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Audio and Video
CGS 3066
Some Common Audio
Formats
Format
MIDI
MPEG
RealAudio
Wave
Use
instrumental music
songs
live broadcasts
sound clips
Extension
.mid
.mp3
.ra
.wav
MIDI (slide 1)
(Musical Instrument Digital Interface)
-developed in the early eighties to allow
synthesizers and other digital devices to
communicate with one another.
- MIDI is a representation of sound describing the note and the instrument that
renders it
- Voice and acoustic instruments cannot be
recorded in MIDI
MIDI - The Advantages
- MIDI files are significantly smaller than
digital audio files
needs less storage space and has a
shorter download time
- MIDI files can be edited and rearranged
MIDI - the Disadvantages
Sounds are not uniform system to system:
-
Why? because the sound card or playing
device of the computer in use defines the
sound
-
Voice and acoustic instruments cannot be
recorded
Places to start for MIDI links
http://www.mididb.com/
http://aitech.ac.jp/~ckelly/midi/good.html
MPEG
(Motion Pictures Expert Group)
Established for video
but because of good file compression is
often used when transferring whole music
recordings (as opposed to clips)
MP3 is the most recent MPEG standard
More on MP3
THE most common sound file format on the Web
No security features
Very easy to share
Beyond the web:
MP3 is also used in car stereos and portable
music players
RealAudio
Designed for real-time playing- like radio
Smaller than au or wav files but quality
Is not as high
WAV
Developed for Windows
One of the most common forms on the web
(but not THE most- that’s MP3)
(Macs use AIFF or SND files)
(unix uses au files)
What’s Required for an
Audio File to be played?
- the user's system must have the appropriate
plug-in for the audio type (WAV, MP3, etc.)
- Browsers identify the plug-in to play the audio file
by looking up the file extension in MIME -(Multipurpose Internet Mail Extensions) in the
browser's preferences settings.
- The user’s server must also be configured to
support the mime type of the audio element.
Some Web Sites with Sound
Clips
http://www.earthstation1.com/
http://www.soundamerica.com/
(240,000 clips by category)
http://www.wavcentral.com/
http://www.musicloops.com/
http://www.coolfreebies.com/wav.html
To add audio to your page
Download free audio clips
Right click on the audio link
Save as Link
on a Mac: hold down the Ctrl key and
click on link.
To link to the sound clip from your Web page:
<a href=“radio.url">listen to this! </a>
(Remember to use the path for the link if it’s not on
the current directory)
How to play an audio clip
directly from your page
The <EMBED> tag
The full command….
<EMBED SRC=“url” WIDTH=“value”
ALIGN=”value”
AUTOSTART=“startvalue”
EMBED attributes
Width and height in pixels
allows for the size of the controls to be
displayed so the user can play the clip
Align
places the controls on the page (default is text
flows below the controls)
Autostart
=true means clip starts when page is loaded
=false means wait for the user to click
A final word on EMBED
The same parameters can be used to
play video clips
Some Common Video Types
Type
AVI
MPEG
QuickTime
File extension
.avi *
.mpg or mpeg
.mov
*The latest MPEG, MPEG4, has .avi extension
different from this
Some Places to Find Video
http://www.jurassicpunk.com/
http://spacelink.nasa.gov/Instructional.M
aterials/Multimedia/OnLine.Multimedia/Video.Archives/.index
.html
To add video to your page
<a href=“video.avi">see this! </a>
Look familiar?
It’s the same technique as audio!
How to play an video clip
directly from your page
The <EMBED> tag
The full command….
<EMBED SRC=“yourclip.avi”
WIDTH=“value”
AUTOSTART=“startvalue”
LOOP=true>
Video EMBED attributes
Width and height in pixels
allows for the video to fit the browser window
Autostart
=true means clip starts when page is loaded
=false means wait for the user to click
Loop
=true means the video will play continuously
until the user does something
Some pointers on
Multimedia
- Tell users what the file size/download time
the clip represents
- If possible, give them more than one
option (sample vs whole thing)
And…
Always Make multimedia an OPTION!
Never set up your Web site or e-mail to begin
playing audio or video automatically,
This may startle and annoy people
Instead, entice people to fetch the audio with a
message such as:
"Click below to hear 5 secrets!"
or “Here’s how the experts do it!”