Dee Mon's blog

A video codec in JavaScript

Sat, 25 Nov 2017 15:55:55 GMT

Recently we released a pure JavaScript implementation of in-browser player for our lossless video codec ScreenPressor. It supersedes our old player made with Flash. Here's some anecdotal evidence of how fast current JavaScript interpreters in browsers are. The chart shows Frames Per Second:

Here we took a screen recordin...

We're in good company

Tue, 30 Aug 2016 15:55:55 GMT

Just noticed our company listed on the page Organizations using the D Language, right under eBay and Facebook. Really nice to find oneself in such a good company!

Indeed, Video Enhancer, BlogSort, Undup and AutoVideoEnhance are all written in D programming language. As well as some minor inte...

Information theory and video upscaling

Sat, 30 Jul 2016 15:55:55 GMT

Often when people first hear about Video Enhancer and its main feature, super resolution video resizing, they say "No way, it cannot work! If information is lost in downsizing you cannot get it back." And when we're talking about total information in a video they are absolutely right. However when looking at particular frames... Here's an experiment for you. I captured a couple of phrases with my two revolutionary ASCII video cameras that capture text, unfortunately one camera has low...

Error-checking smart pointer

Wed, 27 Apr 2016 15:55:55 GMT

As you might know, in the world of Windows programming COM is still actively used, alive and kicking after all these years. It must be usable from plain C so for error handling they use return codes: most functions return HRESULT, an integer that is zero if all went well, negative in case of error and positive if it went "okay but...". Return codes should not be ignored or forgotten, they need to be handled, and in practice it is often the case that all local handling logic reduces to...

Static introspection for message passing

Sat, 23 Apr 2016 15:55:55 GMT

There is a famous in PLT community paper on free theorems, giving praise to generics and parametricity allowing you to infer a lot about some generic function behavior just from its type, because since such generic function does not know anything about the type of value it gets, it cannot really do much with this value: mostly just pass it around, store somewhere or throw away. On the other end of generics spectrum (call it "paid theorems" if you will) we have languages like D where a...

One-pass deshaker

Wed, 25 Nov 2015 15:55:55 GMT

This autumn, by request of our client, we developed a video deshaking method that works in a single pass, in streaming mode. I know there is a very nice Deshaker filter for VirtualDub but it works in two passes: first it collects motion data, then plans for whole movie and in the second pass performs actual changes to the video. When your video processing pipeline is quite heavy, loaded with many filters or something computationally expensive, doing the work twice or saving it into a ...

Dependent types in half of D

Thu, 30 Jul 2015 15:55:55 GMT

Recently I saw a talk by one of active Idris contributors: David Christiansen - Coding for Types: The Universe Pattern in Idris where he shows some uses of dependent types. I'd like to use some of those examples to demonstrate that we actually have dependent types in D, or, really, in part of it. First let me show some original examples in Idris, a full blown depentently typed language, and then we'll translate t...

From native code to browser: Flash, Haxe, Dart or asm.js?

Mon, 17 Nov 2014 15:55:55 GMT

If you developed your own video codec and wanted to watch the video in a browser what would you do? That is a question we faced a few years ago with ScreenPressor and at that time the answer was Flash. It was cross-platform, cross-browser, widely available and pretty fast if you use the right programming language, i.e. Haxe instead of ActionScript. So we implemented a dec...

Optimizations in a multicore pipeline

Thu, 06 Nov 2014 15:55:55 GMT

This is a story that happened during the development of Video Enhancer a few minor versions ago. It is a video processing application that, when doing its work, shows two images: "before" and "after", i.e. part of original video frame and the same part after processing.

It uses DirectShow and has a graph where vertices (called filters) are things like file reader, audio/vide...

The real problem with GC in D

Mon, 29 Sep 2014 15:55:55 GMT

About a year ago one blog post titled "Why mobile web apps are slow" made a lot of fuss in the internets. In the section about garbage collection it showed one interesting chart taken from a 2005 paper "Quantifying the Performance of Garbage Collection vs. Explicit Memory Management":

photo editing app, disk space visualizer and analyzer, a tool for automatic video processing, a tool for reading DirectShow graph files as text, all in D (and all fr...

Recursive algebraic types in D

Mon, 15 Sep 2014 15:55:55 GMT

One of the things D programming language seemingly lacks is support for algebraic data types and pattern matching on them. This is a very convenient kind of types which most functional languages have built-in (as well as modern imperative ones like Rust or Haxe). There were some attempts at making algebraic types on the library level in D (such as Algebraic template in std.variant module of D's stdlib) however they totally failed their name: they don't support recursion and hence are...

On Robin Hood hashing

Sat, 13 Sep 2014 15:55:55 GMT

Recently I played a bit with Robin Hood hashing, a variant of open addressing hash table. Open addressing means we store all data (key-value pairs) in one big array, no linked lists involved. To find a value by key we calculate hash for the key, map it onto the array index range, and from this initial position we start to wander. In the simplest case called Linear Probing we just walk right from the initial position until we find our key or an empty slot which means this key is absent...

D as a scripting language

Fri, 12 Sep 2014 15:55:55 GMT

Many of us encounter small tasks involving some file operations, text processing and running other processes. These are usually solved using either shell or glue languages (often called scripting languages because of this) like Python, Perl or Ruby. Compiled statically typed languages are rarely used in such cases because popular ones usually require too much effort to write and run a simple script. However some static languages can actually be used here easily instead of scripting on...

Special treatment for Deshaker

Tue, 27 May 2014 15:55:55 GMT

There is a nice filter for VirtualDub (supported by Video Enhancer) called Deshaker by Gunnar Thalin which can stabilize shaky video. This filter is different from the others because it works in two passes: first it needs to see the whole video and analyze it (without producing a meaningful video result yet), and on the second pass it uses collected data to actually fix the video. The data collected in first pass is stored in a file which can be specified in filter's options. If you s...