convert existing files to a constant bitrate

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convert existing files to a constant bitrate

Postby danw700 » Wed Nov 25, 2015 6:27 am

Hello, I use GoldWave but not this video editing software yet. I create a lot of video tutorials of the speaker shot against a green screen (me at head and shoulders) my WebCam uses variable bit rate. I record the audio separately on a good quality microphone in a shielded environment using GoldWave. I mark the synchronisation point with the flash from a camera and the sound of the shutter.

I edit the audio in GoldWave to enhance a sound until the vocals are acceptable. In the video editor I mute the audio from the WebCam stream and synchronise the new audio channel to the WebCam. I start out with perfect lip sync but of course I end up losing the lip sync due to variable bit rate in what I believe is the WebCam stream.

How can I overcome this problem?

Cheers for now
Dan
Thanks for a remarkable bit of software in GoldWave. This
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Re: convert existing files to a constant bitrate

Postby GoldWave Inc. » Wed Nov 25, 2015 11:26 am

Whenever you are working with two different audio devices, there may be a slight difference in recording and playback speeds, simply because the hardware is different. Your WebCam may record audio at a slightly different speed than your computer's audio hardware plays it, causing the synchronization problem over time. Or the WebCam's recording software may use the systems clock to timestamp the video frames instead of using the WebCam's audio clock.

Check to make sure the unedited WebCam video maintains synchronization. If not, then you'll need to use GoldWave's "Time" (or "Time Warp") effect to change the speed of the audio slightly.

Sometimes previewing playback of variable bitrate files the video editing software will have synchronization problems, but the final video file won't. If the final video still has synchronization problems, use the "Time" effect to adjust the audio.

If you find that synchronization is off by 1 second in a 30 minute recording, then you'd add or subtract a second from the length in the "Time" effect (enter "30:01" or "29:59"). Figuring out the exact time may take some trial-and-error.
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Re: convert existing files to a constant bitrate

Postby danw700 » Wed Nov 25, 2015 1:32 pm

Thank you for your speedy and detailed reply – generally speaking the audio recorded in the WebCam and then edited in my video editor and then rendered out is okay. Quality of the audio using the microphone recording into GoldWave is a lot better. I haven't used the time affect in GoldWave and I'll certainly be experimenting with that. Thanks so much.

Even when recording in Camtasia I can get the end result out of sync. This program is far too expensive for me so I have developed a way of ending up with the same effect for my narrated PowerPoint decks with an insert of my narration.

Once again thanks for the heads up on adjusting this setting in GoldWave.

Cheers for now
Dan
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