[opendtv] Re: Digital, So Slow

  • From: Kent Borg <kentborg@xxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 6 Jul 2004 18:32:17 -0400

On Mon, Jul 05, 2004 at 09:53:16AM -0400, Mark Schubin wrote:
> In large-venue video, there is often an intentional delay to try to 
> match the acoustic delay from the speakers (1000 feet per second is a 
> convenient rough figure).  Thus, if the bulk of the audience is 300 feet 
> away from the speakers, the video might be delayed roughly 10 frames to 
> match the audio at that point.  Your being to the side might mean you 
> were closer to the speakers and, therefore, found the delay more noticeable.

That makes sense.  But that big a delay should start to feel like a
satellite delay, and it seemed far shorter.  I'll have to think about
it, listen to a couple motown hits and count out the beats-per-minute.

I was probably under 50 feet from the performers, off to the side.  My
wife noticed the delay too, she was probably less than 20 feet from
the corner of the stage, eventually seeing from the front.  (She
slowly migrated around to the front as the crowd shifted, I think her
video view was of the side projector.)

The speakers bolted on the side of the stage didn't seem to have any
delay from what I saw live, which also makes sense.

I have noticed in Boston for the Esplanade show on the 4th that each
speaker tower is fed a delay to match its distance back.  When we
first heard them doing Boston sound checks the other day we were
pretty much in line with the speakers, so I think we were hearing it
with the delays out of the system.

Back to Montreal: I am used to seeing something happen first and the
sound following, but hearing it before I see it is unnerving.


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