LISTSERV mailing list manager LISTSERV 16.0

Help for TEAM-ADA Archives


TEAM-ADA Archives

TEAM-ADA Archives


TEAM-ADA@LISTSERV.ACM.ORG


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

TEAM-ADA Home

TEAM-ADA Home

TEAM-ADA  November 2000

TEAM-ADA November 2000

Subject:

Timing for MIDI: an interesting project

From:

Jesse Farmer <[log in to unmask]>

Reply-To:

Jesse Farmer <[log in to unmask]>

Date:

Sat, 4 Nov 2000 21:49:49 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (144 lines)

Hi.  This is my first post to the list.

I am working with a team designing a midi sequencer.  The problem we are
encountering, is timing.  Because we want high reliability, and a steady,
fast timer, we have chosen ada as the language to code this in.  We are
hoping this is not in error, but our tests so far are not promising.

Let me explain what is necessary.  We have a list of events.  Each event
has a time, given in Bars, Beats, and Ticks.  There are 480 ticks in a
beat, and usually 4 beats in a bar.  What is important, is how fast this
translates to in realtime.  Music tempos are given in beats per
minute.  The fastest tempo we hope to support, is 300bpm.  140bpm is
probabaly the tempo that will be used the most.  To figure out how many
seconds long 1 tick is at a given tempo, the following formula is used.
( 1 / ( BPM / 60 ) ) / PPQ
PPQ is pulses per quarter note, or ticks.  We ideally want to use 480, but
240, or 120 will work also, if necessary.  Many commercial programs use
480, and some use 960 or 1920.

We believe the best way to time the playback of these events, is to have a
timer running as an independant process, looping.  Each iteration of the
loop would take 1 tick, and after each iteration, a location in memory
would be incremented, starting with 0, and counting up to 479.  This
location could then be monitored by other parts of the program, without
effecting the timing process.

Using 140bpm and 480 ppq, one tick is
0.000892857142857142857142857142857143 seconds long.
Now how many of those digits are signifigant?  Well, a comparable tempo,
141, would be 0.00088652482269503546099290780141844 seconds long per
tick.  Difference = 0.000006332320162107396149949341 seconds long
Which essentially means we need 1-2 microsecond resolution.  This probably
can't be done.

So with the same tempos, using 120 ppq, we get,
0.00357142857142857142857142857142857    140
0.00354609929078014184397163120567376    141
0.0000253292806484295845997973657548126  difference
25 microseconds, which is much more doable.

In any case, we need high accuracy, as far as I can detirmine.  The bare
minimum we can have is 96 ticks per beat.  Even this seems to require
rather high resolution timing.

In order to test the timing possible on a given system, we contructed a
test program which does the following:
Reads the current time, and stores it
Loop 17,400 times {
        Wait 0.00344827586206896551724137931034483 seconds
}
Read current time.
Subtract current time from time read at beginning of program.
Display difference.

What this simulates is timing at 145 bpm with a 120 ppq.  With 145 beats in
a minute, and 120 ticks in a beat, this program's loop should take exactly
60 seconds to execute, or reasonably close to that.  Our source code follows:

*********begin code************
    with Ada.Real_Time; use Ada.Real_Time;
    with Ada.Text_Io;
--      with Ada.Standard;

    procedure TestTime is

       -- ----------------------------------------------------------
       --  GET THE STARTING TIME, LOOP, GET THE END TIME, SUBSTRACT
       -- ----------------------------------------------------------

       Time_Start      : Ada.Real_Time.Time;
       Time_End        : Ada.Real_Time.Time;
       Time_Difference : Ada.Real_Time.Time_Span;
       Time_Duration   : Standard.Duration;

    begin

       Time_Start := Ada.Real_Time.Clock;
       for I in 1..1 loop
          delay 60.00;
       end loop;
       Time_End := Ada.Real_Time.Clock;
       Time_Difference := Time_End - Time_Start;

       Time_Duration := Ada.Real_Time.To_Duration(Time_Difference);

       Ada.Text_Io.Put("Time Difference: ");
       Ada.Text_Io.Put(Duration'Image(Time_Duration));

       delay 30.0;

    end TestTime;
**********end code**************

Our results:  Running on a pent 233mhz
92.672597596
90.974294742
88.223668684
88.582477917
89.054762903
89.219054124
88.801019125

Results on an Athlon 1ghz were comparable.  Both systems running Win98se.

Why is this so incredibly off?  iterating a for loop 17,400 times with the
delay statment set at 0 yielded a time of only .47 or so seconds.  One
iteration of the for loop, with the delay at 0 takes only .0004 some
seconds max.


As a side note, our team feels very strongly about this project and its
musical merits.  The design is such that it is incredibly unique, and
unlike any other product currently available, and is intended to fill a
niche that is known to exist, but no solution has been developed for.  As
you can see, this is quite a challenging project, and we have several other
componets of this program that present equally great challenges, such as a
macro-lanaguage.

This project is being developed with the intentions of it eventually
running on Windows, Mac, and Linux systems.  At this point in time, all of
the initial design is complete; object lists, and such, as well as detailed
descriptions of all parts of the program exist.  GUI design is in mid
design stages, with may of the bitmaps as well as general layouts complete.

We are looking for one or two programmers (preferably with ada and/or
musical application and/or realtime system experience.  Please note that
the use of ada is contigent upon the feasibility of its realtime
implementation on Windows systems.  Unfortunetly, this project offers no
financial compensation initially.  This is intened to be a commercial
product however, and development team members can expect to receive equal
distributions of the profit from this project.  This project was not
undertaken with the expectation of attaining wealth, but rather creating a
new tool that, if sucessful, will quite literally revolutionize the
electronic music field.  Working on this project is certainly not a
full-time obligation.  All team members currently have other
responsibilites.  If you feel you would be interested in working with us,
or would like more information, please send us an email:  [log in to unmask]

Musisis: Performance Sequencer

Jesse A Farmer: CEO
S.O.S. Designs
Science of Sound: a Centre for Future Music Systems

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

December 2017
November 2017
October 2017
September 2017
June 2017
May 2017
April 2017
January 2017
December 2016
November 2016
October 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
December 2010
November 2010
October 2010
September 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
June 2007
May 2007
March 2007
February 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003
December 2002
November 2002
October 2002
September 2002
August 2002
July 2002
June 2002
May 2002
April 2002
March 2002
February 2002
December 2001
November 2001
October 2001
September 2001
August 2001
July 2001
June 2001
May 2001
April 2001
March 2001
February 2001
January 2001
December 2000
November 2000
October 2000
September 2000
August 2000
July 2000
June 2000
May 2000
April 2000
March 2000
February 2000
January 2000
December 1999
November 1999
October 1999
September 1999
August 1999
July 1999
June 1999
May 1999
April 1999
March 1999
February 1999
January 1999
December 1998
November 1998
October 1998
September 1998
August 1998
July 1998
June 1998
May 1998
April 1998
March 1998
February 1998
January 1998
December 1997
November 1997
October 1997
September 1997
August 1997
July 1997
June 1997
May 1997
April 1997
March 1997
February 1997
January 1997
December 1996
November 1996
October 1996

ATOM RSS1 RSS2



LISTSERV.ACM.ORG

Secured by F-Secure Anti-Virus CataList Email List Search Powered by the LISTSERV Email List Manager