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List:       kde-multimedia
Subject:    Latency benchmark mp3 & wav
From:       Stefan Westerfeld <stefan () space ! twc ! de>
Date:       2000-07-19 12:17:20
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   Hi!

I've just committed some code you can use to benchmark how long exactly aRts
gets blocked by certain operations (i.e. opening an mp3). The benchmarking
code is in iomanager.cc, and you can easily be enabled by changing an undef
into define.

To add some hard numbers to the PlayObject/loadMedia stuff, I've benchmarked
two things:

 - aRts's standard wave PlayObject
 - mpeglib's mp3 PlayObject

I used mpeglibartsplay to play a file, then repeated it (because at the first
time, aRts will need to read all .mcopclass files, open the library, etc.),
and then repeated the test with an other file. I always used realtime rights.

What you see in the results is that wav is a bit of the proof that you can
write PlayObjects with the current interface in a way that they do not block
the server (there is no latency >= 1.5 ms with repeating the first file).
However, it isn't quite fair, as it uses caching (where you usually would
have diskIO).

Also, it proves that the current wav code is completely broken, as it loads
everything at once.

The mpeglib stuff on the other hand performs quite good, except for the
initialization and destruction times. Now if these could be removed (by using
JEL or whatever else), it would be the first perfect PlayObject. I've added
an output which function was called, so you can associate the latencies to
the code.

   Cu... Stefan

==== WAV: ====

 ** mpeglibartsplay /home/stefan/file01.wav            << what I did

IOManager: latency for operation: 2.064 ms             << server output
IOManager: latency for operation: 877.730 ms
IOManager: latency for operation: 1.897 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
client disconnected: dropped one object reference

 ** mpeglibartsplay /home/stefan/file01.wav

IOManager: latency for operation: 1.681 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
client disconnected: dropped one object reference

 ** mpeglibartsplay /home/stefan/file02.wav

IOManager: latency for operation: 437.010 ms
IOManager: latency for operation: 1.734 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
client disconnected: dropped one object reference

==== MP3: ====

 ** mpeglibartsplay /home/stefan/file01.mp3

IOManager: latency for operation: 2.000 ms
DBO: constructor
DBO: loadmedia
IOManager: latency for operation: 67.839 ms
IOManager: latency for operation: 2.064 ms
DBO: play
IOManager: latency for operation: 25.925 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
DBO: destructor
client disconnected: dropped one object reference
IOManager: latency for operation: 24.778 ms

 ** mpeglibartsplay /home/stefan/file01.mp3

DBO: constructor
DBO: loadmedia
IOManager: latency for operation: 15.943 ms
IOManager: latency for operation: 1.742 ms
DBO: play
IOManager: latency for operation: 12.712 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
DBO: destructor
client disconnected: dropped one object reference
IOManager: latency for operation: 24.637 ms

 ** mpeglibartsplay /home/stefan/file02.mp3

DBO: constructor
DBO: loadmedia
IOManager: latency for operation: 16.594 ms
IOManager: latency for operation: 1.806 ms
DBO: play
IOManager: latency for operation: 12.991 ms

 ** ctrl+c in mpeglibartsplay

client disconnected: dropped one object reference
DBO: destructor
client disconnected: dropped one object reference
IOManager: latency for operation: 21.468 ms

-- 
  -* Stefan Westerfeld, stefan@space.twc.de (PGP!), Hamburg/Germany
     KDE Developer, project infos at http://space.twc.de/~stefan/kde *-         
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