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The 4mb piece size is too small. If the files you add are large you end up with a torrent being rejected on trackers that limit .torrent file size. There should be atleast 2 more piece sizes options 8mb and 16mb

As far as I know this isn't a limiting factor in qbittorrent, specifically, but all torrent clients. Or the limiting factor at all.
And if one client were to increase piece size it would have to be compatible with all torrent clients which it likely is not.

Clients that follow bitorrent specs can already use torrents with larger piece sizes only problem is in making torrent files. Utorrent increased max piece size to 16mb when creating torrents somewhere around version 2.2 and if you want to make a torrent with larger piece size you can always use mktorrent.

Sounds like you solved your own problem then. (mktorrent)

[quote="loki"]
Sounds like you solved your own problem then. (mktorrent)
[/quote]I did solve it myself by patching client now I cam make 8MiB and 16MiB piece size torrent.

If you know how, you could submit that to gitorious. I'm sure they would appreciate it.
Does changing the piece size alone make the resulting torrent file significantly smaller? I thought it was more due to the number of files and length of names of files.

[quote="loki"]
If you know how, you could submit that to gitorious. I'm sure they would appreciate it.
Does changing the piece size alone make the resulting torrent file significantly smaller? I thought it was more due to the number of files and length of names of files.
[/quote]Yea larger piece size means less pieces so the torrent files is smaller. 16 Mib pieces size is 25% of the size of 4MiB. Its a trade off in efficiency but if your making a torrent from very big files torrent file gets too big if you don't raise piece size up.  With the HD files 100GB isn't all that uncommon anymore.

Any way of showing the village idiot (me) on how to patch it maybe do a tutorial please

or is there an updated version with the patch in it

i using this on windows any help would be appreciated

Well, compiling for Windows is not that easy.
We should submit this patch to the Github tracker. (Or gitorious? What do we use at all? I don't even know anymore.)
Anyway. To the current development site.

Then Chris will merge it and the next version will have this feature.