> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/voice-and-media/audio-mixers.md).

# Audio Mixers

### Toolpack Audio Mixers

An audio mixer is used to mix the audio of multiple sources (call legs, playing audio file, tone generator...)

#### Typical usage of audio mixers

Audio mixers can be used, among other things, to:

* Build conferences
* Insert background music into a conversation
* Record both sides of the conversation into a single recorded file.

#### Joining audio source to a mixer

There are 2 ways to join a mixer:

* Join as a listener only
* Join as a speaker. Speakers can be active / or inactive (inactive speakers are not mixed, but monitored for voice activity)

![mixer internal](https://docs.telcobridges.com/w/images/e/e1/Mixer_internal.png)

#### Maximum call legs per mixer

The mixer has the following capabilities:

* The mixer can have any number of listeners (up to maximum number of call legs supported by the TMedia system)
* The mixer can have any number of speakers (up to maximum number of call legs supported by the TMedia system)
  * Among these speakers, up to 10 will be considered as "active" (the 10 from which voice was received the most recently)
  * Among these 10 active speakers, the audio from dominant N speakers will be mixed (N can be configured per mixer)

#### Resource usage of mixers

* An active speaker uses one mixer slot (up to 10 per conference)
* All non-active speakers use one mixer slot (although there is no per-conference limit)
* All listeners *share* the same mixer slot
* IVR on the mixer (playing file, recording file) use one mixer slot. It is possible to record and play at the same time, but the recording does not contain what is played on the mixer
  * It is possible to have a recording that contains what is played on the mixer, but it uses one more mixer slot (total of 2 slots)

**Note:** A delay of 15 seconds occurs when a mixer can be "scaled-down" (any reason making the number of slots required smaller), to reduce the number of times a mixer is being scaled up/down as users join/leave conference (very often, multiple users leave almost at the same time).

#### TMedia conference capacity

In order to use conferences, TMedia must be equipped with DSPs. Each TMP6400 unit can be equipped with DSPs for 1,824 conference "slots" (thus a total of 29,184 for large TMP6400 system). If mixers need to be joined with call legs from different adapters, a TMS switch is needed.

Here are capacity results, depending on the conference type:

* 3 call legs in a conference and no play/record:

> 608 conferences and 1,824 "slots"

* 2 call legs in a conference and play/record activated:

> 680 conferences and 2,040 "slots"

* 1 call leg in a conference and play and record activated (can record what is played):

> 680 conferences and 2,040 "slots"

* 11 call legs in a conference and play/record activated:

> 168 conferences and 2,016 "slots"

* 12 call legs in a conference and no play/record:

> 160 conferences and 1,920 "slots"


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://prosbcdocs.telcobridges.com/telecom-references/voice-and-media/audio-mixers.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.