Open Radar

 
Summary:
Audio received from the system input (by calling AudioUnitRender on a Remote IO unit's bus 1) from within an IAA node app is corrupted when the client-facing scopes of the RIO node are operating at a different sample rate than the session.

Specifically, the first few frames of each buffer appear to contain audio samples from the past (see attached image).

Steps to Reproduce:
1. Create a Remote IO audio unit, with input enabled and client formats on bus 0 input scope, and bus 1 output scope at 44.1kHz.
2. Publish the RIO unit, and host from an IAA host app with session sample rate at a different sample rate (e.g. 48kHz)
3. When rendering, draw input from the RIO unit using AudioUnitRender

Expected Results:
System audio received as normal

Actual Results:
First part of every buffer contains old junk data

Version:
Tested on iOS 9.2 and 9.3

Notes:
See attached sample apps: one generator, one host. After starting host, switch to generator and move switch to oscillator mode to verify that audio reaches host app without issue: problem lies on the RIO input side.

If the IAA node's client-facing scopes are running at the session sample rate, or the node uses a separate Remote IO unit for input, the problem goes away.

Configuration:
Tested on an iPhone 6S Plus without headphones plugged in, causing read-only 48kHz samplerate for session

Attachments:
'IAA Test.zip' and 'analysis.jpg' were successfully uploaded.