Playback error
Also known as: video will not play, playback failure
What somebody actually sees when a video refuses to play: a black rectangle, an endless spinner or a message with nothing useful in it.
Updated
What it means
A playback error is a symptom rather than a cause. The underlying problem is a missing decoder, a damaged file, a network that stopped or or a device that cannot keep up with it.
The message is almost never diagnostic. Players report that something went wrong without saying which of those four it was, which is why diagnosis starts with substitution rather than with reading the message carefully.
It is the visible end of Codec support and of File corruption alike. Two completely different faults produce the same black rectangle, and nothing on screen distinguishes them.
How it works in practice
Substitution is the fastest diagnosis. The same file in a different player, then a different file in the same player, and the answer appears in two attempts rather than in an hour spent reading settings.
Delivering a safe format removes most of the category. H.264 (AVC) in an MP4 at a modest resolution eliminates the decoder case entirely, and the decoder case is the majority of all reports.
A second version helps more than an explanation. Offering a lower-resolution file gives somebody a way forward immediately, where a support message explaining codecs and containers does not.
What to watch out for
It gets reported as a broken file. Somebody whose device cannot decode a format says the video is broken, and that same file is perfectly fine on every other device in the same room.
Partial failures are read as errors. A clip that plays with Stutter because the machine is decoding in software is working exactly as designed and still feels entirely broken.
Nothing is logged where anybody can see it. The browser knows why it declined and the person watching does not, which is what makes this frustrating rather than merely inconvenient for everybody involved.
How RawClip handles it
Results are encoded in a widely supported format precisely to avoid this, since a highlight nobody can open is worth nothing. Where a file still will not play on somebody device, a lower-resolution version is available as the usual answer to it.