alt Hacker NewsThere’s a non-bloat explanation for channel switching taking time at least.
Now that all TV is digital (even OTA), it’s subject to the same quirks as streaming video on the web, and that includes how the picture will become garbled if you render it before gathering a sufficient amount of data. To prevent that, TVs and cable boxes take a moment or two to pull in enough data to render a clean picture when switching channels, which is where the delay comes from.
this is a telephone-game explanation of keyframes. Each video stream periodically includes a keyframe or I-frame (independent frame) which is a complete encoded picture in its own right. Other frames are P-frames which are diffs from the previous frame. A stream typically includes a keyframe every few seconds. If you want to accurately decode a stream starting in the middle of it, you need to start at the next keyframe.
Some players will take an initial placeholder image such as a grey screen and start applying P-frames on top of it anyway, which gives a corrupted image that still has some information (shapes of moving characters are often recognisable) until the keyframe comes. Others wait for the keyframe and display a black screen, a frozen screen or a loading spinner until then.
Related, if you've ever seen a low-bitrate stream whose quality seems to get really bad, then slowly fill in, then get really bad again, then slowly fill in again, repeating forever, that comes from a poorly tuned encoder that's not allocating enough bits to each keyframe (so the quality is bad) and then making up the difference in subsequent P-frames.