M4V to MTS Converter

Convert M4V to MTS: What This Page Covers

.mts is the extension camcorders write for AVCHD, the high-definition recording format Sony and Panasonic introduced in 2006: H.264 video and Dolby Digital or linear PCM audio, packed into an MPEG transport stream and filed inside an AVCHD/BDMV/STREAM folder on the memory card. This tool converts your Apple .m4v into a transport stream with the .mts extension — the same stream type, written as a single standalone file. That distinction is the whole story of this page, and it decides whether this conversion solves your problem: if you need a transport stream, you are in the right place; if you need something a camcorder or AVCHD-strict editor will treat as genuine AVCHD media, no converter can produce that from a single file.

How to Convert M4V to MTS

1. Upload Your M4V File: Drag and drop your file onto the page or click "+ Add Files" to browse. Both .m4v and .mp4 are accepted, and several files queue up and convert with identical settings.
2. Set Video Codec and Audio Codec: Video Codec is pre-selected as H.264, which is what AVCHD uses; H.265, MPEG-2, MPEG-4, MPEG-1, Xvid and DivX are also available for other transport-stream targets. Audio Codec is pre-selected as AAC — switch it to AC3 if you are aiming at AVCHD conventions, since AAC is not one of the audio formats AVCHD defines.
3. Choose a Quality Mode, Resolution or Trim (Optional): File Compression offers Quality Preset (pre-selected at "Very High (Recommended)"), Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality with a CRF slider from 16 to 51, and Constraint Quality with a maximum-bitrate ceiling. Video resolution keeps the source size unless you choose otherwise, and Trim exports a single time range.
4. Convert and Download: Click Convert and save the .mts. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours. No sign-up, no watermark.

Walk-through: What This Tool Writes, and What AVCHD Actually Requires

The AVCHD specification is published by its own format body, and it is specific. Video is MPEG-4 AVC/H.264. Audio is Dolby Digital (AC-3) at 64-640 kbps or linear PCM — AAC is not on the list. The system bit rate tops out at 24 Mbit/s on standard media, 18 Mbit/s when recorded to DVD media, and 28 Mbit/s for the stereoscopic variant. On top of the stream itself, the format defines a directory structure and index files, and the .MTS clips a camera writes use 192-byte source packets: a four-byte arrival-time header in front of each standard 188-byte transport packet, the same framing Blu-ray uses.

What comes out of this converter is the plain broadcast-style transport stream. We checked the bytes: the output is built from unadorned 188-byte packets with no arrival-time prefix, and there is no AVCHD folder, no BDMV/STREAM hierarchy and no clip-information or playlist files, because a single downloaded file has nowhere to put them. So:

• If your target reads any MPEG transport stream — a capture or playout system, a streaming pipeline, an editor that ingests .ts/.mts generically — this output works, and the defaults are fine.
• If your target is a camcorder, a Blu-ray authoring tool or an AVCHD-strict NLE, the missing folder structure and packet framing are what will trip it, not the bitrate. Lowering the bitrate does not turn a plain transport stream into AVCHD media.
• If you want to stay close to AVCHD conventions anyway, choose H.264 video and AC3 audio, keep the resolution at 1080p or 720p, and use Constraint Quality or Constant Bitrate to hold the ceiling at or under 24 Mbit/s.
• If you actually wanted the other extension, M4V to M2TS writes the same stream type under the .m2ts name that computers and Blu-ray tools tend to expect.

AVCHD as Specified vs What This Page Produces

Controls on This Page

Common Errors and How to Fix Them

• "My camcorder or AVCHD-only editor rejects the file" — It is a plain transport stream, not AVCHD media with its folder structure and 192-byte packet framing. No bitrate or resolution setting changes that. Import the footage into your editor as a normal video file instead, or convert to MP4, which almost every editor accepts.
• "The conversion fails on an iTunes purchase" — FairPlay-protected films and TV episodes cannot be decoded by any converter. Only DRM-free M4V works.
• "The output is larger than my M4V" — Transport streams add packet overhead, and if the Quality Preset is high the encoder spends generously. Cap it with Constraint Quality or Constant Bitrate, or trim the clip.
• "The picture looks softer than the source" — This is a re-encode, never a stream copy, so some detail is always lost. Use a low Constant Quality number and keep the source resolution to minimise it.
• "There is no sound in my editor" — Some transport-stream tools are picky about AAC in .mts. Re-run with AC3 selected under Audio Codec, which is the audio format AVCHD tooling expects.
• "Interlaced footage still looks combed" — There is no deinterlacing anywhere in this pipeline. Deinterlace in an editor first if your source is interlaced.

When This Doesn't Work

Two hard walls. The first is FairPlay: a purchased or rented Apple title is encrypted, and the job will fail rather than produce a partial file — only your own exports, recordings and other DRM-free .m4v files convert. The second is genuine AVCHD compliance. AVCHD is a media format, not just a file, and rebuilding a card structure with clip-information and playlist files is outside what any single-file converter does. If a device demands real AVCHD media, use the manufacturer's own software. If you are moving camcorder footage the other way, MTS to M4V handles it, and Trim MTS cuts an existing .mts without a format change.

Frequently Asked Questions

Is the .mts I get here the same as a camcorder's .MTS file?

The video and audio streams are the same kind of thing — H.264 in an MPEG transport stream — but the packaging is not. A camcorder writes 192-byte source packets, each a standard 188-byte transport packet with a four-byte arrival-time header in front, and stores the clips inside an AVCHD/BDMV/STREAM folder alongside index and playlist files. This tool writes plain 188-byte packets as a single standalone file. Anything that reads transport streams generally will play it; anything that validates AVCHD media will not accept it as such.

Why is AAC the default audio if AVCHD requires AC-3 or LPCM?

Because AAC is the audio your M4V already contains and the sensible default for a general transport stream, and because the option list on this page is shared across transport-stream targets. AVCHD itself defines only Dolby Digital (AC-3) at 64-640 kbps and linear PCM, so if you are aiming at AVCHD conventions, change Audio Codec to AC3 before converting. Linear PCM is not offered on this page.

What bitrate should I use?

If you are feeding a generic transport-stream pipeline, leave Quality Preset at "Very High (Recommended)" and let the encoder decide. If you want to stay inside AVCHD's envelope, cap the total at 24 Mbit/s — the specification's ceiling for standard media, with 18 Mbit/s for material recorded to DVD media and 28 Mbit/s reserved for the stereoscopic variant. Constraint Quality is the neatest way to do it: quality-led encoding with a hard maximum bitrate.

Will converting M4V to MTS lose quality?

Some, always. The video is decoded and re-encoded rather than copied, and the AAC soundtrack is re-compressed into whichever audio codec you choose, so each pass discards a little detail that cannot be recovered. Keeping H.264 as the codec, using a low Constant Quality number, and leaving the resolution at the source size keeps the loss small enough to be hard to see. Quality can never exceed the original file.

Can I convert a DRM-protected iTunes or Apple TV M4V?

No. Apple's FairPlay encryption ties decoding to devices authorised with the purchasing Apple ID, and no converter — online or desktop — can read those files, so the job fails outright. Everything DRM-free converts normally: iMovie and Photos exports, QuickTime screen recordings, camera footage, and any .m4v that was never encrypted.

What is the difference between MTS and M2TS?

Mostly the name and where the file came from. .MTS is what an AVCHD camcorder writes on the memory card; .m2ts is what the same material is usually called once imported to a computer, and it is also the Blu-ray naming. Both hold an MPEG transport stream with H.264 video. On this site the two targets produce the same kind of stream under different extensions, so pick whichever your software asks for: this page for .mts, or M4V to M2TS for .m2ts.

Why would I convert to MTS instead of MP4?

Only when something downstream wants a transport stream. Transport streams were designed for broadcast and disc playback: they are packetised, resilient to being cut anywhere, and easy to stream, which is why capture, playout and camcorder ecosystems standardised on them. MP4 is better for everything else — smaller for the same picture, and accepted by every browser, phone and editor. If you are not specifically targeting a transport-stream workflow, M4V to MP4 is the right conversion.

Does this tool rebuild the AVCHD folder structure on my card?

No, and that is worth being blunt about. The conversion produces one file. AVCHD media is a directory tree with stream files, clip-information files, playlists and index files that the camera and its software maintain together. Recreating it requires camcorder or authoring software that writes the whole structure, so if a device is asking for a card it can read, restore the original AVCHD material rather than converting to it.

How long do you keep my uploaded file?

Your M4V is uploaded over an encrypted connection, converted on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public. The main practical limit is transfer time in both directions, since transport-stream output is often larger than the M4V it came from. Setting a Trim range before converting, or cutting the source first with the video cutter, keeps both ends small.