# What is DPCM, and how is derivative defined in it? Are the messages coming with constant time intervals?<br>#
I was thought that the simplest model of the derivative in discrete
signals is calculated by taking the differences between successive
samples and dividing the difference to the time interval between them.
<br># Where do you keep the last 4 values? Maybe using a table is easier.<br><span class="sg">-ugur-</span><br><br><div><span class="gmail_quote">On 9/3/07, <b class="gmail_sendername">Oded Ben-Tal</b> &lt;<a href="mailto:oded@ccrma.stanford.edu">
oded@ccrma.stanford.edu</a>&gt; wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Does anyone know of a patch/object that calculates the derivative of an
<br>incoming sequence of messages (not signal)?<br>I am trying to figure out a way of calculating the derivative (by DPCM)<br>but all I can come up with are very cumbersome and ugly (keeping the last<br>4 values and then switching their positions ready for the next iteration
<br>works in c, but seems awkward in pd) I presume there is a simple elegant<br>way of doing it but I just can&#39;t see it.<br><br>Thanks<br>Oded<br><br>--<br>___________________________________________________<br>Oded Ben-Tal
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