Subject: Re: [linux-audio-dev] MTC, SMPTE, etc.
From: Jörn Nettingsmeier (Udo.Nettingsmeier_AT_t-online.de)
Date: Sat Jul 22 2000 - 14:20:13 EEST
Paul Barton-Davis schrieb:
>
> In message <3978AB66.F0E9B7C9_AT_yahoo.com>you write:
> >Paul Barton-Davis wrote:
> >>
> >> >I'd rather say the solution is to not only decode the SMPTE frame,
> >> >but also keep track of it's exact position in the audio stream. Works
> >>
> >> who says its part of the same audio stream ? i would tend to have
> >> SMPTE streaming in through a cheap interface, and not taking up a
> >> channel on a good multichannel card.
> >
> >Sorry if this is a dumb question, as I've never done anything
> >with SMPTE... but wouldn't this have exactly the same problems as
> >trying to sync audio data from different cards?
>
> i'm not sure. SMPTE is not even close to frame-accurate (the finest
> resolution is 1/30 second or thereabouts). there is therefore a lot of
> room for sloppiness.
???
i'm confused. isn't this 1/30 sec (or 1/29.xyz or 1/24 or
whatever) supposed to be a "frame" (= one image of the
film)? what kind of frames are you talking about ?
as to sloppiness: ok, timestamp granularity is 1/30 sec max,
but sync precision is sufficient for audio. you might
encounter problems putting two channels of phase-sensitive
stereo on two different machines with flaky smpte sync, but
don't do that, then.
> i wish to god that SMPTE had never taken off. its the most ridiculous
> thing since, errr, oh, something like APL. more precisely, its fine
> for video timing, but its *insane* that its become accepted for audio
> timing.
<tender little rant>
erm, well, unlike the perfect solutions that we all here
dream of, smpte is actually *available* and it's *standard*.
which is quite a plus, imvho :-D
</>
out of curiosity, what is apl ?
regards,
jörn
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