“seeking” in media files.
it’s like bus stops. you are dropped off at a stop, not wherever you’d like. you can walk the rest of the way, is the assumption.
does that make sense?
“walking” means decoding several frames until you end up where you want to be.
opencv does all of that for you though, which is why seeking can be expensive in opencv. more expensive than just the jump.
“intra” coding would allow you to jump to any frame. every intra frame is a bus stop.
also: media files don’t have numbered frames. they have timestamps. every frame has a timestamp, not an index.
indices are an illusion. and so is “fixed” frame rate. it’s all calculating with timestamps underneath. some videos have a fixed frame rate because each frame comes the same time after the previous one. some videos don’t have that. or the metadata (“frame rate”) is wrong.