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Re: iphone audiounit mixers
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Re: iphone audiounit mixers


  • Subject: Re: iphone audiounit mixers
  • From: Daniel Elliott <email@hidden>
  • Date: Thu, 2 Oct 2008 16:32:01 +0000 (GMT)

I don't believe it does no. That would be nice though!

this is from the core audio overview....
Converter unit—Provides sample rate, bit depth, and bit format (linear to fixed-point) conversions. The iPhone converter unit’s canonical data format is 8.24-bit fixed-point PCM. It converts to or from this format. Programmatically, this is the AUConverter unit.

----- Original Message ----
From: Richard D <email@hidden>
To: Daniel Elliott <email@hidden>
Cc: email@hidden
Sent: Thursday, 2 October, 2008 5:06:58 PM
Subject: Re: iphone audiounit mixers

Does the AUconverter perform conversions from compressed formats ?  If so, I could get round my problem with not being able to create an AudioConverter instance.
I've looked for info on AUconverter but can't find anything.

RD

On 2 Oct 2008, at 17:02, Daniel Elliott wrote:

nevermind, I hadn't opened the graph before doing the AUgraphnodeinfo to grab the instances of the audiounits. working now.

----- Forwarded Message ----
From: Daniel Elliott <email@hidden>
To: email@hidden
Sent: Thursday, 2 October, 2008 10:51:29 AM
Subject: iphone audiounit mixers

A couple of questions for anyone who knows........


1)I have successfully got 16 bit mono 44.1khz audio to play throught the au3dmixerembedded audiounit. However if I change the type of audiounit to a multichannel mixer, then the audio sounds distorted. The core audio overview states that both the 3dmixer can accept 16 bit linear and output 8.24 bit fixed point stereo. The multichannel mixer is stated to be able to use both 16-bit linear AND 8.24 bit fixed point PCM. Then why does the multichannel mixer behave differently?  Do I have to set any rendering flags or the input ASBD? Does it default to a Stream type of 8.24? 

I tried the AUconverter unit going into the multichannel mixer but still sounds distorted. If the input and output streams need to be set to 8.24 fixed for the audiounits, then what are those settings for the bit-depth and rendering flags in the ASBD? (I am using an AUgraph, which I believe sets the input format to be the same as the downstream node's output format automatically, right?)

2)Assuming I can't get the above to work, and I go ahead with the 3d mixer, I have tried to use AudiounitSetParameter to change the Azimuth parameter (k3dmixerParam_Azimuth) with....

AudiounitSetParameter(mixerUnit, k3dmixerParam_Azimuth, kAudioUnitScope_Input, 0, myFloatValue, 0);


but I'm getting a -50 ParamErr and not sure why. Earlier on in my setup code I have grabbed the instance of the
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