All about QTA files

QTA (QuickTime Audio) is a proprietary file format that Apple introduced at the end of 2024 with iOS 18.2 for the iPhone 16 Pro and iPhone 16 Pro Max. It is used for voice recordings and marks a change from the M4A format used previously.

The admittedly very technical background:

QTA is based on First Order Ambisonics (FOA), a method for recording three-dimensional (i.e. spatial) sound fields. The four microphones on the iPhone 16 Pro/Max capture a spatial sound field that is stored in four channels. A so-called omnidirectional channel (i.e. in all directions), a channel from front to back, a channel from left to right, and a channel for top and bottom.
The audio data itself is stored in the Apple Positional Audio Codec (APAC), a new, proprietary codec developed by Apple for spatial audio. In addition to FOA, APAC also supports HOA (Higher Order Ambisonics) for even greater spatial accuracy. APAC was originally designed for Apple Immersive Video on the Vision Pro.

Structure of a QTA file

A complete QTA file contains:

• A stereo AAC track as a fallback for older devices
• a spatial audio track in APAC format (4 channels FOA)
• at least one metadata track with playback information

Where is QTA used?

QTA was developed for professional and creative applications. Layered recordings can be used, for example, to add one or more audio tracks with instruments to vocal recordings afterwards. Background noise can also be removed more effectively from "normal" voice memos, e.g. with Logic Pro. The playback options are also broader on supported devices: for example, the speaker's voice can be emphasised and ambient noise reduced, or vice versa.

Example ffprobe of a .qta file from the iPhone

The following ffprobe of a QTA file I created clearly shows how the data is stored. The first stream (#0:0) contains the AAC stereo audio track relevant for our conversion at 167kb/s. The other tracks are the spatial APAC data (stream #0:1) and streams #0:2 and #0:3 for the metadata.

Input #0, MOV,mp4,m4a,3gp,3g2,mj2, from 'test-qta.qta':
  Metadata:
    major_brand     : QT
    minor_version   : 0
    compatible_brands: qt
    creation_time   : 2026-02-01T10:13:39.000000Z
    encoder         : com.apple.VoiceMemos (iPhone Version 26.2.1 (Build 23C71))
  Duration: 00:52:03.42, start: 0.000000, bitrate: 564 kb/s
  Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 167 kb/s (default)
    Metadata:
      creation_time   : 2026-02-01T10:13:39.000000Z
      handler_name    : Core Media Audio
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Audio: none (apac / 0x63617061), 48000 Hz, 4 channels, 388 kb/s
    Metadata:
      creation_time   : 2026-02-01T10:13:39.000000Z
      handler_name    : Core Media Audio
      vendor_id       : [0][0][0][0]
  Stream #0:2[0x3](und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
    Metadata:
      creation_time   : 2026-02-01T10:13:39.000000Z
      handler_name    : Core Media Metadata
  Stream #0:3[0x4](und): Data: none (mebx / 0x7862656D) (default)
    Metadata:
      creation_time   : 2026-02-01T10:13:39.000000Z
      handler_name    : Core Media Metadata

Sources

Apple Developer: "Enhance your app's audio recording capabilities" – WWDC25
https://developer.apple.com/videos/play/wwdc2025/251/
Apple Support: "Apply Spatial Playback processing to QTA files in Logic Pro for iPad"
https://support.apple.com/guide/logicpro-ipad/apply-spatial-playback-processing-qta-files-lpip0da1ccfc/ipados
Apple Developer: "Apple Positional Audio Codec" (PDF)
https://developer.apple.com/av-foundation/Apple-Positional-Audio-Codec.pdf