Optimize bDelayPan and divisions

[ann0see]

Short description of changes

Moves delay pan checking slightly out of loop as this setting does not change often.
Moreover replaces some divisions with /2.0f and remove some modulo computations

CHANGELOG: Server: Optimize mixing

Context: Fixes an issue?

Related to: #3662

Does this change need documentation? What needs to be documented and how?

No

Status of this Pull Request

Ready for review

What is missing until this pull request can be merged?

Tested and it seems to work, I still would like an external test.

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

[ann0see]

Got rid of modulo computation

[ann0see]

The function is still way too complex imo.

[ann0see]

To avoid having the clipping to short twice, we may want someting like

    // convert from double to short with clipping
    for ( i = 0; i < ( ( bTargetIsMono ? 1 : 2 ) * iServerFrameSizeSamples ); i++ )
    {
        vecsSendData[i] = Float2Short ( vecfIntermProcBuf[i] );
    }

Maybe...

[softins]

I will study this code soon and make any comments...

[softins]

OK, to be certain, I made separate copies of the MixEncodeTransmitData function, two from main and two from this PR. I then edited one of each to remove the if (bDelayPan) sections and the other one of each to remove the corresponding else sections instead.

I was then able to compare the "before" and "after" with no delaypan, and the "before" and "after" with delaypan, ignoring whitespace, to be sure the logic was still exactly the same in each case. I am satisfied that it is.

So this PR preserves exactly the existing behaviour of Jamulus, appears to be potentially cleaner and more efficient, and I'm approving it for merging as-is on this basis.

I think any proposal to modify and potentially improve the design of this function should be a separate PR, discussed and thoroughly tested on its own merits.

[pljones]

OK, you're right, comparing the full files makes it easier.

It's the mono/stereo and delayPan if statements that are swapped so you do all of delayPan (with mono and stereo versions) and then all of !delayPan (with mono and stereo versions), which does make more sense.

I still prefer the / 2 (rather, / 2f - having cast to float and targeting a vector of floats) to * 0.5f for readability. "Half of" is an easier concept than "50% of".