MTS to OPUS Converter

Extract Opus Audio From AVCHD Camcorder Footage

An .mts file is what a Sony or Panasonic AVCHD camcorder writes to its memory card: MPEG-4 AVC/H.264 video with a Dolby Digital (AC-3) or linear PCM soundtrack alongside it. This page discards the picture and re-encodes only that soundtrack to Opus, the IETF codec defined in RFC 6716 that WebRTC, Discord and most modern voice apps rely on.

This tutorial is for anyone lifting an interview, a recital, a lecture or wildlife ambience off camcorder footage. Two things trip people up on AVCHD specifically — which audio track gets used when the camera recorded more than one, and why asking for 44.1 kHz does not give you 44.1 kHz. Both are covered below.

How to Convert MTS to Opus

1. Upload Your MTS File: Drag the .mts clip onto the page or click "Add Files" to browse. Several clips can queue together and they share one set of settings.
2. Choose a Quality Preset or an Exact Bitrate: Under File Compression, Quality Preset is the active mode when the panel opens — but the preset list itself opens with nothing chosen, so pick one. Or switch the mode to Constant Bitrate, Variable Bitrate, Custom Bitrate or Specific file size and name the number yourself.
3. Set Audio Channel, Audio Sample Rate and Trim: Audio Channel offers Original, Mono and Stereo. Audio Sample Rate offers Original plus 8000, 12000, 16000, 24000, 44100 and 48000 Hz. Trim takes a Start time and a Duration, in Seconds or HH:MM:SS.sss.
4. Convert and Download: Click Convert and save the .opus file. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours — no sign-up, no watermark.

Walk-through: The Three Settings That Actually Matter

Bitrate. Opus reaches transparency far lower than MP3 does, so the MP3 habit of reaching for 320 kbps wastes bytes here. RFC 6716 puts the codec's operating range at 6 to 510 kbit/s and names 64–128 kbit/s as the sweet spot for fullband stereo music. Custom Bitrate accepts anything inside the encoder's 8–512 kbps range, the Constant Bitrate dropdown runs from 8 up to 384 kbps, and the Quality Preset levels are scaled across that same range, adjusted for the channel count and sample rate you picked.

Channels. Audio Channel set to Original keeps whatever the camcorder recorded. That matters more than usual on AVCHD, because 5.1-capable handycams write a six-channel AC-3 track, and Original will carry all six into the Opus file. Choose Mono for a single-mic interview — it roughly halves the data rate at the same perceived quality — or Stereo to force a downmix of a surround track.

Sample rate. This is the AVCHD-specific gotcha. 44100 Hz appears in the dropdown because that list is shared across every audio codec we support, but Opus has no 44.1 kHz mode: RFC 6716 defines exactly five rates — 8, 12, 16, 24 and 48 kHz. Rather than failing the job, our validation layer snaps your request to the nearest legal rate before ffmpeg ever sees it, so 44100 silently becomes 48000. That is worth knowing because running the same request through raw ffmpeg on your own machine would error out.

Opus Bitrate Guide for Camcorder Audio

What Happens to Each Kind of AVCHD Audio Track

Common Errors and How to Fix Them

• "The wrong audio track came out" — we do not emit a track selector, so ffmpeg's default stream selection applies: it takes the audio stream with the most channels, and the lowest stream index breaks a tie. On a camcorder that recorded both a 5.1 mix and a stereo mix, the 5.1 track wins. There is no way to force the stereo track from this page.
• "I asked for 44.1 kHz and got 48 kHz" — expected, not a fault. See the walk-through above; Opus has no 44.1 kHz mode.
• "The output is far quieter or thinner than the camera playback" — an AC-3 track carries dialogue-normalisation metadata that does not travel into an Opus file. Nothing is being applied on our side; the reference level simply stops travelling with the audio.
• "My .mts file is rejected" — check the extension. This page accepts .mts only. If your import software already renamed the clip to .m2ts — Sony's does — the byte-identical stream will be refused here. Use the video to Opus extractor, which accepts both spellings.
• "Upload takes forever for a two-minute clip" — AVCHD records up to 24 Mbps (up to 28 Mbps in the stereoscopic modes), so the video you are about to throw away dominates the upload. Trim the source first with the video cutter, then extract audio from the short clip.

When This Doesn't Work

Opus is an audio codec, so there is no path here that keeps the picture — if you wanted both, MTS to MP4 is the conversion you actually want. Opus also has real playback gaps: it is native in Chrome, Firefox and Edge, on Android, in VLC and Discord, and in Safari on recent Apple systems, but older car head units, legacy portable players and pre-Windows 10 systems generally need a decoder installed. When the file has to open anywhere without discussion, MTS to MP3 is the safer target. And a truncated clip copied out of a camcorder's BDMV folder mid-write may decode a few seconds and stop; re-copy the original file from the card before blaming the settings.

Frequently Asked Questions

Which audio track does this pick when my camcorder recorded 5.1 and stereo?

The one with the most channels — so the 5.1 track. We do not send a stream-selection flag to ffmpeg, which means ffmpeg's own default applies: for audio it scores streams by channel count and picks the highest, using the lowest stream index to break ties. If you specifically need the stereo mix, extract it in a desktop tool that lets you name the stream index.

Why does Opus refuse to give me a 44.1 kHz file?

Because the format has no such mode. RFC 6716 defines Opus at 8, 12, 16, 24 and 48 kHz only, corresponding to narrowband through fullband. 44100 Hz still appears in the dropdown because that list is shared across every audio codec on the site. Our validation layer catches the mismatch and snaps to the nearest supported rate, which is 48000 Hz — you get a working file rather than an error.

Does the AC-3 to Opus step hurt quality much?

It adds one generation of lossy-to-lossy loss, which is real but usually inaudible if you do not starve the bitrate. AVCHD records Dolby Digital between 64 and 640 kbps; re-encoding a 256 kbps AC-3 stereo track to 96–128 kbps Opus is generally transparent for speech and close to it for music. Where it bites is repeated round-trips — extract once at a generous bitrate and edit from that file rather than re-converting the same audio several times.

Is Opus actually smaller than MP3 for the same camcorder audio?

Yes, meaningfully so at the low and middle of the range. Opus was designed to stay intelligible where MP3 becomes watery, which is why it is the codec behind WebRTC and most voice chat. Speech that needs 96–128 kbps as MP3 is usually clean at 32–48 kbps as Opus. The advantage narrows as you climb toward transparency, so at 128 kbps and up the size difference matters less than the compatibility difference.

What quality does the converter use if I never touch the Quality Preset?

Nothing is pre-selected in that dropdown — we checked the option surface for this page rather than assuming, and unlike the video pages there is no highlighted default preset. If bitrate matters for your recording, pick a preset explicitly or switch the File Compression mode to Constant Bitrate and type a number. Leaving it untouched is fine for a rough listen but is not a decision you have made.

Can I keep the 5.1 surround mix in the Opus file?

Yes. Leave Audio Channel on Original and a six-channel AC-3 track is carried through as multichannel Opus. Bear in mind that six channels need proportionally more bits than two, so a bitrate that sounds fine for a stereo track will sound thin spread across 5.1. Set Audio Channel to Stereo instead if the destination is a podcast, a phone or anything that will fold the mix down anyway.

How do I extract just a 30-second section instead of the whole recording?

Two routes, and the better one depends on where the size problem is. If the clip is long and you only need a slice, use the Trim controls on this page — set a Start time and a Duration and only that range is encoded. If the upload is the bottleneck because the AVCHD video is huge, trim the source video first with the video cutter and run the short clip through here. Do not send an .mts file to the audio cutter; that tool takes audio files, not video.

Does the Opus file keep the recording date and camera metadata?

No. The date, camera model and lens data that AVCHD carries live in the container and in the MPEG-TS stream structure, and none of it survives a re-encode into a bare .opus file — you get a Vorbis-comment header with nothing meaningful pre-filled. If the capture date matters for your archive, read it off the original clip and store it alongside, or keep the original .mts and treat the Opus file as a derivative.

What happens to my camcorder footage after the conversion?

The .mts file is uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours. Nothing is shared or made public, there is no sign-up and no watermark. The practical limit you will run into on AVCHD is upload size and time rather than anything about the conversion itself, since a full HD video stream has to travel before the audio can be pulled out of it.