• 1.3.1. Active Talkers
• 1.3.2. Volume Control
• 1.3.3. Resource Allocation

1.3. Software Features

Each DCB/SC board has one or more DSPs. Conferences are associated with DSPs and may not span DSPs. Each DSP has 32 resources. Every time a conferee is added to a conference, a resource is used. When the conferee is removed from a conference and/or a conference is deleted, all associated resources are freed.

An application has the flexibility to associate conferences with any desired DSP. This allows for load balancing and better control over resources. Applications associate conferences with DSPs using a DSP device handle. DSP device handles are obtained using the dcb_open( ) function.

Examples of valid DSP names used in dcb_open( ) are shown below:

dcbBxD1, dcbBxD2, dcbBxD3

where x indicates the board number associated with the DCB/SC board.

1.3.1. Active Talkers

Active talkers are those conferees providing "non-silence" energy. The DCB/SC board can provide indication of the active talkers in a specified conference.

To retrieve active talkers, turn on the active talker feature by setting MSG_ACTID to ACTID_ON using the dcb_setbrdparm( ) function. Then, retrieve active talkers using the dcb_gettalkers( ) function. The frequency of active talker retrieval is determined by the application, although internally the active talkers are updated every 100 ms.

The internal implementation of the active talker feature consists of three parts:

1. The DSPs on the DCB/SC boards are programmed to furnish non-silence information for each of the 32 resources every 100 ms. This information is in bit form and is referred to as active talker indicator (ATI) bits. If the bit associated with a resource is on, it indicates non-silence energy in that resource during the time interval. The ATI bit pattern for a specific instant is retrieved using the dcb_getatibits( ) function.
2. The resource assignment table contains resource assignments of a DSP to conferees in different conferences.
3. A combination of parts one and two is used to provide the output from the dcb_gettalkers( ) function.

1.3.2. Volume Control

A conferee in a conference may wish to change the volume level of the received signal. This is accomplished using the volume control feature.

The MSG_VOLDIG parameter in dcb_setbrdparm( ) allows the application to define the digits that cause the volume level to be adjusted up, down or back to the default value. When a conferee other than a monitor or receive-only party presses a digit programmed to change volume, the received signal is adjusted. The volume control digits do not cause events to be sent to the application, even if digit detection is turned on using the dcb_setdigitmsk( ) function. Volume control digits are used only for controlling volume.

1.3.3. Resource Allocation

As stated earlier, each DSP has 32 resources. The available resource count is retrieved using the dcb_dsprescount( ) function. Calling any of the following functions will cause the available resource count to change:

Function	Result
dcb_estconf( )	Uses the total number of conferees established in the new conference.
dcb_addtoconf( )	Uses one resource every time a conferee is successfully added to a conference.
dcb_remfromconf( )	Frees one resource.
dcb_delconf( )	Frees all resources in use by the conference, including the monitor.
dcb_monconf( )	Uses one resource.
dcb_unmonconf( )	Frees one resource.

NOTE:

The channel selector value of the conferee does not affect the resource usage.

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