AVCHD to FLV Converter

AVCHD to FLV Converter

AVCHD is the HD camcorder recording standard Sony and Panasonic introduced in 2006 — efficient H.264 video wrapped in a Blu-ray-style transport stream. FLV (Flash Video) is the Adobe container that carried nearly all web video through the 2000s, now obsolete as a delivery format since Flash Player's end-of-life. This conversion is almost always a step backward in both codec efficiency and format longevity, so before running it, understand what you are trading away — and whether AVCHD to MP4 is the answer you actually want.

AVCHD Format at a Glance

FLV Format at a Glance

Why This Conversion Loses Ground (and When to Do It Anyway)

The honest summary: AVCHD already stores efficient H.264, and converting to FLV's default codec — Sorenson Spark, an older H.263-based encoder from the early 2000s — moves the picture to a less efficient codec inside a dead container. You give up coding efficiency, and because the source H.264 is already lossy, a lossy-to-lossy re-encode can never add detail back. That is a double step backward: older codec, obsolete format. If your downstream tool accepts it, choosing H.264-in-FLV instead of Sorenson Spark at least keeps the codec efficient — but the Flash container is still dead either way.

There is one genuine reason to do it: an un-migrated Flash-era system — a learning-management system, CMS, or courseware toolchain from the Articulate/Captivate vintage — that still ingests .flv and nothing newer. In that single case, FLV is the right answer. For everything else — phones, browsers, editors, archives — keep the efficient H.264 stream and use AVCHD to MP4, which plays nearly everywhere natively.

How to Convert AVCHD to FLV

1. Upload Your AVCHD File: Drag and drop the .mts or .m2ts files from your camcorder's BDMV/STREAM folder onto the page, or click "+ Add Files" to browse. Batch upload is supported, so you can queue several clips from one shoot and convert them with the same settings.
2. Pick Video Codec and Quality Preset: Under Advanced Options the Video Codec defaults to FLV (Sorenson Spark) for the broadest legacy-player compatibility; switch it to H.264 if your target tool accepts H.264-in-FLV for sharper output at the same size. Leave Quality Preset on "Very High (Recommended)", or open File Compression for Constant Bitrate, Constant Quality, or a Specific file size.
3. Resolution and Trim (Optional): Under Video resolution choose Keep original, a Preset Resolution, Resolution Percentage, or a custom Width x Height. Use Trim → Time Range to cut one segment out of a long take in the same pass.
4. Convert and Download: Click Convert and save your .flv file. No sign-up, no watermark.

Frequently Asked Questions

Is FLV dead now that Flash Player is gone?

The Flash web-delivery workflow is dead, but the file itself is not unreadable. Adobe ended Flash Player support on December 31, 2020 and began blocking Flash content on January 12, 2021, so no browser plays .flv natively and no modern site serves it. The container itself still opens in VLC, ffmpeg, and MPV-class players, because those decoders never depended on the Flash plug-in. This is the key difference from .swf: an FLV is plain audio/video you can still play and re-convert, whereas SWF was an executable application with no standalone runtime left. Convert to FLV only when a specific legacy system demands that extension.

Which video codec does this output put inside the FLV?

By default, FLV (Sorenson Spark) — the original H.263-based codec that every Flash Player from version 6 onward could decode, which makes it the safest choice for old players. AVCHD's source video is H.264/AVC, so that efficient stream is decoded and re-compressed to the older Sorenson Spark codec, which is why the conversion loses coding efficiency. If your downstream tool is newer (Flash Player 9 Update 3, December 2007, added H.264-in-FLV), switch Video Codec to H.264 under Advanced Options to keep the efficient codec and get noticeably better quality at the same bitrate — though the FLV container is still obsolete regardless of codec.

Will converting AVCHD to FLV improve or preserve the picture quality?

No — and that is an honest limit, not a tool flaw. AVCHD holds H.264, FLV's default holds Sorenson Spark, so the default path is a full lossy-to-lossy re-encode to an older, less efficient codec. No detail the camcorder already discarded can be regained, and a 1920×1080 source stays 1080 only if you keep the resolution. In our testing, a 1080/60p AVCHD 2.0 clip re-encoded to a Sorenson Spark FLV needed a higher bitrate than the original H.264 to look comparable, confirming the efficiency loss. To keep second-generation loss as small as possible, leave Quality Preset on "Very High" and Video resolution on Keep original, or choose H.264-in-FLV.

What happens to my AVCHD's AC-3 or LPCM audio in an FLV?

It is re-encoded. AVCHD camcorders record Dolby AC-3 (stereo or 5.1) or linear PCM, but FLV does not carry AC-3 or LPCM, so the track is converted — the output defaults to AAC, with MP3 also available under Audio Codec, both of which Flash-era players expect. That re-encode is lossy and a 5.1 mix is folded toward stereo, so pick a generous preset to keep the result clean. If keeping the original AC-3 or multichannel matters, an MP4 via AVCHD to MP4 can retain AC-3 directly.

Should I really convert to FLV, or to MP4 instead?

For almost everyone, MP4. AVCHD already stores efficient H.264; re-encoding to FLV's default Sorenson Spark codec lands you in an obsolete container with a less efficient codec — two steps backward. FLV made sense only when Flash Player was installed on virtually every desktop, an era that ended in 2021. Choose FLV only when a legacy Flash-based learning-management system, CMS, or courseware tool will not accept anything else. For every other use, AVCHD to MP4 keeps the H.264 stream, stays smaller at the same quality, and plays natively on phones, browsers, smart TVs, and editors.

My camcorder split one long take into several .MTS files — how do I handle that?

AVCHD camcorders write to FAT32 cards that cap a single file at 4 GB (2 GB on older cards), so a long take auto-splits into sequentially numbered .MTS files (00001.MTS, 00002.MTS…) in BDMV/STREAM. The split is at a fixed size boundary, not a scene cut, so audio and video continue across files without gaps. Upload all the segments together; the converter treats each as its own clip, and concatenating them in any editor produces a seamless timeline. To go the other direction — packing video back into an AVCHD camcorder structure — see FLV to AVCHD.

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

Your file is uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after the conversion — no sign-up, no watermark, never shared or made public.