From: Chris <chris88u@we...> - 2007-04-11 21:37:54
Tom Kunz wrote:
> medium. From what I see on previous posts to this list, the maximum
> speed of a CF or SD card on the gumstix is limited to about 600KB/sec to
> 1MB/sec. I'm not sure if this is fast enough to store off high quality
> video. If that is fast enough, the next question is, can the CPU
With mpeg4 you can certainly store high quality video at that rate. Using
the below setup I have captured very nice full-motion D1 video at 300kB/s.
Normally I don't capture to disk (the system is a wireless digital video
streaming solution), but I'm quite familiar with the numbers I used to need
to use in bits/second to get decent video. At 320x240 @ 25fps, for example,
I could get by with 500 kilobits/second and get reasonable video. For D1 as
above, I'd want to be sending roughly 1.5 megabit/second for reasonable output.
> process the frames fast enough to make it worthwhile. Someone mentioned
> the use of the PXA "companion chip" 2700G for multimedia acceleration,
> that would probably do the trick, but gumstix hasn't manufactured one of
> those yet to my knowledge. It's a fascinating concept, however, I would
> love to see things like videophones and other video appliances based on
> the gumstix boards! What kinds of ideas do you have?
I spent most of 2006 working on a project involving a PXA270 (specifically
we used Karo boards - http://www.karo-electronics.de/triton-270.html?&L=1),
plus our own custom base-board which had a bunch of other stuff on it, and
our own daughter board which implemented hardware MPEG 1/2/4, MJPEG, and
H.263 compression in real time at broadcast quality resolution (PAL 720x576
@ 25fps), plus has some other neat stuff like hardware-assisted motion
The chip we used was a WIS GO7007SB. You can see a shot of both the base
board and the video board here:
As we retain rights to do other stuff with the design, I am keen to explore
further uses for this component, and given that I have already worked with
the 270 it seems natural to use a verdex (in fact if it had been available
back in 2005 when we planned the project I probably would have ended up
using it rather than the karo).
That said, there is nothing really PXA270-specific about the daughter card
and it would almost certainly work quite nicely with the 255. The 7007SB's
IO is fairly flexible.
One issue however is size; as you can see it's rather larger than the
gumstix range, however that is a rev #1 board which has almost all
components on the one side. If we wanted to shrink it down to a more
compatible size I believe it could be done.
FWIW the video board pulls about 250ma at 3.3v when encoding and accepts
composite and s-video inputs (PAL/NTSC/SECAM) plus microphone and stereo
Changing the subject to the gumstix range, though: one thing that puzzles
me is the apparent lack of other third-party add-on boards. Either that, or
I'm not looking in the right places. Have others tried and failed to make
3rd-party add-ons? Is there no demand for them? Is there some other issue I
ought to be aware of?