Audio Data Java/Kotlin C++ Interaction Questions

[lilinxiong]

Thank you very much to the Oboe team for opening up such a great project. I now have some questions that I need to ask.
I have read the Can I write audio data from Java/Kotlin to Oboe? I tentatively asked, is it not recommended Audio Data from java/kotlin to Oboe? The same is not recommended Audio Data from Oboe to java/kotlin?
In other words, they can't work? Because I see that an onAudioReady callback is needed in Oboe. Oboe itself is a complete closed loop. Whether data to java/kotlin or data to Oboe will destroy this loop, it will not get a low latency stream.
If you want to use Oboe, then all audio processing needs to use C++. Only in this way, you will eventually get a low latency stream.
Is my understanding correct?
In Can I write audio data from Java/Kotlin to Oboe? I saw if I want to get a low latency stream in the java layer, then I can use the AudioTrack.Builder method setPerformanceMode(AudioTrack.PERFORMANCE_MODE_LOW_LATENCY).
I would like to ask, if I use the AudioTrack method in java, will I get the same stream as the Oboe low latency stream? If the delay of AudioTrack in java is higher than that of Oboe, how much higher is it?
We want to do ear return, but now there are many methods in the java layer, it is difficult to transplant in a short time.
thank you very much. Looking forward to the response from the Oboe team.

[philburk]

It is possible to send data in either direction between Java and Oboe.
If you use a callback then you will probably want to use a FIFO between Java and the Oboe callback. Atomic FIFOs can be implemented using a ByteBuffer.
If you read or write to Oboe then you do that directly in a JNI call from Java.

I would like to ask, if I use the AudioTrack method in java, will I get the same stream as the Oboe low latency stream?

Not exactly. If you are writing to the stream and not using a callback then the Java path might have lower latency.
Oboe will not provide a LowLatency output stream for write() unless the device supports MMAP. On the Legacy path you will get a normal stream with higher latency than Java can get using AudioTrack.PERFORMANCE_MODE_LOW_LATENCY.

Rough comparison of output latency (varies by device)
Oboe LowLatency with callback using MMAP = 10-18 msec
Oboe LowLatency with callback using Legacy = 14-50 msec
Java AudioTrack.PERFORMANCE_MODE_LOW_LATENCY = 40-100 msec
Oboe using write on Legacy path = 100-300 msec

[lilinxiong]

Thank you for your answer, I got what I want, thank you again~

[jet-yangqs]

if I use AudioTrack.PERFORMANCE_MODE_LOW_LATENCY in java on LowLatency path, can I use the Audio effect such as AEC?

[huangxin1985]

so...we have to synthesis audio in the jni layer. right?