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abcwille
06-14-2011, 08:01 AM
Hi there

I know there is a lot of topics about latensy, but there is no answer i think.

I am running the 850 with latest update.
I have tried with sound running through a mixer and directly to the TC.
I have tried with EX-1 and a Panasonics HE-100.
I use 1080i .

Same result. 2-3 frames off sync.

It is not much, but it is still something you can see.

Is there no way to correct it inside the TC instead of doing it in the post editor ?

Thomas

SBowie
06-14-2011, 08:30 AM
I have tried with sound running through a mixer and directly to the TC.Hi - more detail is needed, please. Are you running live sound and video into TC's inputs and finding a sync issue on output directly to speakers and a video monitor? Or do you have some other configuration in which sound takes one path while video takes another?

GeekNews
06-14-2011, 11:43 AM
From day one direct feed audio from mic or mixer does not change things there is always 2-3 frames where audio has always lagged video known issue and to date no fix we figured at this point that it is just the way things are.




Hi there

I know there is a lot of topics about latensy, but there is no answer i think.

I am running the 850 with latest update.
I have tried with sound running through a mixer and directly to the TC.
I have tried with EX-1 and a Panasonics HE-100.
I use 1080i .

Same result. 2-3 frames off sync.

It is not much, but it is still something you can see.

Is there no way to correct it inside the TC instead of doing it in the post editor ?

Thomas

abcwille
06-14-2011, 12:37 PM
Sorry for not being accurate.

Just to eliminate all possible error, I have put a mike directly into the
TCs XLR input.
In the TC audio tab , I have selected mic 1+2 with phantom power
Choosed a camera input and recorded it.

When I playback on our monitor, SDi with embedded audio, there is a lack. Not much, but notable.

When I playback in Speededit, I see the same lack. Still on the same monitor. And still when I render from SE, it is there.
When I transcode the Mpeg to FCPs Prores from TC export, and edit in Final Cut, there is the same lack. 2-3 frames off.

From Geeknews and others it seams to be a well known "feature"

But it would be nice to eliminate this "feature"

Or is just me doing something wrong. I am a kind of newbie with this TC 850 :-)

Just got it a few months ago.

Thomas

SBowie
06-14-2011, 01:35 PM
Sorry for not being accurate.No apology necessary. I just want to be sure I understand your setup before commenting.


Just to eliminate all possible error, I have put a mike directly into the TCs XLR input. In the TC audio tab , I have selected mic 1+2 with phantom power Choosed a camera input and recorded it. When I playback on our monitor, SDi with embedded audio, there is a lack. Not much, but notable.

Let's talk first about live video and audio. One would like to assume these signals were in sync when arriving at TriCaster's inputs. (This isn't actually assured, but let's go with it for now. I'll address the other case at the end.)


With regard to simple live throughput - that is, live video going through the switcher and on to TriCaster's output connector(s), and audio going through the mixer and on to TriCaster's output connectors(s) - there will be a little latency (up to 2 frames, perhaps) as the signals are processed and passed through; but there should be no noticeable sync issues. (Audio and video processing are designed to have the exact same latency, for obvious reasons.)


When you record the a/v program (internally in TriCaster), and then play it back (or examine it in an editor), it's theoretically possible for a/v sync to slip by as much 1 field at times. This small difference can occur because the switcher has a time-base corrector. If video playback from a file starts on an odd field, the video output is delayed one field, but audio playback starts immediately. It's generally accepted that a 1 field variance does not pose an issue.


(It can happen that if someone plays a clip and re-records the output, plays the second file and re-records that output, and so on, a number of times, a 1 field sync mismatch can accumulate into something more obvious because of the multiple passes - but this should be a rare case).


The above has been tested and proven here (recently), and re-testing occurs before each product release. There are a couple of things I can mention that might be helpful. First, as I said, it is by no means guaranteed that there is no video latency right out of the camera - before ever reaching TriCaster. In-camera processing such as image stabilization and color correction can add a frame or two (which would cause a sync offset whenever audio is also not fed through the camera.) Much more likely, consider that roughly two frames of sync mismatch are added by a typical LCD monitor. This means that using an LCD to judge sync is really not a valid approach, and is almost certain to show a 'problem' that really doesn't exist at TriCaster's outputs. (Of course a projector will often be responsible for even more sync mismatch, but I presume we're not talking about that for test purposes.) Use a CRT for testing, or closely examine the waveform and video display of a suitably prepared recorded clip in an NLE, etc.

I hope this helps!


From day one direct feed audio from mic or mixer does not change things there is always 2-3 frames where audio has always lagged video known issue and to date no fix we figured at this point that it is just the way things are.I've spoken with the good Dr. Cross about this today, and if your experience does not jive with my post on the subject, please PM me.

csandy
06-23-2011, 04:00 AM
Same result. 2-3 frames off sync.



I'm not even sure everyone in this thread is talking about the same thing.

2-3 frames off sync in which direction?

Is your audio ahead of your video, or behind it?