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Glossary

Multimedia

Exploring Palm OS®

AC97

Audio codec 97, an open standard defined by Intel and popular with many hardware manufacturers.

ADC

Analog to digital converter (audio recording).

ADPCM

Adaptive Differential Pulse Code Modulation. A form of PCM that produces a digital signal with a lower bit rate than standard PCM.

Audio sample

A single number representing the amplitude of a waveform at a particular time.

Buffer

A storage area for data.

Channel

An audio stream may consist of multiple interleaved channels. A mono stream has one channel, and a stereo stream has two channels. There is one sample per channel.

DAC

Digital to analog converter (audio playback).

Decoder

Converts a particular encoded data format, such as MS-ADPCM or MPEG-1 video into a format that the output device can understand.

Encoder

Converts one multimedia format (typically a raw format) to another encoded format for the purposes of storing that format.

Frame

For audio, a frame consists of interleaved audio samples (one sample per channel) that are output during one quantized time unit. For video, a frame consists of an entire picture.

Media time

The temporal position within media data.

MMLibrary

A shared library included in the SDK that allows multimedia clients to access multimedia features provided by the Movie Server.

Movie Server

A server that runs in the System process and provides all multimedia functionality.

Multimedia client

An application running in the Application process, that accesses the Movie Server through the MMLibrary. A media player is an example of such an application.

Pan

Stereo balance between left and right speakers.

Performance time

The time as specified by an external time source while media data is recorded or played.

PCM

Pulse Code Modulation. A sampling technique for digitizing analog signals.

Property sets

Objects that expose configurable parameters, or properties, which control the object's behavior. Many of the objects in the Multimedia Subsystem are property sets that allow the client application to configure them.

Session

A session provides a context for an application's media playback or recording tasks in the Movie Server.

Stream

In the audio driver, a sequence of stereo sample pairs. In the Movie Server library, an object that defines the media format handled by a source or destination device.

Track

A route for media data from a source device to a destination device.

Track callback filter

A function provided in the multimedia client that receives buffers of data directly from the Movie Server so that the callback can perform whatever tasks it wants with the data, such as storing it locally, modifying it, etc.