Transport stream
Also known as: MPEG-TS, .ts file
A container built for broadcast rather than for filing, a continuous chain of small packets with no index at the start or end.
Updated
What it means
A transport stream is designed to be joined midway. Every packet carries enough information to decode from that point, which is what a broadcast needs and what a file sitting on a disk has no use for.
The consequence is that it has no index. An MP4 knows its own length and where every frame sits; a transport stream has to be scanned from the beginning to answer the same questions.
It survives because of where it came from. Broadcast, satellite capture, some screen recorders and a few cameras write it, and the files turn up long after anybody actively chose the format for anything.
How it works in practice
Converting it is the first step. A Remuxing pass into an MP4 builds the index without re-encoding anything, which takes moments and makes every later tool behave the way it should.
Its one real advantage is resilience. A recording interrupted partway through is still playable, where a damaged MP4 frequently needs a Video file repair pass before anything will open it at all.
Concatenation works unusually well. Two transport streams join simply by appending one of them to the other, which is why broadcast pipelines use it and editing pipelines have no use for it.
What to watch out for
Seeking is slow and unreliable. Scrubbing a long transport stream in an editor is painful, and some applications refuse to open one at all rather than scan the whole thing.
Timestamps can be discontinuous. A stream captured from a broadcast carries jumps in its timing, which produces Sync drift or an incorrect duration once it has been converted.
The extension is unfamiliar enough to look broken. Somebody receiving a .ts file assumes it is damaged, where in fact it is simply a container that nobody outside broadcast ever expects to see.
How RawClip handles it
Transport streams are converted before analysis, since every later step expects a file with an index. Nothing at all is lost in that conversion step, and a recording that was interrupted partway is usable up to the point where it stopped.