Float

Latest revision as of 21:25, 28 October 2019

This page is about the Float audio format.

For the variable type, see Script_variables.

For the Float() function, go to Internal_functions#Float.

For the Deep Color format, go to Float_(color_format)

Float (or fully IEEE floating point with single precision) is one of the AviSynth audio sample formats.

The samples of this type have normal values between -1.0 (= 0xBF800000) and +1.0 (= 0x3F800000). Values outside this range are usable as long as the audio remains in Float format, but will create audio clipping if converted to an integer format: 8, 16, 24 or 32 integer bits. For safety, you can call Normalize before converting from Float to Integer.

ColorBarsHD ## audio format = Float; range -1.0 - +1.0
Amplify(1000.0) ## range -1000.0 - +1000.0
Amplify(0.001) ## range -1.0 - +1.0
## output: unchanged

ColorBarsHD ## audio format = Float; range -1.0 - +1.0
Amplify(1000.0) ## range -1000.0 - +1000.0
ConvertAudioTo16bit ## convert to Integer; severe clipping
Amplify(0.001) ## still clipping

The value of such a IEEE-754 number is computed as: sign * 2^exponent * 1.mantissa, using the following scheme:

[ 1 Sign Bit | 8 Bit Exponent | 23 Bit Mantissa ]

• The sign bit is 1 (negative) or 0 (positive).
• The exponent runs from -127 (00000000) to 0 (0111111) to 128 (11111111).
• The mantissa m1m2m3 ... means m1/2 + m2/4 + m3/8 + ... in decimal. Sometimes people denote "1.m1m2m3..." as the mantissa (like is done in the converter below).

For an on-line converter between decimal numbers and IEEE 754 floating point, see here.

Examples:

0x3F800000 = 00111111100000000000000000000000 (binary, see [1])

Sign Bit      Exp       1.Mantissa
0          01111111  00000000000000000000000

127 - 127 = 0     1.0 bitshift 0 places

Sign bit is positive, exponent = 0, 1.mantissa = 1, so the number is +1.0

and

0xBF800000 = 10111111100000000000000000000000

Sign Bit      Exp       1.Mantissa
1          01111111  00000000000000000000000

127 - 127 = 0     1.0 bitshift 0 places

Sign bit is negative, exponent = 0, 1.mantissa = 1, so the number is -1.0

and

0x800000 = 01001011000000000000000000000000

Sign Bit      Exp       1.Mantissa
0          10010110  00000000000000000000000

150 - 127 = 23     1.0 bitshift 23 places

Sign bit is positive, exponent = 23, 1.mantissa = 1, so the number is 8388608

source: opferman.net