Archive for November, 2014

Blåtand-Passande-X

Sunday, November 23rd, 2014

So, finally there’s a post about some codec.

It is a specialised codec from Oxford Germanium Television (all names are changed just in case) that has 4:1 compression ratio and very niche use. It’s hard to find even a decoder for it so this analysis was done on ARM version of encoder (maybe I’ll be able to RE something more useful next time like VX).

The codec itself is rather simple: you take 4 samples from one channel, compress them, output the 16-bit result and repeat the same for the second channel. Encoding is rather simple too:

  1. feed input to 4-band QMF (with filter looking a lot like D4 wavelet to me);
  2. perform ADPCM on each band (this varies a bit for each band but it’s the same approach);
  3. generate output word (7 bits for band 0, 4 bits for band 1, 2 bits for band 2 and 3 plus a parity bit for them all).

Since I have no samples of it don’t expect a decoder from me any time soon (and I don’t have enough motivation to hook Android encoder directly to make it produce data). Not that anyone cares about it either.

A Bit on Germany

Friday, November 21st, 2014

quote

An excerpt from a book that I have to refer sometimes (here’s the source, it really tells a lot about proper relationship. Ask a nearby German for a translation if you need it.

P.S. Next post will be about a codec technical description, I promise.

A Bit on Italy

Friday, November 21st, 2014

Italy is a good country (piecewise) — nice scenery, decent food (and pasta), nice architecture…
There’s but one thing that annoys me, I think you’ll be able to spot it on those two pictures.

Milan, a corner of via Vitruvio and via Benedetto Marcello.
Milan

Turin, largo Cassini.
Torino

I cannot say it for sure but I remember Ukrainian markets (right after closing time) being cleaner than that.