Blogs

Several weeks ago, I noticed a serious decrease in performance on my local area network. The first indication of a problem was latency when streaming videos from my media-server. My Raspberry Pi Kodi systems were all working fine, but any time I tried to play an HD (or 4K) video on Macbook, I experienced significant stuttering and buffering issues. My initial thought was that it was related to a MacOS update, and I was afraid my venerable Mid-2012 era Macbook was reaching end-of-life. This turned out not to be the case.

After using ffmpeg for a number of years, I've learned that there's virtually nothing it can't do. So when I recently encoded a video with "black bars" by mistake, I thought it might just be quicker to crop it than re-encode it. Naturally, ffmpeg can do that. A quick google revealed the following solution on stackoverflow. Here is a summary of the two-step process:

First, identify the size and position of the black border:

LibreOffice is a great suite of software for your standard "office" needs - Text documents, spreadsheets, presentations, and so on. Occasionally, I find the need to make a LibreOffice text document (odt) searchable via command-line tools such as grep. Since the ODT format is actually a package (somewhat like a zip file), it is not directly searchable. Fortunately, the authors provided a solution for this need. The syntax is simply:

While there's no substitution for good lighting and exposure, every so often I come across a video which is a bit on the light or dark side. While there's no perfect correction for exposure deficiencies, ffmpeg does have some tools to correct for the "middle gray" point, that is, to make an video brighter or darker without affecting the lightest highlights or darkest shadows. This is called a gamma adjustment. First, test a few settings and see how it looks, comparing the playback with the original:

Occasionally I come across a video (generally a WMV/ASF file) which contains an obviously incorrect aspect ratio in the metadata. Coming from the still photography world, I'm a neophyte when it comes to video encoding, but I've come to rely on FFmpeg to handle this type of problem.

Note: this article is about the linux shell command for reading or writing raw data from a storage device, NOT the PHP/Kint function for dumping data in a web application.

Note: this article is about the PHP function for dumping data in a web application, NOT the linux shell command for reading or writing raw data from a storage device.

I like to record the occasional audio stream for offline listening. Sometimes my recording software pauses and I end up with multiple captures and separate files. I've used tools like Amadeus to edit audio, but it decodes, then re-encodes audio upon saving or exporting. What I really wanted was simply to combine the two audio files, similar to how I use the cat command for text (and other format) files. Naturally, there was a solution on stackoverflow.com.

A number of years ago I attended the ARRL Teacher's Institute. In addition to some amazing instruction, we received some amazing gear to take home and play with. One of these was a PicoScope 2204A digital oscilloscope. I was pleasantly surprised to discover that they support the Debian family of Linux distros.

I'm sure I'm late to the party, but I recently started delving into MySQL variables. It may or may note help with the problem I'm currently dealing with, that of excessively lengthy queries.