signal processing - Plotting an audio spectrum -


i'm trying implement app plot spectrum of audio using bass audio (http://www.un4seen.com/). understanding have to:

  1. get fft data stream float[] buffer = new float[256]; bass.bass_channelgetdata(handle, buffer, (int)(bass_data_fft_complex|bass_data_fft_nowindow));

  2. for each fft, compute it’s magnitude

  3. apply window function fft (hanning or hamming do)

  4. then, draw beautiful spectrum analysis

the problem that:

  • it seems bass_data_fft_complex bassdata isn't reachable. can see supposed available in documentation http://www.bass.radio42.com/help/html/a13cfef0-1056-bb94-81c4-a4fdf21bd463.htm cannot use since error bassdata not include such enum
  • further, i'm wondering if i'm doing right. plot spectrum, should plot magnitude of fft or plat magnitude of fft against frequency of fft? in case, how frequency corresponding fft? don't mind code snipped language (c/c++, c#, vb, java, etc..)

note: i'm not sure if helps i'm using: plotting using microsoft chart control. c# bass.net api http://www.bass.radio42.com/ , suggestions in appreciated

you have mixed order of steps - need apply window function time domain data before calculating fft. steps typically:

1. acquire time domain data 2. apply window function 3. calculate fft 4. calculate log magnitude of fft (log(re*re+im*im)) 5. plot log magnitude (with appropriate scaling) against frequency

note using log magnitude y axis gives db scale, more natural , useful way view sound amplitude linear magnitude scale.

normally visualizing audio etc apply steps 1 - 5 above on successive blocks of time domain data, typically overlap of 50%.


Comments

Post a Comment

Popular posts from this blog

php - cannot display multiple markers in google maps v3 from traceroute result -

i'm newbie in php mysql , google maps v3. have problems in google maps v3. made traceroute web based , map traceroute's result in google maps v3 final project of college education. have try many tutorials didn't work. have tried tutorials in forum nothing worked. problem cannot display multiple markers got location data database. maybe because i'm newbie , not know how do. confuse looping show markers. here code <?php error_reporting(e_all ^ (e_notice)); ini_set('max_execution_time', 360); $enable_log_user = false; global $ip, $host_name, $host_ip; $host = @$_post['host']; $trace = @$_post['trace']; $self = $_server['php_self']; include("phpsqlajax_dbinfo.php"); $connection = mysql_connect ('127.0.0.1', $username, $password); if (!$connection) { die('not connected : ' . mysql_error());} $db_selected = mysql_select_db($database, $connection); if (!$db_selected) { die ('can\'t use db : ...
Read more

c# - DetailsView in ASP.Net - How to add another column on the side/add a control in each row? -

i have detailsview control on page used edit various fields of record, works in respect. i looking way add 1 column (and if works, why not more) right, absolutely read-only, show same fields of record comparison purposes. i aware there no obvious way such thing out of box detailsview . have looked other controls (transposed gridview , recommended formview , listview ), nothing satisfies. have special data binding setup using detailsview , can't out of without losing features. anyone on how "hack in" additional columns (for display only) on detailsview ? the solution have now, use second detailsview , visible set false in aspx. in code, make sure databind hidden detailsview hosts data third column first, initial detailsview named itemdetails . and in item created event, pass third column html rendering of hidden controls (in last code block) : protected void itemdetails_itemcreated(object sender, eventargs e) { if (dataite...
Read more

javascript - firefox memory leak -

i have following script (i use raphaeljs also) draws circle, waits 1 second, draws circle again, etc (you can copy paste - functional, need include raphael raphaeljs.com): <div id="holder"> </div> <script src="raphael.js" type="text/javascript"></script> <script> var paper = raphael(10, 50, 320, 200); var rad = math.pi / 180; var finangle = 0; function sector(cx, cy, r, startangle, endangle, params) { var x1 = cx + r * math.cos(-startangle * rad), x2 = cx + r * math.cos(-endangle * rad), y1 = cy + r * math.sin(-startangle * rad), y2 = cy + r * math.sin(-endangle * rad); return ["m", cx, cy, "l", x1, y1, "a", r, r, 0, +(endangle - startangle > 180), 0, x2, y2]; } var path = sector(100,100,50,0,180); var arc = paper.path(path); function draw() { path = sector(100,100,50,0,finangle); ...
Read more