Go Back   Steve's Digicams Forums > Digital Cameras (Point and Shoot) > Hybrid Still/Movie/MP3 Digicams

Reply
 
Thread Tools Search this Thread
Old Dec 27, 2007, 10:04 AM   #1
Senior Member
 
adric22's Avatar
 
Join Date: May 2007
Posts: 359
Default

I've started learning how to use microcontrollers lately and one thing I discovered is that you can interface a microcontroller to a "serial CCD" or "serial CMOS Imager." Which means all of the data is sent across 2 or 3 wires to the CPU. As I read more about these, I found out that they are basically designed for use in Cell-phones and other situations where the manufacturer needs a cheap and easy solution to get an imager on their system without spending a lot of money on R&D to build their own imager circuit. It occurred to me that Aiptek, Mustek, and all of the cheap cameras probably employ this technique because it is cheaper to design. It also occurred to me that because of the bandwidth issue between the imager and the CPU, that is probably the reason why we get the wavy video. The imager is just barely capable of transmitting 18 to 20 frames per second over a serial connection so by the time it reaches the bottom of the picture, it is time to start again at the top.

style="BACKGROUND-COLOR: #000000"A more advanced system would have the imager as part of the system memory bus like a CCD is designed to be used. THe data could be read in a very fast burst, then a pause while the shutter is open and the ccd is collecting light, then another quick burst to read the data for the next frame.

Anyway.. Just thought you might find it interesting. This is very likely the culprit for the infamous wavy video, which means there is probably nothing that can be done via a firmware update as it is a hardware issue.
adric22 is offline   Reply With Quote
Sponsored Links
Old Dec 29, 2007, 8:15 PM   #2
Senior Member
 
Join Date: Dec 2007
Posts: 1,153
Default

My Logitech QuickCam Pro does the exact same thing.

Private Idaho
Private Idaho is offline   Reply With Quote
Old Dec 29, 2007, 9:01 PM   #3
Senior Member
 
adric22's Avatar
 
Join Date: May 2007
Posts: 359
Default

Yes, there is not a webcam made today that does not have that problem. It irritates me highly because I have a quickcam made back around 2002 and it does not have that problem. But recently I bought Logitech's top of the line quickcam pro (it was like $140) and it does suffer from that problem. I found that completely unacceptable. I bought the new one since it did 1.3 MP, but I'd rather stick with the old one because the video isn't wavy.
adric22 is offline   Reply With Quote
Old Jan 6, 2008, 9:05 PM   #4
Junior Member
 
Join Date: Apr 2006
Posts: 27
Default

Actually, most if not all of the hybrids us sensors that use parallel data lines and control lines to control the sensors. The sensors are sometimes "controlled" by 2 or 3 wire serial data lines, ususally in SPI or I2C protocol. But the data is clocked out on parallel data line, usually 9 to 13 data lines. But they vary. You have to have a pretty powerful and fast micro or controlleer to be able to process this bandwidth needed for video. There are a few sensor manufacturers that make smaller scale image sensors that do output motion JPEG streams over serial lines, similar to what you mentioned. But usually these sensors are speed limited by the bandwidth across the serial interface and are intended for VGA frame capture or low FPS motion JPEG. I hope within the next few years, some sensor manufacturer will interface a CCD or CMOS sensor along with a high speed controller to handle all the video interface and video storage. That way all we would have to do is interface their front end video engine to a controlleer chip which act like the master. I attempted to get into digital video design, but pretty much gave up becasue a) the development tool cost is outrageous, and b) I would need to go back and remember all the calculas for all the video algorithms needed for the processing. I really dont want to do that!
jaggermax is offline   Reply With Quote
Old Jan 7, 2008, 12:03 AM   #5
Senior Member
 
adric22's Avatar
 
Join Date: May 2007
Posts: 359
Default

jaggermax wrote:
Quote:
3 wire serial data lines, ususally in SPI or I2C protocol. But the data is clocked out on parallel data line, usually 9 to 13 data lines. But they vary. You have to have a
I suspect the sensor probably has 8 data lines and closer to 24 address lines. But you are right, they are probably using some kind of controller connected to the imager that converts it to serial stream. I'm sure a regular Mini-DV camcorder, or even my Sanyo CG6, or any other video camera that doesn't have wavy-video pronbaly connects the imager directly to the CPU's address/data bus so that it is mapped into physical memory just like a RAM chip.
adric22 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 3:51 PM.