[vlc-devel] Volume change lag fix for OS X CoreAudio [auhal]

[Jon Stacey]

Hello everyone,

I have just submitted a patch to fix the volume lag problem in the auhal audio output module: https://trac.videolan.org/vlc/ticket/5605#comment:7 The patch needs to be reviewed, and tested more broadly on older versions of OS X.

I am using the kHALOutputParam_Volume parameter and the cubic mapping volume adjustment from output.c. [volume = volume * volume * volume]. This value ranges from 0 to 8. The Apple documentation says that this parameter is a linear gain from 0 through 1, but it seems to work just fine with the cubic mapping on the 10.7 SDK. It's possible this documentation is wrong, or referring to an older SDK, but testing is needed on any older versions of VLC that we want to support.

https://developer.apple.com/library/mac/#documentation/AudioUnit/Reference/AudioUnitParametersReference/Reference/reference.html

Besides eliminating the lag, VLC behavior should remain unchanged. Let me know how it looks and works, and if you have any ideas on how to handle the volume conversion more effectively.


Cheers,

Jon

p.s. This is my first foray into the VLC codebase.