Convert MTS (and M2TS) to MP3 - extract audio
AVCHD camcorder files carry AC-3 or LPCM audio alongside their H.264 video. Wave discards the video track, decodes the audio, and re-encodes it to a 192 kbps MP3 you can share or archive. If .mts and .m2ts extensions are new to you, Codecs vs containers explains the wrapper concept.
What actually changes
MTS and M2TS are the AVCHD container used by Sony and Panasonic consumer camcorders and AVCHD Blu-ray discs. Audio inside is nearly always AC-3 (Dolby Digital, stereo or 5.1), with some older Panasonic camcorders and AVCHD Blu-ray tracks using LPCM instead. Both are LGPL-clean codecs and Wave decodes them locally with no server involved.
Because the video track is discarded entirely, extract runs several times faster than a full MTS-to-MP4 conversion - an hour-long camcorder recording usually finishes in under a minute. Wave uses LAME (libmp3lame) at VBR around 190 kbps, which is transparent for the natural-sound recordings camcorders typically produce.
The AVCHD audio spec permits AC-3 at 448 kbps stereo or 640 kbps for 5.1 surround, plus LPCM at 24-bit / 48 kHz for the highest-quality recording mode on prosumer camcorders. AC-3 handles the majority of consumer recordings; LPCM appears mainly on Sony HDR-CX series camcorders and on AVCHD Blu-ray audio tracks that mirror the disc's uncompressed music. Wave decodes both cleanly and downmixes multi-channel to stereo for the MP3 output since MP3 does not carry surround.
The typical use case is extracting audio from event footage: a wedding videographer wants the vows track without the video, a school videographer wants the concert audio for a separate mix, a nature-photography camcorder captured a bird call worth isolating. The MP3 output is share-friendly and preserves whatever the source captured at the resolution the microphone recorded.
Three steps.
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Step 1
Drop your .mts or .m2ts file onto the card.
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Step 2
Pick MP3 as the output format.
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Step 3
Convert and save the MP3.
Answers, specifically.
5.1 surround from an AVCHD Blu-ray - how is it handled?
Wave downmixes to stereo before encoding to MP3. MP3 doesn't carry multi-channel audio at all, so a downmix is the only path; the result sounds like a good stereo mix, not a surround field.
Which audio track gets picked if there are several?
Wave uses the container's default-flagged track, which is what the camcorder or authoring tool marked as primary. Multi-track extraction is on the roadmap.
How fast is it?
An hour of MTS audio typically re-encodes in 30–45 seconds on a modern laptop - much faster than the full video conversion, because Wave never has to decode a single frame.
What if my source file is enormous?
Wave's per-file ceiling is 8 GB. Even a 30 GB Blu-ray-source .m2ts would exceed it - split it first with any AVCHD-aware tool, or drop the individual clip files rather than the concatenated version.
Are timecode markers preserved?
MP3 has no equivalent for AVCHD timecode, so those are dropped. Basic ID3 tags (title from the filename) are written where available.
Does my camcorder's wind-noise reduction survive the extract?
Yes - Wave preserves the audio track exactly as the camcorder captured it. Any noise reduction, gain, or automatic level adjustment applied in-camera is baked into the audio bytes and stays through the extract and MP3 re-encode.
Two AVCHD clips from the same event - can I extract audio and merge later?
Wave handles one file at a time. Extract each clip separately into MP3, then merge with any audio editor (Audacity is free and does this in a few clicks) if you want a single continuous audio track for the event.
The MP3 sounds quieter than the original recording. Why?
Sometimes the source AC-3 track uses conservative levels (peaks around -6 dB rather than 0 dB) that the camcorder's built-in playback compensates for at output. The MP3 preserves the original peaks; you may want to normalize or apply a small gain in an audio editor for consistent playback loudness.