A stream pretending to be a file
Transport streams were designed for broadcast — data that flows and survives interference, not files that sit on disk. That heritage is why an AVCHD camcorder's .mts clips and DVR captures seek badly, show no thumbnails and confuse editors: the container carries no proper index, because a live broadcast never needed one.
Usually just a repack
The video inside is almost always standard H.264, so this tool normally remuxes: the streams are copied into an MP4 with a real index, near-instantly and with zero quality change. Suddenly the file scrubs smoothly and previews everywhere. When a stream carries audio or video MP4 cannot hold, the tool re-encodes automatically instead — slower, still local, still nothing uploaded.
Frequently asked questions
What are .mts and .m2ts files?
AVCHD — the flavor of transport stream that Sony, Panasonic and Canon camcorders recorded to for years. Same family as .ts, same treatment here.
Why does the MP4 behave so much better?
MP4 stores an index of every frame, so players can seek precisely and generate thumbnails. Transport streams lack one by design — they were built for antennas, not hard drives.
Is quality lost?
Not on the usual path — a remux copies the video byte-for-byte. Only when a codec can't live inside MP4 does the automatic re-encode step in, with the normal cost of any encode.