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> Blosc comes with a pre-filter (also called pre-conditioner) called shuffle which rearranges bytes in a clever way for the compression stage. This sounds like
by oofabz 12y ago
> Blosc comes with a pre-filter (also called pre-conditioner) called shuffle which rearranges bytes in a clever way for the compression stage.
This sounds like the Burrows-Wheeler transform, which bzip2 uses:
https://en.wikipedia.org/wiki/Burrows%E2%80%93Wheeler_transform https://en.wikipedia.org/wiki/Burrows%E2%80%93Wheeler_transf...
- pkhuong 12y agoFixed-width binary data (e.g., a sequence of double floats) often benefit from a simpler transform: just transpose the bits/bytes so that, e.g., the least significant bytes form a contiguous region, followed by all the second least significant bytes, etc. > Meant for binary data: can take advantage of the type size meta-information for improved compression ratio (using the integrated shuffle pre-conditioner). makes it sound like that's what Blosc is doing.
- shiningmuppet 12y agoYes, exactly, like so: http://www.blosc.org/images/shuffle.png http://www.blosc.org/images/shuffle.png
- rdc12 12y agoSounds interesting is there a name for that technique? Or more to the point something that can be searched for
- shiningmuppet 12y agowe call it the 'shuffle filter' but that is all