Archive for February, 2010

Open High Definition Video Capture Card

February 21, 2010

Discrete Cosine Transform coefficients

The page I have created for this project over at OpenCircuits.com is here

Here is an excerpt:

Description
This project will capture High Definition Video 1280×720 at 30fps, and hopefully be capable of 60fps and maybe even 1080p. I intend to use a cheap FPGA, A HiSpeed USB PHY, and an Analog Devices Video A/D chip. I will nail down exact chip numbers later. The target platform driver and example code will be written for linux. This project is more a proof of concept and more for fun and excercise rather than to be practical. But I will take any advice and help that I can get and who knows what we might create here. Entire BOM should be less than $40 but we’ll see.

Yes I know about the Hauppage HD-PVR or whatever its called that Capures Component video at 720p. The problem is that device uses H.264 encoding, which is just way too expensive to decode, it takes a Dual Core 1GHz Machine at 99%. It is also not totally open to hacking.

Current Status

  • 04/06/2010 Adding the FPGA to the board now, external devboard is gone.  It will be a spartan3e 250 vq100 pkg.
  • 04/03/2010 Firewire Chip found that offers a High-speed parallel interface, TI TSB12LV32IPZ: http://focus.ti.com/docs/prod/folders/print/tsb12lv32.html
  • 03/25/2010 Mailing List has been added, here is the mailman link to subscribe: https://lists.sourceforge.net/lists/listinfo/openhdcapture-discussion
  • 03/24/2010 USB Chip is the USB3250. Working on schematic capture and part selection.
  • 03/19/2010 USB Chip will likely be the USB3250, the USB3318 would be slightly more difficult to put into the UTMI core from opencores.
  • 03/12/2010 Chris http://twitter.com/chrisindallas has offered to help with the USB portion of the project
  • 03/11/2010 Project now has git hosting on git://openhdcapture.git.sourceforge.net/gitroot/openhdcapture/openhdcapture
  • 03/11/2010 Added “How To Volunteer” section. Found this core that should work with the USB chip here: http://www.opencores.org/project,usb
  • 03/09/2010 Created the ad9883a part and package in Eagle. I Began researching what it takes to get the USB3318 chip to work. I am also Considering maybe using the TSB41AB1 1394/Firewire chip. USB is a PITA to work with because of the protocol overhead. If we do Firewire, it will be in addition to USB.

I am in the planning/brainstorming stages, although I have been researching this for at least the last 6-8 months.

I have a working Forward/Reverse DCT algorithm in matlab (actually Gnu Octave) that can compress an image 5:1 with little loss in quality. I have also done much research on putting a DCT in hardware. Currently the DCT will be broken down into 2 stages, and all multiplies/adds will likely be done using a very parallel bit-wide pipeline to keep clock speeds high.

Data Bandwidth Issues
YUV422 720p data comes in at roughly 1280*720*30*16 = 443 MegaBits/s. HiSpeed USB is 480Mbits/s which, after taxes, is probably not enough. Note that 720p60 is twice that. Either way using the DCT and some Huffman coding along with other simple compression techniques we can squeeze the data down a little without hurting quality too bad. My goal is to get it down to 150Mbits/s

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