Setup for capture, storage and backup of a 250 minute, multi camera, uncompressed video dataset

Javier R. Movellan

October 22, 2002

The goal of this document is to specify the issues related to real time capture of uncompressed video using mutliple synchronized camera and the solution we are adopting. 

Specifications:

1. We want to use at least 3 cameras to avoid hidden surfaces and facilitate reconstruction of 3D structure using current algorithms.
2. We need the cameras to be exactly synchronized so that 3D face structure can be extracted using current algorithms.
3. We want to digitize uncompressed video to avoid compression artifacts. 

Constraints:

Each camera will be capturing at at 30 frames per second 640 * 480 pixel frames, 8 bits per pixel. Thus each camera will need a bandwidth of

(640*480) pixels/frame * 1 Byte/ frame * 30 frames/second  / ( 1024 * 1024) = 8.79 Mbytes/second

4 Camera solution

• DragonFly camera: 8 bit color, 640 * 480 * 30 frames per second progressive scan. Units available at pointgray.com. Approx price: $1200 per camera.

• The capture bus and the storage device need to have a bandwidth of 8.79 MByte per sec per camera* 4 cameras = 35.16 MB/sec

• The fire wire port can handle up to 50 MB/sec so it should have no problems.
• For primary storage device we can use the Medea Video Rack LP. It can sustain 65/MB/sec. For a 250 minute dataset we would need

           250 min * 60 sec/min * 26.36 MBytes/sec /1024= 515.04 GigaBytes. We can buy a 480  Gig unit for $3399. Units available at videoguys.com

• For backup we will use: 4 x 100Gig Western Digital IDE drives = 4 * 155 = $620. Units available at Western Digital.

Cost:

• 4 cameras: 4* 1200 = $4800
• 480 Gig RAID:    $ 3399
• 4x 100 IDE:   $620

Total: $8819

4 Camera solution

• DragonFly camera: 8 bit color, 640 * 480 * 30 frames per second progressive scan. Units available at pointgray.com. Approx price: $1200 per camera.

• The capture bus and the storage device need to have a bandwidth of 8.79 MByte per sec per camera* 4 cameras = 35.16 MB/sec

• The fire wire port can handle up to 50 MB/sec so it should have no problems.
• For primary storage device we can use the Medea Video Rack LP. It can sustain 65/MB/sec. For a 250 minute dataset we would need

           250 min * 60 sec/min * 35.16 MBytes/sec /1024= 515.03 GigaBytes. We can buy a 480  Gig unit for $3399 and a 160Gig unit for $1899. Units available at videoguys.com.

• For backup we will use: 6 x 100Gig Western Digital IDE drives = 6 * 155 = $930. Units available at Western Digital.

Cost:

• 3 cameras: 4* 1200 = $4800
• 640 Gig RAID:    $ 5298
• 6 x 100 IDE:   $930

Total: $11028

The Storage devide should be able to handle a minimum bandwidht of 90MB/sec sustained.
The storage and backup solution should be able to hold 250 min * 60 sec * 30 frame/sec * (640 * 480)pixels/frame * 3 bytes/pixel / (1024 * 1024) = 1158.71 GBytes 

Other alternatives. 

The main difficulty is finding digital cameras that can be synchronized (genlocked). The Dragon-fly cameras seem to be the only alternative at a price below $5,000  per camera. Professional DV cameras can be genlocked but they cost above $5000 per camera. The Sony DFWV50 has an external triger port but it can only be used to take one picture at a time (asynchronous trigger). The Basler A301bc uses the new 200MB/sec Camera-Link (also known as  Channe Llink) port. These cost about $1700 a piece. Unfortunately they can only be synchronized via an asynchonous trigger, ie., they can be synch for single shot but not for continuous video. The color model seems to be configurable to 8 or 10 bit per pixel.  10 bits per pixel may provide a significant improvement over the 8 bit model. Information on the Basler A300 series is available at Basler's web site.

Appendix: Useful facts

Byte = 8 bits
KB = KyloByte = 1024 bytes.
MB= MegaByte = 1024 KB
GB = GigaByte = 1024 MB
TB = TeraByte = 1024 GB

24bit RGB color format uses: 3 bytes per pixel (1 byte per color field)
.

When digitized NTSC resolution is approximately 640 x480  at 30 frames per second

Bandwidth of curretn Firewire IEEE1394 bus: 400Mbit/sec = 50MByte/sec
Bandwidth of USB bus: 12 Mbit/sec = 1.5 MByte/sec
Bandwidth of 32 bit PCI bus on 66 Mhz bus -> 266MByte/sec