ottomatik-ga:
Thank you for your Question regarding how camera phones work.
I will keep this explanation at a non-technical level for the most
part. However, many of the links that I provide below will lead you to
detailed material covering specific aspects of the overall technology,
if you wish to dive into the details.
Taking the Picture
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We can start the explanation with a brief overview of the
picture-taking part of the process. The camera in a camera phone is
very much like the electronics found in a webcam. There is a small
CMOS or CCD sensor behind a relatively cheap lens, capable of 'seeing'
whatever it is aimed at and converting it into an array of data. The
first few camera phones were equipped with <100k pixel resolution CMOS
sensors, resulting in relatively small pictures. When you consider
that most camera phones are only equipped with screens with at most
120 x 160 pixel resolution, a camera capable of taking a 320 x 240
pixel picture is acceptable for just sending pictures to another
phone. However, for sending pictures to a website, or to an e-mail
recipient who will view it on a computer screen, there is a constant
desire on the part of the manufacturers to push the resolution
envelope. That is why there are now 2-megapixel camera phones hitting
the market, capable of taking 1600x1200 pixel pictures.
Once the picture has been taken, it is stored in the camera phone's
nonvolatile flash memory, where it can be viewed (in a much smaller
resolution that the actual file) on the camera phone's screen. At this
point of the process, there is no difference between how the camera
phone works, and how a digital camera works. Like most digital
cameras, the majority of camera phones use JPEG image compression to
reduce the file size of the picture and save on memory. This also
helps to reduce the 'cost' of transmitting the picture, since there is
less data to send.
For more on how a digital camera such as this works, please check out:
"How Digital Cameras Work" - HowStuffWorks.com
http://electronics.howstuffworks.com/digital-camera.htm
Preparing the Picture for Transmission
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Once the picture has been taken, the next step is to prepare it for
transmission. This is where software comes into play. Every camera
phone on the market today comes preloaded with a messaging
application. This application allows the user to compose a message,
address it to either another phone or an e-mail address, and attach a
picture from the phone's memory. The protocol, or standard, that this
message follows is the evolving Multimedia Messaging Service (MMS)
standard. Essentially, this is the natural successor to the original
Short Messaging Service (SMS) protocol which became popular a few
years ago for sending text messages back and forth between cell phones
as well as some instant messaging (IM) PC users.
The problem with the current state of the MMS standard is similar to
the problems that faced the first SMS users. Part of the MMS
definition uses extensible markup language (XML) to allow multimedia
messages to be customized for display on the many different devices
that are available on the market. Since there is no way for the
sending phone to know what the receiving device is, or what it is
capable of, this means that messages are formatted according to a
format that the network operator understands, and the message is sent
to the network operator's MMS server.
More information about the MMS protocol can be found on G. Le Bodic's
very comprehensive website:
http://www.lebodic.net
In particular, check out his paper from 2002, "Mobile Messaging":
http://www.lebodic.net/gwenael/publications/vtsnews.pdf
For Nokia's perspective on this, check out:
MMS:
http://www.nokia.com/nokia/0,8764,32905,00.html
Nokia's "MMS entering into the next phase" white paper (PDF file, 1.31 MB)
http://www.nokia.com/BaseProject/Sites/NOKIA_MAIN_18022/CDA/Categories/Solutions/MobileSoftware/Downloads/_Content/_Static_Files/mms_wp_a4_2706.pdf
Handling the Message
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Once the message has been received by the MMS server in the network
operator's network, it is reformatted according to the needs of the
receiving device. For example, if the MMS is being sent to an e-mail
address, the MMS message is converted into a format that conforms to
e-mail protocols. If the message is going to a phone user who does not
have a MMS-capable phone, then the message is redirected to a web
server, and the recipient receives a SMS with a URL for the website
where they can pick up their message (using a computer).
Where this becomes complicated is when the receiving device is not on
the network operator's network. For example, if you have a phone on
the Orange network in Europe, and you are trying to send a picture to
a Vodafone customer, there is no direct way for the Orange MMS server
to know what the Vodafone customer's phone needs. That's where the MMS
gateway service providers come in. Companies such as NowMMS.com
provide gateway services that allow MMS messages to travel across
networks. The MMS gateway queries the recipient's network for
information about the receiving device, then forwards the message in
the proper format. This provides the seamless experience that
customers expect.
More information about MMS gateways can be found at:
http://www.nowsms.com/
Receiving the Message
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Once the message has been properly formatted, it is sent through to
the recipient. If the recipient is a MMS-capable phone, the software
application on the phone opens up the message, and displays the
attached picture. Note that the recipient does not need to be a camera
phone, it only needs to be capable of receiving a MMS message and
displaying the picture attachment.
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I hope that this explanation provides you with the information you
were looking for. Please let me know if you would like any part of it
clarified.
Regards,
aht-ga
Google Answers Researcher |
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