Objective-C in Mono

Question

I have a .NET application, which I want to port to OSX. Up to now I used a DirectShow DLL for WebCam handling. Can I use an Objective-C DLL for Mono? How? I'm a newbie on Mac. Is there an existing (WebCam handling) solution for this? Is there a better solution?

Answer 1

You want to use the QTKit framework to do this, in particular you can use the QTCaptureView as a reusable NSView that you can embed in an existing window or in an application to do the actual video capturing.

I have just added support for capturing to the MonoMac bindings a few minutes ago after I saw your question, so you will need to do a little bit of work.

Steps:

1. Install Mono, MonoDevelop and the MonoMac addin as described here: http://mono-project.com/MonoMac

2. Download the latest sources for MonoMac and MacCore from Github: http://github.com/mono/maccore and http://github.com/mono/monomac

3. Update the MonoMac.dll to the latest version, by going into the monomac/src directory and typing "make update"

At this point you should be able to use the QTCaptureView in your MonoMac applications like any other NSView. A tutorial showing the use of the API in Objective-C is here:

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/QTKitApplicationTutorial/BuildingaSimpleQTKitCaptureApplication/BuildingaSimpleQTKitCaptureApplication.html#//apple_ref/doc/uid/TP40008155-CH8-SW1

You can just use the equivalent versions in C#

Answer 2

I'm not sure what you mean by "an object-c dll for Mono".

Your absolute best approach is to learn the platform you're targeting and port only the logic and general architecture.

To access cameras, microphones, line-ins, etc. on Mac OS X, use QTKit (Quicktime Kit). It's mind-numbingly simple to set up a web cam view, record to files, grab frames, etc. It's built in and designed to make this sort of thing mostly drag-and-drop for developers.

Answer 3

MonoMac is just one alternative. There are Monobjc, CocoSharp, NObjective, MObjc / MCocoa and ObjC# (I cannot choose between them). Theese are all "bridges" between Mono and Cocoa, what mean you can use Cocoa API in Mono application. But I don't want to use the API directly. I just want a dinamically linked library, which provide me some function for WebCam handling (as I said, I did this up to this time on Windows). In other words: I need a wrapper in Mono for QTKit.

PS: If I rewrite the application in object-c that means several months, and double work in the future when the application will grow. I love object-c but I hate to work unnecessary.

Answer 4

I tried the accepted code in XCode, and when I tried to port to Monodevelop, several classes are missing, eg. QTCaputureSession, QTCaputreDeviceInput, CVimagebuffer. (Sorry, I cannot edit my previous messages, this is another account.)