Re: [linux-audio-dev] munlock and mmap

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Subject: Re: [linux-audio-dev] munlock and mmap
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: Wed Apr 05 2000 - 17:17:13 EEST


>I wonder if you're emulating hardware tape recorders a little more
>closely than is necessary.
>
>Why not do it like this: Don't overwrite any of the existing track
>until recording (AND playback) is stopped. When punch-in happens,
>data goes to a new file (in any standard format you like) & the
>application makes a note of where it's supposed to end up & with
>what sort of crossfade.

Good suggestion, though you're right: I have been considering this
already. However, its actually in the realm of an "implementation
detail". The hard part of punch-in/out is not where to put the data,
but how to do the audible x-fades.

If I give up on "audible x-fades", then maybe I can get rid of all the
hairiness. And you know what ? I checked with some Cubase users, and
as I would have expected, there is a definite "click" when you go
punch in/out.

If you toggle the monitor signal between pre-existing material and the
recorded stuff, there *has* to be a click, because they are delayed
w.r.t. to each other, so you have a waveform jump.

I haven't yet figured out (or checked) if the Alesis ADATs click, but
I doubt it. I don't know know how they would avoid this. If they have
an analog input signal, oh, sure ... they just put an analog delay in
the path of tape monitor outs, and then when they switch back and
forth between monitor in/monitor out, the digital signal from the tape
is in sync with the delayed-analog signal. But this would imply that
the analog signal is always delayed, which seems unlikely.

Anyway, in the 100% digital world there's really going to be a
click. If so, then who cares about doing the x-fade on the fly anyway?
And if there's no on-the-fly-as-we-listen xfade, then life suddenly
becomes unbelievably easier.

Comments from anyone with studio experience ?

--p

--p


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