Buffer Basics

[The feature associated with this page, DirectSound, is a legacy feature. It has been superseded by WASAPI and Audio Graphs. Media Casting have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Media Casting instead of DirectSound, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

DirectSound buffer objects control the delivery of waveform data from a source to a destination. The source might be a synthesizer, another buffer, a WAV file, or a resource. For most buffers, the destination is a mixing engine called the primary buffer. From the primary buffer, the data goes to the hardware that converts the samples to sound waves.

Information about using DirectSound buffers is contained in the following topics:

• Creating Secondary Buffers

• Duplicating Buffers

• Buffer Control Options

• Algorithms for Buffers

• Filling and Playing Static Buffers

• Using Streaming Buffers

• Playback Controls

• Play and Write Cursors

• Play Buffer Notification

• Mixing Sounds

• Looping Sounds

• Buffer Management

For information about capture buffers, see Capturing Waveforms.

Your application must create at least one secondary sound buffer for storing and playing individual sounds.

A secondary buffer can exist throughout the life of an application, or it can be destroyed when no longer needed. It can be a static buffer that contains a single short sound, or a streaming buffer that is refreshed with new data as it plays. To limit demands on memory, long sounds should be played through streaming buffers that hold no more than a few seconds of data.

You mix sounds from different secondary buffers simply by playing them at the same time. Any number of secondary buffers can be played at one time, up to the limits of available processing power.

Secondary buffers are not all created alike. Characteristics of buffers include the following:

• Format. The format of a buffer must match the format of the waveform data it plays.

• Controls. Different buffers can have different controls, such as volume, frequency, and movement in two or three dimensions. When creating a buffer, you should specify only the controls you need; for example, don't create a 3D buffer for a sound that isn't in a 3D environment.

• Location. A buffer can be in memory managed by hardware, or in memory managed by software. Hardware buffers are more efficient but limited in number. Hardware buffers are not supported in 64-bit operating systems.

See Also

• DSBUFFERDESC