The definitive guide to Ableton Live's delay compensation and reduced latency

(A small "Note to self" post, while producing music)

Two options are often misunderstood in Ableton Live: "Delay compensation" and "Reduced latency when monitoring". Even after watching many tutorials, blog articles, videos about this, it might still be unclear.

The best way to clearly understand what is going on is to do this small experiment (do it, it takes 2 minutes and you'll understand this once for all!):

Options > Delay Compensation

• 0: Start with a new empty project
• 1: Set Metronome ON
• 2: Put an audio Clip on Track 1 which is in perfect sync with the beats/metronome (e.g. a kickdrum on each beat)
• 3: Add 20 instances of Compressor with "Lookahead 10ms" (see bottom of the Compressor settings) on Track 1
• 4: Let's say playback is stopped
• 5: Put "Delay compensation" ON => Hit <SPACE> key => there is an initial delay of 200ms (pay attention to it!), but then Metronome + Clip play in sync!

• 6: Put "Delay compensation" OFF => Hit <SPACE> key => the metronome plays immediately, but then the Clip arrives 200ms too late, out of sync!

  TL;DR: when Delay compensation is "ON", everything is in sync, the delays introduced by VSTs are compensated, but the price to pay is that everything is delayed (of 200ms in this example)! Redo steps #5 and #6 until you clearly hear the difference.

Options > Reduced Latency When Monitoring

• Repeat steps #0 to #5 from previous paragraph
• Add a second audio Track with Monitor set to "IN", armed for Recording, for example with your laptop's built-in mic, but leave this track empty with no audio effect/no VST
• Put "Reduced Latency When Monitoring" OFF (default) => Speak in the mic => You'll notice a 200ms delay between your voice and the Live monitoring playback!

• Put "Reduced Latency When Monitoring" ON => Speak in the mic => You'll notice far less delay!

  What happens here? When it is OFF, since Track 1 has to be delayed of 200 ms delay (because of the many Compressors!), ... then Track 2 is also delayed of 200ms, to keep everything in sync.
  When it is ON, then Track 2 doesn't get delayed (it has no latency-generating effect/VST on the track after all!)... Less latency, which is good, but the price to pay is that Track 2 is now no more in sync with Track 1, hehe!

  TL;DR: You go to the cinema with a friend. Your friend is 10 minutes late. "Reduced Latency When Monitoring" OFF basically means "Ok I support my friend, wait for him, and enter the cinema 10 minutes late". "Reduced Latency When Monitoring" ON means "No way, I'm myself not late, why should I wait? Let's go in right now!"

"Keep Latency" buttons

This new Ableton Live 12 option seems pretty interesting, I haven't tested it yet. To be written.

Buffer Size, Input Latency, Output Latency, Driver Error Compensation, Overall Latency

This is documented everywhere, so I won't reexplain this in detail. About Driver Error Compensation, Overall Latency, see end of next paragraph.

Note on monitoring IN / AUTO / OFF setting

• If you do a recording on a track with Monitor set to IN or AUTO, it will be shifted in time, and not in sync.

• If you set Monitor to OFF, then it will be recorded in sync. See this Youtube video on this topic, and the Monitoring in Live article:

  Why are my recordings out of sync? If the track monitor is set to "In" or "Auto" and you start recording, the recorded audio or MIDI is played back using the exact same timing and placement as what you've played. Depending on how large the buffer size or sample rate is, and how many latency-inducing devices are in the set, the recorded notes or audio could be offset in relation to the rest of the clips in the set. If you're playing in by hand then the difference is usually not so perceptible as the timing will already be quite loose in feel. However if you're recording from a fixed source (eg. a hardware synth playing a quantized pattern, or a drum machine) then the offset will probably be quite noticeable. In those cases we recommend setting the monitor to "Off" instead.
  When the monitor is set to "Off" then Live compensates by offsetting the recorded material by the exact amount in the "Overall Latency" section in Audio preferences.

• To finetune this, start a new project, put metronome ON, on a track set to Monitor OFF, do a recording with the microphone to record the "click" of the metronome. If it's not perfectly in sync (example: I have a 28ms offset with my soundcard), then go to Options > Preferences > Audio > Driver Error Compensation and set it to 28ms. Then the reported "Overall latency" will increase (that's normal, it corresponds to the reality and allows a more accurate compensation!). Then the compensation will be perfectly accurate when recording in Monitor=OFF mode. Indeed, once again:

  When the monitor is set to "Off" then Live compensates by offsetting the recorded material by the exact amount in the "Overall Latency" section in Audio preferences.

Why do I always have cables everywhere?