I’ve been very frustrated with my Netflix experience lately, streaming-wise. It used to be pretty damn good, considering.
But recently I’ve really noticed a very herky-jerky pause-stop-start of the video… almost exclusively when something really fast is happening on screen! Is that purely perception, or does the video stream actually somehow need more oomph when the picture is of fast-paced action? isn’t the frame rate consistent whether it’s a flower waving in the breeze or some action hero beating someone up?
WAG, when lots of things are moving around on the screen, that section of the video can’t be compressed as much and takes longer to send to your computer.
IIRC video compression relies parts of the video being static from one frame to the next. For example, if the software notices that this row of parked cars (not that it would recognize it as such) is exactly the same for the next 15 seconds, it might only send it the first time. But if there’s people walking past it, it changes from frame to frame.
It’s a little more complicated than that, in most compression schemes (including MPEG, some version of which is probably used here). They can also handle things changing slowly or smoothly. But when things happen abruptly, they can’t compress as well.
To see the two-dimensional analogue: Make an image file with, say, a face in it, then convert it to JPEG format at lowish quality (say, about 50%). It’ll still look mostly OK, because a face is mostly made up of gradual gradations. Now, make another image file with nothing but text in it, and convert that to a JPEG at the same quality: The text will be unreadable, or at least very hard to read, because there’s sharp edges between the background and the letters, and JPEG doesn’t like sharp edges very much. Well, the same thing that’s going on in the length and width of a still image is also going on as time passes in a movie: Gradual changes get compressed well, sudden changes don’t.
FOX chose to go with 720p because they said, the network was heavily dependent on sports. Progressive scans perform much better on fast action. Interlaced scans show artifacts.
