If the Google issue 24614 owner ask for more information, the USB Audio requirements should be:
1. Support for 24-bit/192kHz digital output
More and more USB DACs can support 24/192, and it is already supported in some Android USB audio implementations:
. USB Audio Recorder PRO
. Modded CyanogenMod CM 10.1
2. Support for USB ACA (Accessory Charger Adapter)
An ACA-compliant Android device operating as a USB host is also able to charge at the same time. It draws power from an external power supply, or from an ACA-compliant USB DAC.
It is not a USB Audio feature per se, but such a USB ACA feature recommended by Google should encourage the mass production of USB OTG – ACA components, and prevent Android device manufacturers from implementing non-standard ACA.
Optional requirement: USB Audio parameter settings like buffer size setting for sound quality tweaking purposes
. "The secret of USB Audio Recorder PRO [my preferred SQ music player]: "source direct" like the audiophile Audirvana player for Mac OS X?"
. "An interesting example is the HRT music streamer II, it IS asynchronous USB, but it is still very sensitive to what happens in the computer. On the SAME COMPUTER I can make simple changes to OS scheduling parameters and get a huge difference in the sound. At one end of the scale it’s dull, lifeless, no depth at all, at the other end of the scale it is wonderfully alive, dynamic, huge depth etc. And all this by just changing a few numbers, NO change in hardware at all."
Any missing USB Audio requirement?
Edited by DanBa - 7/15/13 at 11:05pm