[gmpi] Re: Topic 6: Time representation

  • From: Mike Berry <mberry@xxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Sun, 11 May 2003 09:38:50 -0600



Vincent Burel wrote: 

well, i've nomore time to enter in big explanation, so i propose you to make
the test yourself.
program a audio stream with 500ms buffer size, containing a processing wich
uses 80% of your CPU. And try to timestamp your mousemove (mouse can now
provide at least 50 event per second) to change for example a simple GAIN in
your algorithm. If you get the same reaction type with a 500ms buffer than
with a 20 ms buffer...  i will be obliged to ask you how you did it ! :-)

Vincent Burel


As loathe as I am to jump into this, let me try to explain why to do this. The host is using 500 ms buffers and is recording automation using the mouse click. The host has an automation timing system that is sample-accurate. During the performance that records the automation, the *new* event latency is 500 ms to the plugin. Changes that the user makes live are not heard for 500 ms.

BUT, now consider the second time that we hit play. Now the host is playing back the recorded automation. This automation has sample-accurate timing. The buffers are still 500 ms. But now the host can send down sample accurate events for each 500 ms. buffer. The plugin can now play the events exactly on the right sample.

Furthermore, the user of this host is going to be considerably hampered by the long latency, so they are likely to use other methods to set automation values, like moving points in a timeline. With sample accurate (or better :)) timing, these points can be accurately passed to the plugins no matter what the latency is.

--
Mike Berry
Adobe Systems


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