Audio session's hardware output latency incorrectly reported sometimes

Originator:michael
Number:rdar://15037132 Date Originated:20-Sep-2013
Status:Open Resolved:
Product:iOS SDK Product Version:7.0 (11A65)
Classification:Serious Bug Reproducible:Always
 
Summary:
Under certain circumstances, the audio session's hardware output latency is reported to be zero, incorrectly. This can be reproduced with headphones and the Apogee Jam, and possibly other devices. This may cause issues in some apps that expect a nonzero response, and may result in latency compensation discrepancy.

Steps to Reproduce:
1. Launch an audio app that queries the hardware output latency
2. Plug in headphones and an Apogee Jam (for instance)
3. Query the hardware output latency

Expected Results:
Latency is returned (e.g. 0.002268)


Actual Results:
Zero is returned


Version:
7.0 (11A465)

Notes:
See attached sample app demonstrating the issue: http://cl.ly/0p2D2X061Y0I

Configuration:
This can be reproduced on an iPad 3 running iOS 7.0, with headphones plugged in and an Apogee Jam.

Latency is correctly reported when no headphones are connected. The problem also does not arise when using Native Instruments' Komplete Audio 6 hardware via the Camera Connection Kit.

The problem does not arise on iOS 6.

Comments


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