Subject: Re: [ecasound] Strange behaviour with input files which start at different times
From: Kai Vehmanen (k_AT_eca.cx)
Date: Mon Oct 07 2002 - 23:13:07 EEST
On Mon, 7 Oct 2002, Stane Gruden wrote:
> I tried to mix few wav files made by some other program (which I do not
> want to use anymore...), these files were not alligned in time, so for
> each one I used option -y:... to shift it in respect to the others. This
> works nicely. I defined all the chains and their shifts on the command
[...]
> The problem arises later in the interactive mode
> when I want to use the command
> 'setpos'. After some seconds of playing, the command 'setpos 0' should
> return the playing position to the beginning, I expected that this
> beginning would take into account the -y options, but this is not
> true. Playing after 'setpos 0' starts all the files from their real
> beginnig and the result is a mess, of course. Did I miss something
> or is this a bug?
This is a feature (ie. not a bug). The '-y:x' option is semantically
the same as giving a (single) 'ai-setpos' (or ao-setpos for outputs)
before processing is started. Thus the initial offset will be forgetting
if any later global position changed are done.
Fortunately, as S.Massy already noted, there's a way around this
limitation, and that's using .ewf files. See Ecasound User's Guide
for more info about ewf-files.
In the future I might add a new mechanism for positioning audio
that would not require use of external files. Basically I would
add new special audio object types (like the current 'resample' and
'typeselect' audio objects) that would support position and looping. So
something like:
-i locator,foo.wav,offset,intoffset,length,looping
... ie. the all the parameters currently offered by ewf. This would
makes object position much easier for frontends and in general for
circumstances where you need to change the values. The ewf-file
works better if the ewf-params are set once and then the file is used
just like any normal audio file. Once this new locator gets
implemented, it will be quite straightforward to add other types of
locaters. But so far this just me talking aloud... ie. it's not likely I
manage to add this feature anytime soon. :(
-- http://www.eca.cx Audio software for Linux!
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