Bittorrent and solid archives

[lunaris]

Is it possible to use bittorrent for download only parts of a solid archive?

Ex: Download 2 files of a solid archive using bittorrent.

[Surfer]

None of existing clients aren't able to do this. And I'm doubt about this function.

[Piotr Tarsa]

By definition, every part of a solid blocks depends on the previous data in that solid block.

[lunaris]

By definition, every part of a solid blocks depends on the previous data in that solid block.

Yes. Maybe using non-solid archives like zip it's possible to download only some files.

[Piotr Tarsa]

When using 7z you have an option to specify solid block size. This way you can achieve higher compression when compressing many small files of same type, but you keep reasonable random access time/ amount of data to be decompressed before extracting any file. IIRC CHM (Microsoft format for help files) files uses LZX with a rather small solid block size and even smaller sliding window.

[m^2]

Yes. Maybe using non-solid archives like zip it's possible to download only some files.

Theoretically yes. Theoretically with solid archives you could save too by downloading everything in the block before the file that you need - and ignoring everything afterwards.
Practically no because there's no software capable of doing so.

[Piotr Tarsa]

Zip format stores descriptors at end of file. I think it's possible to extract only the downloaded parts when there's that information. WinRAR has repair option, sometimes it helps.

[m^2]

Zip format stores descriptors at end of file. I think it's possible to extract only the downloaded parts when there's that information. WinRAR has repair option, sometimes it helps.

Theoretically yes. Practically no. :P

[Shelwien]

There's a known implementation for zip+http:
http://www.movsd.com/source/zipdl.zip
(Also some download managers seem to have a similar feature)
I'm not aware of torrent clients supporting that, but its certainly possible.

Now, as to solid archives, it may be possible to only download partial data for some formats, eg. rar/LZH -
where entropy coding is blockwise.