AVCHD to FLAC Converter

Extract FLAC Audio From AVCHD: What This Tutorial Covers

This is for anyone sitting on a card full of camcorder clips — a concert, an interview, a wedding, a lecture — who wants the sound as a standalone lossless file instead of a video they have to scrub through. The tool discards the H.264 picture and writes the clip's audio track as FLAC, the lossless codec standardised as RFC 9639 in December 2024. The steps come first, then a walk-through of the one setting that matters and an honest account of what "lossless" does and does not buy you when the camcorder recorded in Dolby AC-3.

How to Convert AVCHD to FLAC

1. Upload Your AVCHD File: Drag and drop the .avchd, .mts, or .m2ts clip onto the page or click "+ Add Files". Add several clips to extract them all in one batch with identical settings.
2. Set the Compression level: Open Advanced Options and use the Compression level slider, which runs from 1 to 12 and starts at 12. Lower numbers encode faster and leave a slightly larger file; higher numbers squeeze harder for the same audio. Every setting is lossless.
3. Adjust Audio Channel and Audio Sample Rate: Both default to ORIGINAL, which keeps the camcorder's layout and its 48 kHz rate — the right choice for editing. Switch to Stereo or Mono to downmix, or pick a specific rate if a downstream tool insists. Use Trim to keep only a Time Range.
4. Convert and Download: Click Convert and download the FLAC. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours later. No sign-up, no watermark.

Walk-through: What the Compression Level Slider Really Does

The name misleads people constantly. FLAC is lossless at every setting, so levels 1 and 12 decode to exactly the same samples — the slider only decides how much CPU time the encoder spends searching for a smaller representation. Higher settings run slower and typically shave low single-digit percentages off the file. Nothing about the audio changes.

Two related settings are worth leaving alone. Audio Sample Rate on ORIGINAL avoids a resample that would rewrite every sample for no benefit, since 48 kHz is already the video-production standard and what AVCHD records. Audio Channel on ORIGINAL keeps the recorded layout — FLAC handles up to eight channels, so a surround track survives intact rather than being folded to stereo.

What Your Camcorder Recorded, and What FLAC Preserves

AVCHD itself is the format Sony and Panasonic introduced in 2006: H.264/AVC video and one of those audio tracks multiplexed into an MPEG transport stream, written to the card as .MTS files under a PRIVATE/AVCHD folder and usually renamed .m2ts after import.

Common Errors and How to Fix Them

• "The FLAC doesn't sound better than the clip" — expected when the source was AC-3. FLAC preserves that audio bit-exactly but cannot rebuild detail the camcorder's encoder threw away at capture.
• "Where did my video go?" — this tool keeps audio only, by design. To retain the picture in a modern container, use AVCHD to MP4 instead.
• "The FLAC is bigger than I expected" — it is lossless, so it is many times the size of an MP3 of the same clip. Push the Compression level higher, or accept a lossy file with AVCHD to MP3 when the target is email or a phone.
• "My car stereo or old player won't open it" — FLAC plays in VLC, foobar2000, Android, and current Windows and macOS, but plenty of legacy hardware never learned it. Convert to a more universal format for those devices.
• "Only part of the recording came through" — long AVCHD takes are split across multiple files on the card. Copy the whole STREAM folder off first and convert each clip, rather than assuming one file holds the entire event.

When This Doesn't Work

Partially copied cards are the usual failure: pull a card before the camcorder finishes writing and the audio stream can be unreadable even though a player still scrubs the picture. Clips recorded with no audio track have nothing to extract at all. And if what you want is a shorter piece of an existing lossless file rather than a fresh extraction, the audio cutter is the faster route. Because .avchd, .mts, and .m2ts are the same recordings under different names, MTS to FLAC performs an identical extraction for footage that kept the camera's naming.

Frequently Asked Questions

Does converting AVCHD audio to FLAC improve the sound quality?

No. FLAC is lossless, which means it preserves exactly what it is given — if the camcorder recorded Dolby AC-3, you get a perfect copy of a lossy signal, not a restored one. Where it genuinely helps is everything downstream: no repeated lossy decode as you edit, an open format for archiving, and no further generation loss. If the source was Linear PCM, the FLAC is a true lossless copy that also happens to be smaller than the raw samples.

What does the Compression level slider change, exactly?

Only encode time and file size. We checked the encoder behind it while writing this page: FFmpeg's FLAC encoder accepts compression levels 0 through 12 and rejects anything higher, and this page ships the slider at 12 — the maximum. So the default already favours the smallest archive file over the fastest export, and dropping it to 1–3 is the right move when you are converting a whole card and want speed.

What audio codec is inside an AVCHD file?

Dolby Digital (AC-3) on most consumer camcorders, running between 64 and 640 kbit/s across 1 to 5.1 channels, chosen so footage stays Blu-ray compatible. Some professional bodies record uncompressed Linear PCM instead, up to roughly 1.5 Mbit/s for stereo. The video alongside it is H.264/AVC, all carried in an MPEG transport stream.

How much smaller is FLAC than an uncompressed copy?

For typical recorded material FLAC commonly lands somewhere between half and three-quarters of the equivalent WAV, and the result depends entirely on content: quiet, simple, or sparse passages compress hard, while dense full-range recordings compress much less. Because it is lossless, the only way to know your figure is to convert — there is no quality knob trading size for fidelity.

Will a 5.1 surround track survive the extraction?

Yes, as long as you leave Audio Channel on ORIGINAL. FLAC supports 1 to 8 channels under RFC 9639, so a 5.1 AC-3 track from the camcorder is preserved as six discrete channels. Selecting Stereo or Mono instead performs a downmix, which combines those channels irreversibly.

Is a .avchd file the same thing as MTS or M2TS?

Same recordings, different names. AVCHD is the format; the camcorder writes .MTS files into PRIVATE/AVCHD/BDMV/STREAM/ on the card, and those files are commonly renamed .m2ts after import. Whichever extension yours carries, the audio inside is the same and the extraction is identical.

Why extract FLAC instead of just keeping the AVCHD clip?

Because a standalone audio file drops straight into a DAW, a music library, or an editing timeline without dragging a multi-gigabyte H.264 video behind it. FLAC is also the sensible archival choice: lossless, patent-unencumbered, maintained by the Xiph.Org Foundation, and now specified in an IETF standards-track RFC, so it is not hostage to a proprietary licence the way the original AC-3 track is.

What sample rates and bit depths can FLAC store?

Far more than a camcorder will ever hand it. RFC 9639 defines FLAC for 1 to 8 channels, sample rates from 1 Hz to 1,048,575 Hz, and bit depths from 4 to 32 bits. AVCHD's 48 kHz 16-bit audio sits comfortably inside that, which is why the extraction never needs to compromise.

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

The clip is uploaded over an encrypted connection, processed on our servers, and the FLAC is returned for download. Uploads and results are deleted automatically a few hours after conversion, with no account, no watermark, and nothing shared or made public.