Laurent,

What you said about not being able to achieve latency lower than 100ms is
worrisome. I need a realtime MIDI synth, low latency is absolutely crucial.
Does the limitation you mention apply only to signal processing or other
applications of the API as well, in particular MIDI synthesis?

Regards,
Bartosz


On Wed, Jul 11, 2018 at 3:30 PM, Laurent Noudohounsi <
laurent.noudohou...@gmail.com> wrote:

> Thanks Benjamin for the precision. I thought that `installTapOnBus` was
> the successor of `RenderCallback`.
> For me it was not natural to mix old api like `kAudioUnitProperty_
> SetRenderCallback` in AVAudioEngine.
>
> So as Arshia said, I'm also looking for a way to use real-time processing
> with AVAudioEngine.
>
> Le mer. 11 juil. 2018 à 15:05, Arshia Cont <arshiac...@antescofo.com> a
> écrit :
>
>> Interesting thread here!
>>
>> Anyone has achieved low-latency processing on AVAudioEngine?
>>
>> The RenderCallback seems natural to me (which is the good “old” way of
>> doing it with AUGraph). But I’m curious to hear if anyone has done/achieved
>> real stuff here with AVAudioEngine real-time processing and how.
>>
>>
>> Arshia
>>
>>
>> On 11 Jul 2018, at 15:00, Benjamin Federer <benja...@boinx.com> wrote:
>>
>> 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> 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> 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>:
>>>
>>> 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) 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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>>
>>
>>
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