Saturday, August 15, 2015

screencast and tablet notes

These are a few mathematics screencast notes.

Huion 1060 Pro +

A surface to write equations. Against the cost of a Wacom, or the price of a full-blown pressure sensitive tablet PC, I think I saved money with this $65 Huion. It plugs in works with Xournal out of the box. I haven't yet played with programmable keys on its side -- I'll do a separate post downstream. Meanwhile, Xournal is friendly with it, and no problems with basic functions.


The second cable charges the pen, and then there are extra pen nibs in the bottom of that penholder. You can see those programmable keys to the left side of the unit and the pen has two programmable keys. The penholder keeps the nib from pushing against anything -- that uses battery juice. I put mine, nib up, in a jar. A light touch does the trick when writing.

Ardesia - Composite Manager requirement

Ardesia seemed worthy of checking-out against Xournal. Ardesia's dependencies install OK, using pacman, and then Ardesia itself is found using yaourt. All went well, but first run revealed:
$ ardesia
In order to run Ardesia you need to enable a composite manager
Of course, I don't want to install or enable any compositing windows managers, who does? More importantly I don't understand the need for one here. For example, Xournal functions just fine without a composite manager, and I can't see the need for multiple windows in a drawing app the simple ways I will use it. Perhaps Ardesia's coders somehow expected graphics-card intensive usage for superstar effects, or perhaps they're lazy, but I'm not going there. Xournal remains my solution.

VLC recording

As described here, VLC has the capacity to capture, not simply play. I mostly use RecordMyDesktop for this, but have taken to at least experimenting with VLC, for the simple fact of rendering. RecordMyDesktop only produces OGV's and, for editing, I'm pretty much limited to OpenShot. But OpenShot is extremely CPU intensive when rendering OGV's. VLC seems to provide MP4 formats, which are much easier when rendering the final edit.


Recordmydesktop - XGrabKey error

$ recordmydesktop
X Error: BadAccess (attempt to access private resource denied)
Bad Access on XGrabKey.
This appears to be an audio permission or configuration issue, since video was perfect. Usually when sound is a problem, PulseAudio has surreptitiously been enabled by some application. Check with "$ arecord -L", which lists capture devices. If PulseAudio is anywhere on that list, get busy killing it to the last byte. I go over this in a previous post, and
there's also a great link here. But be sure that PulseAudio is well and truly dead on your system.

quick edit

If you don't have to cut stuff out of the middle, just maybe from the start or end, you can edit using ffmpeg, and whatever your audio editor for WAV's is. Just clean it up, put it back together, and then snip the ends. I use mencoder for the snipping step: simpler command than ffmpeg.
$ ffmpeg -i screencast.ogv -vn -ar 44100 -ac 2 sound.wav
[clean your sound]
$ ffmpeg -i screencast.ogv -vcodec libxvid -b:v 500k -an video.avi
[convert ogg to xvid]
$ ffmpeg -i video.avi -i sound.wav -acodec libmp3lame -ar 22050 -ab 192k -ac 2 -vol 330 -vcodec copy -b:v 500k screencast.avi
[reassemble sound and video]
With this all clean, just trim whatever seconds off. In this case, I'm trimming the first 10 seconds off:
$ mencoder -ss 10 -oac copy -ovc copy screencast.avi -o screencastout.avi
YouTube is a 16:9 format, incidentally, another story.

OpenShot (300MB)

Ridiculous size, but it's the most straightforward timeline editor I've seen.

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