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Question on degree of resolution loss

Question on degree of resolution loss

Postby Brain Champagne » Wed Oct 23, 2013 10:15 pm

I have a bunch of HD videos (1080) with separate audio tracks.

The audio tracks were made using a different source (digital audio recorder) and they're hard to synch up with the video- not only the starting point but also slightly changing the speed because the two tracks (audio and video) aren't perfectly the same speed.

I want to make a video that uses a bunch of clips from these videos- and not necessarily in order (so clip 1 might be from video 1, and clip 2 from video 2, and clip 3 from video 1 again...).

The easiest way to do this is to make a new, synched, video from each video. And then take clips from those videos. That way the audio work is already done.

But that means rendering and re-rendering.

Is anybody able to quantify how much loss there might be? I don't need a resulting video higher-quality than a DVD, but I may have to crop a lot in some of the videos so I'm not necessarily starting with full HD in all the videos.
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Re: Question on degree of resolution loss

Postby lata » Thu Oct 24, 2013 5:51 pm

Hi Brian

It seems as though you have your work cut out for you, not that easy what you are trying to do.

Yes repeated rendering will have an effect on the quality of the final video, but it may take a few generations before you recognise that, especially is you are downsizing from HD to SD DVD.

I assume your audio sync is to be lip sync, cropping a lot does not really matter it is the repeated re-renderings, and you are only gonna repeat once.

Why are the audio and video out of sync, or rather not the same speed?

Using VS you can stretch the audio/video clip to change its speed.

Change the duration using an audio editor may be a better option.

Good luck
Regards Trevor
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Re: Question on degree of resolution loss

Postby Brain Champagne » Fri Oct 25, 2013 8:11 pm

Yes, it's work, and it would be one extra rendering, not a lot of them. But when I crop 50% (vertical and horizontal) that leaves me with only 1/4 of the original resolution, so that's going from HD to SD, roughly, before extra rendering losses.

I don't know the reason the synch is off but it's from two different sources (camera and digital audio recorder) and I assume that the chips in them aren't perfectly 100.000% accurate.

Lot of reasons I use a separate audio recorder- someone once told me that the best place to put a camera is often the worst place to put a microphone and it's true in my case. I'm a stand-up comic and the mic on stage pointing at the audience picks up their reaction. Mic on camera in back of the room is essentially pointed at the speakers and gets me, loud, but not as much audience. And if someone in the back talks or uses a fork or orders a drink.... ends up on the recording. Mic in stage is way better.

The difference is only a few frames over 10 minutes but it's noticeable.

I tried using the VS audio speed change but it isn't well-done, so I use audio software (that's free).
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