Audio Support
Codecs, passthrough, channels and music: what altc plays on each device.
Every codec below decodes on the device. Dolby AC-3 and E-AC-3 can instead be passed through as a bitstream to a receiver or soundbar that decodes them itself.
Codecs
| Codec | Apple | Android | Meta Quest | Notes |
|---|---|---|---|---|
| AAC | ✓ | ✓ | ✓ | |
| MP3 · MP2 | ✓ | ✓ | ✓ | |
| AC-3 (Dolby Digital) | ✓ | ✓ | ✓ | Decoded, or passed through. |
| Decoded, or passed through. | ||||
| E-AC-3 (Dolby Digital Plus) | ✓ | ✓ | ✓ | Decoded, or passed through. |
| Decoded, or passed through. | ||||
| Dolby Atmos (E-AC-3 JOC) | ✕ | ✕ | ✕ | Plays as 5.1 E-AC-3. Atmos coming soon. |
| Plays as 5.1 E-AC-3. Atmos coming soon. | ||||
| TrueHD · MLP | ✓ | ✓ | ✓ | Decoded to lossless PCM. Atmos metadata is not applied. |
| Decoded to lossless PCM. Atmos metadata is not applied. | ||||
| DTS | ✓ | ✓ | ✓ | Decoded to PCM. |
| Decoded to PCM. | ||||
| DTS-HD MA · DTS-HD HRA | ✓ | ✓ | ✓ | Decoded to lossless PCM. DTS:X metadata is not applied. |
| Decoded to lossless PCM. DTS:X metadata is not applied. | ||||
| FLAC | ✓ | ✓ | ✓ | |
| ALAC | ✓ | ✓ | ✓ | |
| Opus | ✓ | ✓ | ✓ | |
| PCM · LPCM | ✓ | ✓ | ✓ | 16-, 24- and 32-bit, float, and Blu-ray LPCM. |
| 16-, 24- and 32-bit, float, and Blu-ray LPCM. | ||||
| Vorbis | ✓ | ✓ | ✓ | |
| WMA | ✕ | ✕ | ✕ | |
| APAC (Apple Positional Audio) | ✕ | ✕ | ✕ | Track is skipped. |
| Track is skipped. | ||||
Passthrough
Passthrough sends the encoded stream to the output untouched, so the receiver does the decoding. It is used automatically when the current output supports it.
- Apple: when the active output reports spatial audio, such as AirPods and other spatial-capable headphones. Vision Pro always.
- Android: detected from the audio path: direct-playback support and the external surround setting.
| Codec | Apple | Android | Meta Quest | Notes |
|---|---|---|---|---|
| AC-3 | ✓ | ✓ | ✓ | |
| E-AC-3 | ✓ | ✓ | ✓ | |
| E-AC-3 JOC (Atmos) | ✕ | ✕ | ✕ | Coming soon. The 5.1 bed passes through as E-AC-3. |
| Coming soon. The 5.1 bed passes through as E-AC-3. | ||||
| TrueHD | ✕ | ✕ | ✕ | Decoded to lossless PCM, never passed through. |
| Decoded to lossless PCM, never passed through. | ||||
| DTS · DTS-HD | ✕ | ✕ | ✕ | Decoded to PCM, never passed through. |
| Decoded to PCM, never passed through. | ||||
Channels
Decoded audio keeps the source layout up to 7.1, or 7.1.4 on Android 12L and later. The output channel count follows the connected output.
Music
FLAC, ALAC, AAC and M4A, MP3, Opus, Ogg Vorbis and WAV play natively. Gapless playback, crossfade, loudness normalisation (ReplayGain and LUFS), an equaliser, a waveform seek bar and the MilkDrop visualiser are built in. Multichannel music keeps its source channel count.