TS, MTS and M2TS to MP4 Converter

What a .ts file actually is

A TS file is an MPEG transport stream: a long chain of fixed 188-byte packets, each tagged with the identifier of the stream it belongs to, interleaved so that a receiver can join anywhere and start decoding within a fraction of a second. It was designed for broadcast, where there is no start of file and no end of file, only a signal arriving. MTS and M2TS are the same format with a four-byte arrival timestamp attached to the front of every packet, giving 192-byte packets instead of 188. That is the flavour Blu-ray discs and AVCHD camcorders write.

MP4 is the opposite idea: a file with a table of contents, the moov atom, listing where every frame lives and how long it lasts. Players read that index once and can then jump anywhere instantly. The catch is that the index can only be written when the recording ends — which is exactly why the things that write TS write TS. A dashcam that loses power or a recorder that crashes leaves a transport stream that still plays up to the last complete packet, whereas a half-written MP4 with no moov atom is usually a dead file.

So the reason you are here is not that TS is a bad format. It is that TS is a delivery and recording format, and everything downstream — editors, phones, browsers, smart TVs, messaging apps — expects the indexed one.

Why this is a copy, not a conversion

Nearly every TS, MTS and M2TS that lands on this page already contains H.264 video, and H.264 is perfectly legal inside an MP4. There is nothing to convert. The converter unwraps the packets, writes the same compressed frames into MP4 boxes and builds the index, moving it to the front of the file with faststart so the result streams properly too. No pixel is decoded or re-compressed: the output is bit-for-bit the picture you started with, and it finishes in seconds whether the recording is two minutes or two hours.

Every re-encode throws information away, however high you set the quality, so the right answer for a TS file is usually to refuse the re-encode entirely. The converter above works that out from your actual file before you press anything: it reads the container, video codec and profile, resolution, frame rate and audio codec, then says in plain words whether it will copy or re-encode. If it says copied, the quality question is settled.

The cases where it is not a straight copy

Two kinds of TS file break the easy path, and both come from television rather than from a camera.

MPEG-2 is the one to watch: an MP4 player cannot be relied on to decode it, so the converter re-encodes rather than pretending a copy will work, and a long MPEG-2 recording is the slowest job this tool does. If the sound comes out silent rather than missing, suspect the audio codec, not the conversion — the guide on audio that plays in one app but not another covers it. Unsure what is in the file at all? Check the codec first; it reads the file in your browser without converting anything.

MTS, M2TS and the AVCHD folder problem

Camcorder footage arrives with an extra obstacle. AVCHD is not a file, it is a folder structure copied from Blu-ray: a BDMV directory with the actual video buried in a STREAM subfolder as numbered .MTS files, alongside index and playlist files that no general-purpose player uses. If you dragged the whole card into a folder and cannot see anything to convert, open the STREAM folder and take the .MTS files out. Those are your recordings.

The second quirk is splitting. Camera cards are formatted FAT32, which cannot hold a file larger than 4 GB, so a long take is written as several consecutive .MTS files meant to be played back to back. This converter handles one file at a time and cannot join them: there is no concatenation and no batch queue. Convert each part separately, or join them in a desktop tool first if you need one continuous clip.

What does not survive the conversion

A remux keeps the first video stream and the first audio stream. Everything else is left behind, and the converter says so before it runs:

• Subtitle tracks. Broadcast recordings often carry DVB subtitles or teletext. They are dropped.
• Extra audio tracks. A recording with a second language or a commentary track keeps only the first.
• Data streams. This is the important one for dashcams. If your camera embeds GPS coordinates, speed or G-sensor readings as a private data stream inside the TS, that stream will not be in the MP4. Export the trip data with the camera's own player first if you need it, or keep the original TS alongside the MP4.
• Broadcast metadata such as programme information and the original service name.

The honest limits of doing this in a tab

The converter runs FFmpeg compiled to WebAssembly inside this page. Nothing is uploaded, there is no server and no account, and once your first conversion has fetched the engine, it keeps working with the network off. The trade is memory: a 32-bit WebAssembly heap cannot address more than about 2 GB, so larger files are refused outright, and above roughly 300 MB the page warns you that it wants around three times the file size in free memory.

That ceiling bites less here than you would expect, because a remux never decodes anything: an hour-long transport stream that fits under the limit finishes about as fast as your disk can write it. The build is single-threaded, though, so the MPEG-2 case above is genuinely slow — think roughly real-time at 720p and worse at 1080p. That is where the phone app, with your device's hardware encoder and no size ceiling, earns its place.

The situations that send people to this page

Four, mostly. A dashcam or DVR card full of .ts clips that Windows Photos, Premiere or CapCut refuses to open. An AVCHD camcorder whose .MTS files the editor imports as audio only, or not at all. A screen recording made in MPEG-TS for crash safety that now has to become a normal deliverable — the same argument for remuxing rather than re-encoding applies to an MKV recording. And a TV recording that has to play from a USB stick, where the container is only half the battle and what a TV will actually decode from USB is the rest.

Two neighbours are worth knowing. If your new MP4 still will not play on a Windows PC or an older TV, the file is probably HEVC and the fix is converting the codec to H.264, a real re-encode. If the destination is Final Cut, wrapping the same streams in a MOV is another instant copy. And if the sound slides out of sync as the clip runs on, a variable frame rate is the suspect, not the container.