pvsbufread — This opcode creates and writes to a circular buffer for streaming PV signals.


This opcode sets up and writes to a circular buffer of length ilen (secs), giving a handle for the buffer and a time pointer, which holds the current write position (also in seconds). It can be used with one or more pvsbufread opcodes. Writing is circular, wrapping around at the end of the buffer.


fsig pvsbufread  ktime, khandle[, ilo, ihi] 


ilo, ihi -- set the lowest and highest freqs to be read from the buffer (defaults to 0, Nyquist).

fsig -- output pv stream

ktime -- time position of reading pointer (in secs).

khandle -- handle identifying the buffer to be read. When using k-rate handles, it is important to initialise the k-rate variable to a given existing handle. When changing buffers, fsig buffers need to be compatible (same fsig format).


Here is an example of the pvsbufread opcode.

Example 352. Example of the pvsbufread opcode

With this opcode and pvsbuffer, it is possible to, among other things: 1) time-stretch/compress a fsig stream, by reading it at different rates 2) delay a fsig or portions of it. 3) 'brassage' two or more fsigs by switching buffers, since the reading handles are k-rate. Note that, when using k-rate handles, it is important to initialise the k-rate variable to a given handle (so that the fsig initialisation can take place) and it is only possible to switch handles between compatible fsig buffers (with the same fftsize and overlap), eg.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

fsig1   pvsanal   asig1,1024,256,1024,1
fsig2   pvsanal   asig2,1024,256,1024,1

ibuf1,kt1   pvsbuffer   fsig1, 10  ; 10-sec buf with fsig1
ibuf2,kt2   pvsbuffer  fsig2, 7      ; 7-sec buf with fsig2

khan init ibuf1    ; initialise handle to buf1

if  ktrig  > 0 then   ; switch buffers according to trigger
khan = ibuf2
khan = ibuf1

fsb  pvsbufread  kt1, khan   ; read buffer


Author: Victor Lazzarini
July 2007