What
are different multi-media files and which ones should you use?
What are different multi-media files and which ones should you
use?
The HTML 4.1 standard from the W3C supports inserted components
such as Audio and Video through the Object tag. This is a new catchall
tag that provides the ability to do many things that the Browser
developers wish to add. Unfortunately the specification almost reads
that way. "The Object tag is intended to add many things that
Browser developers would like to add!", whatever they may be.
OK I'm being a little cynical. But why don't Audio and Video Tags
exist? It is not as if these are really esoteric concepts. HTML
is esoteric but audio/video has been around a long time now. I recall
being taught how to thread a 16mm film through a projector. Does
anyone still use those 16mm films?
The closest A/V Tag is BGSOUND in Internet Explorer. This adds
background (B-back G-ground Sound) audio to a HTML document. Even
though it is far better than Netscape's use of the Embed (In Bed?)
tag, it is hardly a sound engineers concept of advanced audio. Video
does not exist at all within HTML whether sanctioned by the W3C
or not. Even so, as you have probably gathered it is possible to
add Audio and Video to your web site, either through the Object
Tag, Embed Tag, BGSOUND tag or through a Streaming Server.
As you will quickly discover however, there is no such format as
Audio or Video. What we have instead is a plethora of file formats
including Wave, Midi, AVI, MPEG, AU, RA, MOV etc. What is the difference
and which ones should you use?
Here is a list of some of the more common formats. I have not attempted
to list them all because they are changing quickly and would require
more space than I have available.
Audio Formats:
MIDI (.mid,.midi) Music Instrument Digital Interface
Midi is a pure digital format. It essentially stores digital information
to represent notes from Musical Instruments. You could if you wanted
to, create a MIDI music file using a text editor. Midi files however
are usually created with specialized authoring programs and a digital
keyboard. Since it is a pure digital format you cannot use a MIDI
file to record real world sounds such as a person talking or a dog
barking. The output quality of a MIDI file is also very dependent
on the quality of the audio card that is playing it back. Old cheap
audio cards would reproduce a midi file so badly that even finger
nails on a blackboard or a crying baby would sound more pleasant.
Fortunately today's audio cards are significantly better. Due to
their extremely small file sizes, MIDI files are the best choice
for playing back digitally authored music on a web page.
WAVE (.wav) Wave Form Audio File Format Wave files
are used to sample real analogue audio into a digital file format.
The frequency of the sample will determine the quality of the recording
and the size of the resulting file. At 44,000 Hz and 16-bits a WAVE
file will be close to CD quality but will generate a huge file.
Since their source is real, they can store a good representation
of the original sound. You could for example, distinguish Ringo
Starr's northern English accent in a recording of his voice or the
nuance of a good violin.
MP3 (.mp3) "Moving Pictures Expert Group"
Layer 3 This is not a new format but it has significantly gained
in popularity lately. Unlike WAVE, MP3 uses a "lossy"
algorithm in order to compress the audio into smaller files. This
type of compression essentially throws information away so that
a side-by-side comparison between a high quality WAVE file and a
highly compressed MP3 file will be quite noticeable. Even so, the
loss of quality is not very pronounced while the gain in compression
is significant. A 1.0 Meg WAVE file for example, can be compressed
into as little as 50K using MP3.
RA G2 (.ra,.rm) Real Audio Real Audio is one of
the oldest formats for distributing audio over the Internet. Their
initial objective was to provide voice transmission over low bandwidth
telephone lines. With G2 they are now moving toward distribution
of music. Real Audio can also be streamed so that the visitor can
start listening before the entire file has downloaded. Unlike MP3,
Real Audio is a proprietary format but the Player is free and already
installed on many computer systems.
Audio/Video Formats:
Video compression has been undergoing significant development in
recent years. The formats that are now available are a lot smaller
than in the past while still maintaining reasonably good quality.
Even so, there is really no such thing as a small video file. They
all require a significant amount of bandwidth. When a typical movie
on DVD requires over a Gigabyte of space you will quickly realize
that even short videos are going to demand a significant amount
of time to download even with a fast connection.
There is a lot of talk about providing TV, Movies and Video feeds
over the Internet. The fact is the technology is just not ready
for it yet. In order to get real time video over a fast connection,
the quality has to be so low that it is the equivalent of a penny
whistle compared to a major symphony orchestra. It may be able to
carry the tune from Beethoven's 9th but wait until you hear what
passes for the Choral Orchestra.
For those of you that have a valid reason to add video to your
web pages, these are the primary choices you have.
AVI (.avi) Audio Video Interleave -Microsoft AVI was developed
by Microsoft to add Multi-Media capabilities to Windows. It is the
most common Multi-Media format if for no other reason than it is
included on every PC running any version of Windows. It is capable
of combining both Audio and Video into a relatively high quality
file.
QUICKTIME (.gt,.mov) ISO standard -Apple. QuickTime is a mature
format that combines both audio and video into a file that is significantly
smaller than AVI at a slight expense in quality. Apple was able
to make the format popular by offering a free player on PC's.
MPEG (.mpg,.mpeg) "Moving Pictures Expert Group" This
is one of the oldest and most popular Audio/Video formats. MPEG
is available on most platforms and probably offers the best compromise
between file size and quality.
There are many other formats either in use, outdated but still
available or in active development. I have not attempted to list
them all since the topic is too extensive for a single article.
Some of the links below will provide additional information for
those of you that are interested in doing more research. You can
also try your favorite Search Engine or Index. I have also not included
links to sites that provide players for these formats. The formats
and players change often and are widely available.
Here are just a very few links to sites with additional information
on these formats. There are many more.
http://www.lib.rochester.edu/multimed/music.htm
http://www.math.auth.gr/~axonis/studies/audio.htm
http://www.communicator.com/mp3itva.html
http://homerecording.com
http://www.lib.rochester.edu/multimed/movies.htm
http://www.wotsit.org/
This is a wrap on my introduction to Internet Multimedia. I hope
it has helped some of you to get an idea of what it is all about.
As you will have no doubt discovered, it is only the tip of the
iceberg on this quite extensive and complex topic. I will no doubt
look at different aspects of it in more detail in the future.
About the Author "IMS Web Tips"
(http://www.imswebtips.com) is a weekly news letter for all web
site managers regardless of experience who are looking for detailed
information on creating, maintaining and promoting their web sites.
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