Nexus devices and audio format

[john oliver]

Hi all

From inspecting the /etc/audio_policy.conf files in various Nexus device stock image file systems and also in their AOSP device folders  it seems that they only support AUDIO_FORMAT_PCM_16_BIT. I'm trying clarify if this means that other formats, including AUDIO_FORMAT_PCM_8_24_BIT and AUDIO_FORMAT_PCM_24_BIT_PACKED cannot be used for local audio capture/playback. It's clear that the Lollipop platform provides them, but I'm wondering if there are other config files in which 24 bit audio capability is added. I'd appreciate it if anybody could please confirm what is the case.

 I'm aware of all the 16 v 24 bit arguments :) but I am more interested in finding out whether a 24 bit/44.1  track needs needs to be reformatted ( a simple >>8 for  I assume) before playing out on these devices.

From researching the audio codec chips available on the latest Nexus devices it seems that they do support 24 bit audio, so it could just these policy file that prevent it. Note, the Sony Xperia Z2 Lollipop's audio_policy supports AUDIO_FORMAT_PCM_8_24_BIT, at least for usb out.

Cheers,

John

[Glenn Kasten]

As announced at Google I/O 2014
session "Building great multi-media experiences on Android",
Android audio is moving from a 16-bit internal data path to floating-point internal data path.
This work started in Android 5.0 Lollipop, and is still ongoing.
Also mentioned at that I/O session is that we are moving towards
supporting > 16-bits at device end points.
This work also started in Android 5.0 Lollipop, and is continuing.

As the internal data path change and support for wider endpoints
are rolling out over a series of releases,
when you look at source code for the generic platform and device-specific HALs
and config files, you may see some partial support already.

I hope this is helpful, but please let me know if you have follow-up questions.

[john oliver]

On Thursday, 21 May 2015 23:29:01 UTC+1, Glenn Kasten wrote:

I hope this is helpful, but please let me know if you have follow-up questions.

 

This is indeed very useful to learn, thanks Glenn.