21 Sep
2009
21 Sep
'09
8:34 p.m.
Paul Davis wrote:
On Mon, Sep 21, 2009 at 12:36 PM, Fons Adriaensen
<fons(a)kokkinizita.net> wrote:
From my experiences with SMPTE you need a minimal pre-roll and for
audio recordings it's common to have one or two bars pre-roll, which is
much more than enough to get in perfect sync by SMPTE. IIRC even with
dropouts my analog tape recorder and Atari were in sync within 1/8 note
and the fine thing is, that when using LTC it should be possible to be
in sync while jogging or winding, but I can't remember that this worked
for me at home. For analog (old professional) VTR a pre-roll simply was
needed to get the spools on speed, I don't think for hard disk audio and
video recording SMPTE will need a noticeable pre-roll. The accuracy
seems to be better than what is needed for audio and video. I don't know
all SMPTE variations and I don't know if there is some newer standard,
but IMO SMPTE is something that should be supported. I never heard of
discontent because of using SMPTE and I also never had any trouble
because of SMPTE. The question might be, if SMPTE would be used by many
Linux users or not. Btw. one real disadvantage of SMPTE can be
crosstalk. I prefer a low level for the SMPTE signal with the risk of
getting more dropouts.
Ralf
On Mon, Sep 21, 2009 at 08:18:00AM -0400, Paul
Davis wrote:
when rolling, sure. i'm thinking about a locate command.
its also true that there are variants of SMPTE that include subframes,
which certainly help the accuracy, but its not clear to me how
commonly this information is actually passed around. SMPTE is a low resolution time code. There is no
reason to be limited
by frame rates of 30 fps when defining a synchronization protocol
between applications running on the same (or even two networked)
computer(s). JACK transport is sample-accurate, and as such is
thousands of times more accurate than SMPTE.
While I'd agree 100% that SMPTE is not what's needed here,
your comments on its potential accuracy are misleading.
The *data* contained in the SMPTE timecode is quantised
to frames. But SMPTE is not just that data. It is data
encoded into an audio signal, and this can be resolved
to sub-microsecond accuracy.