Camtasia synchronisation

cvgh wrote on 2/17/2010, 11:58 AM

Can anyone help with this issue please. I have recorded a PowerPoint lecture using Camtasia with Sennheiser radio mic into a laptop. I have also videod the lecture with a Sennheiser radio receiver on the camera set to the same frequency as the receiver plugged into the laptop. I have saved the Camtasia as an avi file and imported into Vegas Pro 9(c) along with the video capture. I have synched the two audio as best I can on the timelines but after about a minute the synchronisation drifts quite noticably. I feel certain I have never had this problem with earlier versions of Vegas but am I missing something obvious or is there an other reason for this synch drift? Any help much appreciated. Geoff

Comments

Geoff_Wood wrote on 2/17/2010, 5:11 PM

It's nothing to do with Vegas- your interface and video clocks are not synchonised.

Taking a sharp sound with a visual cue at each end of the event(s), and 'stretch' the audio in or out to match. Make sure to 'preserve pitch' .

If the clocks drift is constant, then everything in between should fall into place. If clocks drift is not constant, you are stuck with splitting the event into smaller ones and doing this procedure for each section.

geoff

cvgh wrote on 2/18/2010, 12:10 AM

Geoff, many thanks for getting back to me on this issue and I note your point. However being an educator rather than a film maker I wounder if you could spare another moment or two to tell me what is the 'interface clock' - is this something I can reset? What is the 'video clock' and again is this something I could re-set? When you say take a sharp sound... is this something I can do in post? I have figured out about stretching the audio but was not sure how to insert the sharp sound. In future I will use a clapper board! Again many thanks. Geoff

Geoff_Wood wrote on 2/18/2010, 5:50 PM

Like having two independant wristwatches - they will drift apart over time. But in this case obviously 'more' to the point of being an issue !

If you recorded the video and audio on the camera, both would be synchronised. Otherwise for recording each on separate device, there is no synchronisation, unless both devices can be synchronised via a 'clock' cable/connector, with one being the master, and other slave (or a separate Clock Generator and audio and video recorder both'slaves').

External clock functionality is usually found on pro, and some 'prosumer', gear.

However (having just checked and found what Camtasia actually is - I had assumed it was an external device !), I would imagine that such synchronisation would be a setting within the application. This also possibly makes the issue a sample-rate clash type of thing, and could even be a failing of the soundcard driver to switch to the application's project sample rate.....

External clock functionality is usually found on pro, and some 'prosumer', gear.

geoff

cvgh wrote on 2/19/2010, 2:35 AM

Thanks Geoff. It all makes me realise there is so much to learn in this game. Your advice has been much appreciated, many thanks. Geoff