Sometimes when I have an acute nostalgy I try to cook something from my homeland.
First time I made
Köttbullar (med potatis och lingonsylt självfallet). Too bad I could not do it SWEDISH STYLE! :-(. This time I tried to make Janssons frestelse. Jag hade inget burk ansjovis men bohusmatjessill i stället blev lagom bra.
With the addition of VBLE decoder I thought once again about codecs and how they are written.
There are two approaches:
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.
The codecs are usually more complex, so there are less of them. But there are more ways to create one.
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.
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.
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.
Time from time there are mails from FFmpeg developers to different distributions saying “Oh, we are better, have more features and more secure, pick us and not libav”. In case somebody wonders here are two examples: Ubuntu and Debian.
So let’s walk through and see the claims. Comparison was made from git snapshots made 2011-10-15 11:00 CEST.
More codecs
FFmpeg claims to have more codecs. In numbers that’s true. Let’s see what are those codecs though:
In conclusion, those additional codecs supported by FFmpeg are either hardware acceleration (VDPAU, CrystalHD, stagefright), trivial or some old patches previously rejected but now picked up to maintain impression of superiority.
More muxers and demuxers
Now to muxers and demuxers.
Most of (de)muxers are either for formats we don’t support or trivial. But I admit there are maybe two demuxers and one muxer that can be included into libav after some cleanup.
Filters
I’m not fully familiar with filter subsystem but it still has too many problems and having an ugly wrapper for MPlayer filters (which are also not of the highest code quality) was one of the points that drove FFmpeg-libav split.
Features, security and overall
When FFmpeg claims to have more features than libav it’s true — they merge everything from libav nowadays. And FFmpeg gets more side features for two reasons: the name is more known and it’s easy to get a feature in because nobody seems to bother with proper reviews nowadays. As for security, it’s the same. For example, when there was a report for some minor security flaw in Chinese AVS decoder, original patch from security investigators (applied in FFmpeg) just made decoder more secure but it still crashed on that file, in libav we created our own patch that dealt with both of these problems. FFmpeg often reminds me of a saying “Socialistic system successfully overcomes the problems it creates itself”.
In conclusion, my opinion is that FFmpeg is trying to compete with libav by lowering standards on accepted stuff. Hence the name of this post.
And I’m glad we can’t have commits like this. For those who have not so good C understanding: it compares addresses of two different strings and it’s an undefined operation that works mostly by luck. So my advise is simple: if you want quality then choose libav, if you want some special features — look for suitable fork at github.
There are some codecs that I’d like to RE (mostly for completeness sake) but I don’t have time for that.
Intel Audio Codec
This one seems to be a lot like its predecessor IMC (Intel Music Codec), it even codes coefficients the same way but with different codebooks. I’ve tried to hack IMC decoder to make it use proper tables but it still decodes garbage.
Along with Indeo4 decoder it would make our Intel codec family complete, but unfortunately we have decoder for neither.
ClearVideo
The codec that was present in AVI, QT and RealMedia. My investigations showed that it was not-so-fractal codec, it still codes blocks with DCT and even does that in simpler fashion than H.263. Though a patent assigned to Iterated System describes what can be the base of this codec: DCT-based codec that uses fractal search to determine the best code for the current block or something like this. Maybe that’s the reason why there are no Huffman tables in decoder while it obviously uses some.
RALF
That’s rather special lossless codec that stands aside from other RealMedia codecs: the file format was altered for that codec (so far I’ve seen only standalone RALF files, not, say, RV40+RALF).
It looks like the codec is rather simple and employs context-dependent codes instead of generic ones. I remember finding about eight hundred static Huffman tables in decoder for that purpose.
Also codec developers were very grateful to their source of inspiration, that’s why codec IS is “LSD:”.
WMA Lossless
Nothing much to say about it. As I remember, it uses infinite impulse response filters for compression and least squares method for finding (and maybe updating) filter coefficients. Should be not so hard to RE but nobody bothered so far.
M$ Screen 1 and 2 (aka WM Screen)
I’ve dabbled in REing MSS1, not MSS2 (which was later relabeled as WM Screen) but they should be related.
MSS1 was rather simple screen codec based on classic arithmetic coding (with adaptive models too IIRC) and binary partitioning. So decoding process was simple: get point for subframe division (horizontal and vertical) and modes for decoding those partitions (fill, skip, subdivide).
VoxWare MetaSound
This codec is obviously based on TwinVQ, it even has similar huge tables for different samplerates and bitrates and I found almost the same header reading code.
In conclusion I want to say that if somebody wants to RE those codecs he’ll be more than welcome (especially for Apple ProRes but I don’t care about it much).
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).
This is my look on what happened but I’ll try to remain objective.
A bit about me (in the very unlikely case you don’t know already and care). I’ve learned about FFmpeg in 2004 or so, just saw it along with other packages in Mandrake release. For several months I downloaded source snapshots at cybercafe (even dial-up was impossible then). I had long interest in general data compression methods and some interest in codecs sparkled by XAnim and desire to play M$ ADPCM files on Linux and FFmpeg got new decoders every week or so (mostly for packed YUV formats but nevertheless quite useful).
One day I tried to reverse-engineer some codec (just for fun), looked at sample produced by TechSmith Camtasia and realized that it’s packed with zlib and after some time guessed correctly they use M$ RLE. In order to test it I wrote a decoder and hacked it into FFmpeg. Eventually it worked and I send my decoder to Mike Melanson. On the 14th of August 2004 it was committed to FFmpeg codebase and it made me proud for my work for a week (those were the times!). After another decoder or two I’ve learned and started to read ffmpeg-devel mailing list (it was on SourceForget then). I think I started submitting my patches there with Indeo2 decoder or so.
After a while I was offered CVS commit access which I refused because of technical limitations. Finally in March 2006 I got display for my MacMini and I was ready for more active development. Google Summers of Code gave me opportunity to dedicate a bit more time for FFmpeg since I could say “hey, I’m payed for it!”. I still try to contribute even if I’m no longer student, have job and too little free time.
And now to the business.
As you may know, most active group of developers had disagreements on how FFmpeg was managed. First that resulted into an attempt to move old-style development elsewhere and reinstating new development under old name. Since Fabrice was in favour of old group and controls ffmpeg.org DNS entry, new model development group was forced out and now is known under a name of Libav.
But what is the root of disagreements? The “legendary” leader, Michael Niedermayer. Legendary in the sence that it’s a legend and not a reality.
At least since 2004 (when I joined the project) FFmpeg was rather a self-organizing community of developers, each with his own goals. Somebody wanted to play movie trailers encoded with QuickTime (hi there, Mike!), somebody wanted to play obscure game formats, somebody just wanted to support anything that he could reverse engineer (that’s me and probably Mike and other people as well). Diego Biurrun tried to bring project in shape by introducing formatting conventions (in early days nobody cared about style much), he and later Måns Rullgård made FFmpeg build system almost perfect, also Måns and Baptiste Coudurier (and many other people) worked on improving or introducing support for common formats.
Later when FFmpeg started participating in GSoCs, at first it was handled by Mike and now by Ronald Bultje. Our test system — FATE started as Mike’s experiment for automated testing regressions for many parts. Later it was completely redesigned and rewritten by Måns who also used a lot of his own hardware to provide test results so FFmpeg was tested on variety of platforms and compilers (most non-x86 things at our FATE are because of his work).
Bug tracking system was set up by Luca and he also found a hosting for it. A lot of services for FFmpeg were run on hardware of Attila Kinali (and even bandwidth and hosting for main server was his achievement). And recent Subversion -> Git transition with merging history from SwScaler is mostly done by Janne Grunau.
So, what’s the role of leader in FFmpeg? None! Almost every significant action was done by somebody else. Were they following some roadmap devised by him? There is no such thing either. Maybe it’s his social skills that kept community together? Wrong again, he caused some people to leave project (and not only the last year, Baptiste would serve good example) and different service maintainers too — by forcing his idiosyncrasies on project (like long-standing DTS guessing issue) or ordering service maintainers around.
And his role as lead developer has been diminishing probably since 2004. I can’t deny he did outstanding work on optimising H.263-based encoders and decoders and writing H.264 decoder, writing and developing some other stuff and providing reviews for patches. But what does he do in recent time? I can’t name anything significant. And from technical point he can’t serve as example: he never cared much about architectures beside x86 nor about his code being easily understandable.
Thus, some developers had had enough and forked. It’s still self-organized community with people contributing to what they seem important and nobody to order around (and not that much stalling on patch reviewing like in times of designated maintainers either).
This fork seems to moved murky waters and some trolls (mostly from MPlayer project that have no relation to FFmpeg at all) reappeared after long time; I cannot directly blame Michael on it but it seems suspicious for me. And the messages I’ve read on ffmpeg-devel between forking and creating Libav made me mostly disgusted, so I’ve unsubscribed from FFmpeg mailing lists and don’t participate in FFmpeg anymore. What goes there is not my concern anymore and I’m happy with Libav.
P.S. Also since most of new things in FFmpeg were introduced despite of him (like Git transition and releases), I can’t forget one historical analogy. In German “the leader” is “der Führer”, but that word is rarely used nowadays because there was another Austrian who completely spoiled its meaning.
I have a few harsh words about the countries I’ve visited and I think it’s a good time to present them (well, not worse than any other time).
Germany
Generally it’s a nice country except for big (by German standards) cities. Though I’d like their trains to be more punctual (yes, people abroad think all German trains are always in time while in reality even bahn.de has special mark for trains they suppose to be punctual). And I apologize to Turks who live in Germany but I believe the biggest problem with emigrants in Germany is with people from ex-USSR countries.
Switzerland
People there have bigger ego than Argentinians. First thing I noticed is their national symbolic on locomotives — I don’t know any other country that does it. And their products often have special ingredients like “Swiss milk” or “Swiss beef” (but they are equally expensive even without them). Too bad that no Swiss chocolate contains cocoa grown in Switzerland.
Speaking about products, their prices make me think rösti was invented by/for hundred foreigners who could afford only one frying pan of potatoes together.
Also I find that all Swiss products are overhyped — is any of them much better than elsewhere? Clocks – you have good ones in Japan or Germany (and even cuckoo clock was not invented in Switzerland). Cheeses — again, there are much better ones in other countries, notably Netherlands and Sweden (the latter just doesn’t produce or export much). Chocolate — French, Italian or Swedish chocolate is not worse.
Norway
I’ve been only to Oslo but from what I’ve seen people there should invest money they get from oil into inviting people with sense of taste. All nice buildings in Oslo (yes, all twelve or so) were build by Swedish or Danish architects. And please make sculpting a major criminal offense (at least before you learn the meaning of “lagom” from your neighbours).
France
It doesn’t matter what I think about them because French people (and their ticket vending machines) seem to completely ignore anybody not speaking French (that includes me).
Belgium
From what I saw I conclude they are trying to build another Ukraine (and they are succeeding at it). It’s not hard, just forget that you should maintain buildings, clean streets or that plain concrete is not the best decorating material. Brussels would probably be better had it been built by architects from Oslo.
Douglas Adams was absolutely right.
Sweden
When I heard Russian pop in Skärholmen mall I realized that Skärholmen is, indeed, not a part of Sweden anymore (I was told so before but found it hard to believe, not anymore).
But my main concern is that there’s no proper E4 rail equivalent so I could not travel from Sundsvall to Umeå or Luleå directly (and I’d like less travelling time on route Stockholm-Sundsvall too).
And I wonder what’s better, lutefisk in winter or surströmming in summer?
I’ve attended FOSDEM-2011 solely because of friends. I thought that Belgium is a sad country and Brussels is shitty but it turned out to be even worse than Ukraine in perception so I’m not sure if I’ll visit it again (Berlin is much nicer by comparison even if it still has Ukrainishy feeling).
av500 advertises his new 15'' laptop
Even if I spent not so much time there it’s always nice to see fellow FFmpeg developers and other related people — VLC people, BeagleBoard people, the small guy on the photo.
And shortly after that I’ve managed to get a new decoder accepted (the one used in Wing Commander IV). It was in RE since 2002 or 2003 but people were too lazy to actually complete it. But now it may serve as a memory that while I was at FOSDEM it was reviewed. Hopefully we’ll get more codecs to come even if not from me.
There’s Russian saying “You’ll live a year in a way you meet it”, so just in case I tried to get to my favourite country. Mostly to check how it’s in winter time.
If somebody still thinks I’m normal, here’s a picture of what I mostly drink during my stay there:
(those are different bottles, I’ve tried more few more kinds too). In addition to that I’ve tried few more drinks from certain brewery i Sundsvall. And I’ve finally tried Norrlands national drink in solid form. Somehow these trips always get full support from my stomach.
P.S. Ost, inlagd sill, gravad lax, köttbullar och tunnbröd med julskinka är lagom bra. Och jag har älgkorv att prova.
P.P.S. Trains there seem to be as punctual as in Germany.
This post is an answer to the comment by Alex Converse on my previous post:
It’s interesting how quickly you dismiss SLS for being a hybrid coder with AAC. From a pure lossless standpoint that is a weakness but from a broader perspective it allows for a lossy layer that is widely compatible with existing hardware.
Let’s see why scalable coding is a weakness from lossless coding standpoint.
There are few hybrid lossy+lossless codecs out there which use lossy part in lossless reconstruction, e.g. MPEG-4 SLS, DTS-HD MA and WavPack. First two use two different coding techniques – MDCT or QMF for core coding and usual lossless coding for difference. In WavPack both parts are coded in the same way and correction data is stored in different block. For DCT-based codecs there are many ways of performing DCT (from trivial matrix multiplication to FFT-based implementation to decomposing DCT into smaller size DCTs) which may lead to slightly different output depending on method chosen. Thus, you should have a reference way (i.e. not the fastest one) of doing lossy stuff or you can’t guarantee truly lossless reconstruction. Also residue (the difference between original and lossy coded signal) tends to be more chaotic in this case and thus less compressible.
Another issue is what to do with correction data. If you put it into a separate file, you will have more troubles since you have to manage two files; if you put it all into single file, its size will be bigger than pure lossless coded file (unless you have very stupid method of lossless coding).
And now comes an argument that I really hate: “but it allows legacy players handle those files”. That, in my opinion, is this post title. Making it backward compatible just cripples it. In that case you need to implement new (and sometimes completely different features) in old limits and relying to new technology. So in some case it just degrades quality and/or forces you to encode something twice — for old feature set and its replacement. Another reason is that it just delays that codec adoption: old player can play it so why should I bother about this new codec support? I suspect this was a reason why we have MLP but no DTS-HD support.
The worst offender here is MP3. This codec sucks by design. It uses 36-point (or three 12-point) MDCTs which are not trivial to speed-up unlike power-of-two transforms and the output of MDCTs is used as input to QMF used in MPEG Audio layers I&II, as it claimed “to be compatible with them”. As claimed here, MP3 would perform better and since it comes from one of the leading LAME developers, I believe it. And of course MP3Pro. Most players in existence just ignore extension part and play crippled version of sound. Someone may argue that’s because it’s proprietary. Okay, look at HE-AAC where SBR is documented at least, it may still cause some confusion since it may be detected only when decoding audio frame.
In my opinion both implementing new codec support and special codec extension in general case is just single-time action with comparable effort (hacking existing code for new extension support and detection may be not that easy). And thus, adding a new codec should be preferred. MPEG-2 introduced both AAC (please look how it was called back then) and multichannel extensions to layers I-III. Guess which one works better?
