<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div><div style="margin: 0px; font-size: 12px; font-family: Monaco;"></div><div><br class="webkit-block-placeholder"></div><div>
<span class="Apple-style-span" style="border-collapse: separate; font-family: Verdana; border-spacing: 0px;"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Verdana; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">--<br>Tim<br>:wq</div></span></span>
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<br><div><div>On May 27, 2014, at 9:15 PM, Bob <<a href="mailto:kk6ecm@gmail.com">kk6ecm@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">You make a good point, and I should have said more about my application.<br><br>My issue just happens to be with the ARRL Audio News which uses mp3 format,<br>and the desire to play it once per week via the repeater.<br><br>I am experimenting with both the add-on (thanks for the head-up regarding<br>the output level), and a script to convert the mp3 to ulaw format.<br><br>Thanks,<br>r/Bob<br><br>-----Original Message-----<br>From: Ken [<a href="mailto:ke2n@cs.com">mailto:ke2n@cs.com</a>] <br>Sent: Tuesday, May 27, 2014 5:50 PM<br>To: <a href="mailto:app_rpt-users@ohnosec.org">app_rpt-users@ohnosec.org</a><br>Cc: <a href="mailto:kk6ecm@gmail.com">kk6ecm@gmail.com</a><br>Subject: Re: [App_rpt-users] Playing mp3 files in app_rpt<br><br>Asterisk/app_rpt will play MP3 files alright, using the add-on, although,<br>you may need to change the output level.<br><br>In format_mp3.c<br><br>#define OUTSCALE 32768 <br><br>Seems to be about right (I think the original was 8192 but YMMV as they say)<br><br>I used mp3 for bulletins for a while - I even bought a copy of Adobe<br>Audition CS5.5 (now there is version 6) so I could make "real" MP3 files.<br>MP3's made by Audacity sound *really* weird.<br><br>MP3 files contain a frequency spectrum that depends on the sampling rate of<br>the recording. This is a separate rate from the Bit Rate of the MP3<br>playback. If you reduce the playback bitrate of an MP3 file, you may still<br>have frequency components up through perhaps 12 or 15 kHz, you just get more<br>distortion and artifacts. All those frequency components above about 3.6 KHz<br>will be ignored by Asterisk, which runs its sound system at 8 k-samples/sec.<br>This may produce some strange effects since you are playing back stuff that<br>Asterisk can't "hear". The distortion below 3.6 kHz comes through of<br>course... <br><br>To get a file like ARRL Audio News (44 kHz sample rate, in stereo, with an<br>MP3 bit rate of 192k) to play properly on asterisk, you need some software<br>that can re-sample the original file down to 8 k sampling rate (and 8k bit<br>rate). That way the playback spectrum of the MP3 will have components only<br>up through about 3.4 kHz, which is quite compatible with asterisk. Adobe<br>Audition 5.5 (and later) can do this.<br><br>Audacity will also re-sample (at the "Project Rate"), but it is best used to<br>make ulaw files, not MP3's; but it's free.<br><br>If the original recording was frequency-limited then no re-sampling of the<br>recording is needed. For example, my NWS weather podcasts are a computer<br>voice designed for telephone bandwidth, but distributed as MP3's. Those<br>MP3's played through asterisk sound just like the original played on any MP3<br>player.<br><br>Lots of fun<br><br>73<br>Ken<br><br><br><br><br><br>_______________________________________________<br>App_rpt-users mailing list<br><a href="mailto:App_rpt-users@ohnosec.org">App_rpt-users@ohnosec.org</a><br>http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users<br><br>To unsubscribe from this list please visit http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users and scroll down to the bottom of the page. Enter your email address and press the "Unsubscribe or edit options button"<br>You do not need a password to unsubscribe, you can do it via email confirmation. If you have trouble unsubscribing, please send a message to the list detailing the problem. <br></blockquote></div><br></div></body></html>