Hello W.,
To answer re “drive audio source(1) using audio source(2)” - have you tried
using AudioUnitAddRenderNotify()
Recently, as a test, I successfully sub-classed and used AVAudioUnitEffect with
the following init:
- (instancetype)init {
AudioComponentDescription component =
VEComponentDescriptionMake(kAudioUnitManufacturer_Apple,
kAudioUnitType_Effect,
kAudioUnitSubType_PeakLimiter);
if ( (self=[super initWithAudioComponentDescription:component]) ) {
_audioUnit = self.audioUnit;
_didAddRenderNotify =
VECheckOSStatus(AudioUnitAddRenderNotify(_audioUnit,
VEAVLimiterRenderCallback,
(__bridge void * _Nullable)(self)),
"AudioUnitAddRenderNotify");
}
return self;
}
…with a render function like:
OSStatus VEAVLimiterRenderCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
if ((*ioActionFlags & kAudioUnitRenderAction_PostRender) && (inRefCon)) {
__unsafe_unretained VEAVLimiter * THIS = (__bridge
VEAVLimiter*)inRefCon;
// This is essentially a “tap” do something, e.g. here you could do
some calculations such as
// determine peak amplitude, or whatever, then store those values and
use them to do something like
// “modulate" the “pan” on the source(1) AVAudioNode
}
return noErr;
}
If I understand you correctly, I think this could work.
Kind regards,
Leo Thiessen
http://visionsencoded.com <http://visionsencoded.com/>
> On Jun 6, 2017, at 2:00 PM, [email protected] wrote:
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> 1. Seeking advice for modifying audio input source (Waverly Edwards)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 6 Jun 2017 16:59:05 +0000
> From: Waverly Edwards <[email protected]>
> To: "[email protected]" <[email protected]>
> Subject: Seeking advice for modifying audio input source
> Message-ID:
>
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> Content-Type: text/plain; charset="utf-8"
>
> I've been reworking an existing project that uses core-audio to now use
> AVAudioEngine and I am need of some assistance.
> I am currently forcing AVAudioEngine to render offline, using AudioUnitRender
> on the output node - the setup is non-standard but it works.
> I am using Swift and MacOS, not iOS, it's been a bit of a roller-coaster but
> I'm making (slow) progress
>
> I am seeking direction on how you can drive audio source(1), using audio
> source(2). My specific need to perform a panning effect back and forth at a
> specific frequency.
> I believe that I could also perform other audio magic such as fade-in,
> fade-out using the same basic idea. It would be so much better if there is a
> high-level way to manage this however, I will go low-level if needed.
>
> Here are the ideas that I've investigated or attempted:
>
> Add an audio unit effect.
> Add a tap and use the output as a source make adjustments to the other source
> Adding a render callback to an existing mixer node
> Add an AVAudioIONode?
> Use an AUAudioUnit to access the buffer list data (latest idea being
> investigated)
>
> I looked at AudioUnitV3Example and was completely out of my depth,
> considering writing an audio effect
> Unfortunately, I can't use a tap to monitor and drive the source because
> working offline, the tap doesn't get data - I tried. I would also need to
> decrease the buffer significantly for granularity sake if it did.
> I've been attempting to access the underlying Audiounit of one of the mixer
> nodes or see if it is possible to add or access a render callback - not
> successful yet.
> It took me a couple of weeks to get a render callback on the input node
> working so I thought I could do so on a mixer node - that battle is still
> being fought.
> In researching AVAudioIONode, I haven't determined how do you get access to
> the input stream
>
> Here is the latest idea being investigated, AUAudioUnit
> I looked into AUAudioUnit and have been unable to determine how you can
> create a node that accepts input
> I'm not getting the input but do I need it, since I have access to the
> output. Is access to the input provider necessary?
>
> Q1: should the componentType be kAudioUnitType_Mixer to get input and output?
> Q2: can this be non-interleaved on MacOS
> Q3: how do you get the input provider working? Is this necessary, since I
> have access to the output provider
> Q4: How do you create a component an insert it in the between nodes - let's
> say between a mixer and distortion node, not just at the end
>
> Thank you,
>
>
> W.
>
> do {
>
> let audioComponentDescription = AudioComponentDescription(
> componentType: kAudioUnitType_Output, // Q1:
> should this be kAudioUnitType_Mixer to get input and output?
> componentSubType: kAudioUnitSubType_HALOutput,
> componentManufacturer: kAudioUnitManufacturer_Apple,
> componentFlags: 0,
> componentFlagsMask: 0 )
>
> if (auAudioUnit == nil) {
>
> try auAudioUnit = AUAudioUnit(componentDescription:
> audioComponentDescription)
>
> let upstreamBus = auAudioUnit.inputBusses[0]
>
> let audioFormat = AVAudioFormat(
> commonFormat: AVAudioCommonFormat. pcmFormatFloat32,
> sampleRate: Double(sampleRate),
> channels:AVAudioChannelCount(2),
> interleaved: false ) //
> Q2: can this be non-interleaved
>
> auAudioUnit.isInputEnabled = true
> auAudioUnit.isOutputEnabled = true
>
> auAudioUnit.inputHandler = { (actionFlags, timestamp,
> frameCount, inputBusNumber) in
> print("handling input,calling method to fill audioBufferList
> ") // Q3: not working but is this necessary, since I have access to the
> output
> }
>
> auAudioUnit.outputProvider = { (actionFlags, timestamp,
> frameCount, inputBusNumber, inputData) -> AUAudioUnitStatus in
> print("handling output,calling method to fill audioBufferList ")
> return 0
> }
> }
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