VDPAU Playback Issue (Problem Solved).

One of the facts which apply to Linux computing is, that NVIDIA created an API, which allows for certain video-streams to be played back in a way accelerated by the GPU, instead of all the video decoding taking place on the CPU. And, users don’t necessarily need to have an NVIDIA graphics card, in order for certain graphics drivers to offer this feature, which is called ‘VDPAU’, an acronym that stands for “Video Decode and Playback API for Unix”. Simultaneously, what some Linux users can do, is to experiment with shell-scripts that allow us to click on a specific Application Window, in order to perform screen-capture on that Window for a specified number of seconds, ad then to compress the resulting stream into MP4, AVI, or MPG -Files, once the screen-capture has finished. This latter piece of magic can be performed using elaborate ‘ffmpeg’ commands, which would need to be a part of the script in question. And in recent days, I’ve been tweaking such scripts.

But then an odd behaviour crept up. My NVIDIA graphics card supports the real-time playback of MPEG-1, MPEG-2, DIVX and H.264 -encoded streams, with GPU-acceleration. Yet, when I clicked on the resulting animations, depending on which player I chose to play those with, I’d either obtain the video stream, or I’d just obtain a grey rectangle, replacing the captured video stream. And what I do know, is that which of these results I obtain, depends on whether I’m playing back the video stream using a software decoder purely, or whether I’m choosing to have the stream played back with GPU-acceleration.

I’ve run in to the same problem before, but this time, the cause was elsewhere.

Basically, this result will often mean that the player application first asks the graphics card, whether the latter can decode the stream in question, and when the VDPAU API responds ‘Yes’, hands over the relevant processing to the GPU, but for some unknown reason, the GPU fails to decode the stream. This result can sometimes have a different meaning, but I knew I needed to focus my attention on this interpretation.

Linux users will often need to have some sort of file-format, in which they can store arbitrary video-clips, that do not need to conform to strict broadcasting and distribution standards, even when the goal is ‘just to monkey around with video clips’.

I finally found what the culprit was…

(Updated 8/15/2019, 22h15 … )

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“Weather Widget” for Plasma 5 -based, Linux Computers

One of the observations which I’ve made about the practical use of Linux, is that in recent years and weeks, the number of weather widgets which we can use to decorate our desktops, and which provide some semblance of forecasting, has become more meager.

I suppose that one important reason may be the fact, that companies cannot extract revenues from operating servers, which simply respond to URL-requests, and which hand out weather information on that basis, for the client software to process as client wishes. Companies will only make profits these days, if they can force their clients to view advertisements.

And so recently I installed a widget, to my Debian / Stretch, Plasma 5 -based desktop computer named ‘Plato’, which is named ‘Weather Widget’, and which has the following display available:

screenshot_20180831_105340

This widget has as option to display information from ‘openweathermap.org‘, which has as intention to remain open and available.

There was a detail in how to get this widget running, that wasted some of my time yesterday, for which reason I’d like to share my experience with the reader. First of all, the preferred way to install this widget is, to right-click on the desktop, and then to left-click on “Add Widgets…”. If the desktop widgets are locked, the command must be given to unlock them first. Then, in the side-bar that appears, we click on “Get new Widgets” (at the very bottom), and then on “Download New Plasma Widgets”. In the window that appears, there’s a search field. In it, type ‘Weather’, and the widget in question should appear as available.

One great plus to adding widgets in this way, is the fact that we can do so, in user space, that is, without requiring root. However, here comes the catch: This widget will only display correctly, under Debian / Stretch, if the following two packages are installed:

  • ‘qml-module-qtgraphicaleffects’
  • ‘qml-module-qtquick-xmllistmodel’

Under other Plasma 5 -capable distributions, the same features may be provided by packages, which are named slightly differently.

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