How to Add
Video to your VoIP
already using your
internet data line for VoIP voice communications, why not
add video to your calls as well?
6 of a
7 part series - click for Parts
Faster internet connections
give you enough bandwidth to allow you to add video to your voice calls.
to enjoy video with your voice conversations. Quality varies remarkably among different
video services and
settings, so read on and use this
information to get the best video experience possible.
the Dream of the Picture Phone
phones, offering combined voice and video transmission - have
been talked about, and occasionally offered, for decades, with
the first appearance probably dating back to the New York
World's Fair in 1964. But the technology has been too
expensive, systems usually incompatible with each other, and the
quality too poor to encourage broad acceptance. Without a
ruling standard and a growth towards general use, none of the
various products have ever achieved any significant sales or
underlying premise of the picture phone - sending video over a
regular phone line - at first appeared impossible. But the
development of DSL, allowing high speed data over regular phone
lines, and the complementary development of cable data services,
now makes it possible for reasonably good quality video to be
sent and received; in our homes, and our offices. At the
same time, 3G wireless services are making video increasingly a
standard part of their mobile phone service, growing the
awareness and interest in video phone service.
The Four Compromises
with Internet Video
massively bandwidth hungry. Full uncompressed video would
require about 221 Mbps of bandwidth (4,000 times more bandwidth
than is available on a 56kbps dialup line!). Probably none
of us have sufficient bandwidth for full broadcast quality
video, so it becomes necessary to compromise between the
quality/video experience you'd like and the bandwidth available
need to juggle three aspects of
the video you send to balance against the
fourth compromise - the bandwidth available to you. If you want the best in one of these categories, you'll have to trade-off by accepting poorer
settings in other categories.
Note that not all these
variables can be adjusted. And, depending on the camera
and video software you are using, some adjustments may be done
using the camera software, and other adjustments might be made
through the video software.
The bigger the picture size,
the more bandwidth your video will take. Normal television
pictures have a resolution of 720x486 pixels (and to make things
more complicated, the pixels aren't exactly square). A
comparable computer resolution would be 640x480 square pixels.
Chances are your computer
screen has a resolution of 800x600 or larger, meaning that even
'full resolution' television shouldn't take up the entire
Webcams typically are
theoretically capable of this resolution, and of several smaller
resolutions, too, of which the most common is 'quarter frame' -
160 x 120 pixels (also called QVGA). Note that quarter frame is actually only
one sixteenth the total number of pixels. In other words,
a smaller size can make a big saving in the amount of bandwidth
you need. A similar size is 176x144.
Most people seem content to
use picture sizes between quarter frame and half frame for their
webcams. For general person to person talking, this gives
plenty of picture of the other person's head and shoulders.
biggest saving in bandwidth is made by compressing the picture
information that is transmitted. The higher the picture
quality (the sharper and clearer it is) the more bandwidth your
video will take. Blocky and blurry video has been more
highly compressed than fine clear video.
The difference in bandwidth
between 'okay' quality and visibly poor quality is about a
factor of two. Good quality video requires about twice as
much bandwidth as poor quality. And very poor quality
video will use even less - perhaps one third the amount of good
On the other extreme, to go
from 'good' to 'great' quality video will require an increase of
about four times in bandwidth.
So tune your picture quality
to the lowest acceptable, but you don't need to go lower than
that, because the bandwidth saving starts to be dwarfed by the
loss of quality.
Normal television and movie
pictures have 24 or 30 images every second. This
is sufficient for us to perceive smooth motion. The fewer
the number of images (called frames) per second, the more jerky
the motion becomes.
Once your refresh rate goes
below 10 frames per second, the jerkiness becomes
and below about 3 fps you start to see a series of slowly changing
images rather than experience any sensation of motion.
How much bandwidth
is needed to support acceptable video? The answer is 'it depends'. Obviously
it depends on the settings for the three variables above.
The Yahoo video program has
a helpful feature which shows you how much bandwidth
the video feed
you are sending or receiving is using. These measurements
are in kb/sec - kilobits/sec. Most datalines are rated in
kilobits or megabits per second, making it easy for you to match
the bandwidth being used with the total bandwidth you have.
Yahoo reports that its video
takes anywhere from less than 10kb/sec up to as much as 240
mind you can't use all the rated
bandwidth on your data line for video. You're almost
certainly using some bandwidth for your voice communication,
plus you'll have other things communicating with the internet as
well (for example, your mail program might be regularly checking
for email and downloading new messages).
Plus, if you and the person
you are communicating with are both sending video to the other
person, then you'll be using twice as much bandwidth - half to
send and half to receive. Some datalines have separate
bandwidth for sending and receiving channels, other types of
dataline have total bandwidth for both sending and receiving,
and some datalines have much more download bandwidth (ie for
receiving video) than they do for uploading (ie sending
In calculating your video
bandwidth requirements, don't forget also that the limiting
factor will be who has the slower internet connection - you or
the person you're sharing video with. Or, perhaps you both
have extremely fast internet connections, but maybe there is a
bottleneck somewhere else on the internet between the two of
you. This can particularly be the case if you are in two
different countries; there might be plenty of internet bandwidth
within each country, but sometimes there can be bottlenecks on
the international circuits between the countries.
One more comment about
bandwidth - if you're not sure what your dataline is actually
capable of giving you in the form of real world bandwidth, then
you should use
site to test your speed. The results might surprise
Best Strategy for
If bandwidth isn't an issue,
go for as high a quality, large picture and high refresh rate as
you and the other person/people can support.
But if bandwidth is a
problem - either at your end, or at the other person's end, then
cut back first on picture size down to a minimum acceptable size
for your purpose, then slow down refresh rate to
frames per second, then trim quality back to where you start to
see visible degradation in picture quality.
If that still uses too much
bandwidth, slow down the refresh rate some more, and then
perhaps drop the picture quality a bit more.
If that still doesn't work,
then - alas - there simply
isn't enough bandwidth for video.
The importance of the camera
There are many different
webcams available for sale, ranging in price from
as low as $20 and up to $100 or more. There's commonly
available in computer stores, and (as with many other things)
Amazon has an extensive range and at good prices.
cases, even the $20 webcam is going to have greater capabilities
than most of the free video communication programs can handle.
cameras use a USB connection. USB cables should be no
longer than about 15' for best performance, but hopefully this
doesn't restrict your ability to conveniently position the
And, talking about
positioning, a flexible tilt/swivel mounting base is a great
help when trying to work out where to put the camera and how to
mount it in its place.
True or Interpolated
to be careful of, when reading camera specs, is whether the
resolution being quoted is the true resolution or an
interpolated resolution. An interpolated resolution is a
meaningless measure - it is what happens when the camera's base
resolution is artificially boosted by simply inserting extra
pixels that have artificial data sort of midway between the real
pixels. It gives you no more resolution or clarity, it
just makes for a bigger picture and more bandwidth, but with no
more picture quality. Be sure to always compare true
resolution data, not interpolated resolution data.
Field of View/Focal Length
quoted measure is the camera's focal length or field of view
(the two being related - the shorter the focal length, the more
'wide angle' it becomes and the greater the field of view).
camera will be close to you, then a wide field of view is a good
thing to have, so you will be able to get your entire head and
shoulders into the image. If the camera will be further
away, then a narrower field of view (and longer focal length)
would be better.
problem with cameras that have very wide fields of view is that
you get a distorted image - a 'pin cushion' or 'fish eye'
effect, such that the middle of the sides push out, and square
shapes become more like circles.
Normal fields of view seem
to range from about 42 degrees up to about 55 degrees.
Wide angle cameras can go up to almost 80 degrees.
Refresh Rates/Frame per Second
look at camera refresh rates if you will be using your camera
within a LAN environment (where bandwidth isn't a problem).
Some cameras can't give a full 30 fps when sending large (ie
640x480 size) images. But if your usage will be mainly
over the internet, you're unlikely to ever have enough bandwidth
to allow for 30 fps at 640x480 resolution.
Manual or Fixed Focus
webcams have a short focal length and small aperture, it is
often acceptable for them to be fixed focus.
quality webcams will have a manual focus ring on them. If you get a
webcam with manual focus, be sure to remember to adjust this
from time to time if you change the distance between the webcam
and whatever it is viewing (eg yourself).
regular film camera, most of the adjustments in a webcam (or any
other digital camera) are electronic rather than physical.
means the flexibility of the camera is usually determined by the
driver software that comes with it, and so obviously this can be
almost as important as the
If you can adjust the 'white balance' of
the camera, and if you can adjust the brightness and contrast, then
you'll have more control over your image quality than if these
are all done automatically (or not at all).
positioning and lighting
The camera is best
positioned if it is looking straight at you, and you looking
straight at it.
This means the camera should
be very close to the side of your screen. It is best to
not have the camera looking up at an angle at you, or down from
an angle, because this creates an image different from what
people would see when looking at you normally.
I also put the windows for
conferencing on the same side of my monitor as the camera is, so
when I'm looking at the windows on the computer, it appears as
though I'm looking more closely at the camera than if the
windows were on the far side of the computer screen. This
also reduces the 'shifty eye' effect which can sometimes be
quite noticeable, being caused when you swap focus between the
camera and the screen.
Cameras generally work
better in moderately bright even lighting conditions.
Ideally, you should have soft white light falling on your face, and you want to
avoid extremes of light and shade in the picture (including
whatever is in the background).
a diffuse light is better than a single spot light - it reduces
the harshness of shadows in the picture.
to have any lights that shine directly into the camera.
This can upset the camera's auto exposure.
Adding a video feed to your
conversations is now easy and inexpensive. A webcam costs
about $30 or less, and the video sharing software is usually
free and sometimes already pre-installed on your computer.
If you have a broadband
internet connection, why not get even more use out of it by
having video as well as voice conversations via the internet.
Read more about video over your
The next part of this
series tells you all you need to know about
choosing the best (and free!)
software to use with your webcam.
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9 Sep 2005, last update
19 Dec 2013
You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.