New DIY HD Cinema Camera Project

[Seth Kersey]

Isn't that 56 MB/s or am I calculating wrong?

Some 2.5" SATA drives can reach 56 MB/s, but only as burst not sustained write speeds.

I believe the best average write speed is about 44 MB/s, will that work with lossless compression so no RAID is needed?


That Pleora board only works with parallel data, maybe they have something else that uses serial... because the Micron is serial, I think?

EDIT: I tried browsing the Micron Datasheet, but I am still unsure if that Pleora will or will not interface.

Does anyone know how the Micron head board interfaces with the dev board?

[Jose A. Garcia]

Ok, I tested it and I can't write 2K frames at 24fps to a 7200 rpm sata disk. It only gets to 18-19fps.

I can get to 24fps with a 10000 rpm HDD.

So we need to find another solution. Recording to RAM allows about 40 seconds per gigabyte in RAW. We can only add 2Gb of RAM to the board, so we'd be limited to about 1:20 min for every take. RAM's not cheap though.

Well... First BIG problem. This is basically where all previous camera projects have failed and where successful cameras have gone from low cost to really expensive.

So... What can we do now? Anything faster than a standard HDD that we can plug to the mainboard?

[Seth Kersey]

Well, RAID 0 should allow us to capture and it would be relatively cheap compared to SSD solutions... it just means giving up Firewire with the LS-371.

Here are a couple of other boards that offer additional expansion possibilites, but I do not know any prices.

http://www.aaeon.com/PD_Products_Det..._US_utf-8.html
http://www.axiomtek.com/products/Vie...t.asp?view=490

Also, here are some PC/104 expandable boards that allow up to 4 Gigs of RAM.

http://www.digitallogic.com/english/....asp?id=MSM945

I tried finding a RAID controller that we could build into a "pack" of 2 HDDs, and then connect via either eSATA or external PCIe... but no luck yet. There are a couple of Firewire RAID solutions though.

http://www.g-technology.com/Products/G-RAID-mini.cfm
http://www.lacie.com/products/product.htm?pid=10724

This would allow the use of the Firewire mini-PCI card with the LS-371, since it has multiple ports.

http://www.globalamericaninc.com/new...ec2.php?id=691

[Take Vos]

Originally Posted by Seth Kersey

Isn't that 56 MB/s or am I calculating wrong?

Some 2.5" SATA drives can reach 56 MB/s, but only as burst not sustained write speeds.

I believe the best average write speed is about 44 MB/s, will that work with lossless compression so no RAID is needed?

I was talking about a 3.5" SATA disk, Western Digital SE16 disks have a sustained transfer rate of 60 MB/s. With a large enough ring buffer between the camera and the disk, this is enough.

[Steven Mingam]

Originally Posted by Jose A. Garcia

Well... First BIG problem.

Huh ? If you are planning to use a decent OS, you can easily compress the video stream with any lossless codec out there and divide the datarate by at least two...

[Igor Babic]

Maybe this can help us
http://www.globalamericaninc.com/new...ec2.php?id=748

and this also: MiniPCI to 2xminiPCI
http://www.costronic.com/
search for Mini PCI series SK2

Now we can have RAID SATA and FW cards. But they are probably dont have enough bandwith when operating at the same time. There is also question of compatibility to LS-371.

[Jose A. Garcia]

Ok, this is getting a bit too crazy... First of all, I received the pdf I'm attaching to this post from the Omnivision distributor here in Spain. They seem to be representatives of many different companies. What do you think? It looks like a LS-371 with another name.

On the other hand, there're many different options. We need to focus on one so we can put all our efforts on it.

First and foremost, the camera board. I'm reading lots of posts talking about firewire, GigE... And everytime I read them it looks like the camera gets a few more miles away from us. This is complex hardware engineering (I mean, it's not like installing a HDD in a computer) so if someone can do it and also wants to do it, then great, cause we'll have a proper interface. You can get just the camera head from Micron for about $300. If not, then we stay with USB.

Second, recording hardware. There're two ways:

- We encode the stream so data rate is way lower. I think we should try this if it's really possible.

- We find a cheap way to record the full stream.

Now, we're sure we want to go for a mini computer solution. Also we're quite sure 3.5" boards are the way to go. Now, what else do we need?

RAID? Single SATA drive? I tested it yesterday and I can't record full 2k at 24fps to a standard 7200rpm SATA disk. If we want to have just one HDD, it has to be SATA 10000rpm.

We have different solutions. Which one's the most balanced in terms of cost/performance?

[Take Vos]

I have tested (with Boom Recorder) recording 1800 x 750 x 14bit @ 24fps, on a single SATA 7200 rpm WesterDigital SE16 (250 GB) for 20 minutes as a single take without problems (the ring buffer was 250 MB). This is of course in uncompressed bayer format.

[Jose A. Garcia]

I can record 1920x800@24fps to disk in RAW Bayer, but the problem is getting to full 2k.

[Igor Babic]

Here is what I think.
1. Simplest solution is recording to removable 2.5" SATA HDD like we want. It is not safest way, but good simple and cheap for start. We have a motherboard with probably great potential for everything, even encoding/compresing. But as I can see, here is very few people that are eable to do it ( I can't code at first place.) We need someone that is willing to do software for this, even find someone to pay to do it. This is the biggest milestone as you said in your previous post. ( not enough bandwith for uncompressed bayer )

2. Not so practical, but somewhat cheaper solution is miniPCI SATA RAID 0 add on card. Put two sata 2.5 disks and keep your project going on until something better came up. You are not waisting money because you will need two disks anyway. Download recorded clips thru Glan to your Laptop or PC.

3. Another not so practical is that you can maybe record directly thru Glan on some simple nas or laptop and not have any disk inside your camera. This is the safest way but it has to be field proven. I can go with my server to server Glan board with Intel Pro Glan over 60MB/sec very easy. Other machines goes from 30-45MB/s. SI2K says that they can go thru max 100MB/sec with special software.

Big guys are already done all those solutions. You have your hardware so you have to do testing and decide what is best solution. On the table some stuff will work but you have to fill your disk to the top couple of times to see if all is ok. Dont forget audio, because this will also take you some bandwith.
Firewire is just simple way to put aditional storage but I will toss it out and go for Raid0. 2x2.5" SATA in Raid 0 will give you max what mini PCI can handle anyway. If you have mini PCI on your laptop this is cheapest way to try it.

[Igor Babic]

It has special expansion slot that for now has no aditional boards as I can see on their site. But they are talking about PCIe addon card. Seth has already give as a link for it. NO miniPCI and it has ATX for power. LS-371 has simple 8-12V jack.

[Jose A. Garcia]

I think realtime encoding is the best way to do it. If we cut data rate to let's say a half, then we'll have no problem recording it and also we won't need an ultra fast mini computer.

[Igor Babic]

You mean ultra fast storage. You have to have fast computer to do relatime ncoding....

[Take Vos]

Originally Posted by Jose A. Garcia

I can record 1920x800@24fps to disk in RAW Bayer, but the problem is getting to full 2k.

Ah, ok, then you can use two disks in a software raid-0 configuration. No need to spend cash on an raid card (the cheap ones are done in software (in the driver) anyway).

Or look for a 10000 or 15000 rpm SATA disk, which may be able to handle it. The SATA bus is fast enough (3 Gbit/sec).

You may also check the new modern serial attached scsi "SAS" disks. They are used in servers and are a more expensive. But they are incredibly fast because they are 10000 rpm (some 15000 rpm), in a small 2.5" form factor (which increases the bit density and thus speed), and hot swappable. But I think you will need a special extender card or SAS bus on the motherboard.

[Igor Babic]

http://www.digit-life.com/articles2/sas-and-sata/

I dont quite understand this but as I can see from the bottom of this article, you just hook up SAS disk to your existing SATA controller and your inn.
Has anybody try that?