Quote:
Originally Posted by knc1
...
Seems like we could run one of those, with the most recent set of samples taken from the audio stream buffer, just before each e-ink update. Even at a blazing e-ink update rate of 15fps. 
I.E: Adding another 6 us in front of each e-ink update to display a rt, graphic, equalizer with a spectral display isn't going to be noticeable - not even to the processor. |
The K3 does not return from the eink update calls until it is (usually) ready for you to write to the framebuffer again. How long it takes depends on the complexity of the scene change. For dithered animation the average speed is 7.7FPS (if you add a slight delay for less artifacts). If you go "by the book" you are supposed to wait longer (about 4 FPS) to avoid visible artifacts, and if you go even a little faster (7.8FPS) the animation quality does deteriorate significantly (which is why I settle on the 7.7FPS compromise). Although a K4/K5 can go faster with its different (SoC integrated) eink controller, it looks okay at 7.7FPS so I used that as my "standard" framerate in the GMV files.
The K4/K5 can run up to 45FPS with VERY carefully chosen animation, but for general unfiltered animation, 7.7FPS (average) is about as good as it gets. I can push out a little more speed without significant artifacts by doing spatiotemporal smoothing (averaging across multiple frames) to the video, which I did in a couple of tests, but that does not speed things up on the K3 so I do not make a habit of encoding with that smoothing.
It may turn out that how you display the FFT data may be able to do 15FPS on a K5 (and a K4 in diags mode), but the K4 in main mode emulate K3 eink (mostly) so it limits what kindle model you can use.
There is not much CPU left over on a K3 either while playing video with sound.