Setting and Retrieving Global Parameters
By using the IDirectMusicPerformance::SetGlobalParam and IDirectMusicPerformance::GetGlobalParam methods, you can set and retrieve parameters that affect the entire performance, rather than a single track.
The parameter to be set or retrieved is identified by a GUID in the rguidType parameter of the method. Each parameter is associated with a particular data type, whose size is given in the dwSize parameter. The predefined GUIDs and their data types are shown in the following table.
| Parameter type GUID (rguidType) and data (*pParam) |
Description |
|---|---|
| GUID_PerfAutoDownload BOOL |
This parameter controls whether instruments are automatically downloaded when a segment is played. By default, it is off. For more information, see Downloading and Unloading Bands. |
| GUID_PerfMasterGrooveLevel char |
The master groove level is a value that is always added to the groove level established by the command track. The resulting value is adjusted, if necessary, to fall within the range from 1 through 100. |
| GUID_PerfMasterTempo float |
The master tempo is a scaling factor that is applied to the tempo by the final output tool. By default, it is 1. A value of 0.5 would halve the tempo, and a value of 2.0 would double it. This value can be set in the range from DMUS_MASTERTEMPO_MIN through DMUS_MASTERTEMPO_MAX. |
| GUID_PerfMasterVolume long |
The master volume is an amplification or attenuation factor, in hundredths of a decibel, applied to the default volume of the entire performance. The range of permitted values is determined by the port. Legacy hardware MIDI ports do not support changing master volume. |
Applications can also use custom types of global parameters. To create a new type, establish a GUID and a data type for it.
When a parameter is set, the performance allocates memory for the data in a linked list of items identified by GUID. The data can be retrieved by a call to IDirectMusicPerformance::GetGlobalParam. Even predefined parameters have to be set before they can be retrieved. GetGlobalParam fails if SetGlobalParam has never been called on the parameter.
Last updated on Monday, April 12, 2004
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