Extract Audio from MKV to OGA — Free Online Tool
Extract audio from MKV video files and save it as OGA using the Vorbis codec — an open, patent-free audio format ideal for archiving or distributing audio from Matroska containers. The tool runs entirely in your browser via FFmpeg.wasm, so your files never leave your device.
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FFmpeg Command
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Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
This conversion strips the video stream entirely from the MKV container and re-encodes the audio into Vorbis format inside an Ogg-based OGA container. Because MKV files most commonly carry AAC or MP3 audio by default — neither of which is natively stored in OGA — the audio must be transcoded to Vorbis using the libvorbis encoder. Quality is controlled via Vorbis's variable bitrate quality scale (-q:a), where the default value of 4 targets roughly 128–160 kbps. If the source MKV already contains a Vorbis or Opus audio track, this still re-encodes to Vorbis to conform to the OGA output format. Chapter metadata from the MKV is preserved in the output OGA file, but subtitles and additional audio tracks are dropped since OGA only supports a single audio stream.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In this browser-based tool, FFmpeg runs as a WebAssembly binary (FFmpeg.wasm) entirely inside your browser — no server is involved. The same command can be run locally if you have FFmpeg installed on your desktop. |
-i input.mkv
|
Specifies the input Matroska file. FFmpeg reads all streams present in the MKV — video, audio, subtitles, chapters — but subsequent flags determine which are actually processed and included in the output. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the video stream from the MKV. This is what makes the conversion an audio extraction — no video data is written to the OGA output file, keeping the output small and purely audio. |
-c:a libvorbis
|
Encodes the audio using the libvorbis encoder, producing an Ogg Vorbis audio stream. Vorbis is the default and most compatible codec for OGA files, and because MKV source audio is typically AAC or MP3, a full transcode is required here rather than a simple stream copy. |
-q:a 4
|
Sets the Vorbis variable bitrate quality to level 4 on a 0–10 scale, targeting approximately 128–160 kbps. This is the default quality setting and provides a good balance between file size and perceptual audio quality for most speech and music content. |
output.oga
|
Defines the output filename and, by its .oga extension, instructs FFmpeg to write the encoded Vorbis audio stream into an Ogg container formatted as an audio-only OGA file. |
Common Use Cases
- Extract the audio commentary track from an MKV film rip to listen to offline in a media player that supports Ogg Vorbis
- Convert an MKV lecture recording into a lightweight OGA audio file for distribution on open-source or libre media platforms that require patent-free formats
- Strip the audio from an MKV screen recording of a software tutorial to repurpose as a podcast or audio walkthrough
- Extract Vorbis-compatible audio from an MKV for use in a game engine or open-source multimedia project that specifically requires OGA/Ogg Vorbis assets
- Archive the audio portion of MKV concert recordings in a lossless-capable open container (OGA with FLAC) without keeping the large video stream
- Prepare audio extracted from MKV files for use in libre/open-source video editors that prefer Ogg-based audio formats
Frequently Asked Questions
Yes, there will be a generation of quality loss because AAC audio must be decoded and then re-encoded into Vorbis. This is a transcode between two lossy formats, so some audio quality is degraded in the process. To minimize the loss, use a higher -q:a value (such as 7 or 8) when running the conversion. If the source MKV contains lossless FLAC audio, you can avoid generational loss by re-encoding to FLAC inside the OGA container instead.
Both OGG and OGA use the same underlying Ogg container format. The distinction is purely by convention: .ogg was the original catch-all extension, while .oga was introduced to specifically indicate an audio-only Ogg file (as opposed to .ogv for video or .ogx for general data). Most media players treat them identically. OGA is the more semantically precise choice when the file contains only an audio stream, which is exactly the case here.
Yes, the Ogg container format supports chapter metadata, and FFmpeg will carry over chapter information from the MKV into the OGA output. This means chapter navigation can still work in compatible players like VLC or foobar2000. However, MKV subtitle tracks and any secondary audio tracks present in the source file are dropped, since OGA supports only a single audio stream and no subtitle data.
Adjust the -q:a value in the command to control Vorbis quality. The scale runs from 0 (lowest, roughly 64 kbps) to 10 (highest, roughly 500 kbps), with 4 as the default targeting around 128–160 kbps. For example, replacing '-q:a 4' with '-q:a 6' targets approximately 192–256 kbps and is suitable for critical listening. Unlike fixed-bitrate encoding, Vorbis -q:a uses variable bitrate, so the actual file size will vary depending on the audio content.
Yes, but you need to modify the FFmpeg command to select the desired track using the -map flag. For example, to select the second audio track, add '-map 0:a:1' before the output filename: 'ffmpeg -i input.mkv -map 0:a:1 -vn -c:a libvorbis -q:a 4 output.oga'. Without specifying -map, FFmpeg defaults to the first audio track it finds. This is particularly useful for MKV files containing multiple language tracks or a director's commentary alongside the main audio.
Yes. Replace '-c:a libvorbis -q:a 4' with '-c:a flac' in the command: 'ffmpeg -i input.mkv -vn -c:a flac output.oga'. FLAC is lossless, so the output will be a bit-perfect copy of whatever the decoded source audio contains. Note that FLAC files are significantly larger than Vorbis-encoded files, and if the source MKV audio was already lossy (e.g., AAC or MP3), encoding to FLAC preserves that lossy signal losslessly — it does not restore any quality lost upstream.
Technical Notes
The OGA format is an audio-only profile of the Ogg container and natively supports three codecs: Vorbis (lossy), FLAC (lossless), and Opus (lossy, modern). This tool defaults to libvorbis because Vorbis is the historical default codec associated with the OGA/OGG format and enjoys the broadest compatibility among media players. The Vorbis -q:a quality scale is logarithmic and maps to variable bitrate targets: q:a 0 ≈ 64 kbps, q:a 4 ≈ 128–160 kbps, q:a 6 ≈ 192 kbps, q:a 10 ≈ 500 kbps. One notable limitation of OGA is that it supports only a single audio stream per file — any secondary audio tracks in a multi-track MKV will be silently discarded unless you explicitly remap them. Metadata tags (artist, title, album) from the MKV are passed through to the Ogg/Vorbis comment header where field names match. Chapter data is preserved via Ogg's native chapter support. OGA files are not supported by Apple devices or browsers natively, so if cross-platform compatibility is a concern, OGG (with the same settings) or Opus inside OGG may be better choices. Files larger than 1GB should be processed using the displayed FFmpeg command locally on your desktop.