Digital audio

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Draft

Audio file formats[edit | edit source]

“It is important to distinguish between a file format and a codec. A codec performs the encoding and decoding of the raw audio data while the data itself is stored in a file with a specific audio file format” (Wikipedia).

Formats[edit | edit source]

Read:

Audio File Format (Wikipedia)

Example of lossy compression

MP3 - MPEG Layer-3
OGG - Vorbis (most often with OGG container, therefore also known as OGG-Vorbis)
AAC, MP4, M4a - MPEG 4 audio

Lossless examples

WMA - Microsoft
FLAC
WAV mostly for Windows PCs. Can use several compression codecs (most often uncompressed PCM as in standard audio CDs)
AIFF (The Mac equivalent of WAV)

Overview of CD Formats[edit | edit source]

Most of these are called CD Rainbow Books (referring to the color of the specification documents)

Red Book (CD Digital Audio). The basic standard for all CDs, including music CDs. Digital audio encoding: 2-channel signed 16-bit PCM sampled at 44,100 Hz.
Yellow Book (CD-ROM and CD-ROM XA). CDs for data (software)
Orange Book (CD-R and CD-RW). Recordable CDs
White Book (Video CD). CDs with video content that plays in most DVD players.
Blue Book (Enhanced CD, CD+G, and CD-Plus). Music CDs with extra features like videos or photos.
Beige Book (Photo CD). Kodak's format for storing photos on a CD.
Green Book (CD-i). Rarely used. CD-Interactive contains educational material and games.
Purple Book (DDCD) hold more storage than CDs and require a special reader, not popular
High Density CD (HDCD), an alternative to DDCD, not popular
Scarlet Book (SACD). Super Audio CDs uses Direct Stream Digital (DSD) recording, a proprietary Sony/Philips format. Quality is superb but needs a special player to work. There are three separate versions, one of which includes a red-book layer so that music will also play on an old CD player.
DVD-Audio (DVD-A) is a Digital Versatile Disc (DVD) format that is specifically designed to hold high-quality audio data. An alternative to SA-CD

Audio in web pages[edit | edit source]

HTML5 Audio[edit | edit source]

Audio works quite nicely in HTML5

See HTML5 audio and video

HTML4 and XHTML1 Audio[edit | edit source]

Audio URLs[edit | edit source]

This is quite a nightmare. If you just use normal URLs, behavior will entirely depend on the configuration of your navigator and your system set-up. In any case, if you use firefox, you must install a mediaplayer plugin, e.g. Real Player, Quicktime, Windows Media.

E.g. in Firefox, select "Edit->Preferences" 'or "Tools->Options" (depending on your version). Then select the "Applications" tab. It will show how various audio files will be played and you can change that. E.g. on windows I use "Quicktime" and on Ubuntu the "mplayer" plugin.

Using the embed tag[edit | edit source]

Using the embed tag is probably the best solution for HTML4 audio, even if this tag is not an official part of HTML 4.x. Since the embed tag is official in HTML 5 it will survive, but it has different attributes. It also allows to adopt a user-friendly strategy, i.e. you can show a little control widget for playing the sound.

Attributes:

src= "URL": The URL of the sound file

loop= "true/false/N": Whether it should loop or how many times

autostart = "true/flase": Whether it should automatically start.

controls = "console|smallconsole|pausebutton|stopbutton|volumelever": Whether it will display a full console, a small one, juste a stop button or a volumelever

hidden = "true/false": Hide/unhide. Hide if you really need background music

height=XX: defines the height of the player in pixels

width=XX: defines the width of the player in pixels

border

frameborder

align = "top|bottom|baseline|left|right

Using Flash[edit | edit source]

Simply include a Flash file. Make it very small if you don't want controls...

Using JavaScript[edit | edit source]

Source: Demonstration of Different Ways to Play a Sound from a Web Page:

<script>
function PlaySound(soundobj) {
  var thissound=document.getElementById(soundobj);
  thissound.Play();
}
</script>

<embed src="sound.mp3" autostart=false width=0 height=0 id="sound1"
enablejavascript="true">

Then call this function, e.g. from a button

<form>
<input type="button" value="Play+" onClick="PlaySound('success.wav')">
</form>

Using the object tag[edit | edit source]

In HTML4.x and XHTML 1.x, this should be the "standard" solution, but not as well implemented as the unofficial embed. Read HTML5 audio and video for better approach.

Software[edit | edit source]

Editing tools[edit | edit source]

Audacity is probably the most popular free editing tool. Read Wikipedia's Audacity article.
- Audacity wiki (manuals, tips, etc.)

Clients[edit | edit source]

All web browsers can support audio in one or another way. HTML4/XHTML 1.1 only supports audio through plugins, HTML5 has built-in support for some formats
A lot of audio players (by default each OS includes a player).