Hit counter

Greetings traveler,

Welcome to tech mag. You can read how is this site done.

Converting picture to AVIF

Format AVIF is open-sourced and royalty free optimised image format. AVIF offers significant file size reduction compared with JPEG, PNG and WebP. AVIF is 30% smaller than WebP and 50% smaller than JPEG. AVIF is based on AV1 video codec created by Alliance for Open Media. It’s supported by major browsers and major multimedia manipulation programs FFmpeg and ImageMagick. FFmpeg conversion After some testing, I found that SVT-AV1 library works the best. [Read More]

Installing Redmine 5.0 on Windows

Let’s install Redmine 5.0 - flexible project management on Windows. Official installation instructions are here. Study them carefully. Here are my notes based on trial and error while attempting to install Redmine 5.0.3 on Windows 10. Same steps can be used for upgrading installation. Download Redmine 5.0 installation zip. Install scoop In scoop add versions bucket Use scoop install -g ruby27 msys2 Run ridk install to finish ruby installation. On prompt press ENTER. [Read More]

Simple FFmpeg audio mastering

Before releasing video, audio part need to be mastered. We already write about audio level normalization. Today, we focus on most common cases in applying equalizer to audio. Filter adeclip Removes some artefacts created by clipping and prints clipping statistics. Always use. It will not lower volume under 0.0 dbFS, in fact true peaks will be slightly raised. Filter volume If volume is too hot, use filter volume to lower true peaks under 0 dbFS. [Read More]

Simple H264 Internet encoding with FFmpeg

Most common use case is to normalize audio level and reduce video bitrate before placing video on Internet. We will use patented H264 codec, High profile 4.2 for FullHD (1920x1080) footage. This profile is supported by iPhone 6 and iPad mini see here. Because we are running ffmpeg on command line manually and want just quick conversion we will use single pass encoding. Choose any target bitrate you want, in this example we choose 4500k. [Read More]

50 Intermediate Codecs compared

One of most often linked pages in video editing tutorials is Compare 50 Intermediate Codecs. This page compares bitrates of several industry standard intermediate codecs: DPX, Cineform, DNxHD, DNxHR, ProRes.

Intermediate codecs are used during editing video. Their advantage over highly compressed codecs like VP9 or H265 is very fast decompression at cost of much larger files.

Distributed randomness

Organization called League of Entropy is working on providing decentralized randomness beacon. Software implentation is called drand. League of entropy runs public pool where anybody can get high quality randomness. Entropy is collected from high quality randomness sources, such as lava lamps. Pool endpoints are listed here. Here you can see pool metadata. Randomness is 32 bytes long and its changing every 30 seconds. You can get not only current randomness but also all past numbers. [Read More]

IEEE-754 storing of floating point numbers

How are floating point numbers stored in computer? To understand how IEEE-754 Floating Point numbers works internally visit IEEE-754 Floating Point Converter.

It can convert floating point numbers from or to their internal binary representation. 32-bit floating point numbers are stored 1 sign bit, 7 bit exponent, 24 bit mantissa.

Video file size calculator

When you are working with professional video formats its always good to know estimated file sizes. Files are pretty big - up to 2 GB/minute for FullHD 1080p 30fps video.

There is pretty nice Omni Video size calculator where you can compute size of most common professional video formats such as AVID, Cineform, DNxHD, ProRes, REDCODE, DVCPROHD. Note that very common DNxHR codec is not included.