Opus is common in modern MKV files
Opus is a newer open codec, and many recent MKV files use it, especially video saved from web platforms and files encoded with modern free tools. If your MKV already has an Opus track, converting MKV to OPUS with Original audio copies it out unchanged. No quality is lost, and even a long file is done in moments. Other tracks are decoded and encoded to Opus. Opus always runs at 48 kHz, so other sample rates are converted automatically, without audible change.
Small files for listening
Opus is the most efficient general audio codec in wide use. That makes it ideal for turning a video collection into something you can carry on a phone:
| Content | Bitrate | Size per hour |
|---|---|---|
| Lectures, talks, audiobooks | 32 kbps | about 14 MB |
| Series and film dialogue | 64 kbps | about 29 MB |
| Music and concerts | 128 kbps | about 58 MB |
A season of a talk show, a course of recorded lectures or a set of concert films becomes a small audio collection that fits easily on any phone.
Surround sources
Film MKVs often have 5.1 Dolby or DTS sound. The input list shows the number of channels. For film sound on headphones or a phone speaker, 96 to 128 kbps sounds clear and full. Dialogue-heavy content works well at lower rates.
Compatibility
Opus plays in Chrome, Firefox and Edge, on Android, in VLC, foobar2000, Kodi and most modern players, and recent Apple systems support it in some apps. Older iPhones and many car stereos do not. For those, choose MKV to M4A, which can also copy AAC tracks without loss, or MKV to MP3 for maximum compatibility. If the MKV has Vorbis sound instead, MKV to OGG can copy it.
Practical tips
For a talk inside a longer recording, use Trim & tags to set the start and end, and give the file a clear title. If the MKV has several languages, play a moment first to check you hear the right one. The tool says so clearly when a file has no sound track. All work happens on your device, and nothing is uploaded.