Saturday, January 9, 2010

Re: [Avid-L2] Re: HDCam SR 24p q

> On Jan 8, 2010, at 3:34 PM, johnrobmoore previously wrote:
>
>> Another way around the issue would be to adjust the phase of the
>> Avid's output. Anybody know if adjusting the phase in the video
>> output
> tool effects the SDI output? It is labeled as the component phase so
> I don't know if that would effect SDI. Anybody have an idea?
>
> I answered:
>
> Phase adjustment is analog only (component HD-SD and/or composite
> SD). It doesn't affect SDI, as that is self-clocking/timing.
>
> Dennis Degan, Video Editor-Consultant-Knowledge Bank
> NBC Today Show, New York

On Jan 10, 2010, at 12:37 AM, johnrobmoore wrote:

> There is most definitely timing in the SDI world. There are windows
of tolerance that can be exceeded which will cause problems. The tek
scopes and others have timing functions. I have seen issues with Kona3
card outputs where a Sony 5500 would not except a 720P signal seeing it
as unrecognizable or something like that. Adjusting the vertical
timing of the Kona control panel a vertical line's worth got the deck
to accept the signal. At the same time a 5800 deck was okay with the
signal. IIRC according to Sony the window of tolerance for these decks
is 2.5 lines. Of course if the deck was set to input reference that
would not be an issue. I actually prefer to run external sync for a
5500/5800 to reduce the chance of punching a hole in the master tape if
the Avid dumps out of a digital cut. The garbage the Avid spits out
when crashing out of record wreaks havoc on the 5500 servo reference
when it is locked to video in. When locked to external I've had fewer
instances of this problem. It's hard to narrow it down precisely but
after adopting external reference I definately have had fewer problems
of that nature, coincidence? I think not.

While there is no subcarrier phase there is both horizontal and
vertical timing in an SDI system. Of course in a non linear bay with
only one source or record at a time the old issues aren't prevalent as
in a linear bay. I'm not saying there is a timing function for the
Avid sdi out but there are timing adjustments for studio environments
etc... So timing is not just for analogue.

I say:

You asked if the phase adjustment controls affect the SDI output. It
WAS my understanding that they do not. But to clarify, the presence of
an external reference DOES affect the SDI output and allows it follow
that reference. Unless I'm simply misinformed (which is becoming
clearly likely), the SDI output will sync with an external reference
but cannot be phased to it. However, the analog outs (component HD/SD
and composite SD) CAN be phase-adjusted.
There are, as you pointed out, a window of tolerance of SDI inputs.
Perhaps I am wrong and the phase adjustments DO affect the timing of
the SDI outputs, putting them more within range of the next device's
input timing window. This is an issue I've not seen, since as you've
noted I have no need to adjust the timing in a single Avid system.
As for using the external reference setting, I say if it works for
you, fine. I'm old-school and feel that if there's a problem with
using the AUTO setting, it should be addressed, not worked around (In
this, I'm not referring to you, John. I mean that Avid should address
it).

Dennis Degan, Video Editor-Consultant-Knowledge Bank
NBC Today Show, New York

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