A loose connector for interacting with Ableton Link.
Carabiner is a program that embeds the C++ Link library and listens for local TCP connections to allow other programs, like beat-link-trigger and Afterglow, to participate in some aspects of a Link session, even though they were not written using C++ compatible languages and runtimes.
Carabiner does not support the full power and elegance of Link, so if you are writing a program that can use the library directly, you are much better off doing that instead. Carabiner is for cases where that is impossible or impractical.
If you are on a Mac OS X system, you can download the executable from the releases page. Then just open a terminal window, and run it:
> Carabiner
Starting Carabiner on port tcp://127.0.0.1:17000
Link bpm: 128.5 Peers: 1 Connections: 0
By default it listens on port 17000. If this port is already in use on
your system, you can specify a different port using the --port
command-line argument.
The status line shows the current tempo of the Link session, and the number of Link Peers which have been found. It also shows how many TCP connections are currently open to Carabiner from client programs like beat-link-trigger. See the documentation of the client program for instructions on how to have it connect to Carabiner.
You can shut down Carabiner by typing Control-C in the Terminal
window, or simply closing that window.
- link-to-py is a Python 3 module for interacting with Carabiner written by Benjamin Yetton.
If you want to run Carabiner on a different platform, or make and test modifications to its source code, you can build it yourself.
Carabiner relies on link and gflags as git submodules (and link
relies on its own submodules), so after you have cloned the main
carabiner repository, you need to cd into it and set up the
submodules by running:
git submodule update --init --recursive
Carabiner uses CMake to manage its build
process. Once again, from the top-level directory of your carabiner
repository:
mkdir build
cd build
cmake ..
cmake --build .
Once the build completes you will find the executable in
bin/Carabiner under the build directory.
Client programs interact with Carabiner by sending and receiving simple single-packet messages. The currently supported messages are:
Sending the string status to Carabiner requests an update containing
the current status. It will respond with a packet like the following:
status { :peers 0 :bpm 120.000000 :start 73743731220 :beat 597.737570 }
As with all non-error messages from Carabiner, this consists of a message type identifier followed by an edn structure containing the message parameters. In this case, it identifies the current number of Link peers, the current tempo of the Link session, the timestamp of when the session timeline started, and the current beat position.
A status response will also be sent when you first connect to Carabiner, and whenever the Link session tempo changes, as well as whenever the number of Link peers changes.
⏱️ About Link Timestamps: The
:startvalue in the above message, and the time and:whenvalues sent and returned in the commands below, are expressed in microseconds, but they are not interchangeable with values returned by the normal "wall clock" system clock you use to determine the current time of day. Link needs to use a monotonically increasing clock that is not affected by things like leap seconds or NTP server synchronization. In Java you can obtain Link-compatible timestamps using theSystem.nanoTime()method. If you are working in other languages, you will need to experiment in order to find out how to read the same clock that Link is using.
Sending the string bpm followed by a floating-point value, for
example bpm 140.0, tells Carabiner to immediately set the Link
session's tempo to the specified value. If this is a change from the
previous value, it will result in a status response as described
above.
If the bpm value is missing, cannot be parsed as a floating point
number, or is outside the range from 20.0 to 999.0, the session tempo
is left unchanged and Carabiner responds with the message bad-bpm
followed by the argument you supplied.
If your client wants to use a tempo outside the range supported by Link, Ableton recommends setting the Link tempo to the closest multiple or fraction which is in range. For example, if the user wants 15 BPM, set the session tempo to 30 BPM.
Sending the string beat-at-time followed by a microsecond timestamp
(an integer relative to the :start value returned in the status
response), and a quantum value (which identifies the number of beats
that make up a bar or loop as described in the Phase Synchronization
section of the Link documentation),
asks Carabiner to identify the beat which falls at the specified point
on the Link session timeline. For example, sending beat-at-time 73746356220 4 to the link session used in the above examples would
result in a response like the following:
beat-at-time { :when 73746356220 :quantum 4.000000 :beat 5.250000 }
This response indicates that at the specified microsecond along the Link session timeline, we are a quarter of the way from the sixth to the seventh beat (Link numbers beats starting with 0).
If one of the parameters is missing or cannot be parsed, Carabiner
responds with bad-time or bad-quantum followed by the arguments
you gave it.
Sending the string phase-at-time followed by a microsecond
timestamp (an integer relative to the :start value returned in the
status response), and a quantum value (which identifies the number
of beats that make up a bar or loop as described in the Phase
Synchronization section of
the Link documentation), asks
Carabiner to identify the phase which falls at the specified point on
the Link session timeline. A phase is a floating point value ranging
fom 0.0 to just less than the quantum. For example, sending
phase-at-time 73746356220 4 to the link session used in the above
examples would result in a response like the following:
phase-at-time { :when 73746356220 :quantum 4.000000 :phase 1.250000 }
This response indicates that at the specified microsecond along the Link session timeline, we are just over a quarter of the way from the second to the third beat of the four beats in a quantum period.
If one of the parameters is missing or cannot be parsed, Carabiner
responds with bad-time or bad-quantum followed by the arguments
you gave it.
Sending the string time-at-beat followed by a beat number (a
floating point value, since you can inquire about points that fall
between beats), and a quantum value (which identifies the number of
beats that make up a bar or loop as described in the Phase
Synchronization section of
the Link documentation), asks
Carabiner to return the microsecond timestamp (an integer relative to
the :start value returned in the status response) at which the
specified beat (or fraction of a beat) falls on the Link session
timeline. For example, sending time-at-beat 100 4 to the link
session used in the above examples would result in a response like the
following:
time-at-beat { :beat 100.000000 :quantum 4.000000 :when 73793731220 }
This response indicates that the hundred and first beat falls at the
specified microsecond within the timeline. As a sanity check, you can
ask about the first beat, and verify that the :when value matches
the :start value reported by the status message. Sending
time-at-beat 0 4 in the session used in these examples results in
the following response, which you can compare to the status response
above:
time-at-beat { :beat 0.000000 :quantum 4.000000 :when 73743731220 }
Sending another status command now shows that the current beat has
moved on while these examples were being written, but the timeline
start point has remained the same:
status { :peers 0 :bpm 120.000000 :start 73743731220 :beat 2560.623742 }
If one of the parameters is missing or cannot be parsed, Carabiner
responds with bad-beat or bad-quantum followed by the arguments
you gave it.
Sending the string force-beat-at-time followed by a floating-point
beat number, a microsecond timestamp (an integer relative to the
:start value returned in the status response), and a quantum value
(as described above) tells Carabiner to forcibly and abruptly adjust
the Link session timeline so that the specified beat falls at the
specified point in time. The change will be communicated to all
participants, and will result in audible shifts in playback.
Continuing the previous example, sending force-beat-at-time 1.0 73746356220 4 will tell Carabiner to adjust the Link session timeline
so the second beat starts as close as possible to the specified moment
(which previously was 25% of the way from the sixth to the seventh
beat). Carabiner responds with a status message which reports the
new :start timestamp of the timeline.
status { :peers 0 :bpm 120.000000 :start 73745856220 :beat 2989.161370 }
At this point, repeating the beat-at-time command we used in the
section explaining that command, beat-at-time 73746356220 4, will
return a beat value that is very close to 1.0 (in this example it was
exact):
beat-at-time { :when 73746356220 :quantum 4.000000 :beat 1.000000 }
If one of the parameters is missing or cannot be parsed, Carabiner
responds with bad-beat , bad-time , or bad-quantum followed by
the arguments you gave it.
This command should only be used when synchronizing a Link session to an external timing source which cannot participate in the consensus-based Link timeline, and should be done only when the session has drifted beyond some reasonable threshold, so that external jitter does not lead to excessive adjustments.
If you are building an application that can perform quantized starts, and thereby participate in a Link session more graciously, without requiring the other participants to shift the timeline, you should use the following command instead:
Sending the string request-beat-at-time followed by a
floating-point beat number, a microsecond timestamp (an integer
relative to the :start value returned in the status response), and
a quantum value (as described above) tells Carabiner to ask Link to
try to gracefully adjust its timeline so that the specified beat will
occur at the specified time. If there are no other peers in the Link
session, this will behave the same as force-beat-at-time, above.
However, if there are any peers, it will avoid the kinds of audible
discontinuities described above, by adjusting the local timeline so
that the specified beat will instead fall at the next point in time
after the requested time which has the same phase as the specified
beat.
Carabiner responds with a status message which reports the
new :start timestamp of the timeline.
If one of the parameters is missing or cannot be parsed, Carabiner
responds with bad-beat , bad-time , or bad-quantum followed by
the arguments you gave it.
As the Link documentation explains, this command is specifically designed to enable the concept of "quantized launch". If there are no peers, the deisred mapping is established immediately when requested. Otherwise, we wait until the next time at which the session phase matches the desired event, so we can seamlessly join the peers that are already in the session.
I am not a C++ programmer; the last time I wrote anyting in it before Carabiner was in the early 1990s. This seems to work, but I am sure it could be written much better. Suggestions for improvement are definitely welcome!
Carabiner is Copyright © 2016-2017 Deep Symmetry, LLC
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.
Link and Mongoose are dual-licensed. While available through the same GPL v2 as Carabiner itself, they are also available through proprietary licenses for embedding in non-free software, by contacting their respective developers.
gflags is Copyright © 2006, Google Inc. It has its own license.