Convert OPUS to M4A Online
Convert Opus voice messages to M4A for iPhone, iTunes, and Apple Podcasts.
.opus · up to 100 MB
What it's for
Discord and Telegram voice ready for Apple Podcasts
Native Apple Podcasts
M4A is the preferred format of Apple Podcasts Connect. Upload episodes directly without additional conversion.
GarageBand and Logic Pro
Import converted voice messages directly into GarageBand, Logic Pro X, or Final Cut Pro without friction.
Artwork and chapters
The M4A container supports embedded album artwork (covr atom) and ChapterTrack chapters, unlike raw .aac streams.
100% private
Your voice messages are not uploaded to any server. Complete local processing with FFmpeg.wasm.
How it works
Three steps, no hassle
Upload your Opus file
Drag or select your .opus file from Discord, Telegram, or WhatsApp. Up to 200 MB.
Conversion to AAC in M4A
FFmpeg.wasm transcodes Opus audio to AAC-LC inside an M4A container in your browser.
Download your M4A
File ready for iTunes, iPhone, Apple Podcasts, GarageBand, and Final Cut Pro.
FAQ
Got questions?
AAC is the audio codec (Advanced Audio Coding), while M4A is the container: an MPEG-4 Part 14 file (ISO/IEC 14496-14) that holds AAC audio. The relationship is similar to that of MP3 and the .mp3 file: the codec is MP3, and the container shares the same name. Apple adopted the .m4a extension to distinguish audio-only files from video MP4 files (.mp4 or .m4v). All Apple products read M4A natively: iTunes since version 4 (2003), iPhone since its 2007 launch, and Final Cut Pro, GarageBand, and Logic Pro since their respective versions.
Apple Podcasts and Apple production tools (GarageBand, Logic Pro) prefer the M4A container because it supports chapters (ChapterTrack atoms), embedded album artwork (covr atom), and complete iTunes metadata (©nam, ©ART, ©alb, aART, cpil, tmpo, etc.) that the raw .aac stream format does not support as robustly. A podcast with episode artwork, chapters, and ID3-equivalent metadata requires M4A. Apple's podcasting technical specification explicitly recommends AAC in M4A.
Yes, it is a lossy-to-lossy transcode: Opus is decoded to PCM and re-encoded to AAC-LC in the M4A container. Quality lost in the original Opus is not restored. For voice messages (Discord, Telegram, WhatsApp at 32–64 kbps), the impact is minimal and generally imperceptible. For music, use 256 kbps AAC. This process is honest: no quality miracles are promised, but additional degradation is minimized using FFmpeg's high-quality AAC-LC encoder.
Yes. Apple Podcasts Connect accepts M4A with AAC as an episode format. Apple's 2024 technical requirements for podcasts specify: AAC or MP3, mono or stereo, 44.1 kHz or 48 kHz, minimum 128 kbps for acceptable quality audio. The resulting M4A from this tool meets all those requirements if you select 128 kbps or higher.
Yes. Android has supported AAC decoding in M4A since version 1.0 (2008). Google Play Music (discontinued), YouTube Music, Spotify, and all modern Android players read M4A without issues. The M4A format is an ISO standard, not an Apple-exclusive creation, though Apple popularized it.
Opus files can include album artwork as METADATA_BLOCK_PICTURE metadata (the same system as FLAC). FFmpeg transfers it to the covr atom of the M4A container, which is the field iTunes, the iOS Music app, and Apple Podcasts use to display the album or episode image. If the original Opus has no artwork, the M4A will not have it either.
Convert Opus to M4A: voice messages for iPhone, iTunes, and Apple Podcasts
M4A is Apple's audio container based on the MPEG-4 Part 14 standard (ISO/IEC 14496-14, published in 2003). The .m4a extension was introduced by Apple with iTunes 4 in April 2003 to distinguish audio-only files from the .mp4 video format. Internally, an M4A file contains audio encoded in AAC (Advanced Audio Coding, standardized in ISO 13818-7 in 1997 and extended in ISO 14496-3), the same codec Apple uses in Apple Music (distributed at 256 kbps AAC-LC), the iTunes Store, FaceTime, and AirPods over Bluetooth A2DP. The MPEG-4 container of M4A supports features that the raw .aac stream format cannot express as robustly: iTunes metadata atoms (©nam, ©ART, ©alb, ©day, trkn, aART, cpil, tmpo), album artwork in the covr atom, chapters in the ChapterTrack atom, and timestamps. These capabilities make M4A the preferred format for podcasts in the Apple ecosystem. The Apple Podcasts technical specification published by Apple Developer Documentation explicitly recommends AAC in M4A for episode distribution. Opus, standardized in RFC 6716 of September 2012, is the native codec of Discord, Telegram, WhatsApp Web, and the entire WebRTC stack. Its superior efficiency at 32–64 kbps makes it ideal for voice communication, but its adoption in Apple production tools remains inconsistent, making conversion to M4A necessary for podcast workflows and content production.
Converting Opus to M4A involves transcoding the Opus audio (lossy codec) to AAC-LC (also lossy) inside the MPEG-4 container. This introduces a second generation of compression loss that cannot be avoided mathematically. The magnitude of the audible impact depends on the bitrates at both ends of the chain: Discord voice messages at 32 kbps Opus transcoded to AAC-LC at 128 kbps have minimal perceptible degradation because AAC-LC is very efficient for voice and 128 kbps greatly exceeds the original bitrate; musical recordings at 160 kbps Opus transcoded to 256 kbps AAC will have additional but moderate artifacts in the high frequencies. Apple Podcasts Connect's 2024 technical requirements specify AAC or MP3 as accepted formats, stereo or mono, 44.1 kHz or 48 kHz sample rate, with a recommended minimum of 128 kbps for acceptable quality audio and 192 kbps for professional-quality production. The M4A produced by this tool meets all those requirements with the appropriate bitrate selection. The iTunes metadata contained in the M4A (title, artist, album, track number, album artwork if the original Opus included it) is correctly read by the iOS Music app, iTunes for Windows, Apple TV, HomePod, and AirPods in the Now Playing app context. GarageBand on iOS and macOS imports M4A directly as an audio track without requiring additional conversion, facilitating the use of messaging voice recordings as base material for podcast or music projects.
Convertir.ai performs the Opus to M4A conversion entirely in the browser with FFmpeg.wasm. The process decodes the Opus with libopus to 48 kHz PCM (native sample rate of Opus per RFC 6716 of September 2012), applies if necessary a resample to 44.1 kHz using FFmpeg's Kaiser-windowed sinc filter, and encodes to AAC-LC with FFmpeg's AAC implementation at the user-selected bitrate. The output container is MPEG-4 Part 14 with .m4a extension, Apple's standard format for AAC audio. Vorbis Comment metadata from the original Opus file are converted to MP4/iTunes atoms (©nam for title, ©ART for artist, ©alb for album, ©day for year, trkn for track number, ©gen for genre) for full compatibility with iTunes and the iOS Music app. If the original Opus includes album artwork as METADATA_BLOCK_PICTURE, it is transferred to the covr atom of the M4A so it is visible in iTunes, Apple Podcasts, and compatible players. Processing occurs entirely locally in the user's browser: no audio file is transmitted to external servers at any point. There is no per-session file limit, no watermark, no signup required, and the service is completely free.