Overview: How streaming media works

COM 597Streaming Media

Lecture 1

June 21, 2007

What the heck is today’s drill?

My background

Definition of Streaming

A little data to get you started

A discussion of terms

Why compress media

Workshop setup

The class website can be found here:

http://courses.washington.edu/smedia/2007/index.shtml

Review the Syllabus

What is streaming media?

• Data that is transferred in an orderly and logical fashion.

• 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 communicating

• Faster time to market

• Create more options for communication

• Tracking and profiling

• Global delivery• Use infrastructure

more efficiently

Some Personal Favorites:

Paul Potts

Flagpole Sitta

Pandora

Yes, even my kids

More or less memorable media

Who should be concerned about the nuances of streaming?

• Web designers• Web programmers• Videographers• Audio engineers• Media producers• Post-production

managers

• EducatorsCommunications and journalismDistance learningComputer science

• Business leaders interested in new opportunities

Media compression is all about trade-offsVariables to consider when considering a compression strategy:• Image quality• Sound quality• Frame rate• Disk space• Bandwidth• 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?

• Television• Radio• CD player• DVD player• TiVo• VCR• 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.

The Melon Patch SchottischeA snappy band number from 1895, The Melon Patch Schottische,

played by the 23rd Regiment Band of New York

Click Me! http://www.tinfoil.com/

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 media landscape?

Some implications of the Arbitron|Edison research

• 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 a fad.

• As media becomes ever more portable and flexible, it will require new advertising approaches. Shorter spots, testing of new approaches

Some implications of the Arbitron|Edison research

• Video on demand is ever expanding and approaching critical mass

• More information at:

www.edisonresearch.com

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 following: 'Compressor-Decompressor', 'Coder-Decoder', or 'Compression/Decompression algorithm'

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 playback.

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

KB

MB

GB

TB

PB

byte

Kilobyte

Megabyte

Gigabyte

Terabyte

Petabyte

One

Thousands

Millions

Thousands of Millions

Millions of millions

Thousands of terabytes

How fast do you want to go? Bits per second

Thousands of bits per second (“kila-bits”)

Millions of bits per second (“mega-bits”)

Thousands of millions of bits per second (“giga-bits”)

•bps

•Kbps

•Mbps

•Gbps

How loud do you want to be?

dB

Sound is measured in tenths of Bels, better known as decibels.

What is your speed?

• fps(frames per second)

• Super 8 is 16 fps• 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(inches per second)

Used for analog audio tapeMagnetic tape speeds are commonly an even fraction of

30 ips:

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 machines1 7/8 ips: The standard speed for compact cassettes

How big do you want to be?

dpi

dpmm

dots per inch

dots per millimeter

screen resolution

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 Coding)

• 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 VC1.

Evolution of a codec

MPEG-1 The first compression codec in this family

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 channel

MPEG-4 part 10 A more recent standard, and a significant improvement in

compression

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.

Digitizing• 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• DVD• TiVo / PVD• Video Acquisition

Data can not be put back once it has been removed.

Spatial Compression

• 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 out"

• Common image file examples are .jpg, .tiff, .gif and .png

Spatial Compression

Points are usually described with Cartesian values (X-Y)

• X side to side• Y up and down• Z close and far away

Temporal Compression

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 KbpsMedium motion example 344 KbpsFast motion example 354 Kpms

When not to compress

• Acquisition and origination• Archiving• Mastering

You (your client or boss) have to decide what is an acceptable level of compression based upon the variables we will be discussing in class.

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 streamed efficiently.

• 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:

http://www.streamingmedia.com/magazine/http://www.digitalproducer.com/http://www.streamingmediabible.com/http://www.w3.org/AudioVideo/