diff options
Diffstat (limited to 'backends/sacn.md')
| -rw-r--r-- | backends/sacn.md | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/backends/sacn.md b/backends/sacn.md new file mode 100644 index 0000000..3d245a4 --- /dev/null +++ b/backends/sacn.md @@ -0,0 +1,58 @@ +### The `sacn` backend + +The sACN backend provides read-write access to the Multicast-UDP based streaming ACN protocol (ANSI E1.31-2016), +used for lighting fixture control. The backend sends universe discovery frames approximately every 10 seconds, +containing all write-enabled universes. + +#### Global configuration + +| Option | Example value | Default value | Description | +|---------------|-----------------------|-----------------------|-----------------------| +| `name` | `sACN source` | `MIDIMonster` | sACN source name | +| `cid` | `0xAA 0xBB 0xCC` ... | `MIDIMonster` | Source CID (16 bytes) | +| `bind` | `0.0.0.0 5568` | none | Binds a network address to listen for data. This option may be set multiple times, with each descriptor being assigned an index starting from 0 to be used with the `interface` instance configuration option. At least one descriptor is required for transmission. | + +#### Instance configuration + +| Option | Example value | Default value | Description | +|---------------|-----------------------|-----------------------|-----------------------| +| `universe` | `0` | none | Universe identifier | +| `interface` | `1` | `0` | The bound address to use for data input/output | +| `priority` | `100` | none | The data priority to transmit for this instance. Setting this option enables the instance for output and includes it in the universe discovery report. | +| `destination` | `10.2.2.2` | Universe multicast | Destination address for unicast output. If unset, the multicast destination for the specified universe is used. | +| `from` | `0xAA 0xBB` ... | none | 16-byte input source CID filter. Setting this option filters the input stream for this universe. | +| `unicast` | `1` | `0` | Prevent this instance from joining its universe multicast group | + +Note that instances accepting multicast input also process unicast frames directed at them, while +instances in `unicast` mode will not receive multicast frames. + +#### Channel specification + +A channel is specified by it's universe index. Channel indices start at 1 and end at 512. + +Example mapping: +``` +sacn1.231 < sacn2.123 +``` + +A 16-bit channel (spanning any two normal 8-bit channels in the same universe, also called a wide channel) may be mapped with the syntax +``` +sacn.1+2 > sacn2.5+123 +``` + +A normal channel that is part of a wide channel can not be mapped individually. + +#### Known bugs / problems + +The DMX start code of transmitted and received universes is fixed as `0`. + +The (upper) limit on packet transmission rate mandated by section 6.6.1 of the sACN specification is disregarded. +The rate of packet transmission is influenced by the rate of incoming mapped events on the instance. + +Universe synchronization is currently not supported, though this feature may be implemented in the future. + +To use multicast input, all networking hardware in the path must support the IGMPv2 protocol. + +The Linux kernel limits the number of multicast groups an interface may join to 20. An instance configured +for input automatically joins the multicast group for its universe, unless configured in `unicast` mode. +This limit can be raised by changing the kernel option in `/proc/sys/net/ipv4/igmp_max_memberships`.
\ No newline at end of file |