[opendtv] Re: Digital, So Slow
- From: "John Willkie" <johnwillkie@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 5 Jul 2004 06:11:58 +0100
Kent;
Sounds pretty bad, but before one can think about the video delay, you have
to talk about 1) how far away you were from the stage, 2) describe the
speaker set up (were they all on the stage) and 3) how many feet you were
away from the nearest set of speakers.
You were, after all, at a festival.
You might think that the video delay controls. Frankly, a three frame delay
is just barely perceptible by trained people. One of our local stations had
a audio leading video problem of 250 ms for many years. It bugged the hell
out of me, but few mere mortals ever noticed it, even when I pointed it out
live to them.
Once we figure out how long it took the audio from the nearest speaker to
reach you, we then can contemplate if the sound system was time-aligned
(properly or at all) and see how long the audio led the video.
I see video-audio sync problems from time to time on TV, usually on live TV.
It's really odd in the rare event when video leads audio.
It's best not to talk in terms of frames, unless you know the frame rate:
24, 23.996, 30, 29.97, 60 or 59.94?
John Willkie
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx
[mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Kent Borg
Sent: Monday, July 05, 2004 6:49 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Digital, So Slow
Tonight we saw the "Funk Brothers" at the Montreal Jazz Festival.
They put the stage in the intersection of Saint-Urbain and
Maisonneuve/President Kennedy. We didn't have the best standing room
locations, we were off to the side, so part of the time I looked at
the TV projection up top on our (right) side of the stage.
How confusing! The video was significantly delayed. (My wife
commented on it too.) I tried to estimate the delay. My early guess
was 10-frames, but I quickly dismissed that and started paying more
attention.
When Joan Osbourne sang "For Once in My Life" one of the Funk Brothers
was hitting a tambourine and the audio+video combination made for
double-time. (IE, video 180-degrees out of phase with live.) When
they did "Heard it Through the Grape Vine" his live tambourine was in
apparent sync with his video avatar, so single-time for that number.
I decided the delay was 3-frames or less.
Where did such a big delay come from? There was a TV broadcast coming
from the venue (they sat around until 9:31 PM to start playing), but
we were watching local video (complete with a please-wait graphic
before the start).
There were three cameras on stage and one crane close to
down-stage-right. 200-some-feet out in the crowd was a pair of
cameras, and roughly even with them, stage-left side on top of the
Place des Arts, was a second crane.
How many frame buffers were we running through? How much do digital
switchers delay things these days? What else would delay the local
feed.
Analogue might have had generational losses but there are still are
things to miss about it.
Thanks,
-kb, the Kent who is currently listening to his favorite jazz radio
statio, via the internet, from France.
P.S. Walking over the Charles River in Boston the other day they were
testing the sound system for the 4th concert. Very echo-y. I am
guessing the delays they put on each tier of speakers farther from the
stage weren't turned on yet.
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