB/sec which would be about 200fps. But, because of the packing, you are talking 100MB/sec to disk - maybe on a 32 bit split backplane or simple 64 bit system (2 SATA drives?). It is cheap (a relative word for sure) at $2495 USD - single piece without the DVInfo discount. Here is a funky sample:

http://siliconimaging.com/Samples/SI...0eye%20seq.avi

[Richard Mellor]

steve: that is very cool!

[Wayne Morellini]

Sorry Juan, that is one of my weaknesses, is name memory (and advanced mathematics, which helps me simplify designs).

I assumed it was portability/battery life, because that is one of the main reasons people have been using the 2.5inch disks, and their has been people acting like it is going to easily fit into a portable camera before.

With the packed 8-bits, having an unclear head, I hedged my bets. Being reasonably sure you can transfers 8 bits at a time unpacked, I wasn't sure there wasn't a scheme that required 8 bits to be packed into 16-bits, so I just covered all basis. I know we can get away with 8 bits, so I wasn't bothering with 10 or 12 bits.

The rest of your post I will have to get back too (I have just written these two posts). I am just trying to hit performance objectives in the ideas for cost, fps, and size. By minimising the data rate (or buffering), and making it modular with a extra drive module, one camera system can do it all. Eventually at a cheaper price than now.

[Wayne Morellini]

Thanks guys, slow motion isn't really my app, I have advised people to rent the things instead before, but some people want slow motion in the camera, so it is interesting to discuss things. I started this thread for such discussions, think tanking is a very good way to realise better alternatives. I don't believe in real think tanking at this level though, if we put in objective ideas and we have to be prepared to have them examined and challenged on an objective quantified, and even qualified, basis. At the same time the same goes for objective objections, we have to be prepared to have them examined and challenged on an objective quantified etc basis. Call it intelligent process - think tanking, to quickly reach conclusions, you examine down the line of thought and branch onto the next idea, by the end of it you have a handful of really suitable ideas.

Psychology: Normal think tanking is a established industry technique used to come up with new solutions and is useful to make logical leaps to new unrealised answers. In the original you all throw ideas in (don't matter how unsuitable, make a list then (if I can remember discuss them). It probably was made in that way because, by human nature, people are excitable, and you rarely find a group without them that can objectively discuss things, or be challenged to think outside the box to find new answers. So the process (rules) were there to keep the peace.

[Steve Nordhauser]

Tossing one more thought out on slow motion. You could capitalize on the modularity of your cameras here. If you were to say use a pair of camera modules that had the same mounting and appoximately the same sensor size and digital interface from a company we both know, you could change your Altasens based camera to a high speed camera for the cost of the fast camera module. Same interface, recording path and cables - it is "just software".

So, how many people rolled their eyes on that last "just"?

[Richard Mellor]

thank's steve : that.s realy the best part of this camera .
being able to invest in quality components , and upgrading
- when the latest technology arrives. retaing 80% of your hardware investment -and also having a state of the art
camera . and don't forget storing all this on the cheapest medium of that time . this reminds me of my custom /racing /motorcycle days . We always had a better motorcycle then anyone could buy in a store. Wish I could be of more help.

[Rob Scott]

Steve Nordhauser wrote:
So, how many people rolled their eyes on that last "just"?

Do rude hand motions count?

:-) :-) -- Just kidding!!! :-) :-)

[Wayne Morellini]

Steve N

Yeah, I agree, simple, good design, I had the same idea.