about low latency opensl es programing

[bobi wang]

I have read the opensl doc in NDK.

at the topic "performance",I don't understand about "The lower output latency path is used only if the application requests a buffer count of 2 or more, and a buffer size and sample rate that are compatible with the device's native output configuration.".

what is mean that "a buffer count of 2 or more"?

Is it a example code about that?

[Glenn Kasten]

This is referring to the application-level buffer count, which is specified when you create the buffer queue ... see the corresponding field pcm buffer queue data locator structure. 

There was a recent change that removed the requirement for >= 2 app-level buffers. 

  https://android.googlesource.com/platform/frameworks/wilhelm/+/92e53bc98cd938e9917fb02d3e5a9be88423791d%5E!/

Your note reminds me that the documentation needs to be updated regarding this.

[Michael Moussa]

Glenn, in what API level was this change made? Was it 19 (Android 4.4)

Thanks,
Mike

[Glenn Kasten]

The change was committed on Thu Jun 06 10:11:52 2013 -0700

but I don't recall which Android version that corresponds to.

[Michael Moussa]

Thanks Glenn, I saw the commit date, just was not sure if there was some easy way to know what version it made it in. I'll check out the various git branches to see where it landed. Based on the date it had a chance to make it in for 4.3, but maybe it didnt make it until 4.4.

Mike

[Achim Leubner]

It's an old thread, but anyway, in case somebody wonders: looks like it didn't make into 4.3. But it seems to be in 4.4.

Btw. it also looks like the requirement never was "exact" 2 buffers, but "at least". Oh and canUseFastTrack() also checks a blacklist of opensl interfaces.

Achim