[opensource-dev] Review Request: STORM-830 Volume slider isn't properly remembered if set to zero

[Kent Quirk]

> On Jan. 6, 2011, 5:37 p.m., Aleric Inglewood wrote:
> > This is really not how you want to deal with this bug :/.  It's a known fact that audio mixers are very bad with low volumes. Setting a volume to 0 (or something really small) can put a very high load on the CPU for the audio mixer, which causes severe problems. See https://jira.secondlife.com/browse/VWR-14914
> > 
> > So, on the contrary (as VWR-14914 fixed a horrible bug that made FPS drop drastically): when the volume is set to 0 (or even close to zero) the audio channel has to be muted and not mixed, ever. Assuming that VWR-14914 is in Viewer 2, and wasn't broken in the meantime, a volume of 0 would cause the channel to be muted, but setting it to 0.000001 will not cause it to be muted, but result in a high CPU load.
> >
> 
> Aleric Inglewood wrote:
>     After discussion on IRC Jonathan explained to me what this is all about. The patch is correct.
>     Nevertheless, I was confused about the fact that this value of 0.000001 is never going to be USED.
>     Perhaps a different value and comment can avoid that in the future when other coders look at it.
>     mInternalGain is only ever compared with, and the whole point of this patch is to make sure
>     that the first comparison fails (I now understand). A common value used to make sure that
>     a first comparison fails is a value outside the valid range of that variable. The valid
>     range being [0, 1], I'd suggest using -1 and adding a comment in the lines of:
>     
>         // Make sure that the first call to setMasterGain will cause setInternalGain to be called.
>         mInternalGain = -1.f;
>

Aleric is correct, and if the approach is technically possible it would be preferred to use an out-of-range value. It appears to me that his suggested fix will work, but I haven't tried it myself. Jonathan, can you try it, please?


- Kent


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On Jan. 6, 2011, 2:37 p.m., Jonathan Yap wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> http://codereview.secondlife.com/r/72/
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> 
> (Updated Jan. 6, 2011, 2:37 p.m.)
> 
> 
> Review request for Viewer.
> 
> 
> Summary
> -------
> 
> There is an edge case in setMasterGain during startup which prevents setInternalGain from being called if the master volume setting and mInternalGain both equal 0.
> 
> Setting mInternalGain to a very low but non-zero value fixes this issue.
> 
> 
> This addresses bug STORM-830.
>     http://jira.secondlife.com/browse/STORM-830
> 
> 
> Diffs
> -----
> 
>   indra/llaudio/llaudioengine.cpp 6d44f0d85a80 
> 
> Diff: http://codereview.secondlife.com/r/72/diff
> 
> 
> Testing
> -------
> 
> In Preferences / Sound & Media tested:
> Buttons
> Ambient
> Sound Effects
> Stream Music
> Media
> Voice Chat
> 
> 
> Thanks,
> 
> Jonathan
> 
>

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