Re: [LAU] Building a DAW

From: Fons Adriaensen <fons@email-addr-hidden>
Date: Tue Jun 02 2009 - 23:40:11 EEST

On Tue, Jun 02, 2009 at 03:28:43PM -0400, Paul Davis wrote:

> On Tue, Jun 2, 2009 at 12:46 PM, Fons Adriaensen <fons@email-addr-hidden> wrote:
>
> > Is that sync with varispeed ? If the analog machine
> > runs 0.5% slow because it has been a long day, will
> > Ardour do the same, and without loss of quality ?
>
> there are "hidden" options. the default settings assume that the
> timecode source and the audio interface that is driving JACK share a
> sample/word clock, so that 1 second of timecode time == 1 second of
> audio samples, and thus no varispeeding is necessary. essentially, we
> just notice that timecode starts, stops and jumps non-linearly, and
> respond appropriately.
>
> however, you can change this setting (there is no GUI for it because
> i've yet to find anyone who can actually defend adding this option to
> the GUI), and in that mode ardour will varispeed to stay locked to the
> master. it will stay locked to within 8-30 samples of the master's
> timecode position. the varispeed interpolation (linear, fixed point)
> is weak, and so technically quality will suffer. whether its suffering
> worth fixing is a matter that reasonable people might reasonably
> disagree about.

It will be audible on any track that contains significant HF energy.
Some instruments, voice, cymbals, etc.
 
> when i initially developed MTC slaving, i used an Alesis M20 ADAT
> *without* sample/word clock sync. ardour would follow the wow+flutter
> of the M20 perfectly. it would even follow it if i used the
> shuttle/scrub controller on the M20.

<Mr. Spock style> Interesting...

Note that if you varispeed you have to resample recorded streams
as well to keep things consistent.

AFAICS, there are currently three options:

1. Sync the word clock to an SMPTE signal, as suggested by Florian,
2. Sync the analog machine to an SMPTE signal generated by something
   locked to the word clock used by the Ardour session.
3, Sync the analog machine to an SMPTE signal recorded as a Ardour
   track, which amounts to the same thing as 2.

-- 
FA
Io lo dico sempre: l'Italia è troppo stretta e lunga.
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Received on Wed Jun 3 00:15:02 2009

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