Does re-rendering hit the quality of the video?

PDB wrote on 10/18/2016, 11:52 AM

Evening!

Back in the old days, if a clip was re-rendered with no new effects and the same codec was used, Vegas would not actually re-render the clip: ie, the rendering process only affected the frames which had changes made to the original which was on the timeline.

Is that the case with all the codecs today?

I have been working on a project involving different stages so I opted to work on each stage in a different Veg file. I Have succeeded in building the final project using nested veg files, but it takes ages to open and is a bore to tweak if necessary. I am therefore considering rendering out each veg file into:

a. an intermediate codec and the simply put all these rendered clips on a final timeline (for example using Cineform's codec) and render an mp4 as the final output.

b. render each Veg using the final codec/resolution (mp4), add each clip to one final timeline and render out again using the same codec used to render each individual clip.

Does that make sense?

Thanks for any suggestions. 

Comments

john_dennis wrote on 10/18/2016, 12:02 PM

Render to a lossless or visually lossless codec and you shouldn't have to worry about generation loss. Don't render to the final codec unless you have verified that you can combine the individual files without re-encoding, which is unlikely.

NickHope wrote on 10/18/2016, 10:50 PM

+1 John.

Back in the old days, if a clip was re-rendered with no new effects and the same codec was used, Vegas would not actually re-render the clip: ie, the rendering process only affected the frames which had changes made to the original which was on the timeline.

Is that the case with all the codecs today?

You're referring to "smart-rendering", or "no-recompression" rendering. From the VP14 help (note that AVC is not included):

""Enable no-recompress rendering" - Select this check box if you want to pass through unedited frames without recompression (smart render) for the following formats:

  • DV AVI
  • DV MXF
  • IMX MXF (IMX 24p MXF is not supported for no-recompress rendering)
  • XAVC Intra MXF
  • HD MXF
  • MPEG-2 (for files such as those from HDV and DVD camcorders)
  • Panasonic P2
  • XDCAM EX supports smart rendering across the following formats:
    • SP 18.3 Mbps CBR 1280x720p to/from XDCAM EX and HDV HD-1
    • SP 25 Mbps CBR 1440x1080i to/from XDCAM EX, XDCAM HD, and HDV
    • HD-2HQ 35 Mbps VBR 1440x1080 to/from XDCAM EX and XDCAM HD 
    • HQ 35 Mbps VBR 1280x720p to/from XDCAM EX
    • HQ 35 Mbps VBR 1920x1080 to/from XDCAM EX

In order to perform rendering without recompression, the width, height, frame rate, field order, profile, level, and bit rate of the source media, project settings, and rendering template must match. Frames that have effects, compositing, or transitions applied will be rendered."

Musicvid wrote on 10/19/2016, 7:18 AM

If rendering VBR (such as mpeg-2), the Max and Avg bitrates must also match the source or it will not smart render.

This is especially important when copying material for/from DVDs. In this case, set the Min bitrate at 2,000,000.

PDB wrote on 10/19/2016, 11:15 AM

Thank you to all who have helped me out with suggestions!

I did actually try the search before posting but got lost in posts dating back a few years and was unable to find specifics on codecs.

Nick, it never ocurred to me to look up in the VP Help! Must take note to check in there when in doubt about the software specifics...

Some of the stuff included in the project was shot on old film cameras (super 8?) back in the 60's, which was then put on VHS and finally on DVD, so is has taken a bit of a hit in the different processes...Since it's interlaced, I take it my best bet is to keep it that way and let the large Smart TV (which is the first screen it will be shown on) do its thing on playback.

I have tried a render to progressive using Vegas' smart de-interlace option (even though one clip's render keeps freezing at 68% - tried pre-rendering from there onwards and still had no success...), but the final product is poor (not really surprising). I'm going to try rendering interlaced and see if it any better.

Once again thanks for the suggestions,

 

Best regards,

Paul.

NickHope wrote on 10/19/2016, 12:26 PM

Yes, let the TV do the deinterlacing. Different matter for computer playback. Not sure why your render is freezing. If you're using V14 then it might be due to the memory handling bug(s) in the first release (version 161). You could try simply splitting the clip and rendering in 2 halves.

PDB wrote on 10/21/2016, 3:55 AM

Thanks Nick,

the rendering issue is a mystery, and may be due to the memory issues. However, I even tried rebooting and the problem was still there on that particular clip. I tried pre-rendering about 30 seconds beginning at where the 68% freeze was happening and still no luck. 

So I gave up and rendered out to progressive interpolate instead of smart de-interlace and that worked. What I find weird is that it didn't happen on three other clips I rendered using smart de-interlace, two of which where longer. 

Anyway I moved on, and a couple of hours later tried one last time with the problematic clip and it rendered using smart de-deinterlace without a hitch! All very mysterious...

the project has evolved so I will have to do a final render soon, but will stick to interlaced and thus avoid losing more hair in the process...

My next task is editing and polishing the VO which is going to be a fun learning curve...

+ the very "entertaining" audio ducking exercise which will take me a while of course. I am aware of a few paid scripts which are useful for all this but can't justify the cost since I don't do this for a living and have already invested in an upgrade of Vegas and Soundforge to help me along....

any freeby scripts available??

thanks again for all your help and interest.

best regards,

Paul

 

NickHope wrote on 10/21/2016, 6:01 AM
any freeby scripts available??

No scripts that I know of but it's not too difficult:

  1. Preferences > Editing > Time selection envelope fades (ms) > 2000 or whatever you want > Alignment > Outside (or maybe Centred)
  2. Put a volume envelope on your music track.
  3. Put a selection area across your bit of narration (double-click the event if you've chopped them into separate events).
  4. Drag the volume envelope down within the selection area. Holding <CTRL> while dragging can help precision.
  5. Hold <ALT> while dragging the keyframes left and right to refine the alignment.

(P.s. Always wanted to write a V/O script just so I could call it "Funky Ducker". In the meantime the Vegasaur feature is spot-on but obviously you need to buy the whole extension)

PDB wrote on 10/21/2016, 6:08 AM

Thanks Nick, I'll give your method a go!

I did actually buy a license to Ultimate S way back when, (I can't for the life of me remember under which credentials so upgrading if at all possible seems unlikely) and did check out Vegasaur and Excalibur today. I came across FASST plugins at just under 10$ apiece which would be an ideal option, but alas they aren't VP 14 compatible. 

Anyway I will try your suggestion which I'm sure will be a huge timesaver so thank you again for your help. And please do write a VO script: just the name is worth it!!