Archive for September, 2014

A Codec Family Proposal

Monday, September 29th, 2014

There are enough general use standardised codecs, there’s even VPx family for those who want more. But there are not enough niche codecs with free/open specifications.

One of such niche codecs would be an intermediate codec. It’s suitable for capturing and quick editing of video material. Main requirements are modest compression rate and fast processing (scalable is a plus too). Maybe SMPTE VC-5 will be the answer, maybe Ogg Chloe, maybe something completely different. Let’s discuss it some other time.

Another niche codec that desperately needs an open standard is screen video codec. Such codec may be also used for recording webcasts, presentations and such. And here I’d like to discuss a whole family of such codecs based on the same coding principles.

It makes sense to make codec fast by employing multithreading where possible. That’s why frame should be divided into tiles that should be not so large and not so small, maybe 192×128 pixels or so.

Each tile should be coded independently, preferably its distinct features coded separately too. It makes sense to separate tile data into smooth features (like gradients and real life pictures) and sharp transitions (like text and UI elements). Let’s call the former a natural layer and the latter a synthetic layer. We’ll need a mask to tell which layer to use for the current pixel too. And using these main blocks and employing different coding methods we can make a whole family of codecs.

Here’s the list of example codecs (with a random FOURCC assigned):

  • J-B0 — employ JPEG for natural layer and GIFPNG for mask and synthetic layer coding;
  • J-B1 — employ Snow for natural layer coding and FFV1 for synthetic layer coding;
  • J-B2 — employ JPEG-2000 for natural layer coding, JBIG for mask coding and something like PPM modeller for synthetic layer;
  • J-BG — employ WebP for natural layer and WebP LL for synthetic layer.

As one can see, it’s rather easy to build such codec since all coding blocks are there and only natural/synthetic layer separation might need a bit of research. I see no reasons why, say, VLC can’t use it for recording and streaming desktop for e.g. virtual meeting.

On Railways Electrification

Sunday, September 21st, 2014

So what I’ve discovered today.

There’s a Schwarzwaldbahn going through Schwarzwald from Offenburg to Konstanz and there’s a station there — Villingen. That station bears a plaque that it had 10000th kilometre of electrification of DB network done in 1975 (DDR railways on the other hoof lost most of its electrification after the war because it was more important to electrify Soviet railways but that’s another story).

And there’s a branch connecting Villingen (Baden) with Rottweil (Württemberg) — unelectrified. And that branch has its own subbranch to Trossingen Stadt. That subbranch is also served by a diesel railbus. But unlike the branch it connects to it’s electrified! And that electrification is used only by museum vehicles from 1930s-1960s that are electric only (or in one case it’s a carriage with an electric locomotive).

On most such lines in Germany one usually has trains hauled by a steam locomotive or a diesel rail buses and the main traffic is electrified but in this case it’s the other way round. I have only one possible explanation — Württemberg.

P.S. Still it’s hard to find stupider situation with electrification than in Denmark. The only countries it has connections to had chosen 15 kV 16â…” Hz system. Denmark settled on 25 kV 50 Hz. But looking at their other railway-related decision (i.e. IC4) it seems logical.

P.P.S. For Ukraine the situation is sadder — once I was in Uzhgorod-Kharkiv train and it had to change locomotive twice because there are two electrification systems there (which make three areas). They claim it was done to better account for relief, i.e. different electrification for the flatter and mountainy regions. Hopefully there will be more two-system trains in the future (and there will be the future too).

On Anime

Saturday, September 20th, 2014

I’ve finally bought a DVD with an anime I wanted to watch. And it was awesome. Here are some screenshots.









P.S. I should probably visit Småland next summer.

On Quack VPx

Tuesday, September 16th, 2014

I think most of you have read this piece of news about G**gle VPx plans already. After some thoughts I’ve decided to comment on it as well.

So, here’s a bit of history:

  1. Duck TrueMotion — an original codec;
  2. Duck TrueMotion 2 — a development of TrueMotion 1 (same coding principles but now Huffman coding is employed);
  3. On2 TrueMotion VP3 — something like TrueMotion 2 and MPEG-2(aka H.262) mixed together;
  4. On2 TrueMotion VP4 — most likely some improvements over VP3 (shame on Mike and/or Peter for not REing it yet!);
  5. On2 TrueMotion (or was it TrueCast?) VP5 — MPEG-4 ASP/H.263 ripoff with On2-specific stuff (no B-frames, different coder etc.);
  6. On2 TrueMotion VP6 — minor improvements over VP5;
  7. On2 TrueMotion VP7 — H.264 ripoff with On2-specific stuff (no B-frames, different coder etc.);
  8. On2 TrueMotion VP8 — minor improvements over VP7;
  9. G**gle VP9 — H.265 ripoff with some On2-specific stuff (almost the same as in VP7/VP8);
  10. G**gle VP10 — is not released yet but I can predict it will be just VP9 with some minor improvements and no real specification available (you have Chromium source, just look at the stable branch there).

It is easy to see that there’s a huge issue to deal with if they want to release a new VPx every 18 months — they should have a corresponding ITU H.26x standard (or at least some draft of it) available. The only alternatives are polishing VP9 and calling it a new version when some incompatible feature is added or start ripping off Daala, Dirac and Bink 3. Good luck.