- The famous phrase " a picture paints a thousand words"
has particular relevance when thinking about the way video
and sound information is stored.
This kind of media isn't a single image displayed
with a particular file size.
The total amount of data used
to store it is spread over time.
The more data used to store picture information,
the better the quality of the image
up to a maximum amount of data, where there just
isn't anymore image to store.
Think of the amount of data used as sheets of paper.
Imagine being asked to write a detailed description
of a landscaped image but you only have one sheet
of paper to use with a fixed layout.
Every extra page you have to write your description
allows you to add more detail.
However, each page takes more time and effort to write
and the paper takes more space to store.
If you are given an unlimited supply of paper,
time and energy, you'd still reach a point eventually
where you simply had nothing left to write.
Everything you could possibly think about writing
has been written and you feel pretty sure every imaginable
way to capture the nuance
of the scene before you has been captured.
It would take a long time and lots of work
and lots of storage space.
Now let's imagine each single page of information
is used to describe one frame of video.
If you're working at 30 frames per second,
that's 30 pages of text per second.
If you use two pages of text to record a single frame,
it'll be 60 pages of text per second.
Each time you decide to use more pages of text,
for each frame of footage, you're increasing the quality,
and the effort to read it
and the amount of space taken to store it.
Data rates for video and audio are a lot like this;
it's not just how much data is used to store the image
or sound in a particular moment,
it's how much data is used over time,
and it's usually measured as per second.
Data is measured in bits, bytes, kilobytes,
megabytes, gigabytes and so on in ascending order.
Now you know if you see footage described as 200 Kbps,
you're looking at a file that's 200,000 bits per second.
If it's 20 Megabits per second,
it would be described as 20mbps,
and sometimes this is abbreviated if it's shown
in a clear context where everyone knows
we're talking about the data rate per second.
So you'll see 20mb instead of 20mbps.
Standards are set for data rates just as they're set
for frames per second, pixel aspect ratios,
color modes and so on.
When you're preparing video for delivery,
it'll be one of the details you'll look for.