1. The aspect ratio of either an image or screen describes the proportional relationship
between its width an height
It is commonly expressed as two numbers hat are separated by a colon as in the two we
see at the top 1:1 and 4:3.
For an X:Y aspect ratio, no matter how big or small the image is if the width is divided
into x units of equal length and the height is measured in y units. It is easier to visualise
if the units are equate to whole numbers rather than decimals.

2. In still camera photography the most common aspect ratios are 4:3, 3:2 and 16:9. 16:9 is most
commonly found in consumer cameras.
With Television, DVD and Blu-ray Disc, converting formats of unequal ratios is achieved by
enlarging the original image to fill the receiving formats display area and cut of any parts of
the picture that aren't wanted or needed.
As you can see in this image, they usually get rid of the unwanted parts by just
simply cropping or zooming in.

3. Letterboxing: This is when you add horizontal mattes to retain the original formats
aspect ratio.
Pillarboxing: When you add vertical mattes to retain the original formats aspect ratio.
By stretching an image to fill the receiving formats ratio or by scaling different factors in both
directions or even possibly scaling by a different factor in the centre and at the edges.

4. Pixel aspect ratios
This describes the relationship between the width and height of a single pixel.
Different pixel aspect ratios are the reason why two video images that have identical
frame sizes can look like different sizes on screen.
If the width is bigger than the height then the pixel is non square and the aspect ratio
is greater than 1.0
Then if the width is smaller than the height then the pixel is non square and the aspect
ratio is less than 1.0.

5. This is also known as frame frequency, it is the rate at which imaging devices produces
unique consecutive images called frames.
The term applies well to film, video cameras, computer, graphics ad motion capture
systems.
Frame rate is most often expressed in frames per second and it is also expressed in
progressive scan monitors as hertz.
The human visual system can process 10 to 12 separate images per second, perceiving
them individually. Early silent films had a frame rate from 14 to 24 fps which was enough
for the sense of motion.
The persistence of vision was a commonly-accepted although somewhat controversial
theory which states at the human eye always retains images for a fraction of a second, this
means that everything that we see is a subtle blend of what is happening now and what
happened a faction of a second ago.
This is how many frames per second there are when recording or playing video. Animation
works by recording each frame individually and then playing them back at a frame rate.
Video camera in Europe use 25 frames per second.
USA ad Japan use either 29.97 or 30fps.

6. A video format defines the way that video is recorded and stored.
It normally specifies:
Codec/compressor
Frame rate
Frame size
Frame aspect ratio
Pixel aspect ratio
Scanning method
There are different layers of video transmission and storage, each with its own set of
formats to chose from. A physical link can carry certain “display standards” which specify a
particular refresh date, display resolution and colour space.

7. Most video formats are compressed during encoding so the terms codec and
compressor are usually used for the same thing.
Codec is shot for a coder-decoder and describes the method that data is encoded into a
file and decoded when the file is played back.
Transcoding is the process of converting from one codec to another codec. They can be
lossless which means that they don’t throw away any of their data. Lossless codecs are
higher quality than lossy codecs but they produce larger file sizes.
Some examples of common codecs: