MTS to FLAC Converter

Extract FLAC Audio from MTS: What This Tutorial Covers

An MTS file is an AVCHD camcorder recording — H.264 video and a separate audio track wrapped in an MPEG-2 transport stream. This converter discards the video and saves only the audio track as a FLAC file, so you end up with the soundtrack of your clip in a lossless container. This walk-through is for anyone archiving camcorder audio or pulling a clean track into an editor, and it explains exactly what you get (and what you don't) when the source audio is Dolby AC-3.

How to Convert MTS to FLAC

1. Upload Your MTS File: Drag and drop your .mts clip onto the page or click "+ Add Files". Add several clips to extract their audio in one batch with the same settings.
2. Set the Compression Level: Open Advanced Options and use the Compression level slider (1-12). A lower number encodes faster and produces a slightly larger file; a higher number squeezes the file smaller for the same audio. Every level is lossless — the slider trades encode time for size, never quality.
3. Adjust Audio Channel and Sample Rate (Optional): Leave Audio Channel and Audio Sample Rate on "Original" to copy the source exactly, or downmix surround to stereo / change the sample rate if your target tool needs it. Use Trim to keep only a portion of the track.
4. Convert and Download: Click "Convert" and download your FLAC file. No sign-up, no watermark.

Walk-through: Getting the Result You Actually Want

The single most important setting is Compression level, and it does not work the way the name suggests. FLAC is lossless at every level from 1 to 12, so all of them reproduce the source audio bit-for-bit. The slider only changes how hard the encoder searches for a smaller file: higher levels spend more CPU time and shave a few more percent off the size. The audio is identical either way.

• Want the fastest export, file size doesn't matter: set the slider low (1-3). Good when you have many clips to batch.
• Want the smallest archive file: set it high (8-12). The difference over the default is usually only a few percent, and it takes longer to encode.
• Want to feed a video editor or DAW: leave Audio Channel and Audio Sample Rate on "Original" so the track lines up with your source clip; FLAC keeps full resolution that editors decode losslessly.
• Want just a portion of the clip: use Trim to set a start point and duration before converting, so you don't have to cut the FLAC afterward.

A note on the audio itself: AVCHD camcorders record audio as Dolby AC-3 (Dolby Digital) or uncompressed Linear PCM (LPCM). AC-3 is a lossy format, so storing it in FLAC keeps a perfect copy of the AC-3 stream as it exists today, but it cannot rebuild audio detail that AC-3 already discarded when the camcorder recorded the clip. If the source track was LPCM, the FLAC is a genuine lossless re-wrap of already-lossless audio. Either way, FLAC's value here is a clean, royalty-free archival container — not a quality upgrade.

Common Errors and How to Fix Them

• "My FLAC doesn't sound better than the original clip" — Expected. If the camcorder recorded in AC-3 (the AVCHD default), that audio was already lossy; FLAC preserves it exactly but cannot add back detail. You're getting a faithful copy, not a higher-fidelity version.
• "Where did my video go?" — This tool extracts audio only; the H.264 video is intentionally dropped. To keep the picture, use the MTS to MP4 converter instead, which re-wraps the whole clip.
• "The FLAC file is bigger than I expected" — FLAC is lossless, so it's much larger than an MP3 of the same clip. If the audio came from LPCM at 48 kHz, the FLAC stays sizeable; raise the Compression level slider or pick a lossy format like MTS to MP3 if you need a small file to share.
• "My player won't open the FLAC" — FLAC is widely supported (VLC, foobar2000, modern Android, recent Windows and macOS), but some older car stereos and legacy devices don't decode it. Convert to a more universal format if your target device chokes on it.

When This Doesn't Work

If the MTS file is partially corrupted (a common result of pulling the card before the camcorder finished writing), the audio stream may be unreadable even when a video player can still scrub the picture. The same is true for clips with no audio track at all. In those cases there's nothing to extract. If you only need the sound trimmed and re-saved rather than re-encoded, the audio cutter handles an already-extracted track. And if you want an uncompressed copy instead of FLAC's compressed-but-lossless container, MTS to WAV writes the same audio out as a plain PCM WAV.

Frequently Asked Questions

Does converting MTS audio to FLAC improve the sound quality?

No. AVCHD camcorders usually record audio as Dolby AC-3, which is a lossy format. FLAC stores that audio losslessly — a perfect copy of what's in the file now — but it cannot recover detail AC-3 already discarded during recording. You get a faithful archival copy, not a fidelity upgrade. If the source happened to be Linear PCM, the FLAC is a true lossless copy of already-lossless audio.

What audio codec is inside an MTS file?

Most AVCHD recordings use Dolby AC-3 (Dolby Digital), chosen so the footage stays compatible with Blu-ray authoring. Some camcorders instead record uncompressed Linear PCM (LPCM). The video alongside it is H.264/AVC, all carried in an MPEG-2 transport stream. This converter reads whichever audio codec is present and re-encodes it to FLAC.

Why extract FLAC instead of just keeping the MTS file?

A FLAC file is a standalone audio file you can drop into a DAW, music library, or editing timeline without dragging along the H.264 video. It's also a sensible archival format: lossless, royalty-free, patent-unencumbered, and open-source per the Xiph.Org FLAC project, so it isn't tied to a proprietary codec license the way the original AVCHD audio can be.

How much smaller is the FLAC than an uncompressed copy?

FLAC typically compresses audio to roughly 50-70% of the equivalent uncompressed WAV, depending on the content — quiet or simple passages compress more, dense recordings less. In our testing, a 60-second AVCHD clip with stereo 48 kHz audio produced a FLAC around half the size of the same track saved as WAV, with no change to the audio itself.

Can I use the extracted FLAC for video editing?

Yes. FLAC is lossless, so an editor or DAW decodes it back to full-resolution audio with no generation loss — useful when you're re-syncing a cleaner soundtrack to footage. Keep Audio Channel and Audio Sample Rate on "Original" during extraction so the track matches the timing and sample rate of your source clip.

How are my files handled, and how long are they kept?

Your MTS file is uploaded over an encrypted connection, processed on our servers, and the result is sent back for download. Uploaded files and outputs are deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public.