ResampleAudio

High-quality change of audio sample rate.

• Accepts any number of channels.
• The conversion is skipped if the sample rate is already at the given rate.
• Supports fractional resampling (where new_rate_denominator != 1).

Syntax and Parameters

ResampleAudio(clip clip, int new_rate_numerator [, int new_rate_denominator ] )

int  new_rate_numerator =

Set new sample rate, or if new_rate_denominator != 1, set the numerator.

int  new_rate_denominator = 1

Set the denominator for the new sample rate. Default 1.

When using fractional resampling (where new_rate_denominator != 1) the output audio sample rate is given by :

int(new_rate_numerator / new_rate_denominator + 0.5)

However internally the resampling factor used is :

new_rate_numerator / (new_rate_denominator * AudioRate)

This causes the audio duration to vary slightly (which is generally what is desired).^{[clarification needed]}

Examples

• Resample audio to 48 kHz:

source = WavSource("c:\audio.wav")
return ResampleAudio(source, 48000)

• Exact 4% speed up for PAL telecine:

Nfr_num = 25
Nfr_den = 1
AviSource("C:\Film.avi") # 23.976 fps, 44100Hz
Ar = AudioRate
# intermediate sample rate:
ResampleAudio(Ar*FramerateNumerator*Nfr_den, FramerateDenominator*Nfr_num)
# final sample rate:
AssumeSampleRate(Ar)
AssumeFPS(Nfr_num, Nfr_den, False)

In the example above, the intermediate sample rate needs to be

(44100 * 24000 / 1001) / (25 * 1) = 42293.706294

but because audio sample rates are always integers, 42293.706294 must be rounded to 42294,
which results in a time slippage of about 30ms per hour.

Changes

v2.56

Added new_sample_rate=float.