Mixers allow video and audio to be switched and mixed together.
A mixer can have any number of sources. Sources can be either inputs or the output from other mixers.
Outputs can then take a mixer as a source, to deliver its mix elsewhere (e.g. as an RTMP stream, or writing to a file).
Mixers can also have overlays applied to them.
There can be any number of mixers. They can be created, updated, and deleted using the API. They can also be created at start-up using a config file.
All together, this allows mixers to be interconnected in interesting ways, for example:
There is only one type of mixer, and it has the following properties:
| Name | Can be set initially? | Can be updated?? | Description | Default value (if not set) |
|---|---|---|---|---|
id |
No | No | ID of the mixer. Positive integer. Starts at 1 and increases by 1 for each new mixer. | n/a |
uid |
No | No | Unqiue ID - a string in the format 'mixerX' where X is the ID | n/a |
state |
Yes | Yes | Either NULL, READY, PAUSED or PLAYING. What are the four states? |
PLAYING |
sources |
Yes | Yes (both directly and also via helper API methods cut_to_source and overlay_source) |
An array of inputs and mixers that are the source of this mixer. See below for more. | None |
pattern |
Yes | Yes | The pattern used for the background, as an integer. See the test video input type for the list of available patterns. | 0 (SMPTE 100% color bars) |
width and height |
Yes | Yes | Override of the width and height | The values of default_mixer_width and default_mixer_height in the config file. |
The sources properly is an array of dictionaries, for each source that the mixer is currently including. An empty array shows that the mixer has no source. The order of the array has no meaning.
Properties of each source:
| Name | Description | For audio or video sources? | Default |
|---|---|---|---|
uid |
the unique ID of the source (e.g. input1 or mixer2) |
Both | n/a (required) |
in_mix |
true iff source is overlayed into mix |
Both | true |
zorder |
The z-order (aka z-index) of the video. Sources with a higher z-order will appear over the sources with a lower z-order. | Video | 1 |
width and height |
The size of the video. It is useful to set these for 'picture in picture' or 'video wall' use-cases. | Video | If omitted, defaults to the full size of the mixer. |
xpos and ypos |
The location of the video. | Video | Defaults to 0,0 (i.e. the top-left corner). |
volume |
The volume that the input should be mixed at, between 0 (silent) and 1.0 (full volume). | Audio | 1.0 |