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Re: Output Capture
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Re: Output Capture


  • Subject: Re: Output Capture
  • From: email@hidden
  • Date: Wed, 18 Jul 2007 14:52:02 -0600

On Jul 18, 2007, at 1:50 PM, Jeff Moore wrote:

On Jul 18, 2007, at 12:29 PM, email@hidden wrote:

The trouble is that I have 2 carbon sound callbacks in my app, one for voice, and one for our game sound fx, and I can't mix those easily (for one thing their sample rates and number of channels are different, and for another, the code is leftover from OS 9 days and pretty complicated to dive into). But I COULD pipe these into core audio in a thread safe way from the 2 callbacks, and get 1 output. I just have no idea how to do this. I've read over the core audio manual pdf, it's just a lot to take in. So while the concepts are fairly simple, I don't feel ready to just start typing code, and was hoping for an example.

The right thing to do is to update this code to stop using the Sound Manager and to take more control over things by using the various Core Audio APIs.

Ya I guess that's what I have to do. Does anyone have any introductory guides to core audio? The main pdf is extremely dry, reminds me of reading about the OS 9 display manager or asynchronous file parameter block programming. This is odd considering that conceptually, core audio is about 10x easier to use than the OS 9 sound manager, from what I have tried so far. In fact, I can honestly say that the documentation is what's scaring people away from adopting it, based on the types of google results I get for core audio vs. the sound manager.


then a built-in echo cancelled sound input is a requirement. This would be extremely easy for apple to do, since they are already doing it in iChat I believe. Also, this needs to be included in a system update retroactively for 10.3.9, or as a small lib we can include in our app's package, so that we can use it in games.

The fact that iChat does it's echo cancellation entirely on its own without needing any of what you are talking about proves that it most certainly is not a requirement. There's nothing stopping you from doing the same thing iChat does other than how willing you are to take on the task of understanding and implementing echo cancellation. The system is certainly not getting in your way.

Technically I need the full output of the whole computer to do echo cancellation properly. Luckily games are a special case since they tend to take over the whole interface. But what I am saying is, there is no way to do echo canceling properly right now, because I can only capture my own app, so it would be good if echo cancelled input was provided at the OS level. Another way to do this would be to allow the user to feed mic input into a routine that strips the current output (avoiding any DRM issues). Several VOIP APIs provide voice cancellation built in, I just don't have output to feed them, so will do my best getting the output from my app. Just my two cents,


--Zack
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References: 
 >Output Capture (From: email@hidden)
 >Re: Output Capture (From: Jeff Moore <email@hidden>)
 >Re: Output Capture (From: email@hidden)
 >Re: Output Capture (From: Jeff Moore <email@hidden>)

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