Skip to content

src_conv

Converts the sample rate of an audio file at sample rate Rin to a sample rate of Rout.

Optionally the ratio (Rin / Rout) may be linearly time-varying according to a set of (time, ratio) pairs in an auxiliary file.

Syntax

src_conv [flags] infile

Initialization

Flags:

  • -P num = pitch transposition ratio (srate / r) [don't specify both P and r]
  • -Q num =quality factor (1, 2, 3, 4 or 5: default = 3)
  • -i filnam = auxiliary breakpoints file (no breakpoint by default. i.e. No ratio change)
  • -r num = output sample rate (must be specified if no P)
  • -o fnam = sound output filename (default: test.wav)
  • -A = create an AIFF format output soundfile
  • -J = create an IRCAM format output soundfile
  • -W = create a WAV format output soundfile (default after Csound version 6.15)
  • -h = no header on output soundfile
  • -c = 8-bit signed_char sound samples
  • -a = alaw sound samples
  • -8 = 8-bit unsigned_char sound samples
  • -u = ulaw sound samples
  • -s = short_int (16 bit) sound samples (default)
  • -3 = 24-bit sound samples
  • -l = long_int sound samples
  • -f = float sound samples
  • -r N = orchestra srate override
  • -K = Do not generate PEAK chunks
  • -R = continually rewrite header while writing soundfile (WAV/AIFF)
  • -H# = print a heartbeat style 1, 2 or 3 at each soundfile write
  • -N = notify (ring the bell) when done

This program performs arbitrary sample-rate conversion with high fidelity using the libsamplerate library.

The five levels of accuracy are:

  • 1: A linear converter. The quality is poor, but the conversion speed is blindingly fast.
  • 2: A Zero Order Hold converter (interpolated value is equal to the last value). The quality is poor but the conversion speed is blindingly fast.
  • 3: This is the fastest bandlimited interpolator and has an SNR of 97dB and a bandwidth of 80%.
  • 4: This is another bandlimited interpolator much like the previous one. It has an SNR of 97dB and a bandwidth of 90%. The speed of the conversion is much faster than the next one. Blindingly fast.
  • 5: This is a bandlimited interpolator derived from the mathematical sinc function and this is the highest quality sinc based converter, providing a worst case Signal-to-Noise Ratio (SNR) of 97dB at a bandwidth of 97%.

Examples

Here is an example of src_conv. It uses the file src_conv.csd.

Example of src_conv.
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac   
; For Non-realtime ouput leave only the line below:
; -o src_conv.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 48000  ; sample rate of drumsMlp.wav = 44100
ksmps = 32  ; and will be resampled to 48000
nchnls = 2
0dbfs  = 1

; by Menno Knevel 2021

; resample in the highest qualty, name the new sample 'beats48.wav'
gires system_i 1,{{ src_conv -r48000 -Q5 drumsMlp.wav -o beats48.wav }}

instr 1
ires system_i 1,{{ sndinfo -i beats48.wav }} ; check sample rate
aout    diskin2 "beats48.wav", 1
outs    aout, aout  
endin

</CsInstruments>
<CsScore>
i1 0 2              

e
</CsScore>
</CsoundSynthesizer>

Credits

Author: John ffitch; based on code by Erik de Castro Lopo

May 2015