---
title: "Audio import settings and memory"
slug: /workflows/audio-import-memory/
markdown: /workflows/audio-import-memory.md
section: audio
tier: 2
summary: "Load type, compression format and per-platform overrides, then gains read from the imported clip."
sources: ['https://docs.unity3d.com/6000.0/Documentation/Manual/class-AudioClip.html', 'https://docs.unity3d.com/6000.0/Documentation/ScriptReference/AudioClip.GetData.html']
canonical: https://unityworkflowlibrary.dev/workflows/audio-import-memory/
read_first: /read-first.md
---

> Read first, on every prompt: [non-destructive rules](/read-first.md).

# Audio import settings and memory

> Load type, compression format and per-platform overrides, then gains read from the imported clip.

## What the import settings do

From the [Audio Clip Import Settings reference](https://docs.unity3d.com/6000.0/Documentation/Manual/class-AudioClip.html):

| Setting | Documented behaviour |
|---|---|
| Decompress On Load | Decompresses when loaded. Vorbis decompressed on load uses about ten times the memory of keeping it compressed (ADPCM about 3.5 times), so not for large files |
| Compressed In Memory | Stays compressed and decompresses while playing, on the mixer thread (DSP CPU in the Profiler's Audio module) |
| Streaming | Decodes from disk with a minimal buffer, on a streaming thread; each streaming clip has about 200 KB overhead even with no audio loaded |
| PCM | Uncompressed; for short effects; lightest on CPU |
| ADPCM | 3.5 times smaller than PCM, much lower CPU than MP3/Vorbis; for noisy, frequent sounds such as footsteps, impacts and weapons |
| Vorbis/MP3 | Smaller files at lower quality; for medium-length effects and music; Quality slider sets compression |
| Force To Mono | Down-mixes to one channel, then peak-normalizes the result |
| Preload Audio Data | When off, playing the clip loads it on demand, which can delay larger files; call `AudioClip.LoadAudioData` first |
| Load In Background | Loads asynchronously; play requests wait until the clip is loaded; query `AudioClip.loadState` |

- **Overrides are per platform.** Load Type, Compression Format, Sample Rate Setting and Quality are set per platform
  tab, so Android and desktop can differ.
- **Tuning quality.** The reference's method: start high, lower Quality until the loss is audible, then raise it
  slightly until it is not.

## AUDIO-IMPORT-PER-PLATFORM

- World SFX: Force To Mono; Vorbis quality 0.7 or more on desktop (pack clips imported at quality 0.0 are audibly
  degraded); Android override Vorbis 0.5 at 22,050 Hz; Decompress On Load under about 1.5 s, Compressed In Memory
  above. UI clicks stay stereo, ADPCM on Android for clicks under 0.25 s.
- Retire long clips nothing needs (a 6.8 s, 5 MB mp3 on a weapon row) rather than compressing them harder.

## SET-GAIN-FROM-THE-IMPORTED-CLIP

- Import settings change level: Force To Mono raised measured stereo loudness by up to about 4 dB (see
  FORCE-TO-MONO-GATES-NORMALIZE). Change imports first, then read loudness from the imported clip and set each row's
  gain against a per-topic target in dBFS. Frequent small sounds sit lowest (shots about -27, impacts -24), rare
  moments highest (-15 to -20). Row loudness went from an unplanned -19.8 to -5.8 spread to an authored -27 to -15.
- A source clip sitting 5 dB or more under its target is swapped, not gained: gain cannot fix a quiet click without
  raising its noise.

## AUDIO-IMPORT-COMPARES-FIELDS-NOT-EQUALS

- `AudioImporterSampleSettings.Equals` never matched a freshly read copy, so an authoring step that "reimports only when
  the settings changed" reimported on every run. Each reimport unloads the clip, and the next sample read failed with
  "Cannot read clip".
- Compare loadType, compressionFormat, quality and sampleRateSetting field by field, and write only on a real difference.
- Before reading samples, call `AudioClip.LoadAudioData` in a separate step and wait until `loadState` is Loaded.
  The load is asynchronous, so a read in the same call can still find the clip empty.

## GETDATA-NEEDS-A-DECOMPRESSED-CLIP

- `AudioClip.GetData` fails on clips imported as CompressedInMemory or Streaming. Those are the load types this spoke
  recommends for clips longer than about 1.5 s, so a loudness census that reads every clip through `GetData` breaks on
  exactly the long clips.
- For those clips, measure loudness from the source audio file (decode the WAV and take the loudest 100 ms RMS), then
  add the import's own level change: Force To Mono can raise a stereo clip up to ~4 dB (SET-GAIN-FROM-THE-IMPORTED-CLIP).
  Alternatively, measure a temporary DecompressOnLoad import and restore the original settings. Record in the census
  which method measured each clip.

- The [GetData reference](https://docs.unity3d.com/6000.0/Documentation/ScriptReference/AudioClip.GetData.html) confirms it: compressed clips return samples only
  with Load Type Decompress On Load, streamed clips never do, and a failed read fills zeroes, logs an error and returns
  false.

## Related

- [Audio topic](/topics/audio/): every audio page in reading order.
- Next: [Mixers, snapshots and ducking](/workflows/audio-mixing/).