How SDL Accelerates Video Output under Linux.

What we might know about the Linux, X-server, is that it offers pure X-protocol to render such features efficiently to the display, as Text with Fonts, Simple GUI-elements, and small Bitmaps such as Icons… But then, when it’s needed to send moving pictures to the display, we need extensions, which serious Linux-users take for granted. One such extension is the Shared-Memory extension.

Its premise is that the X-server shares a region of RAM with the client application, into which the client-application can draw pixels, which the X-server then transfers to Graphics Memory.

For moving pictures, this offers one way in which they can also be ~accelerated~, because that memory-region stays mapped, even when the client-application redraws it many times.

But this extension does not make significant use of the GPU, only of the CPU.

And so there exists something called SDL, which stands for Simple Direct Media Layer. And one valid question we may ask ourselves about this protocol, is how it achieves a speed improvement, if it’s only installed on Linux systems as a set of user-space libraries, not drivers.

(Updated 10/06/2017 : )

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Getting Some Software To Run On My Linux Tablet, which Was Not Meant To Run

One of the computing adventures which I’ve been blogging about, is that I’ve been able to install a Linux Guest System, under the Android Host System, on my Samsung Galaxy Tab S, First-Generation tablet. I use the two Android apps, ‘GNURoot’ and ‘XSDL’, which can be obtained from Google Play, and which do not require root.

In this posting, I had as a message to my readers, that certain types of Linux applications are poor candidates for this sort of environment – a chroot-Linux-Shell, that connects externally to an X-server, which in turn seems to provide pure X-server protocol as well as a port, to connect PulseAudio clients to.

But in the same posting, I had named a specific Linux-application, which would solve each of the two purposes, and which in my opinion at the time, might have the best chances to run – assuming that any have a chance to run:

  1. ‘mhWaveEdit’
  2. LiVES

As some of my readers might expect, since that posting, I have nevertheless pressed ahead, and experimented with installing each of these Linux-applications, on the guest-system.

Long story short, I found that mhWaveEdit seems to work fine, and installed effortlessly, while LiVES does not.

screenshot_2017-10-04-01-27-35

One observation which I’ve made, is that the PulseAudio server built-in to the Android app ‘XSDL’, offers sound output, but not sound input. Hence, I cannot connect to the mike, which is built-in to the tablet. But this is a very minor issue, since I’ve exceeded typical usage-scenarios in what I’ve already been able to do.

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