iOS 3D mixer works in iOS 5+ but not in iOS 4.3

Question

I've set up a kAudioUnitSubType_AU3DMixerEmbedded as part of a functional AUGraph. I've set the output ASBD of the mixer to the following:

Sample Rate:              44100
Format ID:                 lpcm
Format Flags:                 C // (kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked)
Frames per Packet:            1
Channels per Frame:           2
Bits per Channel:            16
Bytes per Packet:             4
Bytes per Frame:              4

This audio graph works great when running on iOS 5+, but on iOS 4.3, it outputs really weird distorted sounds that sound nothing like the inputs. To better understand this, I only used one mixer input and compared the input bytes versus the output bytes. On iOS 5+, the input and output bytes were identical, as you would expect. However, on iOS 4.3, the output bytes are different. Even when I'm inputting in all 0s to the mixer (0x0000, 0x0000, ...) , the output bytes are printing out as a stream of 0x8000 0x8000.

Does anyone have any idea why the 3D mixer behaves strangely on iOS 4.3?

iOS 3D mixer works in iOS 5+ but not in iOS 4.3

0 Answers0