Convert MKV to M4A Online
Extract M4A audio from MKV files — movies, anime, series. Free, in your browser.
.mkv · up to 100 MB
What you can do
MKV to M4A: movie and anime soundtracks for Apple Music
DTS and AC-3 to AAC
Multichannel movie and anime audio converted to AAC stereo with intelligent downmix for Apple Music.
Apple TV compatible
The resulting M4A works in the Apple TV app, Apple Music, and any Apple ecosystem player.
100% private
Your MKV file never leaves your device. FFmpeg.wasm processes everything locally in WebAssembly.
Automatic first track
Extracts the audio track marked as default in the MKV — usually the original language.
How it works
Three steps, no hassle
Upload your MKV file
Drag or select your .mkv file — movie, anime episode, TV series, or concert. Up to 500 MB, no signup.
Extraction and conversion to M4A
FFmpeg.wasm analyzes the Matroska container, selects the first audio track, and converts to M4A/AAC optimized for Apple Music, Apple TV, and iPhone.
Download your M4A file
Soundtrack ready for your Apple Music library, Apple TV app, or export as .m4r ringtone.
FAQ
Got questions?
The Matroska container (MKV) is one of the most flexible in the multimedia ecosystem and can contain up to 127 audio tracks simultaneously, unlike MP4 or M4A which in practice limit audio tracks to one or two. In anime MKV files, typical multiple tracks are: track 0 original Japanese (AAC or FLAC), track 1 Latin Spanish (AC-3 or AAC), track 2 English (AC-3 or DTS). In movie MKVs it's common to find: track 0 DTS-HD Master Audio in original language, track 1 Dolby TrueHD, track 2 AC-3 in multiple languages. Convertir.ai automatically selects the first audio track (stream 0:a:0, the one marked as default=1 in the TrackFlagDefault element of the Matroska header).
DTS and AC-3 (Dolby Digital) are multichannel audio codecs (5.1 or 7.1) that are not natively compatible with the M4A container. When FFmpeg detects DTS or AC-3 audio in the MKV, it transcodes: decoding the DTS/AC-3 (including all surround channels) and re-encoding to AAC-LC. The multichannel to stereo downmix applies a mixing algorithm that combines front left/right channels with weighted surround channels (typically Ltotal = L + 0.707*C + 0.707*Ls). The result is a stereo M4A that preserves information from all original channels intelligently mixed. Perceived quality with transcoding to AAC at 192 kbps from DTS-HD is excellent for casual listening.
Completely. The Apple TV app on iPhone, iPad, Apple TV 4K, and Mac accepts M4A/AAC for locally imported audio content. Apple Music imports M4A directly to the library without any additional plugin. For the Apple TV app, adding local content means copying the M4A to the app's media folder (on macOS) or transferring it via iTunes File Sharing. One important limitation: Apple TV 4K plays native multichannel audio from MKV files when in Infuse or VLC, but M4A is always stereo. If you need 5.1 audio for home theater, the correct flow is adding the original MKV to Infuse (iOS/tvOS) which decodes DTS/AC-3 directly.
The most common use cases are: (1) Building an anime soundtrack library in Apple Music — M4A from endings/openings of series like Attack on Titan, Demon Slayer, or Jujutsu Kaisen extracted from MKV can be organized with full metadata in iTunes; (2) Extracting specific dialogues or sound effects to create iPhone ringtones (.m4r) with memorable scenes; (3) Archiving the original soundtrack of independent films or documentaries where you only have the MKV; (4) Creating language learning content by extracting audio from series in the original language for listening practice.
Many high-quality MKV files (Blu-ray rips, anime BD) include FLAC audio (Free Lossless Audio Codec, CodecID A_FLAC in the Matroska identification scheme), which is lossless audio. When transcoding FLAC to AAC-LC for M4A, some quality loss is inherent to lossy encoding, but at 256 kbps AAC-LC (the bitrate Convertir.ai uses by default for high-quality sources), blind listening tests from Hydrogenaudio and the AES community show that AAC-LC is transparent (indistinguishable from original) for most listeners with varied musical material.
Yes. The Matroska container is extremely flexible and can encapsulate AAC with CodecID A_AAC, as well as ALAC with CodecID A_ALAC. MKV files with AAC audio allow direct stream copy to the M4A container without transcoding, exactly like with MP4. MKVs with ALAC (relatively rare, more common in files remuxed from original M4As) require ALAC to AAC transcoding if the target is M4A with AAC encoding.
Convert MKV to M4A: extract movie and anime soundtracks for Apple Music and Apple TV
Converting MKV to M4A is the fundamental operation for those who want to bring soundtracks from their movies, TV series, and anime in Matroska format to the Apple audio ecosystem. The Matroska container (extension .mkv, specification based on EBML — Extensible Binary Meta Language) was created in 2002 as an open, patent-free alternative to proprietary AVI and MP4 containers, with multi-track, chapter, subtitle, and metadata capabilities that no other container of the era matched. In 2025, MKV is the standard format for high-quality content distribution in digital archiving communities: Blu-ray rips of theatrical films, anime in BD (Blu-ray Disc) quality, documentaries and concerts in 4K resolution. The Matroska format can encapsulate virtually any known audio codec: AAC (A_AAC), FLAC (A_FLAC), AC-3/Dolby Digital (A_AC3), DTS and DTS-HD Master Audio (A_DTS), TrueHD (A_TRUEHD), MP3 (A_MPEG/L3), Opus (A_OPUS), and Vorbis (A_VORBIS), making it extremely versatile but also complex to handle in the Apple ecosystem, which only natively plays AAC and ALAC. The M4A conversion resolves this incompatibility by generating an audio file in Apple's native format that works perfectly in Apple Music, Apple TV app, iTunes, AirPods, HomePod, and all devices with iOS, iPadOS, macOS, and tvOS.
The highest practical-value use case in 2025 is building anime and movie soundtrack libraries in Apple Music. Japanese anime in MKV format from distributors typically includes audio tracks in AAC-LC (for recent season episodes) or FLAC (for high-quality BD remuxed files). Extracting M4A audio from endings and openings of popular series like Attack on Titan, Demon Slayer, Jujutsu Kaisen, Chainsaw Man, or One Piece allows organizing an anime music collection with complete metadata in Apple Music: artist (LiSA, YOASOBI, Ado, King Gnu, Official HiGE DANdism), album, single cover art, and release year. Anime fans who use iPhone and AirPods to listen to music can have their favorite openings in high quality directly in the Music app without relying on streaming services that frequently don't have these songs or have them with regional restrictions. For theatrical films in MKV with DTS-HD or TrueHD audio, conversion to AAC at 256 kbps for M4A produces a casual listening version of the soundtrack that is transparent for most listeners according to Hydrogenaudio benchmarks.
Convertir.ai runs MKV to M4A conversion entirely in the browser using FFmpeg.wasm with full support for the Matroska ecosystem audio codecs. The technical process begins with parsing the EBML header to confirm DocType 'matroska' and schema version, followed by reading the Segment element with its SeekHead to efficiently locate Tracks, Info, and Cues elements without linear file scanning. The Tracks element contains one or more TrackEntry elements, each with TrackType=2 (audio) for audio tracks. FFmpeg identifies the track with TrackFlagDefault=1 (marked as default track in MKV metadata, typically the original language audio in anime) or in its absence the first audio track by TrackNumber order. The CodecID stored in TrackEntry determines the processing pipeline: A_AAC with configuration in CodecPrivate allows direct stream copy to M4A container; A_FLAC requires decoding with libflac and subsequent encoding with libfdk_aac or native AAC encoder; A_AC3 and A_DTS require decoding with libdca/liba52 and AAC encoding with multichannel to stereo downmix using the standard ITU-R BS.775 downmix matrix; A_OPUS requires decoding with libopus. The resulting M4A file includes duration, sample rate, and channel metadata from the original MKV transferred to the MPEG-4 container's mvhd atom, and complete WebAssembly processing guarantees that the MKV file content — whether a private movie collection or an anime archive — remains completely on the user's device without any transmission to external servers.