<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size: 14px; font-family: Calibri, sans-serif; "><div>Though with DC you don't have the issue of phase. I'm not an expert in filter math, but I assume that by the time your filtered audio (assuming its not DC) gets subtracted by the [-~] object it is out of phase with the original signal. Moreover, I hear a distinct difference. Maybe I'm not conceiving your statement properly and perhaps this discussion has been about DC all along…</div><div><br></div><div>Regards</div><div><br></div><div><br></div><span id="OLK_SRC_BODY_SECTION"><div style="font-family:Calibri; font-size:11pt; text-align:left; color:black; BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt"><span style="font-weight:bold">From: </span> Alexandre Torres Porres <<a href="mailto:porres@gmail.com">porres@gmail.com</a>><br><span style="font-weight:bold">Date: </span> Tuesday, April 22, 2014 3:51 PM<br><span style="font-weight:bold">To: </span> GCC <<a href="mailto:robert@urbanstew.org">robert@urbanstew.org</a>><br><span style="font-weight:bold">Cc: </span> <<a href="mailto:apvague@gmail.com">apvague@gmail.com</a>>, Ingo <<a href="mailto:ingo@miamiwave.com">ingo@miamiwave.com</a>>, pd-lista puredata <<a href="mailto:pd-list@iem.at">pd-list@iem.at</a>><br><span style="font-weight:bold">Subject: </span> Re: [PD] WG: Inverse bandpass filter<br></div><div><br></div><div dir="ltr"><div>can;t remember where I saw about this, but check this link</div><div><br></div><a href="http://msp.ucsd.edu/techniques/v0.11/book-html/node141.html">http://msp.ucsd.edu/techniques/v0.11/book-html/node141.html</a><br><div><br></div><div>see the quote "An easy and practical way to remove the zero-frequency component from an audio signal is to use a one-pole low-pass filter to extract it, and then subtract the result from the signal. The resulting transfer function is one minus the transfer function of the low-pass filter:"</div><div><br></div><div>doesn't it agree with what I said?</div><div><br></div><div><br></div><div>cheers</div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2014-04-22 14:37 GMT-03:00 Robert Esler <span dir="ltr"><<a href="mailto:robert@urbanstew.org" target="_blank">robert@urbanstew.org</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="font-size:14px;font-family:Calibri,sans-serif;word-wrap:break-word"><div><div>I could be wrong, but I don't think it's quite the same thing. I believe the signal would be out of phase negating many of the effects of the filter. I would recommend using [biquad~] and in pd-extended there is a [notch] object which takes care of the coefficients. This sounds much cleaner and more notch-like to my ear than subtracting the filtered output. </div><div> There is an explanation in Miller's book if you like unit circle math: <a href="http://msp.ucsd.edu/techniques/latest/book-html/node144.html" target="_blank">http://msp.ucsd.edu/techniques/latest/book-html/node144.html</a></div><div>-----------</div><div>Message: 4</div><div>Date: Tue, 22 Apr 2014 01:59:07 -0300</div><div>From: Alexandre Torres Porres <<a href="mailto:porres@gmail.com" target="_blank">porres@gmail.com</a>></div><div>Subject: Re: [PD] WG: Inverse bandpass filter</div><div>To: Ingo <<a href="mailto:ingo@miamiwave.com" target="_blank">ingo@miamiwave.com</a>></div><div>Cc: pd-list <<a href="mailto:pd-list@iem.at" target="_blank">pd-list@iem.at</a>></div><div>Message-ID:</div><div><span style="white-space:pre-wrap"> </span><<a href="mailto:CAEAsFmhD0HanLmv9vutcSQZjkZY69i7wMeBqQ+20S2riWYaakw@mail.gmail.com" target="_blank">CAEAsFmhD0HanLmv9vutcSQZjkZY69i7wMeBqQ+20S2riWYaakw@mail.gmail.com</a>></div><div>Content-Type: text/plain; charset="utf-8"</div><div><div class="h5"><div><br></div><div>isn't it just subtract the audio from the filtered output?</div><div><br></div><div>I guess you can get inverse freq response just by that</div><div><br></div><div>cheers</div><div><br></div><div><br></div><div>2014-04-18 17:21 GMT-03:00 Ingo <<a href="mailto:ingo@miamiwave.com" target="_blank">ingo@miamiwave.com</a>>:</div><div><br></div><blockquote style="border-left-color:rgb(181,196,223);border-left-width:5px;border-left-style:solid;padding:0px 0px 0px 5px;margin:0px 0px 0px 5px"><div style="font-family:Consolas;font-size:medium">You could send the original signal in parallel and invert the phase by</div><div style="font-family:Consolas;font-size:medium">multiplying with -1. You might have to delay the original signal in case</div><div style="font-family:Consolas;font-size:medium">that the processed signal gets also delayed by one or more blocks.</div><div style="font-family:Consolas;font-size:medium"><br></div><div style="font-family:Consolas;font-size:medium">
Ingo</div><div style="font-family:Consolas;font-size:medium"><br></div><div style="font-family:Consolas;font-size:medium">_______________________________________</div><div style="font-family:Consolas;font-size:medium">> Von: <a href="mailto:pd-list-bounces@iem.at" target="_blank">pd-list-bounces@iem.at</a> [<a href="mailto:pd-list-bounces@iem.at" target="_blank">mailto:pd-list-bounces@iem.at</a>] Im Auftrag</div><div style="font-family:Consolas;font-size:medium">von</div><div style="font-family:Consolas;font-size:medium">> AP Vague</div><div style="font-family:Consolas;font-size:medium">> Gesendet: Freitag, 18. April 2014 18:49</div><div style="font-family:Consolas;font-size:medium">> An: <a href="mailto:pd-list@iem.at" target="_blank">pd-list@iem.at</a></div><div style="font-family:Consolas;font-size:medium">> Betreff: [PD] Inverse bandpass filter</div><div style="font-family:Consolas;font-size:medium">></div><div style="font-family:Consolas;font-size:medium">> Is there a simple way to make [bp~] or [vcf~] have an inverse function?</div><div style="font-family:Consolas;font-size:medium">
To</div><div style="font-family:Consolas;font-size:medium">> filter out, rather than pass a changing frequency value. Is the easiest</div><div style="font-family:Consolas;font-size:medium">> way to do this with a combination of [lop~] and [hip~]?</div><div style="font-family:Consolas;font-size:medium"><br></div><div style="font-family:Consolas;font-size:medium"><br></div><div style="font-family:Consolas;font-size:medium">_______________________________________________</div><div style="font-family:Consolas;font-size:medium"><a href="mailto:Pd-list@iem.at" target="_blank">Pd-list@iem.at</a> mailing list</div><div style="font-family:Consolas;font-size:medium">UNSUBSCRIBE and account-management -></div><div style="font-family:Consolas;font-size:medium"><a href="http://lists.puredata.info/listinfo/pd-list" target="_blank">http://lists.puredata.info/listinfo/pd-list</a></div><div><br></div></blockquote></div></div></div></div></blockquote></div><br></div></span></body></html>