[OSM-dev] Compression types in PBF Format

Jochen Topf jochen at remote.org
Tue Nov 30 20:10:46 GMT 2010


On Tue, Nov 30, 2010 at 10:53:16AM -0600, Scott Crosby wrote:
> On Tue, Nov 30, 2010 at 2:21 AM, Jochen Topf <jochen at remote.org> wrote:
> > The PBF format supports three compression types: zlib, lzma, and bzip2. Do
> > we have to support all of them? What is the currently existing software
> > using?
> 
> Good question. I think that the bzip2 compression option is useless.
> Too slow, especially on the decompression side. I'm not sure what to
> do about LZMA. It offers higher compression ratio's at little loss in
> decompression speed. The catch is that while everything supports
> deflate, LZMA decompressor support is a lot less widespread. It might
> be a valuable future option, but it is also untested.
> 
> To my knowledge, Osmosis has the only implementation of a PBF writer,
> it only uses uncompressed and zlib? Has anyone else implemented a
> writer?
> 
> If nobody else has their own writer, then would anyone object to me
> unilaterally removing (not depreciating) bzip2 entirely, and
> disabling/marking lzma as a proposed future extension?   If tests in
> the future show that LZMA offers significant size decreases, it can be
> enabled and support can be added.

+1

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298




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