undefined | Better HN

0 pointsfreeone30005y ago0 comments

The screen refresh rate on these devices is measured in seconds, so a few hundred millis of network latency is impossible to display.

0 comments

8 comments · 5 top-level

shajznnckfke5y ago· 2 in thread

That doesn’t seem right. Let’s consider the screen refresh to be like a subway station, where the train shows up every few seconds. We need the text we want to show to the user to be at the stop waiting when the train arrives. If we miss the train, we need to wait for the next train to get our text on the screen. The network latency delays when we show up to wait at the station.

If the refresh rate is 5 seconds, and the network response time is 500ms, than eliminating the 500ms response time means we are 10% less likely to miss the train. On average, the time for the text to appear on the screen decreases by 500ms.

All this assumes the refreshes happening on a static schedule. If the software can trigger the refresh, then it’s a lot simpler. The 500ms improvement in latency would apply equally to every engagement with the translate feature.

freeone3000OP5y ago

There's no static schedule. It's an e-ink display. Refreshes happen when software tells it to display something new and take several hundred millis per blank - and a screen can be up to three blanks (because if it doesn't go white-black-display, then some pixels get stuck "on" or "off" or "halfway").

shajznnckfke5y ago

In that case, it’s clear that eliminating the network request before triggering the refresh directly reduces the amount of time the user has to wait to see the result.

notatoad5y ago· 1 in thread

have you actually used a kindle? it certainly doens't take seconds for the definitions to pop up. a full-page refresh might take a second, but most page turns or UI interactions are partial draws and are much faster.

II2II5y ago

I suspect that they were overstating a limitation of these devices rather than speaking from inexperience. While it has been years since I've used a Kindle, I do use Kobo devices and the delays are perceptible. While changing a page may be quite quick, user interface elements (such as a box containing a definition) seem to take longer. I suspect that they have to be more agressive when refreshing the screen before and after these user interface elements are displayed in order to make the ghosting less perceptible.

If you want to see what I mean by the ghosting of user interface elements being more perceptible, try using KOReader. The ghosting after using a menu can be quite noticable (at least on Kobo devices, which are based on the same technology).

fouric5y ago

This isn't universally true - Dan Luu's computer latency page[1] lists three Kindles, all below 900 ms of latency. And, since some devices have latency as low as 570 ms, it makes sense that they would use this optimization.

[1] https://danluu.com/input-lag/

1 more reply

dahfizz5y ago

You're exaggerating how slow the screens are.

And the fact that the screens are slow should be motivation to make the rest of the system as responsive as possible. A good software engineer will work around bottlenecks, not shrug their shoulders and introduce new ones.

lapetitejort5y ago

Also remember that "Kindle" can refer to an app on your phone or desktop computer, all of which may share code related to highlighting and translating.

j / k navigate · click thread line to collapse