Kostya's Boring Codec World

This post is inspired by the fact that in these two days I’ve passed by two towns named Eberbach. For people without German knowledge: this name translates as “Wild Boar’s Spring”. For people with French knowledge — feel free to laugh that the second town is actually called Eberbach(Fils).

It may be insignificant name for you but not for me. There is no official animal for Ukraine, but if you ask people, most chances it will be pig (like bear for Russia). Thus, one may ask “do they name any towns or villages after it in Ukraine?”. Guess what? I’m aware of only one village named “??????”, which can be translated as “Little Boar (village)” or this (hopefully). In the same time (if German Wikipedia doesn’t lie) there’s maybe half a dozen of Eber… towns in Germany (mostly in Baden-Wuerttemberg and Bavaria) and one Schweinfurt (i.e. “Swine Ford”, also in Bavaria).

Pig is the only animal that Tatars and Turks didn’t take during their raid on Ukrainian territory, that’s why Ukrainian population should have very reverent position to pigs (and if you ask, say, Russians you’ll hear that Ukrainians are obsessed with “salo” which is obtained from pigs). Despite that there’re no towns named after it and only two or three monuments to pigs in whole Ukraine (IIRC all of them were installed in last ten years or so). It’s definitely a shame and may partially explain why Ukraine is in such deep you-know-what.

Since I stuck in Germany for a while, I like to explore nearest places (though I’d better go see Malmö, Sundsvall, Uppsala and, of course, Stockholm). Here are my impressions after visiting a dozen of different towns.

Due to my location I mostly visited places situated near Rhine, so my sampling may be biased.

My first observation is that smaller towns are usually better (look more beautiful, nicer and more comfortable) than larger ones. For example, in Baden-Württemberg I’ve seen: Baden-Baden, Bruchsal, Donaueschingen, Eberbach, Freiburg, Heidelberg, Karlsruhe, Mannheim, Offenburg, Pforzheim, Stuttgart. Among those I liked Mannheim and Stuttgart the least. Guess what are two biggest cities in this region? Stuttgart also serves for a capital. It’s famous for one guy who invented bicycle and one of the first to invent typewriter (what do you know, Germans still love bikes) and several other guys inventing car (there are still Daimler-Benz and Porsche works in Stuttgart along with their own museums).

Köln (aka Cologne) is the fourth biggest city in Germany. While it has very impressive architecture and interesting museums, it’s queer. Seeing slogan “From Cologne to Cleveland. Gay games 2014” does not improve my impressions. Seriously, Cleveland? It’s rumoured to be one of the worst cities in USA. I’m pretty sure that, for example, Bonn is better despite being former governmental place. Also I’ve heard that they have special dialect, even less understandable than Schwabish (not a problem for me, I can’t understand any German dialect anyway).

Rhineland-Pfalz (aka Rhineland-Palatinate) has no big cities, its capital Mainz has around two hundred thousand people but those towns are beautiful! Well, except Ludwigshafen unless you like concrete panel buildings and chemical industry. Also it’s worth reminding that Mainz was a cradle of one of the most important inventions ever – printing.

I’ve been in Hamburg for about an hour but this (the second largest German city) is also not impressive.

Well, guess what German city sucks most in my opinion (and not only because it’s built on a swamp)? Of course, it’s Berlin. The only good place I’ve seen there is musical instruments museum. The rest looks a lot like Kiev – skyscrapers in the city centre and mostly neglected buildings in other areas. Not to mention that even S- and U-Bahn stations look too spartan and underdesigned. Makes you think that West Berlin was a myth.

The only major exception is Bavaria (even some Germans consider it to be a separate country and not a real part of Germany). They make good cars, they have wonderful tourist attractions, they have very good music (though Wagner was born in Leipzig), they have wonderful nature too. They even had special Monty Python Flying CircusFliegender Zirkus series filmed there, it’s hard to beat that.

I still have to visit Central and East Germany but I don’t think it will change my opinion. And maybe I’ll have a chance to compare Strasbourg to Paris. I suspect result will be quite similar.

Since I work on multimedia stuff, I had some chances to look at different specifications for audio codecs as well as video ones. And comparing those specifications led me to rather surprising conclusion:

Video codec specifications are better than audio ones

I admit that I might miss some details or interpret something wrong yet here’re my impressions.

Video codec specifications tend to be complete and while they are not always easy to comprehend you can write codecs after them (well, maybe in VP8 case you need to add some glue code to reference decoder disguised as specification). And those specs usually cover everything, including extensions and rather freely obtainable (usually drafts are good enough for all practical purposes). I know mostly ITU H.26x, MPEG video and SMPTE VC-1 codecs but that seems to apply to all of them.

Audio codec specifications often lack those features. Looks like they offer you more or less complete version of core decoder and good luck finding description of extensions. And even then they manage to lie or omit some things.

MPEG Audio Layers I-III — no objections (except for Layer 3 bitstream design, of course).

AAC — nothing wrong with core bitstream parsing. Heck, I even managed to write something that produces valid AAC stream (sometimes) that can be decoded into recognisable sound (with a bit of luck). Now look at the extensions — they are very poorly documented. That was the reason why FFmpeg got AAC SBR and AAC PS support that late.

ATSC A/52 (some call it AC3) — again, nothing wrong with core decoder. FFmpeg even got encoder for it long before native decoder (you can blame liba52 for that too). But E-AC-3 is a different beast. It’s mostly okay unless you try implementing enhanced coupling or dependent streams. The former has some bugs so implementing it right by the specification will result in decoder failing to parse bitstream sometimes and the latter is almost fine but in version available in the wild there’s no mention that some of extension channels are actually channel pairs. Good luck figuring it out by yourself.

DCA — it was fun when I discovered that actual CRC calculation is performed with polynomial different from the one given in specification. Luckily nobody bothers about it. Some of the tables are not given in specification — DCA is the codec with the largest amount of tables if you count its extensions (TwinVQ is a close competitor though), so they decided not to give tables with more than 1024 elements in specification. You need reference code for that. And good luck finding specifications for extensions. And I assure you that like in case with E-AC-3 reference decoder sometimes does different things than written in spec. The most wonderful part? Your decoder should be bitexact if you want lossless mode operating properly and looks like the only way to do that is to copy a lot of stuff from reference decoder.

Speech codecs (AMR-NB, AMR-WB, ITU G.72x, RFC xxxx) — some of them nice but I still have that impression that most of them had specifications written by the next formula: “Here’s how it should operate in principle, I don’t remember exact detail anyway but we need to write something here, you have your reference decoder source so bugger off”. I remember looking at
those G.72x specs (some are quite nice though), I remember troubles Robert Swain had with AMR-NB decoder (I tried to help him a bit with it too) and there’s some speech codec (iLBC?) that simply dumped all source code files into RFC body without much explanation.

That’s why I claim that audio codec specifications are generally worse than video codec specs. I think if somebody ran simple test on specs assigning penalty points for things like:

• containing non-obvious pseudocode constructs like QTMODE.ppq[nQSelect]->inverseQ(InputFrame, TMODE[ch][n])
• containing five-line pseudocode for what can be expressed in one clear sentence
• containing source code listings (bonus points for spanning more than one page)
• omitting details essential for implementation
• lying about details (i.e. when reference decoder and specification disagree)
• assigning decoder to do irrelevant tasks (like upsampling, postfiltering and such)

virtually no audio codec would have zero score unlike video codecs.

While I’m extremely lazy maybe it’s time to write about my new work.

Yes, I’ve finally got a job in civilised country (Germany). I admit, I’ve chosen the offer based mostly on environment and what I got:

• my work — working on multimedia technologies implementation (codecs for now).
• my colleagues — nice and friendly people with good knowledge so I don’t feel alone and can talk about technical stuff too.
• my living place from consumer position — maybe not ideal but with very good infrastructure and mostly I can easily get what I want.
• geographical position — not far from Rhine and near Schwarzwald, so I can enjoy scenic landscapes as well.

Overall conclusion: I was lucky to pick this job. Though I still miss Sweden but life is not ideal.

There is only one thing that may taint the joy of REing yet another codec. It’s when you realize that most of the samples you want to decode are coded with another codecs.

While recent Indeo 5 decoder addition allows playing many files, I found out that I have more samples encoded with Indeo 4. Even though I have Bink Video decoder it looks like I don’t have much samples for it. But there are many other games with custom codecs worth REing.

Yet it’s not that bad as sounds. M$ Video 1, Cinepak, Smacker and Sierra VMD seem to cover most of the samples I have interest in. Luckily for me there are many codecs left to RE for which I have some interest. Another guy had fulfilled his dream of being able to watch movie trailers in QuickTime format, so there’s almost no new work from him.

P.S. After I’d published that “looking for a job” post, I got many proposals, but for some reason they are mostly for USA and some people asking if I’d consider Australia too (BTW, answer is no, it’s too warm place for me and I plainly can’t work in such conditions). Either I want something unrealistic (i.e. job in Europe) or it’s Murphy Law in action.