Most browsers recognize several types of audio files.
The three types that are supported by almost all browsers are Musical
Instrument Digital Interface (MIDI), Windows WAVE sound file (WAV) and Moving
Pictures Experts Group (MPEG). Other fairly common audio file formats include
AU, which is the UNIX sound file format, AIFF is the audio file format that is
used by Macintosh, MOV. Is the QuickTime movie audio format, Dolby Digital is
the Dolby standard for DVD sound and SWF is native to Macromedia’s Flash and
Shockwave software. Here we will discuss the three most popular file formats.
More information on
Digital Audio.
MIDI is an audio format that that is used to enable
electronic sounds and make electronic music. Sound cards communicate using this
medium. This format generates the electronic sounding music that was used on
the web in the early years of sound. The MIDI file does not contain sound
information as most sound files. A MIDI file is a set of instructions for a
computer or electronic instrument uses to produce a sequence of electronic
sounds. Because of this it takes a relatively small amount of data for a MIDI
file to produce sound in comparison to other audio file types.
WAV is a format that was created by Microsoft and IBM
to store music files. The WAV format stores each sound in a wave pattern. This
makes for very large audio files. One minute of music stored in a WAV file will
contain about 10Mb of data. When someone refers to the “quality” of a CD the
are referring to the WAV format.
MPEG sound files have
become the most popular sound file format on the internet. This file format
supports compression types that can produce quality audio with files that are
small enough to be suitable for use on the net. For instance, when a WAV file
is converted to the MPEG-3 (audio layer 3) format it can be compressed between
10 and 17 times their normal size. This makes storing and downloading music and
sounds much less time consuming and much more convenient. Due to this
compression ability typical storage media such as hard drive and CD’s can store
much more audio data than if it were stored in WAV format. Due to this
compression sound quality is sacrificed to some extent, but due to the
frequencies that can be heard by the human ear the reduction in quality usually
goes unnoticed. (Pitts, p. 132-133).
The current MPEG technology is MP 4. Apple uses the MP-4 format as a
compression platform for its QuickTime movies. According to Apple “MPEG-4 is
the global multimedia standard, delivering professional-quality audio and video
streams over a wide range of bandwidths, from cell phone to broadband and
beyond.” In touting the advantages of MP-4 Apple states “MPEG-4 is designed to
deliver DVD-quality video at lower data rates and smaller file sizes…the new Advanced Audio Coding (AAC) codec, provides much
more efficient compression than MP3 with a quality rivaling that of uncompressed
CD audio.” (MPEG-4:
The container for digital media).
More information
on Audio Compression.
Microsoft’s WM-9 format is the latest file format
developed for the windows Media Player. This technology has the ability to
compress both audio and video files and is widely accepted and supported.
Microsoft Claims:
Powerful new audio and video compression
technology is the foundation of Windows Media 9 Series. The Windows Media Audio
and Video 9 Series codecs deliver unmatched audio and video quality at any bit
rate, with features designed to provide superior quality at dial-up rates, and
home-theater-like experiences over broadband connections or for download and
play (Windows
Media 9 Series Audio and Video Codecs).
Digital Video
Digital video and
film video have one distinct common characteristic. They both show the viewer a
series of still pictures at a rate that is fast enough to give the illusion of
movement. Film video runs at a rate of about 24 frames (aka: individual still
pictures) per second. Since the human eye can only see flutter at less than 18
frames per second (fps) this medium gives the illusion of lifelike fluid
motion. High quality digital video processes electronic pictures at a rate of 29 times a second.
Early internet video was plagued with a variety of problems. This was
due mainly to bandwidth restrictions and the shortcomings of early compression
technologies. Jerky movements, due to slow frame rates (generally about 12 to
15 fps), were an identifying attribute of early Internet video. Small frame
sizes and low image resolution were necessary to keep file sizes manageable,
but it made the videos difficult to see and often the viewer would have to lean
close to the screen to see the video. Compression issues often caused problems
with image pixilation and overall image quality.
However, with
increasing bandwidth and improvements in compression technologies, Internet
video has made colossal improvements in recent years. Like audio, the two most
popular video formats currently used online are MPEG-4 and Microsoft’s WM-9,
which are fully discussed in the Audio section.
More Information on Digital Video
More Information on Video File Formats
Streaming for Animation, Audio and Video
Streaming technologies allow audio or video files to begin playing as they download. This
shortens the waiting time for the uaer as they do not have to wait for the
entire file to download before it can be played. Most current audio/video
players support several types of streaming technology.
The most commonly used
type is Unicast streaming. This is also known as one to one streaming.
This is the technology that is used when an individual client requests a file
from a server. Typically this is the technology used when a user requests a
video or audio file over the internet. Another type of streaming is Mulitcast,
or one to many streaming. This is an efficient way to deliver information to
more than one person, as only one copy of the information is streamed over a
network. Reflected multicast streaming takes media from another source and streams it to users as
a series of unicast streams. This technology is used for online radio and
television broadcasts (Quick time streaming, your media in real time).
