Absolute volume feature, part of AVRCP 1.4 specification provides capability to control volume at the A2DP sink side. Refer section 6.13 in AVRCP 1.4 specification. All iOS devices supports this feature. When an A2DP sink device connects - that supports "Absolute Volume" feature, iOS device will disable local gain level change (with the volume of the source audio set to 100%) . Change in volume level will be notified in percentage to the sink device, which can then modulate the gain level. Thanks. Aarti. On Jan 18, 2013, at 8:03 AM, Gordon Rankin wrote:
Gang,
I am looking to get information on the best quality of audio output I can get from Bluetooth. I know the codec has a lot to do with it, but I am looking even further than that.
So I am designing a A2DP sink with an AVRCP source.
~~~
Volume control? In general all digital volume controls will reduce the resolution of each sample so I am wondering... do I signal the A2DP source with AVRCP to make the volume = 100% will that result in the best data available at my A2DP sink? Digital volume controls in the source will basically multiply the float32 sample with the digital volume percent to create the new sample. But since we get fixed point samples at the endpoint this basically means we loose resolution if the volume control is set to something other than 100%.
I can control the actual volume in the analog domain which will result in the best support of the digital samples.
Or is there some other way of handling this?
Thanks, Gordon
-- J. Gordon Rankin Owner and Chief Scientist ====== Wavelength Audio, ltd ======
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