Putting Sound and Video into Web Pages

Sound Formats

AIFF

• AIFF was developed by Apple and is suited for storing high-quality sound.
• There are players for Mac, PC, Unix
• The whole file needs to be downloaded before playing.
• The file size tends to be large.
• Not a commonly used format on the WWW.
• Sound clip by Celine Dion (0.6Meg)

AU

• Players for Mac, PC, Unix
• File size tends to be large.
• The whole file needs to be downloaded before playing.
• The file size tends to be large.
• Not a commonly used format on the WWW.

MPEG Audio: Levels 1, 2, 3

• Level 1 accomodates two audio channels that can deliver stereo.
• Level 2 accomodates intensity stereo, where the high-frequency portions of both signals (above 2kHz) are combined.
• Level 3 accommodates m/s stereo, one channel carries the sum of the two signals (left+right), the other carries the difference (left-right).
• For real time audio, you would need a bit rate of 192Kbps for level 1, 128Kbps for level 2, 64 Kbps for level 3.
  Note: 64Kbps is 8,000 bps, which is around 3 times the bandwidth of a 28,800 bps modem.
• MPEG audio files must be download before being able to playback.
• Most players actually convert MPEG audio files to a native format for playback, especially for level 2 and 3 which would require at least one DSP chip to playback in real time.

Real-Time Audio

• Version 1 provided audio quality at the level of a good AM radio station
• Version 2 provided audio quality at the level of a nonstereo FM station
• Version 3 is suppose to bring the audio quality up to the level of a CD ROM
• Real-Time Audio is real time audio, with only a short buffering at the start. The file is played as it is received, rather than waiting until the whole file is received.
• Real-Time audio is not good for uses where the user is likely to move around the audio file and listen to bits and pieces of the file.
• Real-Time audio needs a good TCP connection, if there is a loss rate of even 2% with a 14.4 modem things can be brought to a standstill.
• Real-Time audio will try to use the TCP/IP protocol called user datagram protocol (UDP) which does not guarentee delivery, but just sends out the packets as fast as possible. If a packet is lost/damaged, then the program fills in from the surrounding packets.
• There are three speeds for Real-Time Audio 14,400 bps, 28,800 bps, and 3.0 each corresponding to a high speed connection and providing better quality sound.

RIFF WAV or WAV

• developed by Microsoft and IBM
• Comparable to but not compatible with AIFF
• Players for Mac, PC, Unix
• File size tends to be large.
• The whole file needs to be downloaded before playing.
• The file size tends to be large.
• The native sound format for Windows
• Common on the WWW due to Windows.

Quicktime Sound File

• Apple's Quicktime support sounds as well as movies.
• The native sound format of Mac systems.
• Easily played back on Mac's as well as Windows machines with Quicktime installed.
• Fairly common on the WWW.

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