DX8 effect implementations

DX8 effects are otherwise known as DirectX Media Object (DMO) effects, and as the name suggests, requires DirectX 8 (or above) to be installed. BASS provides 2 different implementations of DX8 effects, each with its advantages. The method used by a channel depends on whether the BASS_SAMPLE_FX flag is used in its creation.

With the BASS_SAMPLE_FX flag

This is the standard way of using DX8 effects. The main advantage of this method is that effect parameter changes are audible instantaneously. The main disadvantages are that the channel's sample rate cannot be changed (can with DX9), and it cannot be used with decoding channels or speaker assignment.

Without the BASS_SAMPLE_FX flag

The advantages/disadvantages of this method are basically the opposite of the other method; the channel's sample rate can be changed, but there's a delay in effect parameter changes being audible. The reason being that, using this method, the effects are applied at the same stage as user DSP functions. There are also other advantages to this method, as shown in the table below.

With FX flagWithout FX flag
Adding & removingChannel needs to be stopped when adding or removing an effect.Can add and remove effects without stopping playback.
Decoding channelsNot possible.Automatically used for decoding channels.
Speaker assignmentNot possible.Can be used with speaker assignment.
RecordingNot possible.Automatically used for recording channels.
Parameter changesAudible instantaneously.Delayed by the length of the channel's buffer; using a smaller buffer means less delay.
Channel sample rateCan only be changed when using DirectX 9.Can be changed.
Effected sample dataNot available. DSP functions, BASS_ChannelGetData and BASS_ChannelGetLevel receive the original data (without the effects applied).The effected data is available to BASS functions.
Effect chain orderingNot possible.The effects can be applied in any order you want, and can be intermingled with DSP functions.
Channel buffer lengthMust be at least 150ms.No restriction.
CPU usageCPU use is not included in BASS_GetCPU.CPU use is included in BASS_GetCPU. Also slightly lower CPU usage.

In both cases, DX8 effects are not supported on channels that are more than stereo, and floating-point support requires DirectX 9.


The "With FX flag" system is only available when using DirectSound output on Windows. Away from Windows, the DX8 effects are emulated by BASS, floating-point is supported, and the PARAMEQ effect also supports more than stereo.

See also

BASS_ChannelSetFX, BASS_MusicLoad, BASS_StreamCreate, BASS_StreamCreateFile, BASS_StreamCreateURL