[ardour-dev] testing plugin latency compensation and alignment

Paul Davis paul at linuxaudiosystems.com
Sun Jul 31 14:39:12 PDT 2005

For those of you who wish to test the new PLC/alignment "fixes"
("redesign" is perhaps more accurate), there are two approaches to
take. One of the duplicates the testing I have done, the other is a
bit more "real world". 

If any of this description makes no sense to you, don't ask for
help. Thanks. :))

* Using a loopback cable

1) connect the output of your audio interface to the input
2) run JACK with large period sizes to make errors more obvious
2) set up a session with 3 tracks
3) record the click track on one channel, and set its output to the be
      h/w outs. be sure to disable rec-enable for the track after
      you are done.
4) put the "artificial latency" plugin on another channel, or any
    other plugin with substantial latency
5) start the tests, which all involve recording the input signal on
    the remaining channel. Start by making sure the tracks inputs
    are connect to the h/w inputs.
     a) leave plugin disabled, set alignment style to "existing material"
        1) start recording at zero, and stop.
	     - recorded material should line up *exactly* with the
	       click sounds in the first track. They might be off
	       by a few samples because of A/D delays in your system
	       if you do not have an all-digital interface.
             - delete recorded region
        3) start recording not at zero, and stop
	     - ditto for alignment
	     - delete recorded region
        2) setup an auto-punch range, record using it
	     - ditto for alignment
	     - delete recorded region
        3) rec-enable the track, start transport, punch in/out manually
	     several times. stop transport, start again from where
             you stopped.
	      - ditto for alignment

     b) repeat (a), but use "exact capture time" for alignment style
           - all new material should be roughly 1 period later than
             in the source track

     c) as (a) but enable the plugin (switch back to "existing material")

         1) set the plugin latency to something substantial (in the
            range of 0.5-5 seconds)
	 2) replicate (a) tests, results should be the same

     d) as (b) but with plugin enabled (use "exact capture time for alignment)
         1) replicate (a) results, results should match (b)

* Real World

Read the above, set up some scenarios, record some stuff, play along
with it. You expect me to know how to record music? :))



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