Laurent,

`installTapOnBus` is not intended for realtime processing as a tap only 
provides the current frame buffer but does not pass it back into the signal 
chain. The documentation reads `Installs an audio tap on the bus to record. 
monitor, and observe the output of the node`.

Although I have not done that myself yet my understanding is that for realtime 
processing you can still retrieve the underlying audio unit from an AVAudioNode 
(or at least some nodes?) and attach an input render callback via 
AudioUnitSetProperty with kAudioUnitProperty_SetRenderCallback.

I assume the other way would be to subclass AUAudioUnit and wrap that into an 
AVAudioUnit which is a subclass of AVAudioNode. Yes, it confuses me, too. 
Random Google result with further information: 
https://forums.developer.apple.com/thread/72674

Benjamin


> Am 11.07.2018 um 14:34 schrieb Laurent Noudohounsi 
> <laurent.noudohou...@gmail.com>:
> 
> Hi all,
> 
> I'm interested in this topic since I've not found any information about it 
> yet.
> 
> Correct me if I'm wrong but AVAudioEngine is not able to lower than 100ms 
> latency. It's what I see in the header file of `AVAudioNode` with its method 
> `installTapOnBus`: 
> 
> @param bufferSize the requested size of the incoming buffers in sample 
> frames. Supported range is [100, 400] ms.
> 
> Maybe I'm wrong but I don't see any other way to have a lower latency audio 
> processing in an AVAudioNode.
> 
> Best,
> Laurent
> 
> Le mer. 11 juil. 2018 à 13:57, Arshia Cont <arshiac...@antescofo.com 
> <mailto:arshiac...@antescofo.com>> a écrit :
> Benjamin and list,
> 
> I double Benjamin’s request. It would be great if someone from the CoreAudio 
> Team could respond to the question.
> 
> Two years ago, after basic tests I realised that AVAudioEngine was not ready 
> for Low Latency Audio analysis on iOS. So we used AUGraph. I have a feeling 
> that this is no longer the case on iOS and we can move to AVAudioEngine for 
> low-latency audio processing. Anyone can share experience here? We do 
> real-time spectral analysis and resynthesis of sound and go as low as 64 
> samples per cycle if the device allows.
> 
> Thanks in advance.
> 
> 
> Arshia
> 
> 
> PS: I actually brought the deprecation issue of AUGraph in a local Apple Dev 
> meeting where the EU director of developer relation was present. According to 
> him, when Apple announces a deprecation, it WILL happen. My interpretation of 
> the conversation is that AUGraph is no longer maintained but provided as is.
> 
>> On 11 Jul 2018, at 12:36, Benjamin Federer <benja...@boinx.com 
>> <mailto:benja...@boinx.com>> wrote:
>> 
>> Since it was mentioned in another email (thread) I’m giving this topic a 
>> bump. Would be great if someone at Apple, or anyone else in the know, could 
>> take the time to respond. The documentation at the link cited below still 
>> has no indication of deprecation. Will it come with one of the next Xcode 
>> Beta releases?
>> 
>> On another note I am really interested in how transitioning over to 
>> AVAudioEngine is working out for everyone. I know AVAudioEngine on iOS. What 
>> I am interested in is any macOS specifics or hardships.
>> 
>> From my experience AVAudioEngine is relatively robust in handling multiple 
>> graphs, i.e. separate chains of audio units. I had some issues with the 
>> AVAudioPlayerNode connecting to multiple destinations in that scenario. Also 
>> connect:toConnectionPoints:fromBus:format: did not work for me as it only 
>> connected to one of the destination points. Anyone else experienced problems 
>> in that regard?
>> 
>> Thanks
>> 
>> Benjamin
>> 
>> 
>>> Am 08.06.2018 um 16:59 schrieb Benjamin Federer <benja...@boinx.com 
>>> <mailto:benja...@boinx.com>>:
>>> 
>>> Last year at WWDC it was announced that AUGraph would be deprecated in 
>>> 2018. I just browsed the documentation 
>>> (https://developer.apple.com/documentation/audiotoolbox?changes=latest_major
>>>  
>>> <https://developer.apple.com/documentation/audiotoolbox?changes=latest_major>)
>>>  but found 
>>> Audio Unit Processing Graph Services not marked for deprecation. The 
>>> AUGraph header files rolled out with Xcode 10 beta also have no mention of 
>>> a deprecation in 10.14. I searched for audio-specific sessions at this 
>>> year’s WWDC but wasn’t able to find anything relevant. Has anyone come 
>>> across new information regarding this?
>>> 
>>> Judging by how much changes and features Apple seems to be holding back 
>>> until next year I dare ask: Has AUGraph API deprecation been moved to a 
>>> later time?
>>> 
>>> Benjamin
>> 
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