Multichannel USB audio in Android M

[Felix Homann]

Hi,

I'm quite excited about the a) NDK support arriving in Adnroid Studio and b) the announcement of multichannel USB audio in Android M. I have already downloaded the Android M Preview SDK and documentation but failed to find any information on multichannel audio. Could someone (*) please give me a hint if there already is something and where to find it in that case?

Thanks,

Felix

(*) here "someone" most probably means Glenn ;-)

[Glenn Kasten]

First, the good news: yes as mentioned at http://developer.android.com/preview/api-overview.html#audio

there is improved support for configuring audio in M preview SDK, such as multichannel.

Most of M preview SDK documentation is online, 

but the API reference must downloaded from http://developer.android.com/preview/download.html#docs

After installing the docs, open these files in your browser: 

m-preview-1-developer-docs/reference/android/media/AudioTrack.Builder.html

m-preview-1-developer-docs/reference/android/media/AudioRecord.Builder.html

m-preview-1-developer-docs/reference/android/media/AudioFormat.Builder.html

The key change that permits better configuration of multichannel I/O over USB

is the concept of "indexed multi-channel" in addition to the previous "positional multi-channel" concept.

Positional multichannel associates each channel with a location or semantics,

such as front left, front rear, etc.

Indexed multichannel gives no semantics to each channel.

Rather each channel is identified by an index (number).

For example a 4-channel USB audio peripheral would have indices 0 to 3.

Indexed fits with USB audio much better than positional (which fits better with HDMI).

Now, the bad news:  the indexed multi-channel is currently only for SDK, not NDK.

I can't make any commitments or give a schedule.

[Felix Homann]

Thank you very much, Glenn!

(I try focus on the good news and forget about the *very* bad news at the end... )

[Olivier Roblin]

Hi all,

Any update concerning this "bad news" ? Is multichannel audio still not available from ndk ? Still no schedule for this ?

(Multichannel audio is an advanced audio feature that concerns advanced audio apps, that all use native OpenSL....Such a feature is not really useable if only available for Java API.)

[Glenn Kasten]

The process to see the SDK documentation that I posted earlier is obsolete.

The documentation is now online at these URLs:

  https://developer.android.com/reference/android/media/AudioTrack.Builder.html

  https://developer.android.com/reference/android/media/AudioRecord.Builder.html

  https://developer.android.com/reference/android/media/AudioFormat.Builder.html

There is no change for NDK since the May 29 post.

I am tracking your request, but I can't promise any commitment or schedule

for either explicit routing control or indexed multi-channel in NDK APIs.

In the mean time, traditional positional multi-channel I/O over USB

(where the channels have names and semantics such as "left" and "right")

is available for some USB peripherals such as Alesis iO4 with automatic routing.