I have taken to monitoring audio through the audio output of my program monitor so it is deembedded audio from the HDSDI signal sent to the monitor. This helps to keep things closer in sync but still depending on the monitor video processing delay it's not perfect just closer. This also helps when I switch to monitor my tape deck output it automatically monitors the tape audio for proper sync evaluation. I think you can do the same feeding a monitor through HDMI. Might be something to consider.
---In avid-l2@yahoogroups.com, <blafarm@...> wrote :
Thank you Rich and Mark. I am glad that you are both seeing some amount of latency. That "squares" with what AJA told me.
And yes, one can entirely abandon looking at the MC GUI and just concentrate on the audio/video output of the AJA interface. However, this video latency issue creates audio sync issues which are not insignificant.
in another down-and-dirty test, I aligned one audio frame of Avid-generated tone media with a hard cut in the same test footage that has already been transcoded to MXF. Then I shot the resulting short sequence twice with a camera running at 23.976 -- once operating MC in "Software Only" mode and pointing the camera at the MC GUI (audio from the computer) -- and then a second time using the AJA Io4k and pointing the camera at the external monitor (audio from the Io4k). Both shots were subsequently imported back into MC (MXF) and the audio/video offsets were measured.
When operating MC in "Software Only" mode the audio was in dead sync.
Conversely, when using the AJA Io4k, there are a solid 3 (three) frames of video delay between the first modulation of the tone media -- and the video frame it should be associated with.
So, unless you are using an audio delay box, or your audio signal chain somehow naturally induces 3 frames of delay, simply concentrating on the audio/video output of the AJA interface means everything you are looking at is out of sync.
Of course, you may not be seeing the 3 frames of delta that I am seeing. But it is worth knowing that this problem can impact lip sync, dialog replacement, sound effects spotting and precise cutting to music queues.
</Captain Obvious rant over>
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Posted by: bigfish@pacbell.net
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