Is Re-rendering .mov Intermediate OK?

Byron K wrote on 8/5/2014, 9:18 PM
I rarely have problems rendering but I've been running into an issue w/ Vegas 12 crashing on one particular render at different frames so I split the 10 minute clip into two approx 5 minute clips rendering to .mov intermediate. (GPU is disabled and Render threads set to 2)

I import the two .mov segments into another blank project and render out as a whole 10 minute .mov to import into handbrake for the "Better" method final video. The video renders very fast, in 15minutes, so it seems that there's no re-compression going on.

Just curious if there is any known issues w/ quality loss doing this or is there a better intermediate to render the two clips to?

Thanks.

Comments

Chienworks wrote on 8/5/2014, 10:16 PM
Depends on which codec you're using to create the intermediate files. If it's relatively lossless or at least very high bitrate then you're probably fine. If it's lossy or low bitrate then you'll take a quality hit.

Just saying ".mov" doesn't really say anything. As with .avi, .mov can contain hundreds of different codecs and compression types.
Byron K wrote on 8/5/2014, 11:23 PM
Thanks Chienworks for your reply.
The video format codec is Avid DNxHD, 24bpp color, Quality: 100%
musicvid10 wrote on 8/5/2014, 11:25 PM
You can render multiple generations of DNxHD without visible loss. Personally I wouldn't go more than five generations.

The quality slider is inactive with DNxHD; it only affects interframe compressors.
Chienworks wrote on 8/6/2014, 9:22 AM
The quality slider is also not the same as bitrate. All it means is that the encoder will take more time to do the best job it can at the given bitrate, but as they say, you can't make a silk purse out of a sow's ear. Too low a bitrate will still result in a bad image no matter what the quality setting. In addition to having the quality set at 100% one should also use a high enough bitrate to assure minimal loss.
Byron K wrote on 8/7/2014, 6:36 PM
Thanks again Musicvid, Chienworks,
The one time .mov re-render didn't have any noticeable quality degradation and the split is pretty much unnoticeable.

I'm not sure why this particular project was having such a difficult time rendering, I suspect that I was using lots of video clean up effects, 2 Boris RED Denoise and Sharpen filters to clean up the video along w/ Color Curves,Track Motion, Pan/Crops, Neat Video. Lots of stuff going on.

If interested you can see the improvement between two videos. The videos are of some friends jamming w/ some walk in musicians (guitar and trumpet) joining in. Lighting was horrible very dark lot's of camera noise but Neat Video and Boris Cleaned the first track up pretty well. The 2nd track was only Neat Video.

The audio is OK. Recording was remixed from a single Edirol R9 recorder.
(For better audio watch in HD)
With video clean up effects Rendered from Vegas 12 to .mov then Handbrake:


Minimal effects and rendered from Vegas 12 to .mp4: