Convert M2TS to MP3 - extract audio
Blu-ray M2TS files carry rich audio: Dolby Digital, DTS, TrueHD, and LPCM are all common (see Audio codecs explained for where each fits). Wave decodes the primary track through the on-device ffmpeg engine, respects the source's downmix metadata to fold surround into stereo, and re-encodes to a portable 192 kbps MP3.
What actually changes
Blu-ray's audio palette is far richer than DVD's. Where DVD-Video specified AC-3 (Dolby Digital) as the mandatory primary audio, Blu-ray added E-AC-3 (Dolby Digital Plus), DTS, DTS-HD Master Audio, DTS-HD High Resolution, Dolby TrueHD, and Linear PCM up to 24-bit / 96 kHz. Wave decodes any of these through ffmpeg-wasm's bundled decoders and re-encodes to MP3 at 192 kbps through libmp3lame. Video is discarded entirely, so the extract runs in a small fraction of the time a full M2TS-to-MP4 video conversion would take.
For 5.1 and 7.1 surround sources - which is essentially every Blu-ray - Wave uses the source's downmix metadata to fold surround into stereo. Dolby Digital and Dolby TrueHD both carry Lt/Rt (Left-total / Right-total) and Lo/Ro (Left-only / Right-only) downmix coefficients that specify how the surround channels fold into the front pair without losing dialogue intelligibility. DTS uses similar downmix hinting. Wave respects these coefficients so the MP3's stereo image sounds like the mix engineer intended, not a naive channel average.
Blu-ray audio was designed for home-theatre systems that could reproduce the full lossless quality. Dolby TrueHD and DTS-HD MA are both lossless codecs, technically preserving every bit of the studio master; DTS-HD HR and E-AC-3 are lossy but at bitrates (768 kbps to 1.5 Mbps) that were considered "audiophile" for a consumer format. Even after downmix and re-encode to 192 kbps MP3, the result is transparent on any consumer playback chain - the MP3 preserves everything a human ear can detect.
The catch with TrueHD Atmos and DTS-X sources is object-based audio: those formats carry not just channels but 3D audio-object metadata that a compatible receiver renders into a specific speaker layout. Stripping the object metadata during downmix loses the height / overhead placement information; the resulting stereo MP3 sounds like a good stereo mix of the same content but doesn't preserve the immersive layout. That's a fundamental limitation of any downmix, not a Wave-specific one.
Three steps.
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Step 1
Drop the .m2ts file onto the card.
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Step 2
Pick MP3 as the output format.
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Step 3
Convert. Save the MP3.
Answers, specifically.
Dolby TrueHD decoding?
Yes. ffmpeg-wasm bundles the MLP decoder (the underlying bitstream of TrueHD), and Wave decodes it to PCM before re-encoding to MP3.
DTS-HD Master Audio?
Yes. The DTS decoder in ffmpeg-wasm handles DTS-HD MA as an extension of the core DTS stream. Wave decodes and downmixes.
Is Dolby Atmos preserved?
No. Atmos rides on TrueHD as an object-based metadata layer for compatible AV receivers. Stripping the metadata during downmix (which any stereo conversion has to do) loses the object placement. The resulting stereo MP3 is a clean fold-down of the base 7.1 mix, not an Atmos-preserving output.
AACS-encrypted M2TS files?
Wave cannot decrypt AACS. If your M2TS was extracted with a tool that stripped the encryption (MakeMKV, DVDFab BluRay Ripper), the resulting plaintext file works normally.
Multiple language tracks - which one gets extracted?
Default-flagged, which on a Blu-ray corresponds to the primary language. Multi-track extraction is on the roadmap for a later Wave release.
LPCM at 24-bit / 96 kHz - does that lose fidelity in MP3?
LAME operates in floating-point internally and preserves the full audible range regardless of source bit depth. 24-bit gives more dynamic-range headroom than any consumer playback chain can reproduce (144 dB vs 60-70 dB in a listening room), so nothing audible is lost.
M2TS from a camcorder rather than a disc rip?
Same handling. AVCHD camcorder M2TS files use LPCM or AC-3 audio, both of which decode cleanly through Wave.