Hardware decoding
Also known as: hardware acceleration, GPU decoding
Using a dedicated part of a chip to turn compressed video back into pictures, rather than doing the arithmetic in software.
Updated
What it means
Every device has a decoder block. It handles a fixed list of codecs extremely efficiently, and it knows nothing at all about anything outside that fixed list. Support is built into the silicon rather than added later.
The difference is not subtle. A 4K stream decoded in hardware plays while the chip stays cool; the same stream in software heats the device, drains the battery and produces Stutter.
Which codecs are covered is decided when the chip is made. That is why Codec support is a hardware question as much as a software one, and why old devices never get better at it.
How it works in practice
Delivery codecs are chosen for it. H.264 (AVC) is accelerated on essentially everything, which is the practical reason it remains the default long after more efficient codecs became available.
Editing applications expose it as a setting. Enabling it makes a timeline responsive on modest hardware, and disabling it again is occasionally the only fix for a decoding bug in one application.
It also decides export speed. Hardware encoding is faster and slightly less efficient than software, which is a trade worth taking for a review copy and and not for a master copy.
What to watch out for
Partial support is the confusing case. A chip can accelerate H.265 in one profile and not in another, so two similar files behave differently for no reason a user can see from the outside.
A fallback to software is silent. Nothing announces it; the symptom is a hot device and a Playback error that looks like a network problem rather than the decoding one it is.
Professional codecs are rarely accelerated. ProRes decodes quickly because it is simple rather than because any hardware is helping, which is a different mechanism with a broadly similar result.
How RawClip handles it
Decoding happens on the processing side rather than on anybody's device, so camera codecs that a phone would struggle with are read without any difficulty at all. The delivered file is encoded in a format that hardware everywhere is able to play.