Renders unmodified mpeg-2 (VMS 9.0a)

Darylmtb wrote on 9/2/2008, 10:05 PM
Hi,

So this is my first project, so I could be way off. Before I put all of my mpeg2's together and start editing I wanted to understand rendering and make sure that smart rendering works and I understand its limitations (VMS 9.0a). I'm pulling in a short clip, configuring project properties to match, and then rendering. The quality is quite poor. But before I get to that, I don't understand why it's even rendering.

Using GSpot, I know the mpeg-2 file is upper field first, NTSC widescreen 720x480. So I configured project properties to match that. Changing field order creates custom template (default ntsc one is lower field first). Then I render using MC mpeg-2 plugin w/ DVDA template. I sware the 1st time I did this it did NOT render (and I saw "Recompression not required" on preview screen). But once I started tweaking rendering quality and deinterlace method - to address quality issues - it renders the whole thing. Am I missing something? And when I check the rendered file using GSpot, it's lower field order! Maybe that's how the MC encoder is setup ... ?

Also - once I get back to it not having to render the whole thing, shouldn't the quality be identical to the original? Or because I'm using VMS, does it mean it will always render since I can't customize MC mpeg-2 template to match the source bitrate, so it uses CBR? And by doing a render iteration w/ mpeg-2, there will always be quality degradation?

My source is mpeg-2 from DCR-DVD408 camcorder. According to help: width, height, frame rate, field order and bit rate of source media, project settings and rendering template must match. I have control (I think) over all of that except bit rate.

Thanks,
Daryl

Comments

Chienworks wrote on 9/3/2008, 4:17 AM
"But once I started tweaking rendering quality and deinterlace method - to address quality issues - it renders the whole thing. Am I missing something? And when I check the rendered file using GSpot, it's lower field order! Maybe that's how the MC encoder is setup ... ?"

That pretty much answers your whole question. If your output doesn't exactly match the input then the video is being changed, and that requires a render.
Darylmtb wrote on 9/3/2008, 12:43 PM
Right - I understand if I change certain settings to not match the input, then it will be rendered. But how does changing rendering quality trigger a render? How do I match "good" and "best" to the input?

Also, the help file states: width, height, frame rate, field order and bit rate of source media, project settings and rendering template must match.

Once it started rendering the file I was never able to get it to not render, no matter what I made the settings. I changed them back to the original values and, of course, to values that match the input. But it still renders.

Thanks.
Darylmtb wrote on 9/3/2008, 4:25 PM
Ok now I know what happened. The reason I saw "Recompression Not Required" that one time was because I pre-rendered. I forgot I did that.

So now I have a new clean project with the properties setup to match a mpeg-2 video file... and it always renders it. Is this normal? Maybe my expectations are off. I would think I could setup the project properties to match the input. But no matter what I make the settings it always renders the whole video. The input is mpeg-2 and I'm rendering for DVD using the settings I mentioned above. Perhaps this is a limitation of MC encoder in studio version, where I can't tweak bit rates .. ?

I'm confused. I'm starting to think I should have bought a HDV camera, if mpeg-2 always gets rendered, even without editing... :)

Thanks,
Daryl