Ableton/Live/UG/39 Audio Fact Sheet
- How Ableton tested Live's audio engine, which operations change the sound and which don't, and tips for sound quality.
- Every Live release runs through automated tests that cover the program's functions, and Ableton adds tests as it adds features. A release ships only when it passes all of them.
- A neutral operation leaves the audio unchanged. Recorded audio stays identical to what the A/D converter delivered, imported files stay identical to the files on disk, and an export is at least as good as what played back.
- Neutral operations usually happen alongside non-neutral ones. Any neutral step that follows an effect or a gain change still carries that change.
- Export Audio/Video is neutral when the file's sample rate matches the audio hardware rate in Live's Settings and no non-neutral operation was applied.
- Ableton's phase-cancellation tests rendered white noise, sine waves and sine sweeps at 16, 24 and 32 bits:
- Same or higher bit depth than the original: complete cancellation.
- Lower bit depth: the smallest distortion a 32-bit system allows.
- An unstretched file plays back neutrally when its sample rate matches Live's Settings and it is not transposed. This covers audio inside Live only, before it reaches the audio hardware.
- A clip at the Set's tempo plays unstretched. In Beats, Tones, Texture or Re-Pitch Warp modes that playback is neutral; Complex and Complex Pro are not.
- Tempo changes stretch only while they last. Tracks recorded at 120 BPM play back neutrally again once the tempo returns to 120 BPM.
- Arrangement tempo automation in Beats mode with transient preservation can cause artifacts. Preserving 16ths or using Re-Pitch avoids them.
- Grooves move Warp Markers, so a clip with a groove is never neutral, even at its original tempo.
- Live sums signals in 64-bit double precision at every mix point: clip and return track inputs, the Main track and Racks. Mixing at a single point is therefore neutral.
- Internal processing stays 32-bit, so a signal mixed across several summing points can lose a very small amount of quality.
- Recording an external signal is neutral when the bit depth in Live's Settings is equal to or higher than the A/D converter's. Neutral here means identical to what the converter delivered.
- Recording through internal routing is neutral at 32 bits. Use 32 bits for plug-in instruments and effected signals.
- A source that is already at a lower bit depth records neutrally at that depth; recording a 16-bit file at 32 bits adds no quality.
- Freeze writes 32-bit files, so frozen audio is no worse than what played before freezing. Some cases still change the result:
- Frozen Session View clips are two loop cycles long, so longer tails get cut off. Arrangement View freezes keep tails past the clip end.
- Frozen reverb and delay tails stop abruptly when playback stops, because they are rendered audio.
- Frozen Arrangement clips include their automation. Frozen Session clips keep the parameter values found at the Arrangement's 1.1.1 position.
- Frozen clips always play with Warp on in Beats mode.
- Random device parameters, such as Beat Repeat's Chance, stop being random after freezing.
- A bypassed effect is taken out of the signal flow, for Live's devices and for VST and AU plug-ins alike, so its output equals its input.
- Devices with built-in delay, such as Compressor's Lookahead, keep that delay while bypassed so delay compensation stays correct.
- Routing a signal is neutral: the destination receives the same signal the source sends.
- Tapping a signal partway through a chain, such as before a track's effects or from a single Impulse sample slot, gives a different signal than the end of that chain.
- Splitting a neutral clip keeps it neutral. A split changes only the playback position in the sample, and playback across the split has no gap and is sample-accurate.
- Ableton tested unwarped clips and warped-but-unstretched clips, with loop on and off, against unsplit renders.
- A non-neutral operation always changes the signal in some way. Imported files then differ from the files on disk, and exports differ from what played in real time.
- Complex and Complex Pro use a different technology from the other Warp modes. They can sound better on mixed material but are never neutral, even at the original tempo, and they use more CPU.
- Ableton recommends them only when the other Warp modes fall short.
- Playing a file whose sample rate differs from Live's Settings degrades it. Transposition is a form of sample-rate conversion and is also non-neutral.
- Convert sample rates offline before importing rather than mixing rates within one Set.
- Exporting at a different rate from the project's also converts. Live uses the SoX Resampler library for this, which keeps distortion very low.
- Volume automation changes gain, so it is non-neutral. Live updates volume automation for every sample, which keeps distortion very low.
- Dither when rendering to a lower bit depth. Dither is low-level noise, so it is non-neutral.
- Any gain change in Live produces 32-bit audio. Apply dither only once; unless you master in Live, render at 32 bits and skip dither.
- Recording at a bit depth lower than the A/D converter's loses quality. Ableton does not recommend it.
- Internal recordings below 32 bits lose quality. A source already at that lower depth, with no effects, still records neutrally.
- Consolidating Arrangement clips writes new, normalized files with clip volume adjusted to sound the same. Normalizing is a gain change.
- The new files use the sample rate and bit depth from Live's Settings, which can differ from the originals.
- Create Fades on Clip Edges, in the Record, Warp & Launch Settings, adds fades of up to 4 ms at clip edges to prevent clicks. Session clips have a Clip Fade button for the same purpose.
- These fades, and Arrangement clip fades and crossfades, are all non-neutral.
- Live pans with constant power and sinusoidal gain curves: 0 dB at center, +3 dB fully left or right.
- Narrowing stereo width first, with Utility's Width control, reduces the level jump from extreme panning.
- A warped clip at the Set's tempo normally plays neutrally, but once a groove is applied playback is non-neutral at every tempo.
- Practices for the highest audio quality:
- Pick the project's sample rate before starting and keep it.
- Record with good hardware at the highest sample rate and bit depth your interface and computer support.
- Keep all samples at one sample rate; convert others offline first.
- Turn off Warp and Fade for every audio clip in Clip View.
- Leave clip Transpose and Detune alone.
- Render at 32 bits.
- These settings give up stretching and synchronization.
- The fact sheet covers the operations that have caused the most confusion. Its lists of neutral and non-neutral operations are not complete.