Kostya's Boring Codec World

Sometimes I’m asked what codec I’ll do next. So here’s the answer: I don’t really know.

Since I’m no longer student I don’t have much time to dedicate to reverse-engineering.
Thus I work on different codecs time from time and select such codecs more or less in random.
When I see that it’s nearly completed I spend more time on it till I write a decoder.
That’s how I got RALF decoder, for example.
Or that’s how I have not got Discworld III BMV decoder: long time ago I’ve figured out container format and audio compression, a month ago I’ve advanced in video decoder; but it’s far from completion and I don’t know when I’ll work on it again.

Of course some factors affect my selection of codecs: if I have some interest in it, if it serves some theoretical purpose (e.g. I did Indeo Audio and RALF not because I needed them but to have respective families of codecs fully supported) or if somebody convinces me to do it (two words – GSoC 2007).

So if you ask for some decoder you might get it after a while (but no obligations unless you send me a box of Trocadero).
Don’t forget that samples should be present too (and decoder for the more complex formats).

For one of my friends – Lost Eden finally running on Amiga.
(screen grabber output only HAM8 CDXL thus screenshot quality is not the best, click it for fullsize version).

Though someone should write HNM4 decoder one day…

With the addition of VBLE decoder I thought once again about codecs and how they are written.

Lossless Video Codecs

There are two approaches:

• Take a frame, apply one or two general compression schemes to it. Can be zlib, RLE+zlib or motion compensation from previous frame + zlib.
• Discover spatial prediction (usually from left neighbour or median) and add some coding for residues. HuffYUV, Lagarith, UtVideo, VBLE, LOCO, FFV1, whatever.

Lots of people try it, find that their codec is faster/compresses better than HuffYUV and release results. Usually those codecs don’t live long and the only bad thing about it is they being released to public in the first place.

Lossy Video Codecs

The codecs are usually more complex, so there are less of them. But there are more ways to create one.

• lossily quantise raw data or DCT output Every self-respecting company producing frame grabbing cards has written such codec.
• take a draft of some standard codec and base your work on it That’s how we got Window$ Media, R3al and Off2 video codecs.
• WAVELETS!!!!111oneone
• another approach to compression like vector quantisation, binary or quad tree decomposition, object-oriented representation (though this one is mostly used in screen capturing codecs), etc.

The main problem with these codecs is achieving good compression parameters without much hassle. For example, libavcodec MPEG-4 encoder may be the best around here but (like Soviet machinery) one has to work real hard to find out which parameters he/she needs to set to which values to get good compression. That’s the reason why people often choose Xvid instead.

Lossless Audio Codecs

There is one approach to those: add lots of crazy filtering (usually several chained filters) and equally crazy coding of residues. There you got it. Simple filters = faster compression, complex filters = slightly better compression with significantly longer compression times.

Last abstract from lossless video codecs applies to audio as well.

Lossy Audio Codecs

Those appear not too often because it’s very hard to satisfy everybody’s ears. Thus (IMO) it’s mostly limited to speech codec development. And there’s Xiph of course.

I’m rather picky person, so I don’t drink alcohol, try to avoid drinking Coca-Cola or Pepsi and hate still water (especially Danish one). So here’s my review of what I could drink in different countries.

Ukraine

There are many different soft drinks, mostly of mediocre quality, but some are quite good. There are some good mineral waters too (the best one is hard to find outside the region where I lived, sometimes it’s hard to find there as well).

And usually drinks are sold in all varieties of bottles — from 0.5l to 2l

Germany

Mostly you get here is very good selection of mineral water, Apfelschorle and variations of Spezi (aka tyska oriktiga Trocadero). There are also some strange flavours like cherry+ginseng or bitter lemon (tastes mostly like lemon skin). Oh, and 0.5l bottles for those drinks made by Coca Cola company (seems Germans prefer local inventions to their main product) look like designed by Norwegian, the bottle is made from too thick plastic and maybe it was designed in 3D CAD without Bezier curves support.

Switzerland

Mostly the same as in Germany but with more pathos and higher prices (while in Austria Apfelschorle is called something like “sprudel Apfelsaft”, in Switzerland I’ve seen “Shorley”). That goes for most Swiss products anyway.

Denmark

Those people seem to hate carbonated mineral water (usually Danish mineral water with gas has only two bubbles to distinguish it from still water) and the only time I tasted their drink it was too sugary.

Belgium

Looks like it’s better to buy orange juice there instead.

Finland

Very good selection of drinks.

Norway

Limited but rather decent selection of drinks. The bottles look like they were made from single piece of plastic mostly with axe.

Sweden

One of the reasons I love Sweden. Excellent selection of drinks, including special seasonal ones (Julmust and Påskmust). Here’s an example of Påskmust:

And of course, there’s the ultimate drink (IMO):

There are about eight different breweries producing it, I have tried it all except for two breweries.
And I have tried all but one soft drinks from Vasa Bryggeri. Probably I should go to Norrland again.

As for mineral water, they have Ramlösa, good water from Bergslagen region and even from the tap in many regions (it’s drinkable everywhere in Sweden, but tastes especially good in some places).