COPYING.txt
author Ryan C. Gordon <icculus@icculus.org>
Tue, 15 May 2018 01:04:11 -0400
changeset 11987 0c284754e25b
parent 11811 5d94cb6b24d3
child 12503 806492103856
permissions -rw-r--r--
audio: converting int32 to/from float shouldn't use doubles.

The concern is that a massive int sample, like 0x7FFFFFFF, won't fit in a
float32, which doesn't have enough bits to hold a whole number this large,
just to divide it to get a value between 0 and 1.
Previously we would convert to double, to get more bits, do the division, and
cast back to a float, but this is expensive.

Casting to double is more accurate, but it's 2x to 3x slower. Shifting out
the least significant byte of an int32, so it'll definitely fit in a float,
and dividing by 0x7FFFFF is still accurate to about 5 decimal places, and the
difference doesn't appear to be perceptable.
     1 
     2 Simple DirectMedia Layer
     3 Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
     4   
     5 This software is provided 'as-is', without any express or implied
     6 warranty.  In no event will the authors be held liable for any damages
     7 arising from the use of this software.
     8 
     9 Permission is granted to anyone to use this software for any purpose,
    10 including commercial applications, and to alter it and redistribute it
    11 freely, subject to the following restrictions:
    12   
    13 1. The origin of this software must not be misrepresented; you must not
    14    claim that you wrote the original software. If you use this software
    15    in a product, an acknowledgment in the product documentation would be
    16    appreciated but is not required. 
    17 2. Altered source versions must be plainly marked as such, and must not be
    18    misrepresented as being the original software.
    19 3. This notice may not be removed or altered from any source distribution.
    20