A quick look on Rududu

Since I had nothing better to do I decided to look at Rududu codec. It is one of old more exotic codecs that nobody remembers.

I did not want to look that deep into its details (hence it’s just a quick look) so here are the principles it seems to employ:

  • it seems to employ some integer approximation of wavelet transform (instead of e.g. LeGall 5/3 transform employed by lossless JPEG-2000);
  • it probably has intra- and interframes but it does not employ motion compensation, just coefficients updating;
  • DWT coefficients are quantised (and common bias is removed) with scale and bias calculated for the whole frame;
  • coefficients are coded using quadtree (i.e. some parts of the bands can be left uncoded in addition to skipping the whole DWT subbands);
  • and finally, data is coded using adaptive models for absolute values and bits for both signs and “region coded” flags and the probabilities from these models are fed to the range coder.

So while this codec is nothing outstanding it’s still a nice change from the mainstream video coding approach defined by ITU H.26x codecs.

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