MP4 to OPUS Converter

Convert MP4 to Opus Online

Pull the soundtrack out of an MP4 and re-encode it as Opus, the IETF codec standardised in RFC 6716 that scales from 6 kbit/s narrowband speech to 510 kbit/s stereo music. For a lecture, podcast, interview or game capture where you only want the audio, Opus produces the smallest usable file of any format on this site. The video track is discarded; what you download is an .opus file — Opus packets in an Ogg container. Files upload over an encrypted connection, convert on our servers, and are deleted automatically a few hours later.

How to Convert MP4 to Opus

1. Upload Your MP4 File: Drag and drop or click "+ Add Files" to add MP4 or M4V files. Several can be queued and converted with the same settings.
2. Choose a File Compression Mode: Quality Preset opens with no value selected, so either pick one (Highest to Lowest) or switch to Variable Bitrate, Constant Bitrate, Custom Bitrate, or Specific file size for an exact target.
3. Set Audio Channel and Audio Sample Rate: Audio Channel takes Original, Mono, or Stereo — Mono asks the encoder for roughly two-thirds the bitrate of Stereo at the same preset. Leave Audio Sample Rate on Original or pick 48000 HZ, which is Opus's fullband rate.
4. Convert and Download: Use Trim first if you only need one section, then click Convert and download the .opus file. No sign-up, no watermark.

Which Bitrate Setting to Use

The Variable Bitrate dropdown shows ranges, but each range resolves to one target rate that the encoder aims at in VBR mode. Those targets are worth knowing before you choose:

Constant Bitrate offers fixed steps from 8 kbps to 384 kbps, Custom Bitrate takes any number you type, and Specific file size solves backwards from a byte target — useful when a forum or chat platform enforces an attachment cap.

Audio Sample Rate: Why 44,100 Hz Comes Out as 48,000 Hz

Opus does not have a 44.1 kHz mode. RFC 6716 defines exactly five internal rates — 8, 12, 16, 24 and 48 kHz — mapped to five audio bandwidths, and the codec never encodes content above 20 kHz because that is the accepted limit of human hearing. The sample-rate dropdown on this page is shared across every audio target on the site, which is why 44100 HZ appears even though Opus has no such mode. Rather than failing the job, our pipeline validates the requested rate against the codec and snaps it to the nearest rate Opus actually defines before the encoder starts.

Nothing audible is lost by landing on 48 kHz — a 44.1 kHz source already carries no content above 22.05 kHz, and Opus does not code above 20 kHz in any case. Picking 48000 HZ explicitly just makes the outcome predictable.

Frequently Asked Questions

I chose 44100 Hz but the file says 48000 Hz. Did the conversion go wrong?

No. Opus has no 44.1 kHz mode — RFC 6716 defines 8, 12, 16, 24 and 48 kHz only. We traced this through our own pipeline: the requested rate is validated against the codec's rate list and snapped to the nearest supported value before the encoder runs, so 44,100 becomes 48,000 and the job completes normally. The resample is clean and the result is fullband audio. Selecting 48000 HZ yourself avoids the surprise entirely.

What bitrate should I use for speech versus music?

For a single voice, the 24k-40k Variable Bitrate range (about 32 kbps) with Audio Channel set to Mono is usually indistinguishable from the source in normal listening. For music, 96k-128k (about 112 kbps) is the sweet spot where Opus stops sounding compressed on most material; going above 192k-256k rarely pays for itself. Opus was designed to handle both cases in one codec, switching internally between its speech-oriented and music-oriented layers.

Does extracting Opus from an MP4 re-compress the audio?

Yes. MP4 soundtracks are almost always AAC, and Opus is a different codec, so this is a lossy-to-lossy transcode — there is no passthrough anywhere in the pipeline. Choose a bitrate at or slightly above the source track's to keep the second generation inaudible. If the MP4's audio was already thin (a 64 kbps AAC stream, say), no Opus setting will improve it.

Why is the Quality Preset dropdown empty when I open it?

Audio targets on this site do not pre-select a preset value; the mode is selected but the value is left for you to choose. Pick one from Highest to Lowest, or ignore it and use a bitrate mode, which is more predictable anyway. Presets are translated into a bitrate scaled to the codec's supported range and to the channel count you asked for — mono requests roughly 65% of the stereo bitrate at the same preset.

What plays an .opus file?

Opus in Ogg is broadly supported: MDN's container/codec table lists Opus as playable in all browsers inside Ogg, VLC and Foobar2000 handle it natively, and it is built into Android. Older desktop software, some car stereos, and hardware players are the usual holdouts. If something refuses the file, MP4 to MP3 gives you the universally playable fallback, and Opus to MP3 converts a file you have already made.

Can I convert just one part of the MP4?

Yes — use Trim on this page, which takes a Start time and a Duration in plain seconds or HH:MM:SS.sss and cuts before encoding, so you are not paying encode time for footage you discard. The standalone audio trimmer does not accept video files, so if you want to work on the source visually first, cut it with the Video Cutter and convert the clip.

How small will the audio actually be?

The arithmetic is simple because Opus is a rate-targeted codec: at the 96k-128k range (about 112 kbps) one minute of audio is roughly 0.8 MB, and at the 24k-40k range (about 32 kbps) it is roughly 0.24 MB per minute. An hour-long lecture at 32 kbps mono lands near 14 MB regardless of how large the source MP4 was, because the picture is thrown away entirely.

Can Opus keep 5.1 audio from the MP4?

Opus supports multichannel, and the encoder used here accepts up to 8 channels, so a surround soundtrack is not automatically collapsed — leave Audio Channel on Original to keep the source layout. Set it to Stereo explicitly if the tool you are feeding expects two channels, and be aware that a multichannel encode needs a proportionally higher bitrate to sound as good as stereo at the same setting.

How are my uploads handled?

Each file travels over an encrypted connection, is processed on our servers, and is deleted automatically a few hours after conversion — never shared, never made public, and no account is required. The realistic constraint is upload time for a large source video, not the audio encode itself, which is fast. To shrink an audio file you already have, use the Audio Compressor.