Sunday, January 06, 2008

Banshee now has support for MTP devices in trunk. It's a long and torturous story, but here's the short of it:

Way back when, the work on implementing MTP support was started by a guy called Patrick. At the time, there were two options:
1) libgphoto
2) libmtp

libmtp was still in it's early stages of development and wasn't mature enough to be a viable option, so libgphoto was chosen althought it wasn't that much better. At this time, libgphoto didn't have metadata reading/writing implemented, didn't show any stats on the different filesystems in the device. Note: libmtp was no better at the time. So, a C# binding to libgphoto was started and basic support for syncing was eventually pushed into banshee.

Fast forward about 18 months. libgphoto has matured significantly in its support for mp3 players. Track metadata has full read/write support, you can get stats on the filesystems, patches and optimisations have been pushed in so that all the basic operations are fast. However, there's still issues with long filename support - there are hardcoded limits in libghoto itself which means if it encounters a path or filename longer than the limit, it just bails out. For mp3 players, this was a serious issue as these limits were quite frequently reached. For instance, if you were a fan of Sufjan Stephens, you were out of look. His incredibly long track titles like 'Out of Egypt, Into the Great Laugh of Mankind, and I Shake the Dirt From My Sandals as I Run' really throw a spanner in the works

Around this time, i stepped in to complete the binding and complete banshee MTP support. I pestered poor Marcus for quite a while until i got various fixes/updates into libgphoto such as the change to allow unlimited filename length and path length, and also to remove 'long' types from the public API (as a 'long' type can be 32bit or 64bit depending on architecture and leads to nasty complications binding it in C#). I also completed the initial revision of the libgphoto-sharp API restructuring. The entire endevour probably took about 2 months from start to finish.

However, the problem now was that in order to have MTP support in banshee, you needed SVN head of libgphoto, svn head of libgphoto2-sharp and a pot of luck that you could get it installed without screwing up your packaged version. A new release of libgphoto was several months away and probably still a further few months until it managed to trickle down into the various distros.

It was then that i was reminded by Aaron that libmtp still existed and was quite mature. I took a quick look at the API showed that it was tailored specifically for the kind of tasks that banshee was trying to do. Better yet, it had a faster release cycle, it didn't require svn head of anything in order to get all the features that were required and it was already available in nearly every distro.

I spent about 4 days writing a brand new C# wrapper for libmtp and then replaced the libgphoto-sharp code in banshee with the new libmtp-sharp code. While there are things in libmtp that are missing as compared to libgphoto, the simplicity of the new API makes it trivial to implement features which previously would have been quite complicated. For example, Playlist support under libmtp is trivial to implement, yet under libgphoto i'm not 100% sure how i'd go about it!

What i regret most of all out of this is that i put Marcus through so much hassle for minimal benefits as Banshee is no longer using libgphoto. While i do feel bad about putting so much effort into the libgphoto-sharp binding to never use it myself, it was still the best decision from banshee's point of view.

So, if anyone out there has an MTP device and wants to make sure that their device works with banshee before the release (so i can fix any bugs should there be any), check out the guide here. Post any bug reports on under the DAAP component in Banshee.


Igor said...

Good to see that you're the type of developer that change his mind for something better.

I do remember that I helped you to debug the 32/64 bits issue, and by that time you were not willing to check libmtp even though Rhythmbox read my device.

But remember that F-Spot still uses GPhoto2 so the binding is still used.

Alan said...

Well, the reason what i didn't check out libmtp was because i was assured that libgphoto was the right choice ;) I believed what i was told.

If i had taken a serious look at libmtp, i would have jumped ship earlier, i just never bothered because to my knowledge, there was no point. Patrick had researched the topic, had made his decision, and at the time it was right. Unfortunately by the time i got around to it, the decision was no longer right.

Either way, a lesson was learned.

Patrick said...

Long as it works, that's what matters most :) Hacking around a lot of the libgphoto2 things was tough, and I'm sure libmtp makes that oh-so-much easier. Back when I first started hacking mtp support in Banshee, libmtp was something like v0.0.1 and was very troublesome. I went down the libgphoto2 road because I figured it'd be easier in the short term and with discussions w/ the gphoto developers, we thought libgphoto2 would work better in the long run. However libmtp has matured quite a bit, so I don't doubt that it's much easier to use :)

Good work! Sorry I haven't been around to help, but it probably made it easier for you to do your thing.

Good news is that f-spot will always need the libgphoto2-sharp bindings, so no effort lost there!

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