Overview: How streaming media worksPresentation Transcript
June 21, 2007
What the heck is today’s drill?
Definition of Streaming
A little data to get you started
A discussion of terms
Why compress media
The class website can be found here:
Review the Syllabus
What is streaming media?
• Data that is transferred in an orderly and logical
• For this class it will be defined as audio and video
media that is interpreted in real time by a player
application on a computer.
• This will also include media that is handled in
something called a “progressive download”
• Streaming is often confused with media that is
downloaded to a hard drive for later use. That is
just saving a file.
Why use streaming media?
• Cost effective way of • Tracking and
• Faster time to • Global delivery
market • Use infrastructure
• Create more options more efficiently
More or less memorable media
Some Personal Favorites:
Yes, even my kids
Who should be concerned about the
nuances of streaming?
• Web designers • Educators
• Web programmers Communications
• Videographers and journalism
• Audio engineers
• Media producers
• Business leaders
interested in new
Media compression is all about trade-offs
Variables to consider when considering a compression strategy:
• Image quality
• Sound quality
• Frame rate
• Disk space
• Platform --- how will it play on older processors
• Portability and cross-platform compatibility
• Licensing for tools
• Digital rights management
• Labor costs (time and money)
Consider the context of how it will be
used… UI, environment
(TV, computer, portable device)
What is a media player?
• CD player
• DVD player
• Movie projector
If you think about it, Thomas Edison created a media player
that transformed the peaks and valleys in the groove of a wax
cylinder into electronic signals that moved a speaker, creating
pressure waves we could hear. The principal is essentially the
same with today’s players.
Click Me! http://www.tinfoil.com/
The Melon Patch Schottische
A snappy band number from 1895, The Melon Patch Schottische,
played by the 23rd Regiment Band of New York
Where are we today?
How are on-demand media devices such as the
TiVo/DVR and the iPod, along with Video On
Demand and other digital media delivery
platforms, continuing to alter the traditional
Some implications of the
• Content producers will need to track the
“Heavy” on-demand media consumers closely.
The growth in this arena are showing that
these new broadcasting platforms are not just
• As media becomes ever more portable and
flexible, it will require new advertising
approaches. Shorter spots, testing of new
Some implications of the
• Video on demand is ever expanding and
approaching critical mass
• More information at:
What the heck is a “Codec”?
• A Codec is a device or program capable of
performing encoding and decoding on a
digital data stream or signal. The word
"codec" is a portmanteau of any of the
What really is a codec?
• It is the software and/or hardware that
squeezes video and audio down and then
expands it back out so it can be viewed on
Codecs need to be the same on both point of
origin and reception. In other words, you will
need the proper software to uncompress and
view a file. Codec families include the big five,
QuickTIme, Real, Windows Media, Flash and
MP3. There are countless other codecs, and
specific iterations within different families.
What are you after when encoding?
• Make the file as small as possible with the
least quality loss. But this is a judgment call,
and just like art, somewhat subject to
interpretation what is best.
What follows are some common terms we will
need to commit to memory:
How big do you want to be?
B byte One
KB Kilobyte Thousands
MB Megabyte Millions
GB Gigabyte Thousands of Millions
TB Terabyte Millions of millions
PB Petabyte Thousands of terabytes
How fast do you want to go?
•bps Bits per second
•Kbps Thousands of bits per second (“kila-bits”)
•Mbps Millions of bits per second (“mega-bits”)
•Gbps Thousands of millions of bits per second
How loud do you want to be?
Sound is measured in tenths of Bels, better
known as decibels.
What is your speed?
• fps • Super 8 is 16 fps
(frames per second) • Film is 24 fps
• European standard definition
video is 25 fps
• North American standard
definition video is 29.976 fps
• High definition video can be 23.9,
24, 25, 29.976, 30, 59.9 or 60 fps
What is your speed?
• ips Used for analog audio tape
(inches per second) Magnetic tape speeds are commonly an even fraction of
30 ips: The highest professional speed.
15 ips: The most common professional and studio speed
for reel to reel including multitrack.
7 1⁄2 ips: The lowest professional speed, The most
common speed for pre-recorded reel to reel tapes.
3 ¾ ips: Used on later single speed domestic machines
1 7/8 ips: The standard speed for compact cassettes
How big do you want to be?
dpi dots per screen resolution
dots per film resolution
Can’t we just all get along?
Some codecs that we will review have several names for
the same thing.
• Exhibit A: MPEG-4 part 10 This is usually referred to a
H.264, but can also be called AVC (Advance Video
• Exhibit B: Windows Media 9 or WM9 The format started
life as WM6.5, then WM7, then WM8 before landing on
WM9. Because it is becoming a standard for more than
just Microsoft products (HDVD) it is officially known as
Evolution of a codec
MPEG-1 The first compression codec in this
MPEG-2 Probably the most popular. This is
what a DVD is made of
MPEG-4 part 2 The first of the MPEG 4
standards. Supports an alpha
MPEG-4 part 10 A more recent standard, and a
significant improvement in
Why do we compress our media?
More than just keeping files small
It is about optimizing throughput on a network.
The process of compressing a file
from 40,000 feet up (the big picture)
What is Video?
Video is basically a three-dimensional array of
color pixels. Two dimensions serve as spatial
(horizontal and vertical) directions of the
moving pictures, and one dimension
represents the time domain.
A frame is a set of all pixels that (approximately)
correspond to a single point in time.
• This is the process of taking an analog signal and turning
it into an approximate digital representation of the
original image and sound.
• Examples of digitizing: scanning a photograph, capturing
video into a computer, capturing a recording
• Ripping a CD is not technically “digitizing” because it is
already data. It is usually referred to as “capturing”
Compression in simple terms is reducing the data used
to display an image, play an audio file or present
video. It is used throughout the industry.
• Cable TV
• Editing platforms
• TiVo / PVD
• Video Acquisition
Data can not be put back once it has been removed.
• Spatial encoding is performed by taking
advantage of the fact that the human eye is
unable to distinguish small differences in color
as easily as it can changes in brightness and so
very similar areas of color can be "averaged
• Common image file examples are .jpg, .tiff, .gif
Points are usually described with Cartesian
• X side to side
• Y up and down
• Z close and far away
With temporal compression only the changes
from one frame to the next are encoded as
often a large number of the pixels will be the
same on a series of frames
Low motion example 276 Kbps
Medium motion example 344 Kbps
Fast motion example 354 Kpms
When not to compress
• Acquisition and origination
You (your client or boss) have to decide what is
an acceptable level of compression based
upon the variables we will be discussing in
Other nifty terms we will be using:
• Metafile: A small file on a web server that includes
information (metadata) that informs a player where to
locate a file on a media server. A roadmap, if you will
• Encoder: a software or hardware application that
transforms a source media file into a file that can be
• FTP Client: software on a client computer or server that
uses File Transfer Protocol to upload or download files
from another computer at a remote location.
Additional websites for reference: