FLV to MTS Converter

FLV to MTS Converter

Flash Video (.flv) is the container Macromedia introduced in 2003 and Adobe kept maintaining after acquiring Macromedia in 2005; it carried most web video through the late 2000s. MTS is the extension AVCHD camcorders write — an MPEG-2 transport stream carrying H.264 video — and a handful of editors, HD ingest pipelines, and disc-authoring tools still ask for that specific wrapper. This page re-encodes a Flash-era clip into that transport-stream form. It is a deliberately niche target: if you just want a file that plays everywhere, convert FLV to MP4 instead.

FLV Format at a Glance

MTS / AVCHD Format at a Glance

How to Convert FLV to MTS

1. Upload Your FLV File: Drag your .flv onto the page or click "+ Add Files" to browse. Several clips can be queued and converted with the same settings in one pass.
2. Check Video Codec and Audio Codec: Open Advanced Options. Video Codec starts on H.264 — the codec the AVCHD spec itself names — and Audio Codec starts on AAC. DivX, H.265, MPEG-1, MPEG-2, MPEG-4 and Xvid are available under Video Codec, and AC3, DTS (DCA), EAC3, MP2 and MP3 under Audio Codec.
3. Set Quality Preset, Video resolution, or Trim: Leave the Quality Preset on "Very High (Recommended)", or switch File Compression to Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality or Constraint Quality. Video resolution stays on "Keep original" unless you pick a Preset Resolution or Width x Height, and Trim → Time Range takes a Start time and Duration.
4. Convert and Download: Click "Convert" and save the .mts. No sign-up, no watermark.

Default Output for This Conversion

Frequently Asked Questions

What codecs end up inside the MTS file?

H.264 video with AAC audio, unless you change them. H.264 is what the AVCHD specification names, so the video essence matches what an AVCHD-aware tool expects. AAC is not one of the two audio codecs the AVCHD spec lists — those are Dolby Digital (AC-3) and Linear PCM — but it muxes cleanly into the transport stream and most software players and editors read it. If a device or authoring tool is strict about the spec, switch Audio Codec to AC3 before converting.

Is the result a real AVCHD file my camcorder software will accept?

It is a real MPEG-2 transport stream with H.264 inside, which is what most software that "reads MTS" actually wants. What it is not is a complete AVCHD volume: a camcorder writes its clips inside a PRIVATE/AVCHD/BDMV/STREAM folder tree alongside index and clip-info files, and it constrains frame size, frame rate and bitrate to the AVCHD profiles. A single converted .mts opens fine on its own, but a tool that insists on importing a whole AVCHD card structure will still want camcorder-native media.

Will converting FLV to MTS improve the picture?

No. FLV holds video that was already compressed and already lossy — Sorenson Spark, VP6 or H.264 — and this conversion decodes that and re-encodes it. Nothing that was discarded at record time comes back. The AVCHD frame-size table goes up to 1920×1080, but a 360p or 480p Flash clip stays a 360p or 480p clip; scaling it up to a 1080p preset only spends bits enlarging pixels you already have.

Should I pick AC-3 or Linear PCM audio instead of AAC?

Only if something downstream requires it. The AVCHD specification lists Dolby Digital (AC-3) at 64–640 kbps and Linear PCM at 1.5 Mbps for stereo, so a strict AVCHD ingest or a disc-authoring tool may reject anything else — pick AC3 in that case. For everyday playback and editing, AAC is smaller than either and is what this page uses by default. Linear PCM is not offered on this page's Audio Codec list; AC3, EAC3, DTS (DCA), MP2 and MP3 are.

What is the difference between .mts and .m2ts, and can I just rename the file?

They are the same MPEG-2 transport stream. .MTS is what an AVCHD camcorder writes to its own storage; .m2ts is what you typically see once the clip has been copied off by import software or authored to Blu-ray. Renaming between the two does not change a single byte, and most players treat them identically — so if a program only lists .m2ts in its file dialog, renaming is a legitimate fix. If you would rather have the other extension from the start, use FLV to M2TS.

My FLV is an old 360p or 480p clip — which resolution setting should I use?

Leave Video resolution on "Keep original". Flash-era video was encoded small for slow connections, so there is no detail waiting to be revealed by picking a bigger preset; upscaling produces a larger file that looks the same or slightly softer. The one time to touch resolution is when the receiving system demands an exact frame size, in which case use Width x Height and type the numbers its spec document lists.

Can I convert only part of a long Flash recording?

Yes. Set Trim to "Time Range" and fill in a Start time and a Duration, in seconds or as HH:MM:SS.sss. That is worth doing before conversion rather than after, because old stream rips and lecture captures are frequently long and mostly filler, and trimming first cuts both the encode time and the size of the file you have to download.

Why would I choose MTS over MP4 at all?

Almost never, unless something in your chain names it. MP4 with H.264 is smaller in practice, plays on essentially every phone, browser, TV and editor, and is the normal destination for rescuing Flash content. The reasons to pick MTS are specific: an older Sony or Panasonic-oriented editing workflow, a broadcast or HD ingest tool that only accepts transport streams, or a disc-authoring project. If none of those apply, FLV to MP4 is the better conversion.

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

Your FLV is uploaded over an encrypted connection, converted on our servers, and the .mts is returned to you. Uploads and outputs are deleted automatically a few hours after the conversion — no sign-up, no watermark, and files are never shared or made public. The practical limit on a big archive clip is upload size and time rather than anything on the conversion side.