ResampleAudio

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{{Template:FuncDef|ResampleAudio(clip, int new_rate_numerator [, int new_rate_denominator])}}
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<div style="max-width:62em" >
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High-quality change of audio sample rate.
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* Accepts any number of channels.
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* The conversion is skipped if the sample rate is already at the given rate.
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* Supports ''fractional'' resampling (where {{FuncArg|new_rate_denominator}} != 1).
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</div>
  
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ResampleAudio performs a high-quality change of audio sample rate.
 
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The conversion is skipped if the samplerate is already at the given rate.
 
  
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When using fractional resampling the output audio samplerate is given by :
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== Syntax and Parameters ==
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<div style="max-width:62em" >
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{{FuncDef
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|ResampleAudio(clip ''clip'', ''int new_rate_numerator'' [, int ''new_rate_denominator'' ] )
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}}
  
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int(new_rate_numerator / new_rate_denominator + 0.5)
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:{{Par2|new_rate_numerator|int|}}
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::Set new sample rate, or if {{FuncArg|new_rate_denominator}} != 1, set the numerator.
  
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However the internally the resampling factor used is :
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:{{Par2|new_rate_denominator|int|1}}
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::Set the denominator for the new sample rate. Default 1.
  
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new_rate_numerator / (new_rate_denominator * old_sample_rate)
 
  
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This causes the audio duration to vary slightly (which is generally what is desired).
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When using fractional resampling (where {{FuncArg|new_rate_denominator}} != 1) the output audio sample rate is given by :
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:int({{FuncArg|new_rate_numerator}} / {{FuncArg|new_rate_denominator}} + 0.5)
  
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Starting from v2.53 ResampleAudio accepts any number of channels.
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However internally the resampling factor used is :
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Starting from v2.56 ResampleAudio process float samples directly. Support fractional resampling.
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:{{FuncArg|new_rate_numerator}} / ({{FuncArg|new_rate_denominator}} * [[Clip_properties|AudioRate]])
  
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# Resamples audio to 48 kHz:
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This causes the audio duration to vary slightly (which is generally what is desired).{{Clarify}}
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source = AviSource("c:\audio.wav")
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</div>
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return ResampleAudio(source, 48000)
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  # Exact 4% speed up for PAL telecine:
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== Examples ==
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* Resample audio to 48 kHz:
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<div {{BoxWidthIndent|26|2}} >
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source = [[WavSource]]("c:\audio.wav")
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  return ResampleAudio(source, 48000)
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</div>
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* Exact 4% speed up for PAL telecine:
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<div {{BoxWidthIndent|56|2}} >
 
  Nfr_num = 25
 
  Nfr_num = 25
 
  Nfr_den = 1
 
  Nfr_den = 1
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  AviSource("C:\Film.avi") # 23.976 fps, 44100Hz
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  [[AviSource]]("C:\Film.avi") # 23.976 fps, 44100Hz
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  Ar = Audiorate()
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  Ar = [[Clip_properties|AudioRate]]
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  ResampleAudio(Ar*FramerateNumerator()*Nfr_den, FramerateDenominator()*Nfr_num)
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''# intermediate sample rate:''
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  AssumeSampleRate(Ar)
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  ResampleAudio(Ar*[[Clip_properties|FramerateNumerator]]*Nfr_den, [[Clip_properties|FramerateDenominator]]*Nfr_num)
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  AssumeFPS(Nfr_num, Nfr_den, False)
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  ''# final sample rate:''
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[[AssumeSampleRate]](Ar)
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  [[AssumeFPS]](Nfr_num, Nfr_den, False)
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</div>
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<div style="max-width:62em" >
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In the example above, the ''intermediate sample rate'' needs to be
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:(44100 * 24000 / 1001) / (25 * 1) = 42293.706294
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but because audio sample rates are always integers, 42293.706294 must be rounded to 42294, <br>
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which results in a time slippage of about 30ms per hour.
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</div>
  
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For exact resampling the intermediate samplerate needs to be 42293.706293 which if rounded to 42294 would causes about 30ms per hour variation.
 
  
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'''Changes:'''
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== Changes ==
 
{| border="1"
 
{| border="1"
 
|-  
 
|-  

Revision as of 08:21, 15 February 2016

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.
Retrieved from "http://avisynth.nl/index.php?title=ResampleAudio&oldid=8634"
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