Beat Analyzer

At a glance

The system’s beat clock: a program on the A³ Core, on the same JACK graph as the audio engine, with no screen. It is the beat clock only; the level meters are the engine’s (Where the meters come from).

  • The beat: /beat (beat in bar, bar, tempo) to every device. A³ Motion follows it in EXT and PIO; the desk’s TAP key (strip 4) blinks with it.

You choose the beat’s source on A³ Motion’s clock key. Source: a3-beat-analyzer (a3-core’s submodule a3-beat-analyzer, versioned with the system), tempo detection by BTrack.

Clock modes

Each tap on A³ Motion’s clock key steps INT → EXT → PIO and sends /clockmode.

A³ Motion reads

/clockmode

Mode

Where the beat comes from

INT

0

a3motion

A³ Motion: tapped there, relayed to all

EXT

1

intern

the music, analysed

PIO

2

pioneer

the Pro DJ Link tempo master: a CDJ, or StemDeck

What each mode needs

INT — a3motion. Only A³ Motion: it sends /beat to beat-analyzer.clock, and the analyzer relays it to every target except motion. Its own clock pauses; /tap does nothing.

EXT — intern. Music on its input (bpm_1, which the engine connects to the rec pair: the I/O map). It finds onsets and a tempo; its clock counts on between beats, and at the last tempo when music stops. Taps:

  • The first tap after a 2 s pause sets the one (beat 1, tempo kept).

  • From the second, the tempo follows your taps (median of the last eight intervals); from the third, every tap resets the beat to 1.

  • Taps outside BPM_MIN–BPM_MAX are ignored.

Note

A tapped tempo holds for 16 bars. After a tap the phase still follows the music, the tempo does not. Sixteen bars after the last tap the analysis takes the tempo back, starting from the tapped one; a new tap starts the 16 bars over. TAP_LOCK_BARS sets the bars (0 = until a restart).

PIO — pioneer. The Core on a Pro DJ Link network: it joins as player 7 on the prolink.* ports and follows the tempo master (the player that says master while playing; until known, any player). Tempo = the master’s track tempo with pitch. /beat’s bar is always 0 (Pro DJ Link knows the beat in the bar, not the bar). Ask the venue before joining their network; not affiliated with AlphaTheta or Pioneer (Trademarks and Pro DJ Link).

No CDJs: StemDeck as master.

Switching modes by hand

Any OSC sender can switch it: /clockmode (int) to the clock port, 7775 in today’s a3-osc.json. On the Core:

oscsend localhost 7775 /clockmode i 2     # 0 a3motion, 1 intern, 2 pioneer

Out-of-range values are clamped. A³ Motion’s clock key does not notice.

Playing without CDJs: StemDeck as the tempo master

With no CDJs, StemDeck drives the clock:

StemDeck, deck with MASTER on
   │  Pro DJ Link: a beat packet on every beat, a status packet every 200 ms,
   │  as its player (deck A: 6), sent as broadcast on UDP 50001 / 50002
   ▼
beat-analyzer, clock mode 2 (pioneer), player 7
   │  takes StemDeck as the tempo master: it says master, and it plays
   │  /beat  beat-in-bar, 0, bpm
   ▼
A³ Motion on PIO, A³ Mixer's TAP key, every other /beat target

  1. Load a set in StemDeck and wait for its BPM (nothing is sent before).

  2. Press MASTER on the deck that leads. Its top bar reads LINK master: A (or B, C, D). The newest press wins: MASTER on another deck takes it over.

  3. Tap A³ Motion’s clock key to PIO. Its BPM follows the master deck, tempo fader included.

  • The one is counted from the first beat of the track’s grid: a wrong downbeat is fixed there.

  • A stopped master sends no beats; A³ Motion carries on at the last tempo.

  • On one machine both share the Pro DJ Link ports; broadcast reaches both whatever started first.

Where it runs and where its settings live

beat-analyzer.service, part of a3-main; the a3-core package installs the unit and builds the program from the a3-system checkout. It runs beside the engine and does not depend on it.

Settings: a .env in its working directory build/. First found of build/.env, ../.env, .env.example. Template: cp .env.example build/.env.

Targets and ports are rendered, not hand-written: a3-core --render-truth user writes a block at the end of build/.env from a3-osc.json:

# >>> a3-osc: rendered from a3-osc.json by a3-core --render-truth -- edit the truth, not this
OSC_HOST_core=127.0.0.1:9000
…
# <<< a3-osc

The rest of the file is yours. Block keys written outside it are commented out (# was: …) at the next install. No targets: it reports the block missing. To change one, change a3-osc.json (truth).

Setting

What it does

OSC_HOST_<name> (block)

a /beat target. motion gets no relayed beat in INT

OSC_PORT_A3MOTION (block)

where /beat, /clockmode, /tap arrive

OSC_ADDRESS_BEAT, _TAP, _CLOCKMODE (block)

its addresses

PIONEER_PORT_ANNOUNCE, _BEAT, _STATUS (block)

Pro DJ Link ports

BPM_MIN, BPM_MAX

tempo range; outside it, doubled or halved in

TAP_LOCK_BARS

bars a tapped tempo holds before the analysis takes over (default 16, 0 = until restart)

PIONEER_DEVICE_NUM

player number, 7

DEBUG_BEAT_CONSOLE, DEBUG_PIONEER_CONSOLE

log every beat / Pro DJ Link beat (with tempo, offset, player, master)

Read at start; restart after a change. The clock mode is not a setting: it always starts in mode 1 (intern).

systemctl --user restart beat-analyzer

Ports: Ports and endpoints. Messages: OSC reference.

Troubleshooting

Symptom

What to do

Motion on PIO/EXT, tempo from the wrong source

The analyzer restarted into mode 1. Step Motion’s clock key once round

EXT: no beat

Service running? bpm_1 connected (jack_lsp -c; the engine makes the link, I/O map)? Music reaching it?

EXT: half or double tempo

BPM_MIN–BPM_MAX one octave around the music, e.g. 70–140

EXT: tempo stopped following

You tapped: it follows again 16 bars after the last tap (TAP_LOCK_BARS)

PIO: nothing arrives

Core on the players’ network, ports free? Log: Pioneer Receiver konnte nicht gestartet werden

PIO: wrong player

It follows whoever says master while playing

No beat targets

build/.env ends with the a3-osc block? Else a3-core --render-truth user, restart

Log: journalctl --user -u beat-analyzer -f.