SSRC

SSRC (int samplerate, bool “fast”)

SSRC Shibata Sample Rate Converter is a resampler. Audio is always converted to float. This filter will result in better audio quality than ResampleAudio. It uses SSRC by Naoki Shibata, which offers the best resample quality available.

Sampling rates of 44.1kHz and 48kHz are populary used, but the ratio of these two frequencies is 147:160, and they are not small numbers. Therefore, sampling rate conversion without degradation of sound quality requires filters with very large order. It is difficult to achieve both quality and speed. This program achieved relatively fast and high quality with two different kinds of filters combined skillfully.

Parameters:

samplerate	Samplerate must be an integer.
fast	This will enable faster processing at slightly lower quality. Set this to false when you are doing large samplerate conversions (more than a factor 2). Default: True.

SSRC doesn’t work for arbitrary ratios of the samplerate of the source and target clip. The following ratios are allowed (see SSRC.cpp):

sfrq = samplerate of source clip
  dfrq = samplerate of destination clip
  frqgcd = gcd(sfrq,dfrq) # Greatest Common Divisor
  fs1 = (dfrq > sfrq) ? sfrq / frqgcd : dfrq / frggcd
Resampling is possible if: (fs1 == 1) or (fs1 % 2 == 0) or (fs1 % 3 == 0)

example for which resampling is possible:
  sfrq = 44.1 kHz
  dfrq = 48 kHz
  frqgcd = gcd(44100,48000) = 300
dfrq > sfrq, hence
  fs1 = sfrq / frqgcd = sfrq / gcd(sfrq,dfrq) = 44100/300 = 147
and 147 % 3 = 0 since 147 = 3 * 49

The samplerate of your source clip can be found as follows

AviSource(...)
Subtitle(string(AssumeFPS(23.976,sync_audio=true).AudioRate))

Example:

# Downsampling to 44,1 kHz:
AviSource("c:\file.avi") # Has 48000 audio
SSRC(44100)

Changelog
v2.54	Initial Release

Some parts of SSRC is: Copyright © 2001-2003, Peter Pawlowski. All rights reserved.

$Date: 2012/04/15 14:59:42 $